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The purpose of this systematic review with meta-analysis was to examine the effects of strength training (ST) on selected components of physical fitness (e.g., lower/upper limb maximal strength, muscular endurance, jump performance, cardiorespiratory endurance) and sport-specific performance in rowers. Only studies with an active control group were included if they examined the effects of ST on at least one proxy of physical fitness and/or sport-specific performance in rowers. Weighted and averaged standardized mean differences (SMD) were calculated using random-effects models. Subgroup analyses were computed to identify effects of ST type or expertise level on sport-specific performance. Our analyses revealed significant small effects of ST on lower limb maximal strength (SMD = 0.42, p = 0.05) and on sport-specific performance (SMD = 0.32, p = 0.05). Non-significant effects were found for upper limb maximal strength, upper/lower limb muscular endurance, jump performance, and cardiorespiratory endurance. Subgroup analyses for ST type and expertise level showed non-significant differences between the respective subgroups of rowers (p >= 0.32). Our systematic review with meta-analysis indicated that ST is an effective means for improving lower limb maximal strength and sport-specific performance in rowers. However, ST-induced effects are neither modulated by ST type nor rowers' expertise level.
The term “bilateral deficit” (BLD) has been used to describe a reduction in performance during bilateral contractions when compared to the sum of identical unilateral contractions. In old age, maximal isometric force production (MIF) decreases and BLD increases indicating the need for training interventions to mitigate this impact in seniors. In a cross-sectional approach, we examined age-related differences in MIF and BLD in young (age: 20–30 years) and old adults (age: >65 years). In addition, a randomized-controlled trial was conducted to investigate training-specific effects of resistance vs. balance training on MIF and BLD of the leg extensors in old adults. Subjects were randomly assigned to resistance training (n = 19), balance training (n = 14), or a control group (n = 20). Bilateral heavy-resistance training for the lower extremities was performed for 13 weeks (3 × / week) at 80% of the one repetition maximum. Balance training was conducted using predominately unilateral exercises on wobble boards, soft mats, and uneven surfaces for the same duration. Pre- and post-tests included uni- and bilateral measurements of maximal isometric leg extension force. At baseline, young subjects outperformed older adults in uni- and bilateral MIF (all p < .001; d = 2.61–3.37) and in measures of BLD (p < .001; d = 2.04). We also found significant increases in uni- and bilateral MIF after resistance training (all p < .001, d = 1.8-5.7) and balance training (all p < .05, d = 1.3-3.2). In addition, BLD decreased following resistance (p < .001, d = 3.4) and balance training (p < .001, d = 2.6). It can be concluded that both training regimens resulted in increased MIF and decreased BLD of the leg extensors (HRT-group more than BAL-group), almost reaching the levels of young adults.
Power training programs have proved to be effective in improving components of physical fitness such as speed. According to the concept of training specificity, it was postulated that exercises must attempt to closely mimic the demands of the respective activity. When transferring this idea to speed development, the purpose of the present study was to examine the effects of resisted sprint (RST) vs. traditional power training (TPT) on physical fitness in healthy young adults. Thirty-five healthy, physically active adults were randomly assigned to a RST (n = 10, 23 ± 3 years), a TPT (n = 9, 23 ± 3 years), or a passive control group (n = 16, 23 ± 2 years). RST and TPT exercised for 6 weeks with three training sessions/week each lasting 45–60 min. RST comprised frontal and lateral sprint exercises using an expander system with increasing levels of resistance that was attached to a treadmill (h/p/cosmos). TPT included ballistic strength training at 40% of the one-repetition-maximum for the lower limbs (e.g., leg press, knee extensions). Before and after training, sprint (20-m sprint), change-of-direction speed (T-agility test), jump (drop, countermovement jump), and balance performances (Y balance test) were assessed. ANCOVA statistics revealed large main effects of group for 20-m sprint velocity and ground contact time (0.81 ≤ d ≤ 1.00). Post-hoc tests showed higher sprint velocity following RST and TPT (0.69 ≤ d ≤ 0.82) when compared to the control group, but no difference between RST and TPT. Pre-to-post changes amounted to 4.5% for RST [90%CI: (−1.1%;10.1%), d = 1.23] and 2.6% for TPT [90%CI: (0.4%;4.8%), d = 1.59]. Additionally, ground contact times during sprinting were shorter following RST and TPT (0.68 ≤ d ≤ 1.09) compared to the control group, but no difference between RST and TPT. Pre-to-post changes amounted to −6.3% for RST [90%CI: (−11.4%;−1.1%), d = 1.45) and −2.7% for TPT [90%CI: (−4.2%;−1.2%), d = 2.36]. Finally, effects for change-of-direction speed, jump, and balance performance varied from small-to-large. The present findings indicate that 6 weeks of RST and TPT produced similar effects on 20-m sprint performance compared with a passive control in healthy and physically active, young adults. However, no training-related effects were found for change-of-direction speed, jump and balance performance. We conclude that both training regimes can be applied for speed development.
The influence of muscular fatigue on tennis serve performance within regular training sessions is unclear. Therefore, the aim of the present study was to examine the within-session sequence of the tennis serve in youth tennis. Twenty-five young male (14.9 +/- 0.9 years) and female (14.5 +/- 0.9 years) players participated in this within-subject crossover study, and they were randomly but sex-matched assigned to different training sequences (serve exercise before tennis training (BTS) or after tennis training (ATS)). Pre- and post-tests included serve velocity performance and accuracy, shoulder strength, and range-of-motion (ROM) performance (internal/external rotation). Results showed that after one week of serve training conducted following the ATS sequence, significant decreases were found in serve performance (e.g., speed and accuracy), with standardized differences ranging from d = 0.29 to 1.13, as well as the shoulder function (strength [d = 0.20 to 1.0] and ROM [d = 0.17 to 0.31]) in both female and male players, compared to the BTS sequence. Based on the present findings, it appears more effective to implement serve training before the regular tennis training in youth players. If applied after training, excessive levels of fatigue may cause shoulder imbalances that could be related to an increased injury risk.
The purpose of this study was to examine the acute effects of short-term Achilles tendon vibration on plantar flexor torque, twitch contractile properties as well as muscle and cortical activity in young athletes. Eleven female elite soccer players aged 15.6 +/- 0.5 years participated in this study. Three different conditions were applied in randomized order: Achilles tendon vibration (80 Hz) for 30 and 300 s, and a passive control condition (300 s). Tests at baseline and following conditions included the assessment of peak plantar flexor torque during maximum voluntary contraction, electrically evoked muscle twitches (e.g., potentiated twitch peak torque [PT]), and electromyographic (EMG) activity of the plantar flexors. Additionally, electroencephalographic (EEG) activity of the primary motor and somatosensory cortex were assessed during a submaximal dynamic concentric-eccentric plantar flexion exercise using an elastic rubber band. Large-sized main effects of condition were found for EEG absolute alpha-1 and beta-1 band power (p <= 0.011; 1.5 <= d <= 2.6). Post-hoc tests indicated that alpha-1 power was significantly lower at 30 and 300 s (p = 0.009; d = 0.8) and beta-1 power significantly lower at 300 s (p < 0.001; d = 0.2) compared to control condition. No significant effect of condition was found for peak plantar flexor torque, electrical evoked muscle twitches, and EMG activity. In conclusion, short-term local Achilles tendon vibration induced lower brain activity (i.e., alpha-1 and beta-1 band power) but did not affect lower limb peak torque, twitch contractile properties, and muscle activity. Lower brain activity following short-term local Achilles tendon vibration may indicate improved cortical function during a submaximal dynamic exercise in female young soccer players.
The aim of this review was to describe and summarize the scientific literature on programming parameters related to jump or plyometric training in male and female soccer players of different ages and fitness levels. A literature search was conducted in the electronic databases PubMed, Web of Science and Scopus using keywords related to the main topic of this study (e.g., “ballistic” and “plyometric”). According to the PICOS framework, the population for the review was restricted to soccer players, involved in jump or plyometric training. Among 7556 identified studies, 90 were eligible for inclusion. Only 12 studies were found for females. Most studies (n = 52) were conducted with youth male players. Moreover, only 35 studies determined the effectiveness of a given jump training programming factor. Based on the limited available research, it seems that a dose of 7 weeks (1–2 sessions per week), with ~80 jumps (specific of combined types) per session, using near-maximal or maximal intensity, with adequate recovery between repetitions (<15 s), sets (≥30 s) and sessions (≥24–48 h), using progressive overload and taper strategies, using appropriate surfaces (e.g., grass), and applied in a well-rested state, when combined with other training methods, would increase the outcome of effective and safe plyometric-jump training interventions aimed at improving soccer players physical fitness. In conclusion, jump training is an effective and easy-to-administer training approach for youth, adult, male and female soccer players. However, optimal programming for plyometric-jump training in soccer is yet to be determined in future research.
Electroencephalographic (EEG) research indicates changes in adults' low frequency bands of frontoparietal brain areas executing different balance tasks with increasing postural demands. However, this issue is unsolved for adolescents when performing the same balance task with increasing difficulty. Therefore, we examined the effects of a progressively increasing balance task difficulty on balance performance and brain activity in adolescents. Thirteen healthy adolescents aged 16-17 year performed tests in bipedal upright stance on a balance board with six progressively increasing levels of task difficulty. Postural sway and cortical activity were recorded simultaneously using a pressure sensitive measuring system and EEG. The power spectrum was analyzed for theta (4-7 Hz) and alpha-2 (10-12 Hz) frequency bands in pre-defined frontal, central, and parietal clusters of electrocortical sources. Repeated measures analysis of variance (rmANOVA) showed a significant main effect of task difficulty for postural sway (p < 0.001; d = 6.36). Concomitantly, the power spectrum changed in frontal, bilateral central, and bilateral parietal clusters. RmANOVAs revealed significant main effects of task difficulty for theta band power in the frontal (p < 0.001, d = 1.80) and both central clusters (left: p < 0.001, d = 1.49; right: p < 0.001, d = 1.42) as well as for alpha-2 band power in both parietal clusters (left: p < 0.001, d = 1.39; right: p < 0.001, d = 1.05) and in the central right cluster (p = 0.005, d = 0.92). Increases in theta band power (frontal, central) and decreases in alpha-2 power (central, parietal) with increasing balance task difficulty may reflect increased attentional processes and/or error monitoring as well as increased sensory information processing due to increasing postural demands. In general, our findings are mostly in agreement with studies conducted in adults. Similar to adult studies, our data with adolescents indicated the involvement of frontoparietal brain areas in the regulation of postural control. In addition, we detected that activity of selected brain areas (e.g., bilateral central) changed with increasing postural demands.
