Refine
Year of publication
- 2019 (32) (remove)
Language
- English (32)
Is part of the Bibliography
- yes (32) (remove)
Keywords
- strength (6)
- elite athletes (4)
- football (4)
- monitoring (4)
- physiology (4)
- power (4)
- running (4)
- young athletes (4)
- injury (3)
- sport-specific performance (3)
- ankles (2)
- blood (2)
- blood sample (2)
- body density (2)
- body limbs (2)
- canoe racing (2)
- core strength (2)
- cross-education (2)
- exercise (2)
- eyedness (2)
- fatigue (2)
- feet (2)
- footedness (2)
- global positioning system (2)
- hamstring muscles (2)
- hematocrit (2)
- hip (2)
- injury risk (2)
- jumping (2)
- knees (2)
- latency (2)
- laterality (2)
- material fatigue (2)
- muscle activation (2)
- passive stretching (2)
- peak torque (2)
- performance (2)
- periodization (2)
- physical fitness (2)
- physical fitness expertise (2)
- range of motion (2)
- rate of torque development (2)
- recovery (2)
- responses (2)
- rotation (2)
- schedule (2)
- skeletal joints (2)
- somatic variables (2)
- strength training (2)
- team sport (2)
- training load (2)
- weight training (2)
- youth (2)
- Bow leg (1)
- Electromyography (1)
- Ground reaction force (1)
- Pediatric gait (1)
- Postactivation potentiation (1)
- Quadriceps strength (1)
- Stretch-shortening cycle (1)
- adolescents (1)
- assessment (1)
- balance (1)
- balance strategy (1)
- balance training (1)
- children (1)
- deconditioning (1)
- electroencephalography (1)
- electromyography (1)
- endurance performance (1)
- energetic systems (1)
- maximum voluntary contraction (1)
- motor-performance (1)
- muscle coactivation (1)
- muscular strength (1)
- of-direction speed (1)
- plyometric training (1)
- randomized controlled-trial (1)
- rate of force development (1)
- resistance training (1)
- rugby league players (1)
- school baseball players (1)
- soccer (1)
- sport profile (1)
- stretch-shortening cycle (1)
- striking combat sports (1)
- tendon stiffness (1)
- training intensity (1)
- whole-body vibratoin (1)
- young soccer players (1)
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.
The aim of this study is to monitor short-term seasonal development of young Olympic weightlifters’ anthropometry, body composition, physical fitness, and sport-specific performance. Fifteen male weightlifters aged 13.2 ± 1.3 years participated in this study. Tests for the assessment of anthropometry (e.g., body-height, body-mass), body-composition (e.g., lean-body-mass, relative fat-mass), muscle strength (grip-strength), jump performance (drop-jump (DJ) height, countermovement-jump (CMJ) height, DJ contact time, DJ reactive-strength-index (RSI)), dynamic balance (Y-balance-test), and sport-specific performance (i.e., snatch and clean-and-jerk) were conducted at different time-points (i.e., T1 (baseline), T2 (9 weeks), T3 (20 weeks)). Strength tests (i.e., grip strength, clean-and-jerk and snatch) and training volume were normalized to body mass. Results showed small-to-large increases in body-height, body-mass, lean-body-mass, and lower-limbs lean-mass from T1-to-T2 and T2-to-T3 (∆0.7–6.7%; 0.1 ≤ d ≤ 1.2). For fat-mass, a significant small-sized decrease was found from T1-to-T2 (∆13.1%; d = 0.4) and a significant increase from T2-to-T3 (∆9.1%; d = 0.3). A significant main effect of time was observed for DJ contact time (d = 1.3) with a trend toward a significant decrease from T1-to-T2 (∆–15.3%; d = 0.66; p = 0.06). For RSI, significant small increases from T1-to-T2 (∆9.9%, d = 0.5) were noted. Additionally, a significant main effect of time was found for snatch (d = 2.7) and clean-and-jerk (d = 3.1) with significant small-to-moderate increases for both tests from T1-to-T2 and T2-to-T3 (∆4.6–11.3%, d = 0.33 to 0.64). The other tests did not change significantly over time (0.1 ≤ d ≤ 0.8). Results showed significantly higher training volume for sport-specific training during the second period compared with the first period (d = 2.2). Five months of Olympic weightlifting contributed to significant changes in anthropometry, body-composition, and sport-specific performance. However, hardly any significant gains were observed for measures of physical fitness. Coaches are advised to design training programs that target a variety of fitness components to lay an appropriate foundation for later performance as an elite athlete.