Purpose: To examine the effects of loaded (LPJT) versus unloaded plyometric jump training (UPJT) programs on measures of muscle power, speed, change of direction (CoD), and kicking-distance performance in prepubertal male soccer players. Methods: Participants (N = 29) were randomly assigned to a LPJT group (n = 13; age = 13.0 [0.7] y) using weighted vests or UPJT group (n = 16; age = 13.0 [0.5] y) using body mass only. Before and after the intervention, tests for the assessment of proxies of muscle power (ie, countermovement jump, standing long jump); speed (ie, 5-, 10-, and 20-m sprint); CoD (ie, Illinois CoD test, modified 505 agility test); and kicking-distance were conducted. Data were analyzed using magnitude-based inferences. Results: Within-group analyses for the LPJT group showed large and very large improvements for 10-m sprint time (effect size [ES] = 2.00) and modified 505 CoD (ES = 2.83) tests, respectively. For the same group, moderate improvements were observed for the Illinois CoD test (ES = 0.61), 5- and 20-m sprint time test (ES = 1.00 for both the tests), countermovement jump test (ES = 1.00), and the maximal kicking-distance test (ES = 0.90). Small enhancements in the standing long jump test (ES = 0.50) were apparent. Regarding the UPJT group, small improvements were observed for all tests (ES = 0.33-0.57), except 5- and 10-m sprint time (ES = 1.00 and 0.63, respectively). Between-group analyses favored the LPJT group for the modified 505 CoD (ES = 0.61), standing long jump (ES = 0.50), and maximal kicking-distance tests (ES = 0.57), but not for the 5-m sprint time test (ES = 1.00). Only trivial between-group differences were shown for the remaining tests (ES = 0.00-0.09). Conclusion: Overall, LPJT appears to be more effective than UPJT in improving measures of muscle power, speed, CoD, and kicking-distance performance in prepubertal male soccer players.
The proportion of elderly people in societies of western industrialized countries is continuously rising. Biologic aging induces deficits in balance and muscle strength/power in old age, which is responsible for an increased prevalence of falls. Therefore, nationwide and easy-to-administer fall prevention programs have to be developed in order to contribute to the autonomy and quality of life in old age and to help reduce the financial burden on the public health care system due to the treatment of fall-related injuries. This narrative (qualitative) literature review deals with a) the reasons for an increased prevalence of falls in old age, b) important clinical tests for fall-risk assessment, and c) evidence-based intervention/training programs for fall prevention in old age. The findings of this literature review are based on a cost-free practice guide that is available to the public (via the internet) and that was created by an expert panel (i.e., geriatricians, exercise scientists, physiotherapists, geriatric therapists). The present review provides the scientific foundation of the practice guide.
Plyometric jump training (PJT) is a frequently used and effective means to improve amateur and elite soccer players' physical fitness. However, it is unresolved how different PJT frequencies per week with equal overall training volume may affect training-induced adaptations. Therefore, the aim of this study was to compare the effects of an in-season 8 week PJT with one session vs. two sessions per week and equal training volume on components of physical fitness in amateur female soccer players. A single-blind randomized controlled trial was conducted. Participants (N = 23; age, 21.4 ± 3.2 years) were randomly assigned to a one session PJT per-week (PJT-1, n = 8), two sessions PJT per-week (PJT-2, n = 8) or an active control group (CON, n = 7). Before and after training, participants performed countermovement jumps (CMJ), drop-jumps from a 20-cm drop-height (DJ20), a maximal kicking velocity test (MKV), the 15-m linear sprint-time test, the Meylan test for the assessment of change of direction ability (CoDA), and the Yo-Yo intermittent recovery endurance test (Yo-YoIR1). Results revealed significant main effects of time for the CMJ, DJ20, MKV, 15-m sprint, CoDA, and the Yo-YoIR1 (all p < 0.001; d = 0.57–0.83). Significant group × time interactions were observed for the CMJ, DJ20, MKV, 15-m sprint, CoDA, and the Yo-YoIR1 (all p < 0.05; d = 0.36–0.51). Post-hoc analyses showed similar improvements for PJT-1 and PJT-2 groups in CMJ (Δ10.6%, d = 0.37; and Δ10.1%, d = 0.51, respectively), DJ20 (Δ12.9%, d = 0.47; and Δ13.1%, d = 0.54, respectively), MKV (Δ8.6%, d = 0.52; and Δ9.1%, d = 0.47, respectively), 15-m sprint (Δ8.3%, d = 2.25; and Δ9.5%, d = 2.67, respectively), CoDA (Δ7.5%, d = 1.68; and Δ7.4%, d = 1.16, respectively), and YoYoIR1 (Δ10.3%, d = 0.22; and Δ9.9%, d = 0.26, respectively). No significant pre-post changes were found for CON (all p > 0.05; Δ0.5–4.2%, d = 0.03–0.2). In conclusion, higher PJT exposure in terms of session frequency has no extra effects on female soccer players' physical fitness development when jump volume is equated during a short-term (i.e., 8 weeks) training program. From this, it follows that one PJT session per week combined with regular soccer-specific training appears to be sufficient to induce physical fitness improvements in amateur female soccer players.
Purpose: To examine the effects of fatiguing isometric contractions on maximal eccentric strength and electromechanical delay (EMD) of the knee flexors in healthy young adults of different training status.
Methods: Seventy-five male participants (27.7 ± 5.0 years) were enrolled in this study and allocated to three experimental groups according to their training status: athletes (ATH, n = 25), physically active adults (ACT, n = 25), and sedentary participants (SED, n = 25). The fatigue protocol comprised intermittent isometric knee flexions (6-s contraction, 4-s rest) at 60% of the maximum voluntary contraction until failure. Pre- and post-fatigue, maximal eccentric knee flexor strength and EMDs of the biceps femoris, semimembranosus, and semitendinosus muscles were assessed during maximal eccentric knee flexor actions at 60, 180, and 300°/s angular velocity. An analysis of covariance was computed with baseline (unfatigued) data included as a covariate.
Results: Significant and large-sized main effects of group (p ≤ 0.017, 0.87 ≤ d ≤ 3.69) and/or angular velocity (p < 0.001, d = 1.81) were observed. Post hoc tests indicated that regardless of angular velocity, maximal eccentric knee flexor strength was lower and EMD was longer in SED compared with ATH and ACT (p ≤ 0.025, 0.76 ≤ d ≤ 1.82) and in ACT compared with ATH (p = ≤0.025, 0.76 ≤ d ≤ 1.82). Additionally, EMD at post-test was significantly longer at 300°/s compared with 60 and 180°/s (p < 0.001, 2.95 ≤ d ≤ 4.64) and at 180°/s compared with 60°/s (p < 0.001, d = 2.56), irrespective of training status.
Conclusion: The main outcomes revealed significantly higher maximal eccentric strength and shorter eccentric EMDs of knee flexors in individuals with higher training status (i.e., athletes) following fatiguing exercises. Therefore, higher training status is associated with better neuromuscular functioning (i.e., strength, EMD) of the hamstring muscles in fatigued condition. Future longitudinal studies are needed to substantiate the clinical relevance of these findings.
Background: Change-of-direction (CoD) is a necessary physical ability of a field sport and may vary in youth players according to their maturation status.
Objectives: The aim of this study is: to compare the effectiveness of a 6-week CoD training intervention on dynamic balance (CS-YBT), horizontal jump (5JT), speed (10 and 30-m linear sprint times), CoD with (15 m-CoD + B) and without (15 m-CoD) the ball, in youth male soccer players at different levels of maturity [pre- and post-peak height velocity (PHV)].
Materials and Methods: Thirty elite male youth soccer players aged 10–17 years from the Tunisian first division participated in this study. The players were divided into pre- (G1, n = 15) and post-PHV (G2, n = 15) groups. Both groups completed a similar 6-week training program with two sessions per week of four CoD exercises. All players completed the following tests before and after intervention: CS-YBT; 5 JT; 10, 30, and 15 m-CoD; and 15 m-CoD + B, and data were analyzed using ANCOVA.
Results: All 30 players completed the study according to the study design and methodology. Adherence rate was 100% across all groups, and no training or test-related injuries were reported. Pre-PHV and post-PHV groups showed significant amelioration post-intervention for all dependent variables (after test > before test; p < 0.01, d = 0.09–1.51). ANOVA revealed a significant group × time interaction only for CS-YBT (F = 4.45; p < 0.04; η2 = 0.14), 5JT (F = 6.39; p < 0.02; η2 = 0.18), and 15 m-CoD (F = 7.88; p < 0.01; η2 = 0.22). CS-YBT, 5JT, and 15 m-CoD improved significantly in the post-PHV group (+ 4.56%, effect size = 1.51; + 4.51%, effect size = 1.05; and -3.08%, effect size = 0.51, respectively), more than the pre-PHV group (+ 2.77%, effect size = 0.85; + 2.91%, effect size = 0.54; and -1.56%, effect size = 0.20, respectively).
Conclusion: The CoD training program improved balance, horizontal jump, and CoD without the ball in male preadolescent and adolescent soccer players, and this improvement was greater in the post-PHV players. The maturity status of the athletes should be considered when programming CoD training for soccer players.
Background: Age-related postural misalignment, balance deficits and strength/power losses are associated with impaired functional mobility and an increased risk of falling in seniors. Core instability strength training (CIT) involves exercises that are challenging for both trunk muscles and postural control and may thus have the potential to induce benefits in trunk muscle strength, spinal mobility and balance performance. Objective: The objective was to investigate the effects of CIT on measures of trunk muscle strength, spinal mobility, dynamic balance and functional mobility in seniors. Methods: Thirty-two older adults were randomly assigned to an intervention group (INT; n = 16, aged 70.8 +/- 4.1 years) that conducted a 9-week progressive CIT or to a control group (n = 16, aged 70.2 +/- 4.5 years). Maximal isometric strength of the trunk flexors/extensors/lateral flexors (right, left)/rotators (right, left) as well as of spinal mobility in the sagittal and the coronal plane was measured before and after the intervention program. Dynamic balance (i.e. walking 10 m on an optoelectric walkway, the Functional Reach test) and functional mobility (Timed Up and Go test) were additionally tested. Results: Program compliance was excellent with participants of the INT group completing 92% of the training sessions. Significant group x test interactions were found for the maximal isometric strength of the trunk flexors (34%, p < 0.001), extensors (21%, p < 0.001), lateral flexors (right: 48%, p < 0.001; left: 53%, p < 0.001) and left rotators (42%, p < 0.001) in favor of the INT group. Further, training-related improvements were found for spinal mobility in the sagittal (11%, p < 0.001) and coronal plane (11%, p = 0.06) directions, for stride velocity (9%, p < 0.05), the coefficient of variation in stride velocity (31%, p < 0.05), the Functional Reach test (20%, p < 0.05) and the Timed Up and Go test (4%, p < 0.05) in favor of the INT group. Conclusion: CIT proved to be a feasible exercise program for seniors with a high adherence rate. Age-related deficits in measures of trunk muscle strength, spinal mobility, dynamic balance and functional mobility can be mitigated by CIT. This training regimen could be used as an adjunct or even alternative to traditional balance and/or resistance training.
Global (whole-body) effects of resistance training (i.e., cross-education) may be pervasive with children. Detraining induces less substantial deficits with children than adults. It was the objective of this study to investigate the global responses to 4 weeks of detraining after 8 weeks of unilateral leg press (LP) training in 10-13-year-old, pre-peak-height-velocity stage boys. Subjects were randomly separated into 2 unilateral resistance training groups (high load/low repetitions [HL-LR] and low load/high repetitions [LL-HR], and control group). Assessments at pre-training, post-training, and detraining included dominant and nondominant limbs, unilateral, 1 repetition maximum (1RM) and 60% 1RM LP, knee extension, knee flexion, elbow flexion, and handgrip maximal voluntary isometric contraction (MVIC), and countermovement jump (CMJ). All measures significantly increased from pre-test to detraining for both training programs, except for elbow flexion MVIC with increases only with HL-LR. All measures except CMJ and handgrip MVIC significantly decreased from post-test to detraining, except for elbow flexion MVIC with decreases only with HL-LR. The dominant trained limb experienced significantly greater LP improvements (pre- to detraining) and decrements (post- to detraining) with LP 1RM and 60% 1RM LP. In conclusion, youth HL-LR and LL-HR global training effects of trained and untrained limbs demonstrate similar benefits (pre- to detraining) and decrements (post- to detraining) with detraining. The findings emphasize that training any muscle group in a child can have positive global implications for improved strength and power that can persist over baseline measures for at least a month.
The purpose of this study was to examine the combined effects of drop-height and surface condition on drop jump (DJ) performance and knee joint kinematics. DJ performance, sagittal and frontal plane knee joint kinematics were measured in jump experienced young male and female adults during DJs on stable, unstable and highly unstable surfaces using different drop-heights (20, 40, 60 cm). Findings revealed impaired DJ performance (Δ5–16%; p<0.05; 1.43≤d≤2.82), reduced knee valgus motion (Δ33–52%; p<0.001; 2.70≤d≤3.59), and larger maximum knee flexion angles (Δ13–19%; p<0.01; 1.74≤d≤1.75) when using higher (60 cm) compared to lower drop-heights (≤40 cm). Further, lower knee flexion angles and velocity were found (Δ8-16%; p<0.01; 1.49≤d≤2.38) with increasing surface instability. When performing DJs from high (60 cm) compared to moderate drop-heights (40 cm) on highly unstable surfaces, higher knee flexion velocity and maximum knee valgus angles were found (Δ15–19%; p<0.01; 1.50≤d≤1.53). No significant main and/or interaction effects were observed for the factor sex. In conclusion, knee motion strategies were modified by the factors ‘drop-height’ and/or ‘surface instability’. The combination of high drop-heights (>40 cm) together with highly unstable surfaces should be used cautiously during plyometrics because this may increase the risk of injury due to higher knee valgus stress.
Purpose:
This study aimed to examine the effects of individualized-load power training (IPT) versus traditional moderate-load power training (TPT) on strength, power, jump performance, and body composition in elite young Nordic athletes.
Methods:
In a randomized crossover design, 10 young male athletes (ski jumpers, Nordic combined athletes) age 17.5 (0.6) years (biological maturity status: +3.5 y postpeak height velocity) who competed on a national or international level performed 5 weeks of IPT (4 x 5 repetitions at 49%-72% 1-repetiton maximum [RM]) and TPT (5 x 5 repetitions at 50%-60% 1-RM) in addition to their regular training. Testing before, between, and after both training blocks comprised the assessment of muscle strength (loaded back squat 3-RM), power (maximal loaded back squat power), jump performance (eg, drop-jump height, reactive strength index), and body composition (eg, skeletal muscle mass).
Results:
Significant, large-size main effects for time were found for muscle strength (P < .01; g = 2.7), reactive strength index (P = .03; g= 1.6), and drop jump height (P = .02; g= 1.9) irrespective of the training condition (IPT, TPT). No significant time-by-condition interactions were observed. For measures of body composition, no significant main effects of condition and time or time-by-condition interactions were found.
Conclusions:
Our findings demonstrate that short-term IPT and TPT at moderate loads in addition to regular training were equally effective in improving measures of muscle strength (loaded back squat 3-RM) and vertical jump performance (reactive strength index, drop jump, and height) in young Nordic athletes.
Background: Infection with human immunodeficiency virus (HIV) affects muscle mass, altering independent activities of people living with HIV (PLWH). Resistance training alone (RT) or combined with aerobic exercise (AE) is linked to improved muscle mass and strength maintenance in PLWH. These exercise benefits have been the focus of different meta-analyses, although only a limited number of studies have been identified up to the year 2013/4. An up-to-date systematic review and meta-analysis concerning the effect of RT alone or combined with AE on strength parameters and hormones is of high value, since more and recent studies dealing with these types of exercise in PLWH have been published. Methods: Randomized controlled trials evaluating the effects of RT alone, AE alone or the combination of both (AERT) on PLWH was performed through five web-databases up to December 2017. Risk of bias and study quality was attained using the PEDro scale. Weighted mean difference (WMD) from baseline to post-intervention changes was calculated. The I2 statistics for heterogeneity was calculated. Results: Thirteen studies reported strength outcomes. Eight studies presented a low risk of bias. The overall change in upper body strength was 19.3 Kg (95% CI: 9.8±28.8, p< 0.001) after AERT and 17.5 Kg (95% CI: 16±19.1, p< 0.001) for RT. Lower body change was 29.4 Kg (95% CI: 18.1±40.8, p< 0.001) after RT and 10.2 Kg (95% CI: 6.7±13.8, p< 0.001) for AERT. Changes were higher after controlling for the risk of bias in upper and lower body strength and for supervised exercise in lower body strength. A significant change towards lower levels of IL-6 was found (-2.4 ng/dl (95% CI: -2.6, -2.1, p< 0.001). Conclusion: Both resistance training alone and combined with aerobic exercise showed a positive change when studies with low risk of bias and professional supervision were analyzed, improving upper and, more critically, lower body muscle strength. Also, this study found that exercise had a lowering effect on IL-6 levels in PLWH.
The load-depended loss of vertical barbell velocity at the end of the acceleration phase limits the maximum weight that can be lifted. Thus, the purpose of this study was to analyze how increased barbell loads affect the vertical barbell velocity in the sub-phases of the acceleration phase during the snatch. It was hypothesized that the load-dependent velocity loss at the end of the acceleration phase is primarily associated with a velocity loss during the 1st pull. For this purpose, 14 male elite weightlifters lifted seven load-stages from 70-100% of their personal best in the snatch. The load-velocity relationship was calculated using linear regression analysis to determine the velocity loss at 1st pull, transition, and 2nd pull. A group mean data contrast analysis revealed the highest load-dependent velocity loss for the 1st pull (t = 1.85, p = 0.044, g = 0.49 [-0.05, 1.04]) which confirmed our study hypothesis. In contrast to the group mean data, the individual athlete showed a unique response to increased loads during the acceleration sub-phases of the snatch. With the proposed method, individualized training recommendations on exercise selection and loading schemes can be derived to specifically improve the sub-phases of the snatch acceleration phase. Furthermore, the results highlight the importance of single-subject assessment when working with elite athletes in Olympic weightlifting.