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.
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
Sand is an easy-to-access, cost-free resource that can be used to treat pronated feet (PF). Therefore, the aims of this study were to contrast the effects of walking on stable ground versus walking on sand on ground reaction forces (GRFs) and electromyographic (EMG) activity of selected lower limb muscles in PF individuals compared with healthy controls.
Methods
Twenty-nine controls aged 22.2±2.5 years and 30 PF individuals aged 22.2±1.9 years were enrolled in this study. Participants walked at preferred speed and in randomized order over level ground and sand. A force plate was included in the walkway to collect GRFs. Muscle activities were recorded using EMG system.
Results
No statistically significant between-group differences were found in preferred walking speed when walking on stable ground (PF: 1.33±0.12 m/s; controls: 1.35±0.14 m/s; p = 0.575; d = 0.15) and sand (PF: 1.19±0.11 m/s; controls: 1.23±0.18 m/s; p = 0.416; d = 0.27). Irrespective of the group, walking on sand (1.21±0.15 m/s) resulted in significantly lower gait speed compared with stable ground walking (1.34±0.13 m/s) (p<0.001; d = 0.93). Significant main effects of “surface” were found for peak posterior GRFs at heel contact, time to peak for peak lateral GRFs at heel contact, and peak anterior GRFs during push-off (p<0.044; d = 0.27–0.94). Pair-wise comparisons revealed significantly smaller peak posterior GRFs at heel contact (p = 0.005; d = 1.17), smaller peak anterior GRFs during push-off (p = 0.001; d = 1.14), and time to peak for peak lateral GRFs (p = 0.044; d = 0.28) when walking on sand. No significant main effects of “group” were observed for peak GRFs and their time to peak (p>0.05; d = 0.06–1.60). We could not find any significant group by surface interactions for peak GRFs and their time to peak. Significant main effects of “surface” were detected for anterior-posterior impulse and peak positive free moment amplitude (p<0.048; d = 0.54–0.71). Pair-wise comparisons revealed a significantly larger peak positive free moment amplitude (p = 0.010; d = 0.71) and a lower anterior-posterior impulse (p = 0.048; d = 0.38) when walking on sand. We observed significant main effects of “group” for the variable loading rate (p<0.030; d = 0.59). Pair-wise comparisons revealed significantly lower loading rates in PF compared with controls (p = 0.030; d = 0.61). Significant group by surface interactions were observed for the parameter peak positive free moment amplitude (p<0.030; d = 0.59). PF individuals exhibited a significantly lower peak positive free moment amplitude (p = 0.030, d = 0.41) when walking on sand. With regards to EMG, no significant main effects of “surface”, main effects of “group”, and group by surface interactions were observed for the recorded muscles during the loading and push-off phases (p>0.05; d = 0.00–0.53).
Conclusions
The observed lower velocities during walking on sand compared with stable ground were accompanied by lower peak positive free moments during the push-off phase and loading rates during the loading phase. Our findings of similar lower limb muscle activities during walking on sand compared with stable ground in PF together with lower free moment amplitudes, vertical loading rates, and lower walking velocities on sand may indicate more relative muscle activity on sand compared with stable ground. This needs to be verified in future studies.
Background
Sand is an easy-to-access, cost-free resource that can be used to treat pronated feet (PF). Therefore, the aims of this study were to contrast the effects of walking on stable ground versus walking on sand on ground reaction forces (GRFs) and electromyographic (EMG) activity of selected lower limb muscles in PF individuals compared with healthy controls.
Methods
Twenty-nine controls aged 22.2±2.5 years and 30 PF individuals aged 22.2±1.9 years were enrolled in this study. Participants walked at preferred speed and in randomized order over level ground and sand. A force plate was included in the walkway to collect GRFs. Muscle activities were recorded using EMG system.