Introduction/Purpose: Aging modifies neuromuscular activation of agonist and antagonist muscles during walking. Power training can evoke adaptations in neuromuscular activation that underlie gains in muscle strength and power but it is unknown if these adaptations transfer to dynamic tasks such as walking. We examined the effects of lower-extremity power training on neuromuscular activation during level gait in old adults. Methods: Twelve community-dwelling old adults (age >= 65 yr) completed a 10-wk lower-extremity power training program and 13 old adults completed a 10-wk control period. Before and after the interventions, we measured maximal isometric muscle strength and electromyographic (EMG) activation of the right knee flexor, knee extensor, and plantarflexor muscles on a dynamometer and we measured EMG amplitudes, activation onsets and offsets, and activation duration of the knee flexors, knee extensors, and plantarflexors during gait at habitual, fast, and standardized (1.25 +/- 0.6 m.s(-1)) speeds. Results: Power training-induced increases in EMG amplitude (similar to 41%; 0.47 <= d <= 1.47; P <= 0.05) explained 33% (P = 0.049) of increases in isometric muscle strength (similar to 43%; 0.34 <= d <= 0.80; P <= 0.05). Power training-induced gains in plantarflexor activation during push-off (+11%; d = 0.38; P = 0.045) explained 57% (P = 0.004) of the gains in fast gait velocity (+4%; d = 0.31; P = 0.059). Furthermore, power training increased knee extensor activation (similar to 18%; 0.26 <= d <= 0.29; P <= 0.05) and knee extensor coactivation during the main knee flexor burst (similar to 24%, 0.26 <= d <= 0.44; P <= 0.05) at habitual and fast speed but these adaptations did not correlate with changes in gait velocity. Conclusions: Power training increased neuromuscular activation during isometric contractions and level gait in old adults. The power training-induced neuromuscular adaptations were associated with increases in isometric muscle strength and partly with increases in fast gait velocity.
Methods: As part of the Potsdam Gait Study (POGS), healthy old adults completed a no-intervention control period (69.1 +/- 4A yrs, n =14) or a power training program followed by detraining (72.9 +/- 5.4 yrs, n = 15).We measured isokinetic knee extensor and plantarflexor power and measured hip, knee and ankle kinetics at habitual, fast and standardized walking speeds. Results: Power training significantly increased isokinetic knee extensor power (25%), plantarflexor power (43%), and fast gait velocity (5.9%). Gait mechanics underlying the improved fast gait velocity included increases in hip angular impulse (29%) and H1 work (37%) and no changes in positive knee (K2) and A2 work. Detraining further improved fast gait velocity (4.7%) with reductions in H1(-35%), and increases in K2 (36%) and A2 (7%). Conclusion: Power training increased fast gait velocity in healthy old adults by increasing the reliance on hip muscle function and thus further strengthened the age-related distal-to-proximal shift in muscle function. (C) 2016 Elsevier B.V. All rights reserved.
There is controversy in the literature in regards of the link between training load and injury rate. Thus, the aims of this non-interventional study were to evaluate relationships between pre-season training load with biochemical markers, injury incidence and performance during the first month of the competitive period in professional soccer players.
Background: The regular assessment of hormonal and mood state parameters in professional soccer are proposed as good indicators during periods of intense training and/or competition to avoid overtraining.
Objective: The aim of this study was to analyze hormonal, psychological, workload and physical fitness parameters in elite soccer players in relation to changes in training and match exposure during a congested period of match play.
Methods: Sixteen elite soccer players from a team playing in the first Tunisian soccer league were evaluated three times (T1, T2, and T3) over 12 weeks. The non-congested period of match play was from T1 to T2, when the players played 6 games over 6 weeks. The congested period was from T2 to T3, when the players played 10 games over 6 weeks. From T1 to T3, players performed the Yo-Yo intermittent recovery test level 1 (YYIR1), the repeated shuttle sprint ability test (RSSA), the countermovement jump test (CMJ), and the squat jump test (SJ). Plasma Cortisol (C), Testosterone (T), and the T/C ratio were analyzed at T1, T2, and T3. Players had their mood dimensions (tension, depression, anger, vigor, fatigue, confusion, and a Total Mood Disturbance) assessed through the Profile of Mood State questionnaire (POMS). Training session rating of perceived exertion (sRPE) was also recorded on a daily basis in order to quantify internal training load and elements of monotony and strain.
Results: Significant performance declines (T1 < T2 < T3) were found for SJ performance (p = 0.04, effect size [ES] ES₁₋₂ = 0.15−0.06, ES₂₋₃ = 0.24) from T1 to T3. YYIR1 performance improved significantly from T1 to T2 and declined significantly from T2 to T3 (p = 0.001, ES₁₋₂ = 0.24, ES₂₋₃ = −2.54). Mean RSSA performance was significantly higher (p = 0.019, ES₁₋₂ = −0.47, ES₂₋₃ = 1.15) in T3 compared with T2 and T1. Best RSSA performance was significantly higher in T3 when compared with T2 and T1 (p = 0.006, ES₂₋₃ = 0.47, ES₁₋₂ = −0.56), but significantly lower in T2 when compared with to T1. T and T/C were significantly lower in T3 when compared with T2 and T1 (T: p = 0.03, ES₃₋₂ = −0.51, ES₃₋₁ = −0.51, T/C: p = 0.017, ES₃₋₂ = −1.1, ES₃₋₁ = −1.07). Significant decreases were found for the vigor scores in T3 when compared to T2 and T1 (p = 0.002, ES₁₋₂ = 0.31, ES₃₋₂ = −1.25). A significant increase was found in fatigue scores in T3 as compared to T1 and T2 (p = 0.002, ES₁₋₂ = 0.43, ES₂₋₃ = 0.81). A significant increase was found from T1 < T2 < T3 intension score (p = 0.002, ES₁₋₂ = 1.1, ES₂₋₃ = 0.2) and anger score (p = 0.03, ES₁₋₂ = 0.47, ES₂₋₃ = 0.33) over the study period. Total mood disturbance increased significantly (p = 0.02, ES₁₋₂ = 0.91, ES₂₋₃ = 1.1) from T1 to T3. Between T1-T2, significant relationships were observed between workload and changes in T (r = 0.66, p = 0.003), and T/C ratio (r = 0.62, p = 0.01). There were significant relationships between performance in RSSAbest and training load parameters (workload: r = 0.52, p = 0.03; monotony: r = 0.62, p = 0.01; strain: r = 0.62, p = 0.009). Between T2-T3, there was a significant relationship between Δ% of total mood disturbance and Δ% of YYIR1 (r = −0.54; p = 0.04), RSSAbest (r = 0.58, p = 0.01), SJ (r = −0,55, p = 0.01), T (r = 0.53; p = 0.03), and T/C (r = 0.5; p = 0.04).
Conclusion: An intensive period of congested match play significantly compromised elite soccer players’ physical and mental fitness. These changes were related to psychological but not hormonal parameters; even though significant alterations were detected for selected measures. Mood monitoring could be a simple and useful tool to determine the degree of preparedness for match play during a congested period in professional soccer.
Background: Agility in general and change-of-direction speed (CoD) in particular represent important performance determinants in elite soccer.
Objectives: The objectives of this study were to determine the effects of a 6-week neuromuscular training program on agility performance, and to determine differences in movement times between the slower and faster turning directions in elite soccer players. Materials and Methods: Twenty male elite soccer players from the Stade Rennais Football Club (Ligue 1, France) participated in this study. The players were randomly assigned to a neuromuscular training group (NTG, n = 10) or an active control (CG, n = 10) according to their playing position. NTG participated in a 6-week, twice per week neuromuscular training program that included CoD, plyometric and dynamic stability exercises. Neuromuscular training replaced the regular warm-up program. Each training session lasted 30 min. CG continued their regular training program. Training volume was similar between groups. Before and after the intervention, the two groups performed a reactive agility test that included 180° left and right body rotations followed by a 5-m linear sprint. The weak side was defined as the left/right turning direction that produced slower overall movement times (MT). Reaction time (RT) was assessed and defined as the time from the first appearance of a visual stimulus until the athlete’s first movement. MT corresponded to the time from the first movement until the athlete reached the arrival gate (5 m distance).
Results: No significant between-group baseline differences were observed for RT or MT. Significant group x time interactions were found for MT (p = 0.012, effect size = 0.332, small) for the slower and faster directions (p = 0.011, effect size = 0.627, moderate). Significant pre-to post improvements in MT were observed for NTG but not CG (p = 0.011, effect size = 0.877, moderate). For NTG, post hoc analyses revealed significant MT improvements for the slower (p = 0.012, effect size = 0.897, moderate) and faster directions (p = 0.017, effect size = 0.968, moderate).
Conclusion: Our results illustrate that 6 weeks of neuromuscular training with two sessions per week included in the warm-up program, significantly enhanced agility performance in elite soccer players. Moreover, improvements were found on both sides during body rotations. Thus, practitioners are advised to focus their training programs on both turning directions.
This study aimed to compare the training load of a professional under-19 soccer team (U-19) to that of an elite adult team (EAT), from the same club, during the in-season period. Thirty-nine healthy soccer players were involved (EAT [n = 20]; U-19 [n = 19]) in the study which spanned four weeks. Training load (TL) was monitored as external TL, using a global positioning system (GPS), and internal TL, using a rating of perceived exertion (RPE). TL data were recorded after each training session. During soccer matches, players’ RPEs were recorded. The internal TL was quantified daily by means of the session rating of perceived exertion (session-RPE) using Borg’s 0–10 scale. For GPS data, the selected running speed intensities (over 0.5 s time intervals) were 12–15.9 km/h; 16–19.9 km/h; 20–24.9 km/h; >25 km/h (sprint). Distances covered between 16 and 19.9 km/h, > 20 km/h and >25 km/h were significantly higher in U-19 compared to EAT over the course of the study (p = 0.023, d = 0.243, small; p = 0.016, d = 0.298, small; and p = 0.001, d = 0.564, small, respectively). EAT players performed significantly fewer sprints per week compared to U-19 players (p = 0.002, d = 0.526, small). RPE was significantly higher in U-19 compared to EAT (p = 0.001, d = 0.188, trivial). The external and internal measures of TL were significantly higher in the U-19 group compared to the EAT soccer players. In conclusion, the results obtained show that the training load is greater in U19 compared to EAT.
Background
It has been demonstrated that core strength training is an effective means to enhance trunk muscle strength (TMS) and proxies of physical fitness in youth. Of note, cross-sectional studies revealed that the inclusion of unstable elements in core strengthening exercises produced increases in trunk muscle activity and thus provide potential extra training stimuli for performance enhancement. Thus, utilizing unstable surfaces during core strength training may even produce larger performance gains. However, the effects of core strength training using unstable surfaces are unresolved in youth. This randomized controlled study specifically investigated the effects of core strength training performed on stable surfaces (CSTS) compared to unstable surfaces (CSTU) on physical fitness in school-aged children.
Methods
Twenty-seven (14 girls, 13 boys) healthy subjects (mean age: 14 ± 1 years, age range: 13–15 years) were randomly assigned to a CSTS (n = 13) or a CSTU (n = 14) group. Both training programs lasted 6 weeks (2 sessions/week) and included frontal, dorsal, and lateral core exercises. During CSTU, these exercises were conducted on unstable surfaces (e.g., TOGU© DYNAIR CUSSIONS, THERA-BAND© STABILITY TRAINER).
Results
Significant main effects of Time (pre vs. post) were observed for the TMS tests (8-22%, f = 0.47-0.76), the jumping sideways test (4-5%, f = 1.07), and the Y balance test (2-3%, f = 0.46-0.49). Trends towards significance were found for the standing long jump test (1-3%, f = 0.39) and the stand-and-reach test (0-2%, f = 0.39). We could not detect any significant main effects of Group. Significant Time x Group interactions were detected for the stand-and-reach test in favour of the CSTU group (2%, f = 0.54).
Conclusions
Core strength training resulted in significant increases in proxies of physical fitness in adolescents. However, CSTU as compared to CSTS had only limited additional effects (i.e., stand-and-reach test). Consequently, if the goal of training is to enhance physical fitness, then CSTU has limited advantages over CSTS.
Background:
Office workers near retirement tend to be sedentary and can be prone to mobility limitations and diseases. We examined the dose effects of exergaming volume and duration of detraining on motor and cognitive function in office workers at late midlife to reduce sedentariness and mobility limitations.
Methods:
In an assessor-blinded randomized trial, 160 workers aged 55-65 years performed physically active video games in a nonimmersive form of virtual reality (exergaming) in small, supervised groups for 1 h, 1x, 2x, or 3x/week for 8 weeks followed by detraining for 8 and 16 weeks. Exergaming comprises high-intensity, full-body sensorimotor coordination, balance, endurance, and strengthening exercises. The primary outcome was the 6-minute walk test (6MWT), and secondary outcomes were body mass, self-reported physical activity, sleep quality, Berg Balance Scale, Short Physical Performance Battery, fast gait speed, dynamic balance, heart rate recovery after step test, and 6 cognitive tests.
Results:
The 3 groups were not different in any of the outcomes at baseline (all p > 0.05). The outcomes were stable and had acceptable reliability (intraclass correlation coefficients >= 0.334) over an 8-week control period. Training produced an inverted U-shaped dose response of no (1x), most (2x), and medium (3x/week) effects of exergaming volume in most motor and selected cognitive outcomes. The distance walked in the 6MWT (primary outcome) increased most (94 m, 19%, p < 0.05), medium (57 m, 12%, p < 0.05), and least (4 m, 1%) after exergaming 2x, 3x, or 0x (control) (all different p < 0.05). The highest responders tended to retain the exercise effects over 8 weeks of detraining, independent of training volume. This maintenance effect was less consistent after 16 weeks of detraining.
Conclusion:
Less was more during training and lasted longer after detraining. A medium dose volume of exergaming produced the largest clinically meaningful improvements in mobility and selected cognitive tests in 60-year-old office workers with mild mobility limitations and intact cognition.
Physical fatigue (PF) negatively affects postural control, resulting in impaired balance performance in young and older adults. Similar effects on postural control can be observed for mental fatigue (MF) mainly in older adults. Controversial results exist for young adults. There is a void in the literature on the effects of fatigue on balance and cortical activity. Therefore, this study aimed to examine the acute effects of PF and MF on postural sway and cortical activity. Fifteen healthy young adults aged 28 ± 3 years participated in this study. MF and PF protocols comprising of an all-out repeated sit-to-stand task and a computer-based attention network test, respectively, were applied in random order. Pre and post fatigue, cortical activity and postural sway (i.e., center of pressure displacements [CoPd], velocity [CoPv], and CoP variability [CV CoPd, CV CoPv]) were tested during a challenging bipedal balance board task. Absolute spectral power was calculated for theta (4–7.5 Hz), alpha-2 (10.5–12.5 Hz), beta-1 (13–18 Hz), and beta-2 (18.5–25 Hz) in frontal, central, and parietal regions of interest (ROI) and baseline-normalized. Inference statistics revealed a significant time-by-fatigue interaction for CoPd (p = 0.009, d = 0.39, Δ 9.2%) and CoPv (p = 0.009, d = 0.36, Δ 9.2%), and a significant main effect of time for CoP variability (CV CoPd: p = 0.001, d = 0.84; CV CoPv: p = 0.05, d = 0.62). Post hoc analyses showed a significant increase in CoPd (p = 0.002, d = 1.03) and CoPv (p = 0.003, d = 1.03) following PF but not MF. For cortical activity, a significant time-by-fatigue interaction was found for relative alpha-2 power in parietal (p < 0.001, d = 0.06) areas. Post hoc tests indicated larger alpha-2 power increases after PF (p < 0.001, d = 1.69, Δ 3.9%) compared to MF (p = 0.001, d = 1.03, Δ 2.5%). In addition, changes in parietal alpha-2 power and measures of postural sway did not correlate significantly, irrespective of the applied fatigue protocol. No significant changes were found for the other frequency bands, irrespective of the fatigue protocol and ROI under investigation. Thus, the applied PF protocol resulted in increased postural sway (CoPd and CoPv) and CoP variability accompanied by enhanced alpha-2 power in the parietal ROI while MF led to increased CoP variability and alpha-2 power in our sample of young adults. Potential underlying cortical mechanisms responsible for the greater increase in parietal alpha-2 power after PF were discussed but could not be clearly identified as cause. Therefore, further future research is needed to decipher alternative interpretations.
Can compression garments reduce the deleterious effects of physical exercise on muscle strength?
(2022)
Background
The use of compression garments (CGs) during or after training and competition has gained popularity in the last few decades. However, the data concerning CGs' beneficial effects on muscle strength-related outcomes after physical exercise remain inconclusive.
Objective
The aim was to determine whether wearing CGs during or after physical exercise would facilitate the recovery of muscle strength-related outcomes.
Methods
A systematic literature search was conducted across five databases (PubMed, SPORTDiscus, Web of Science, Scopus, and EBSCOhost). Data from 19 randomized controlled trials (RCTs) including 350 healthy participants were extracted and meta-analytically computed. Weighted between-study standardized mean differences (SMDs) with respect to their standard errors (SEs) were aggregated and corrected for sample size to compute overall SMDs. The type of physical exercise, the body area and timing of CG application, and the time interval between the end of the exercise and subsequent testing were assessed.
Results
CGs produced no strength-sparing effects (SMD [95% confidence interval]) at the following time points (t) after physical exercise: immediately <= t < 24 h: - 0.02 (- 0.22 to 0.19), p = 0.87; 24 <= t < 48 h: - 0.00 (- 0.22 to 0.21), p = 0.98; 48 <= t < 72 h: - 0.03 (- 0.43 to 0.37), p = 0.87; 72 <= t < 96 h: 0.14 (- 0.21 to 0.49), p = 0.43; 96 h <= t: 0.26 (- 0.33 to 0.85), p = 0.38. The body area where the CG was applied had no strength-sparing effects. CGs revealed weak strength-sparing effects after plyometric exercise.
Conclusion
Meta-analytical evidence suggests that wearing a CG during or after training does not seem to facilitate the recovery of muscle strength following physical exercise. Practitioners, athletes, coaches, and trainers should reconsider the use of CG as a tool to reduce the effects of physical exercise on muscle strength.
Repetitive, monotonic, and effortful voluntary muscle contractions performed for just a few weeks, i.e., resistance training, can substantially increase maximal voluntary force in the practiced task and can also increase gross motor performance. The increase in motor performance is often accompanied by neuroplastic adaptations in the central nervous system. While historical data assigned functional relevance to such adaptations induced by resistance training, this claim has not yet been systematically and critically examined in the context of motor performance across the lifespan in health and disease. A review of muscle activation, brain and peripheral nerve stimulation, and imaging data revealed that increases in motor performance and neuroplasticity tend to be uncoupled, making a mechanistic link between neuroplasticity and motor performance inconclusive. We recommend new approaches, including causal mediation analytical and hypothesis-driven models to substantiate the functional relevance of resistance training-induced neuroplasticity in the improvements of gross motor function across the lifespan in health and disease.
The purpose of this study was to examine the test-retest reliability, and convergent and discriminative validity of a new taekwondo-specific change-of-direction (COD) speed test with striking techniques (TST) in elite taekwondo athletes. Twenty (10 males and 10 females) elite (athletes who compete at national level) and top-elite (athletes who compete at national and international level) taekwondo athletes with an average training background of 8.9 ± 1.3 years of systematic taekwondo training participated in this study. During the two-week test-retest period, various generic performance tests measuring COD speed, balance, speed, and jump performance were carried out during the first week and as a retest during the second week. Three TST trials were conducted with each athlete and the best trial was used for further analyses. The relevant performance measure derived from the TST was the time with striking penalty (TST-TSP). TST-TSP performances amounted to 10.57 ± 1.08 s for males and 11.74 ± 1.34 s for females. The reliability analysis of the TST performance was conducted after logarithmic transformation, in order to address the problem of heteroscedasticity. In both groups, the TST demonstrated a high relative test-retest reliability (intraclass correlation coefficients and 90% compatibility limits were 0.80 and 0.47 to 0.93, respectively). For absolute reliability, the TST’s typical error of measurement (TEM), 90% compatibility limits, and magnitudes were 4.6%, 3.4 to 7.7, for males, and 5.4%, 3.9 to 9.0, for females. The homogeneous sample of taekwondo athletes meant that the TST’s TEM exceeded the usual smallest important change (SIC) with 0.2 effect size in the two groups. The new test showed mostly very large correlations with linear sprint speed (r = 0.71 to 0.85) and dynamic balance (r = −0.71 and −0.74), large correlations with COD speed (r = 0.57 to 0.60) and vertical jump performance (r = −0.50 to −0.65), and moderate correlations with horizontal jump performance (r = −0.34 to −0.45) and static balance (r = −0.39 to −0.44). Top-elite athletes showed better TST performances than elite counterparts. Receiver operating characteristic analysis indicated that the TST effectively discriminated between top-elite and elite taekwondo athletes. In conclusion, the TST is a valid, and sensitive test to evaluate the COD speed with taekwondo specific skills, and reliable when considering ICC and TEM. Although the usefulness of the TST is questioned to detect small performance changes in the present population, the TST can detect moderate changes in taekwondo-specific COD speed.