Results
No statistically significant between-group differences were found in preferred walking speed when walking on stable ground (PF: 1.33±0.12 m/s; controls: 1.35±0.14 m/s; p = 0.575; d = 0.15) and sand (PF: 1.19±0.11 m/s; controls: 1.23±0.18 m/s; p = 0.416; d = 0.27). Irrespective of the group, walking on sand (1.21±0.15 m/s) resulted in significantly lower gait speed compared with stable ground walking (1.34±0.13 m/s) (p<0.001; d = 0.93). Significant main effects of “surface” were found for peak posterior GRFs at heel contact, time to peak for peak lateral GRFs at heel contact, and peak anterior GRFs during push-off (p<0.044; d = 0.27–0.94). Pair-wise comparisons revealed significantly smaller peak posterior GRFs at heel contact (p = 0.005; d = 1.17), smaller peak anterior GRFs during push-off (p = 0.001; d = 1.14), and time to peak for peak lateral GRFs (p = 0.044; d = 0.28) when walking on sand. No significant main effects of “group” were observed for peak GRFs and their time to peak (p>0.05; d = 0.06–1.60). We could not find any significant group by surface interactions for peak GRFs and their time to peak. Significant main effects of “surface” were detected for anterior-posterior impulse and peak positive free moment amplitude (p<0.048; d = 0.54–0.71). Pair-wise comparisons revealed a significantly larger peak positive free moment amplitude (p = 0.010; d = 0.71) and a lower anterior-posterior impulse (p = 0.048; d = 0.38) when walking on sand. We observed significant main effects of “group” for the variable loading rate (p<0.030; d = 0.59). Pair-wise comparisons revealed significantly lower loading rates in PF compared with controls (p = 0.030; d = 0.61). Significant group by surface interactions were observed for the parameter peak positive free moment amplitude (p<0.030; d = 0.59). PF individuals exhibited a significantly lower peak positive free moment amplitude (p = 0.030, d = 0.41) when walking on sand. With regards to EMG, no significant main effects of “surface”, main effects of “group”, and group by surface interactions were observed for the recorded muscles during the loading and push-off phases (p>0.05; d = 0.00–0.53).
Conclusions
The observed lower velocities during walking on sand compared with stable ground were accompanied by lower peak positive free moments during the push-off phase and loading rates during the loading phase. Our findings of similar lower limb muscle activities during walking on sand compared with stable ground in PF together with lower free moment amplitudes, vertical loading rates, and lower walking velocities on sand may indicate more relative muscle activity on sand compared with stable ground. This needs to be verified in future studies.
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.
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 physical exercise training (PET) conducted at the workplace is effective in improving physical fitness and thus health. However, there is no current systematic review available that provides high-level evidence regarding the effects of PET on physical fitness in the workforce. Objectives To quantify sex-, age-, and occupation type-specific effects of PET on physical fitness and to characterize dose-response relationships of PET modalities that could maximize gains in physical fitness in the working population. Data Sources A computerized systematic literature search was conducted in the databases PubMed and Cochrane Library (2000-2019) to identify articles related to PET in workers. Study Eligibility Criteria Only randomized controlled trials with a passive control group were included if they investigated the effects of PET programs in workers and tested at least one fitness measure. Study Appraisal and Synthesis Methods Weighted mean standardised mean differences (SMDwm) were calculated using random effects models. A multivariate random effects meta-regression was computed to explain the influence of key training modalities (e.g., training frequency, session duration, intensity) on the effectiveness of PET on measures of physical fitness. Further, subgroup univariate analyses were computed for each training modality. Additionally, methodological quality of the included studies was rated with the help of the Physiotherapy Evidence Database (PEDro) Scale. Results Overall, 3423 workers aged 30-56 years participated in 17 studies (19 articles) that were eligible for inclusion. Methodological quality of the included studies was moderate with a median PEDro score of 6. Our analyses revealed significant, small-sized effects of PET on cardiorespiratory fitness (CRF), muscular endurance, and muscle power (0.29 <= SMDwm <= 0.48). Medium effects were found for CRF and muscular endurance in younger workers (<= 45 years) (SMDwm = 0.71) and white-collar workers (SMDwm = 0.60), respectively. Multivariate random effects meta-regression for CRF revealed that none of the examined training modalities predicted the effects of PET on CRF (R-2 = 0). Independently computed subgroup analyses showed significant PET effects on CRF when conducted for 9-12 weeks (SMDwm = 0.31) and for 17-20 weeks (SMDwm = 0.74). Conclusions PET effects on physical fitness in healthy workers are moderated by age (CRF) and occupation type (muscular endurance). Further, independently computed subgroup analyses indicated that the training period of the PET programs may play an important role in improving CRF in workers.