Sprint and jump performances in highly trained young soccer players of different chronological age
(2020)
Objective
The aim of this study was to examine the effects of two different sprint-training regimes on sprint and jump performances according to age in elite young male soccer players over the course of one soccer season.
Methods
Players were randomly assigned to two training groups. Group 1 performed systematic change-of-direction sprints (CODST, U19 [n = 9], U17 [n = 9], U15 [n = 10]) while group 2 conducted systematic linear sprints (LST, U19 [n = 9], U17 [n = 9], U15 [n = 9]). Training volumes were similar between groups (40 sprints per week x 30 weeks = 1200 sprints per season). Pre and post training, all players performed tests for the assessment of linear and slalom sprint speed (5-m and 10-m), countermovement jump, and maximal aerobic speed performance.
Results
For all physical fitness measures, the baseline-adjusted means data (ANCOVA) across the age groups showed no significant differences between LST and CODST at post (0.061 < p < 0.995; 0.0017 < d < 1.01). The analyses of baseline-adjusted means for all physical fitness measures for U15, U17, and U19 (LST vs. CODST) revealed no significant differences between LST and CODST for U15 (0.213 < p < 0.917; 0.001 < d < 0.087), U17 (0.132 < p < 0.976; 0.001 < d < 0.310), and U19 (0.300 < p < 0.999; 0.001 < d < 0.049) at post.
Conclusions
The results from this study showed that both, LST and CODST induced significant changes in the sprint, lower limbs power, and aerobic performances in young elite soccer players. Since no significant differences were observed between LST and CODST, the observed changes are most likely due to training and/or maturation. Therefore, more research is needed to elucidate whether CODST, LST or a combination of both is beneficial for youth soccer athletes’ performance development.
Balance, strength and power relationships may contain important information at various maturational stages to determine training priorities. Purpose: The objective was to examine maturity-specific relationships of static/dynamic balance with strength and power measures in young male athletes. Method: Soccer players (N = 130) aged 10-16 were assessed with the Stork and Y balance (YBT) tests. Strength/power measures included back extensor muscle strength, standing long jump (SLJ), countermovement jump (CMJ), and 3-hop jump tests. Associations between balance with strength/power variables were calculated according to peak-height-velocity (PHV). Results: There were significant medium-large sized correlations between all balance measures with back extensor strength (r =.486.791) and large associations with power (r =.511.827). These correlation coefficients were significantly different between pre-PHV and circa PHV as well as pre-PHV and post-PHV with larger associations in the more mature groups. Irrespective of maturity-status, SLJ was the best strength/ power predictor with the highest proportion of variance (12-47%) for balance (i.e., Stork eyes opened) and the YBT was the best balance predictor with the highest proportion of variance (43-78%) for all strength/ power variables. Conclusion: The associations between balance and muscle strength/power measures in youth athletes that increase with maturity may imply transfer effects from balance to strength/power training and vice versa in youth athletes.
Background: There is evidence that frontal plane lower limb malalignment (e.g., genu varus) is a risk factor for knee osteoarthritis development. However, only scarce information is available on gait biomechanics and muscle activity in boys with genu varus. Research question: To examine the effects of knee varus alignment on lower limb kinematics, kinetics and muscular activity during walking at self-selected speed in boys with genu varus versus healthy age-matched controls. Methods: Thirty-six boys were enrolled in this study and divided into a group of boys with genu varus (n = 18; age: 11.66 +/- 1.64 years) and healthy controls (n = 18; age: 11.44 +/- 1.78 years). Three-dimensional kinematics, ground reaction forces, loading rates, impulses and free moments of both limbs were recorded during five walking trials at self-selected speed. Surface electromyography was recorded for rectus femoris and vastus lateralis/medialis muscles. Results: No significant between-group differences were found for gait speed. Participants in the genu varus group versus controls showed larger peak knee flexion (p = 0.030; d = 0.77), peak knee adduction (p < 0.001; d = 1.63), and peak ankle eversion angles (p < 0.001; d = 2.06). Significantly higher peak ground reaction forces were found at heel contact (vertical [p = 0.002; d = 1.16] and posterior [p < 0.001; d = 1.63] components) and at push off (vertical [p = 0.010; d = 0.93] and anterior [p < 0.001; d = 1.34] components) for genu varus versus controls. Peak medial ground reaction force (p = 0.032; d = 0.76), vertical loading rate (p < 0.001; d = 1.52), anterior-posterior impulse (p = 0.011; d = 0.92), and peak negative free moment (p = 0.030; d = 0.77) were significantly higher in genu varus. Finally, time to reach peak forces was significantly shorter in genu varus boys compared with healthy controls (p < 0.01; d = 0.73-1.60). The genu varus group showed higher activities in vastus lateralis (p < 0.001; d = 1.82) and vastus medialis (p = 0.013; d = 0.90) during the loading phase of walking. Significance: Our study revealed genu varus specific gait characteristics and muscle activities. Greater knee adduction angle in genu varus boys may increase the load on the medial compartment of the knee joint. The observed characteristics in lower limb biomechanics and muscle activity could play a role in the early development of knee osteoarthritis in genu varus boys.
Background: There is evidence that fully recovered COVID-19 patients usually resume physical exercise, but do not perform at the same intensity level performed prior to infection. The aim of this study was to evaluate the impact of COVID-19 infection and recovery as well as muscle fatigue on cardiorespiratory fitness and running biomechanics in female recreational runners.
Methods: Twenty-eight females were divided into a group of hospitalized and recovered COVID-19 patients (COV, n = 14, at least 14 days following recovery) and a group of healthy age-matched controls (CTR, n = 14). Ground reaction forces from stepping on a force plate while barefoot overground running at 3.3 m/s was measured before and after a fatiguing protocol. The fatigue protocol consisted of incrementally increasing running speed until reaching a score of 13 on the 6–20 Borg scale, followed by steady-state running until exhaustion. The effects of group and fatigue were assessed for steady-state running duration, steady-state running speed, ground contact time, vertical instantaneous loading rate and peak propulsion force.
Results: COV runners completed only 56% of the running time achieved by the CTR (p < 0.0001), and at a 26% slower steady-state running speed (p < 0.0001). There were fatigue-related reductions in loading rate (p = 0.004) without group differences. Increased ground contact time (p = 0.002) and reduced peak propulsion force (p = 0.005) were found for COV when compared to CTR.
Conclusion: Our results suggest that female runners who recovered from COVID-19 showed compromised running endurance and altered running kinetics in the form of longer stance periods and weaker propulsion forces. More research is needed in this area using larger sample sizes to confirm our study findings.
The aim of this study was to establish maturation-, age-, and sex-specific anthropometric and physical fitness percentile reference values of young elite athletes from various sports. Anthropometric (i.e., standing and sitting body height, body mass, body mass index) and physical fitness (i.e., countermovement jump, drop jump, change-of-direction speed [i.e., T-test], trunk muscle endurance [i.e., ventral Bourban test], dynamic lower limbs balance [i.e., Y-balance test], hand grip strength) of 703 male and female elite young athletes aged 8–18 years were collected to aggregate reference values according to maturation, age, and sex. Findings indicate that body height and mass were significantly higher (p<0.001; 0.95≤d≤1.74) in more compared to less mature young athletes as well as with increasing chronological age (p<0.05; 0.66≤d≤3.13). Furthermore, male young athletes were significantly taller and heavier compared to their female counterparts (p<0.001; 0.34≤d≤0.50). In terms of physical fitness, post-pubertal athletes showed better countermovement jump, drop jump, change-of-direction, and handgrip strength performances (p<0.001; 1.57≤d≤8.72) compared to pubertal athletes. Further, countermovement jump, drop jump, change-of-direction, and handgrip strength performances increased with increasing chronological age (p<0.05; 0.29≤d≤4.13). In addition, male athletes outperformed their female counterpart in the countermovement jump, drop jump, change-of-direction, and handgrip strength (p<0.05; 0.17≤d≤0.76). Significant age by sex interactions indicate that sex-specific differences were even more pronounced with increasing age. Conclusively, body height, body mass, and physical fitness increased with increasing maturational status and chronological age. Sex-specific differences appear to be larger as youth grow older. Practitioners can use the percentile values as approximate benchmarks for talent identification and development.
Background. Dynamic balance is often assessed in athletes using either the Star Excursion Balance Test (SEBT) or the Y Balance Test (YBT). There is evidence that the results for the three common directions are not comparable. Thus, the question is open to debate as to which instrument is better suited to measure training-induced changes over time. Objectives. The aim of this study is to compare the changes in the SEBT and the YBT, measured before and after six weeks of balance and strength exercise programmes in young and healthy athletes. Methods. A total of 30 young male athletes aged 15-17 years participated in this study and were involved in a six-week combined training, including balance and strength exercise. During pre-and post-training periods, the SEBT and YBT were conducted in random order. Results. The comparison between the changes in the SEBT and YBT with a paired sample T-test showed a significant increase in PM (p=0.001) and PL reach directions (p=0.000). No differences were observed in the A reach direction (p=0.38). Conclusion. the responsiveness levels of the SEBT and YBT are similar is valid. Also, because of higher effect size value in the anterior direction in YBT compared with SEBT, this balance test could possibly be preferred in this direction for postural control evaluation.
Lesinski, M, Prieske, O, Chaabene, H, and Granacher, U. Seasonal effects of strength endurance vs. power training in young female soccer athletes. J Strength Cond Res 35(12S): S90-S96, 2021-This study examined the seasonal effects of strength endurance training (SET) vs. power training (PT) on physical fitness and body composition in young female soccer players. Thirty-six young female elite soccer players (15 +/- 1 years; maturity offset +3 +/- 1 years) were allocated to progressive SET (n = 19) or PT (n = 17). Over the course of one soccer season, SET performed slow movement velocity, moderate intensity (50-60% of the 1 repetition maximum [1RM]; 20-40 repetitions) strength exercises while PT performed moderate-to-high intensity (50-95% of the 1RM; 3-8 repetitions), high movement velocity strength exercises (2 sessions center dot wk(-1)). Before and after training, tests were performed for the assessment of muscle strength (1RM leg press), jump performance (countermovement jump [CMJ], drop jump [DJ]), muscular endurance (ventral Bourban test), linear speed (10 m, 20 m), change-of-direction (CoD) speed (T-test), dynamic balance (Y-balance test), sport-specific performance (kicking velocity), and body composition (lean body mass and fat mass). An analysis of covariance was used to test for between-group differences at post-test with baseline values as covariate. No significant between-group differences were observed in terms of total training volume over the respective soccer seasons (p = 0.069; d = 0.68). At post-test, SET showed significantly better ventral Bourban and T-test performances (d = 1.28-2.28; p = 0.000-0.001) compared with PT. However, PT resulted in significantly better 1RM leg press, DJ, 10-m, and 20-m sprint performances (d = 0.85-1.44; p = 0.000-0.026). No significant between-group differences were observed at post-test for CMJ, Y-balance test, kicking performance, and body composition (d = 0.20-0.74, p = 0.051-0.594). Our findings are mainly in accordance with the principle of training specificity. Both SET and PT are recommended to be implemented in young female elite soccer players according to the respective training period.
The present study aims to identify the optimal body-size/shape and maturity characteristics associated with superior fitness test performances having controlled for body-size, sex, and chronological-age differences. The sample consisted of 597 Tunisian children (396 boys and 201 girls) aged 8 to 15 years. Three sprint speeds recorded at 10, 20 and 30 m; two vertical and two horizontal jump tests; a change-of-direction and a handgrip-strength tests, were assessed during physical-education classes. Allometric modelling was used to identify the benefit of being an early or late maturer. Findings showed that being tall and light is the ideal shape to be successful at most physical fitness tests, but the height-to-weight “shape” ratio seems to be test-dependent. Having controlled for body-size/shape, sex, and chronological age, the model identified maturity-offset as an additional predictor. Boys who go earlier/younger through peak-height-velocity (PHV) outperform those who go at a later/older age. However, most of the girls’ physical-fitness tests peaked at the age at PHV and decline thereafter. Girls whose age at PHV was near the middle of the age range would appear to have an advantage compared to early or late maturers. These findings have important implications for talent scouts and coaches wishing to recruit children into their sports/athletic clubs.
The purpose of this study was to investigate the association between variables of lower extremity muscle strength, balance, and mobility assessed under various task conditions.
Twenty-one healthy children (mean age: 9 +/- 1 years) were tested for their isometric and dynamic strength as well as for their steady-state, proactive, and reactive balance and mobility. Balance and mobility tests were conducted under single and dual task conditions.
Significant positive correlations were detected between measures of isometric and dynamic leg muscle strength. Hardly any significant associations were observed between variables of strength and balance/mobility and between measures of steady-state, proactive, and reactive balance. Additionally, no significant correlations were detected between balance/mobility tests performed under single and dual task conditions.
The predominately non-significant correlations between different balance components and mobility imply that balance and mobility performance is task specific. Further, strength and balance/mobility as well as balance under single and dual task conditions seem to be independent of each other and may have to be tested and trained complementarily.
Physical fatigue and pronated feet constitute two risk factors for running-related lower limb injuries. Accordingly, different running shoe companies designed anti-pronation shoes with medial support to limit over pronation in runners. However, there is little evidence on the effectiveness and clinical relevance of anti-pronation shoes. This study examined lower limb kinematics and kinetics in young female runners with pronated feet during running with antipronation versus regular (neutral) running shoes in unfatigued and fatigued condition. Twenty-six female runners aged 24.1±5.6 years with pronated feet volunteered to participate in this study. Kinetic (3D Kistler force plate) and kinematic analyses (Vicon motion analysis system) were conducted to record participants’ ground reaction forces and joint kinematics when running with anti-pronation compared with neutral running shoes. Physical fatigue was induced through an individualized submaximal running protocol on a motorized treadmill using rate of perceived exertion and heart rate monitoring. The statistical analyses indicated significant main effects of “footwear” for peak ankle inversion, peak ankle eversion, and peak hip internal rotation angles (p<0.03; d = 0.46–0.95). Pair-wise comparisons revealed a significantly greater peak ankle inversion angle (p<0.03; d = 0.95; 2.70°) and smaller peak eversion angle (p<0.03; d = 0.46; 2.53°) when running with anti-pronation shoes compared with neutral shoes. For kinetic data, significant main effects of “footwear” were found for peak ankle dorsiflexor moment, peak knee extensor moment, peak hip flexor moment, peak hip extensor moment, peak hip abductor moment, and peak hip internal rotator moment (p<0.02; d = 1.00–1.79). For peak positive hip power in sagittal and frontal planes and peak negative hip power in horizontal plane, we observed significant main effects of “footwear” (p<0.03; d = 0.92–1.06). Pairwise comparisons revealed that peak positive hip power in sagittal plane (p<0.03; d = 0.98; 2.39 w/kg), peak positive hip power in frontal plane (p = 0.014; d = 1.06; 0.54 w/kg), and peak negative hip power in horizontal plane (p<0.03; d = 0.92; 0.43 w/kg) were greater with anti-pronation shoes. Furthermore, the statistical analyses indicated significant main effects of “Fatigue” for peak ankle inversion, peak ankle eversion, and peak knee external rotation angles. Pair-wise comparisons revealed a fatigue-induced decrease in peak ankle inversion angle (p<0.01; d = 1.23; 2.69°) and a fatigue-induced increase in peak knee external rotation angle (p<0.05; d = 0.83; 5.40°). In addition, a fatigue-related increase was found for peak ankle eversion (p<0.01; d = 1.24; 2.67°). For kinetic data, we observed a significant main effect of “Fatigue” for knee flexor moment, knee internal rotator moment, and hip extensor moment (p<0.05; d = 0.83–1.01). The statistical analyses indicated significant a main effect of “Fatigue” for peak negative ankle power in sagittal plane (p<0.01; d = 1.25). Finally, we could not detect any significant footwear by fatigue interaction effects for all measures of joint kinetics and kinematics. Running in anti-pronation compared with neutral running shoes produced lower peak moments and powers in lower limb joints and better control in rear foot eversion. Physical fatigue increased peak moments and powers in lower limb joints irrespective of the type of footwear.
Background: It has previously been shown that conditioning activities consisting of repetitive hops have the potential to induce better drop jump (DJ) performance in recreationally active individuals. In the present pilot study, we investigated whether repetitive conditioning hops can also increase reactive jump and sprint performance in sprint-trained elite athletes competing at an international level. Methods: Jump and sprint performances of 5 athletes were randomly assessed under 2 conditions. The control condition (CON) comprised 8 DJs and 4 trials of 30-m sprints. The intervention condition (HOP) consisted of 10 maximal repetitive two-legged hops that were conducted 10 s prior to each single DJ and sprint trial. DJ performance was analyzed using a one-dimensional ground reaction force plate. Step length (SL), contact time (CT), and sprint time (ST) during the 30-m sprints were recorded using an opto-electronic measurement system. Results: Following the conditioning activity, DJ height and external DJ peak power were both significantly increased by 11 % compared to the control condition. All other variables did not show any significant differences between HOP and CON. Conclusions: In the present pilot study, we were able to demonstrate large improvements in DJ performance even in sprint-trained elite athletes following a conditioning activity consisting of maximal two-legged repetitive hops. This strengthens the hypothesis that plyometric conditioning exercises can induce performance enhancements in elite athletes that are even greater than those observed in recreationally active athletes.. In addition, it appears that the transfer of these effects to other stretch-shortening cycle activities is limited, as we did not observe any changes in sprint performance following the plyometric conditioning activity.
This study sought to analyze the relationship between in-season training workload with changes in aerobic power (VO2max), maximum and resting heart rate (HRmax and HRrest), linear sprint medium (LSM), and short test (LSS), in soccer players younger than 16 years (under-16 soccer players). We additionally aimed to explain changes in fitness levels during the in-season through regression models, considering accumulated load, baseline levels, and peak height velocity (PHV) as predictors. Twenty-three male sub-elite soccer players aged 15.5 ± 0.2 years (PHV: 13.6 ± 0.4 years; body height: 172.7 ± 4.2 cm; body mass: 61.3 ± 5.6 kg; body fat: 13.7% ± 3.9%; VO2max: 48.4 ± 2.6 mL⋅kg–1⋅min–1), were tested three times across the season (i.e., early-season (EaS), mid-season (MiS), and end-season (EnS) for VO2max, HRmax, LSM, and LSS. Aerobic and speed variables gradually improved over the season and had a strong association with PHV. Moreover, the HRmax demonstrated improvements from EaS to EnS; however, this was more evident in the intermediate period (from EaS to MiS) and had a strong association with VO2max. Regression analysis showed significant predictions for VO2max [F(2, 20) = 8.18, p ≤ 0.001] with an R2 of 0.45. In conclusion, the meaningful variation of youth players’ fitness levels can be observed across the season, and such changes can be partially explained by the load imposed.
This study investigated associations between variables of trunk muscle strength (TMS), spinal mobility, and balance in seniors. Thirty-four seniors (sex: 18 female, 16 male; age: 70 +/- 4 years; activity level: 13 +/- 7 hr/week) were tested for maximal isometric strength (MIS) of the trunk extensors, flexors, lateral flexors, rotators, spinal mobility, and steady-state, reactive, and proactive balance. Significant correlations were detected between all measures of TMS and static steady-state balance (r = .43.57, p < .05). Significant correlations were observed between specific measures of TMS and dynamic steady-state balance (r = .42.55, p < .05). No significant correlations were found between all variables of TMS and reactive/proactive balance and between all variables of spinal mobility and balance. Regression analyses revealed that TMS explains between 1-33% of total variance of the respective balance parameters. Findings indicate that TMS is related to measures of steady-state balance which may imply that TMS promoting exercises should be integrated in strength training for seniors.
The purpose of this study was to examine sex-specific effects of different footwear properties vs. barefoot condition during the performance of drop jumps (DJs) on stable and unstable surfaces on measures of jump performance, electromyographic (EMG) activity, and knee joint kinematics. Drop jump performance, EMG activity of lower-extremity muscles, as well as sagittal and frontal knee joint kinematics were tested in 28 healthy male (n = 14) and female (n = 14) physically active sports science students (23 6 2 years) during the performance of DJs on stable and unstable surfaces using different footwear properties (elastic vs. minimal shoes) vs. barefoot condition. Analysis revealed a significantly lower jump height and performance index (Delta 7-12%; p < 0.001; 2.22 <= d = 2.90) during DJs on unstable compared with stable surfaces. This was accompanied by lower thigh/shank muscle activities (Delta 11-28%; p < 0.05; 0.99 <= d = 2.16) and knee flexion angles (Delta 5-8%; p < 0.05; 1.02 <= d = 2.09). Furthermore, knee valgus angles during DJs were significantly lower when wearing shoes compared with barefoot condition (Delta 22-32%; p < 0.01; 1.38 <= d = 3.31). Sex-specific analyses indicated higher knee flexion angles in females compared with males during DJs, irrespective of the examined surface and footwear conditions (Delta 29%; p < 0.05; d = 0.92). Finally, hardly any significant footwear-surface interactions were detected. Our findings revealed that surface instability had an impact on DJ performance, thigh/shank muscle activity, and knee joint kinematics. In addition, the single factors "footwear" and "sex" modulated knee joint kinematics during DJs. However, hardly any significant interaction effects were found. Thus, additional footwear-related effects can be neglected when performing DJs during training on different surfaces.
Previous studies have not considered the potential influence of maturity status on the relationship between mental imagery and change of direction (CoD) speed in youth soccer. Accordingly, this cross-sectional study examined the association between mental imagery and CoD performance in young elite soccer players of different maturity status. Forty young male soccer players, aged 10-17 years, were assigned into two groups according to their predicted age at peak height velocity (PHV) (Pre-PHV; n = 20 and Post-PHV; n = 20). Participants were evaluated on soccer-specific tests of CoD with (CoDBall-15m) and without (CoD-15m) the ball. Participants completed the movement imagery questionnaire (MIQ) with the three- dimensional structure, internal visual imagery (IVI), external visual imagery (EVI), as well as kinesthetic imagery (KI). The Post-PHV players achieved significantly better results than Pre-PHV in EVI (ES = 1.58, large; p < 0.001), CoD-15m (ES = 2.09, very large; p < 0.001) and CoDBall-15m (ES = 1.60, large; p < 0.001). Correlations were significantly different between maturity groups, where, for the pre-PHV group, a negative very large correlation was observed between CoDBall-15m and KI (r = –0.73, p = 0.001). For the post-PHV group, large negative correlations were observed between CoD-15m and IVI (r = –0.55, p = 0.011), EVI (r = –062, p = 0.003), and KI (r = –0.52, p = 0.020). A large negative correlation of CoDBall-15m with EVI (r = –0.55, p = 0.012) and very large correlation with KI (r = –0.79, p = 0.001) were also observed. This study provides evidence of the theoretical and practical use for the CoD tasks stimulus with imagery. We recommend that sport psychology specialists, coaches, and athletes integrated imagery for CoD tasks in pre-pubertal soccer players to further improve CoD related performance.
Swimming performance can be improved not only by in-water sport-specific training but also by means of dry land-training (e.g., plyometric jump training [PJT]). This study examined the effects of an 8-week PJT on proxies of muscle power and swimming performance in prepubertal male swimmers. Participants were randomly allocated to a PJT group (PJT; n = 14; age: 10.3 +/- 0.4 years, maturity-offset = -3 +/- 0.3) or a control group (CG; n = 12; age: 10.5 +/- 0.4 years, maturity-offset = -2.8 +/- 0.3). Swimmers in PJT and CG performed 6 training sessions per week. Each training session lasted between 80 and 90 minutes. Over the 8 weeks in-season training period, PJT performed two PJT sessions per week, each lasting between 25 to 30 minutes (similar to 1 hour per week) in replacement of sport-specific swimming drills. During that time, CG followed their regular sport-specific swimming training (e.g., coordination, breathing, improving swimming strokes). Overall training volume was similar between groups. Pre- and post-training, tests were conducted to assess proxies of muscle power (countermovement-jump [CMJ]), standing-long-jump [SLJ]) and sport-specific swimming performances (15-, 25-, and 50-m front-crawl, 25-m kick without push [25-m kick WP], and 25-m front-crawl WP). No training or test-related injuries were detected over the course of the study. Between-group analyses derived from magnitude-based inferences showed trivial-to-large effects in favour of PJT for all tests (ES = 0.28 to 1.43). Within-group analyses for the PJT showed small performance improvements for CMJ (effect-size [ES] = 0.53), 25-m kick WP (ES = 0.25), and 50-m front crawl (ES = 0.56) tests. Moderate performance improvements were observed for the SLJ, 25-m front-crawl WP, 15-m and 25-m front-crawl tests (ES = 0.95, 0.60, 0.99, and 0.85, respectively). For CG, the within-group results showed trivial performance declines for the CMJ (ES=-0.13) and the 50-m front-crawl test (ES = -0.04). In addition, trivial-to-small performance improvements were observed for the SLJ (ES = 0.09), 25-m kick WP (ES = 0.02), 25-m front-crawl WP (ES = 0.19), 25-m front-crawl (ES = 0.2), (SLJ [ES = 0.09, and 15-m front crawl (ES = 0.36). Short-term in-season PJT, integrated into the regular swimming training, was more effective than regular swimming training alone in improving jump and sport-specific swimming performances in prepubertal male swimmers.
Introduction:
In children, the impact of hearing loss on biomechanical gait parameters is not well understood. Thus, the objectives of this study were to examine three-dimensional lower limb joint torques in deaf compared to age-matched healthy (hearing) children while walking at preferred gait speed.
Methods:
Thirty prepubertal boys aged 8-14 were enrolled in this study and divided into a group with hearing loss (deaf group) and an age-matched healthy control. Three-dimensional joint torques were analyzed during barefoot walking at preferred speed using Kistler force plates and a Vicon motion capture system.
Results:
Findings revealed that boys with hearing loss showed lower joint torques in ankle evertors, knee flexors, abductors and internal rotators as well as in hip internal rotators in both, the dominant and non-dominant lower limbs (all p < 0.05; d = 1.23-7.00; 14-79%). Further, in the dominant limb, larger peak ankle dorsiflexor (p < 0.001; d = 1.83; 129%), knee adductor (p < 0.001; d = 3.20; 800%), and hip adductor torques (p < 0.001; d = 2.62; 350%) were found in deaf participants compared with controls.
Conclusion:
The observed altered lower limb torques during walking are indicative of unstable gait in children with hearing loss. More research is needed to elucidate whether physical training (e.g., balance and/or gait training) has the potential to improve walking performance in this patient group. (C) 2019 Elsevier Ltd. All rights reserved.
Growth and maturation affect long term physical performance, making the appraisal of athletic ability difficult. We sought to longitudinally track youth soccer players to assess the developmental trajectory of athletic performance over a 6-year period in an English Premier League academy. Age-specific z-scores were calculated for sprint and jump performance from a sample of male youth soccer players (n = 140). A case study approach was used to analyse the longitudinal curves of the six players with the longest tenure. The trajectories of the sprint times of players 1 and 3 were characterised by a marked difference in respective performance levels up until peak height velocity (PHV) when player 1 achieved a substantial increase in sprint speed and player 3 experienced a large decrease. Player 5 was consistently a better performer than player 2 until PHV when the sprint and jump performance of the former markedly decreased and he was overtaken by the latter. Fluctuations in players' physical performance can occur quickly and in drastic fashion. Coaches must be aware that suppressed, or inflated, performance could be temporary and selection and deselection decisions should not be made based on information gathered over a short time period.
There is growing evidence that aging and muscle fatigue result in impaired postural reflexes in humans. Therefore, the objective of this study was to examine the effects of ankle fatigue on functional reflex activity (ERA) during gait perturbations in young and elderly men. Twenty-eight young (27.0 +/- 3.1 years, n = 14) and old (67.2 +/- 3.7 years, n = 14) healthy active men participated in this study. Fatigue of the plantarflexors and dorsiflexors was induced by isokinetic contractions. Pre and post-fatigue, subjects were tested for their ability to compensate for decelerating gait perturbations while walking on a treadmill. Latency, ERA of lower extremity muscles and angular velocity of the ankle joint complex were analysed by means of surface electromyography and goniometry. After the fatigue protocol, no significant main and interaction effects were detected for the parameter latency in m. tibialis anterior (TA). For both groups, a significant pre to post-test decrease in ERA in TA (P<.001) was observed coming along with increases in antagonist coactivity (P=.013) and maximal angular velocity of the ankle joint (p=.007). However, no significant group x test interactions were found for the three parameters. Ankle fatigue has an impact on the ability to compensate for gait perturbations in young and elderly adults. However, no significant differences in all analysed parameters were detected between young and elderly subjects. These results may imply that age-related deteriorations in the postural control system do not specifically affect the ability to compensate for gait perturbations under fatigued condition.