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Institute
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.
Associations between measures of physical fitness and cognitive performance in preschool children
(2022)
Background:
Given that recent studies report negative secular declines in physical fitness, associations between fitness and cognition in childhood are strongly discussed. The preschool age is characterized by high neuroplasticity which effects motor skill learning, physical fitness, and cognitive development. The aim of this study was to assess the relation of physical fitness and attention (including its individual dimensions (quantitative, qualitative)) as one domain of cognitive performance in preschool children. We hypothesized that fitness components which need precise coordination compared to simple fitness components are stronger related to attention.
Methods:
Physical fitness components like static balance (i.e., single-leg stance), muscle strength (i.e., handgrip strength), muscle power (i.e., standing long jump), and coordination (i.e., hopping on one leg) were assessed in 61 healthy children (mean age 4.5 +/- 0.6 years; girls n = 30). Attention was measured with the "Konzentrations-Handlungsverfahren fur Vorschulkinder" [concentration-action procedure for preschoolers]). Analyses were adjusted for age, body height, and body mass.
Results:
Results from single linear regression analysis revealed a significant (p < 0.05) association between physical fitness (composite score) and attention (composite score) (standardized ss = 0.40), showing a small to medium effect (F-2 = 0.14). Further, coordination had a significant relation with the composite score and the quantitative dimension of attention (standardized ss = 0.35; p < 0.01; standardized ss = - 0.33; p < 0.05). Coordination explained about 11% (composite score) and 9% (quantitative dimension) of the variance in the stepwise multiple regression model.
Conclusion:
The results indicate that performance in physical fitness, particularly coordination, is related to attention in preschool children. Thus, high performance in complex fitness components (i.e., hopping on one leg) tends to predict attention in preschool children. Further longitudinal studies should focus on the effectiveness of physical activity programs implementing coordination and complex exercises at preschool age to examine cause-effect relationships between physical fitness and attention precisely.
Objectives: Postural control in elderly people is impaired by degradations of sensory, motor, and higher-level adaptive mechanisms. Here, we characterize the effects of a progressive balance training programon these postural control impairments using a brain network model based on system identification techniques. Methods and Material: We analyzed postural control of 35 healthy elderly subjects and compared findings to data from 35 healthy young volunteers. Eighteen elderly subjects performed a 10 week balance training conducted twice per week. Balance training was carried out in static and dynamic movement states, on support surfaces with different elastic compliances, under different visual conditions and motor tasks. Postural control was characterized by spontaneous sway and postural reactions to pseudorandom anterior-posterior tilts of the support surface. Data were interpreted using a parameter identification procedure based on a brain network model. Conclusion: Balance training reduced overactive proprioceptive feedback and restored vestibular orientation in elderly. Based on the assumption of a linear deterioration of postural control across the life span, the training effect can be extrapolated as a juvenescence of 10 years. This study points to a considerable benefit of a continuous balance training in elderly, even without any sensorimotor deficits.
This study aimed at examining physiological responses (i.e., oxygen uptake [VO2] and heart rate [HR]) to a semi-contact 3 x 3-min format, amateur boxing combat simulation in elite level male boxers. Eleven boxers aged 21.4 +/- 2.1 years (body height 173.4 +/- 3.7, body mass 74.9 +/- 8.6 kg, body fat 12.1 +/- 1.9, training experience 5.7 +/- 1.3 years) volunteered to participate in this study. They performed a maximal graded aerobic test on a motor-driven treadmill to determine maximum oxygen uptake (VO2max), oxygen uptake (VO2AT) and heart rate (HRAT) at the anaerobic threshold, and maximal heart rate (HRmax). Additionally, VO2 and peak HR (HRpeak) were recorded following each boxing round. Results showed no significant differences between VO2max values derived from the treadmill running test and VO2 outcomes of the simulated boxing contest (p > 0.05, d = 0.02 to 0.39). However, HRmax and HRpeak recorded from the treadmill running test and the simulated amateur boxing contest, respectively, displayed significant differences regardless of the boxing round (p < 0.01, d = 1.60 to 3.00). In terms of VO2 outcomes during the simulated contest, no significant between-round differences were observed (p = 0.19, d = 0.17 to 0.73). Irrespective of the boxing round, the recorded VO2 was >90% of the VO2max. Likewise, HRpeak observed across the three boxing rounds were >= 90% of the HRmax. In summary, the simulated 3 x 3-min amateur boxing contest is highly demanding from a physiological standpoint. Thus, coaches are advised to systematically monitor internal training load for instance through rating of perceived exertion to optimize training-related adaptations and to prevent boxers from overreaching and/or overtraining.
Purpose
The objective of the investigation was to determine the concomitant effects of upper arm blood flow restriction (BFR) and inversion on elbow flexors neuromuscular responses.
Methods
Randomly allocated, 13 volunteers performed four conditions in a within-subject design: rest (control, 1-min upright position without BFR), control (1-min upright with BFR), 1-min inverted (without BFR), and 1-min inverted with BFR. Evoked and voluntary contractile properties, before, during and after a 30-s maximum voluntary contraction (MVC) exercise intervention were examined as well as pain scale.
Results
Inversion induced significant pre-exercise intervention decreases in elbow flexors MVC (21.1%, Z2p = 0.48, p = 0.02) and resting evoked twitch forces (29.4%, Z2p = 0.34, p = 0.03). The 30-s MVC induced significantly greater pre- to post-test decreases in potentiated twitch force (Z2p = 0.61, p = 0.0009) during inversion (75%) than upright (65.3%) conditions. Overall, BFR decreased MVC force 4.8% (Z2p = 0.37, p = 0.05). For upright position, BFR induced 21.0% reductions in M-wave amplitude (Z2p = 0.44, p = 0.04). There were no significant differences for electromyographic activity or voluntary activation as measured with the interpolated twitch technique. For all conditions, there was a significant increase in pain scale between the 40-60 s intervals and post-30-s MVC (upright< inversion, and without BFR< BFR).
Conclusion
The concomitant application of inversion with elbow flexors BFR only amplified neuromuscular performance impairments to a small degree. Individuals who execute forceful contractions when inverted or with BFR should be cognizant that force output may be impaired.
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.
This study aimed to investigate the effects of eight weeks of barefoot running exercise on sand versus control on measures of walking kinetics and muscle activities in individuals with diagnosed pronated feet. Sixty physically active male adults with pronated feet were randomly allocated into an intervention or a waiting control group. The intervention group conducted an 8-weeks progressive barefoot running exercise program on sand (e.g., short sprints) with three weekly sessions. Pre and post intervention, participants walked at a constant speed of 1.3 m/s +/- 5% on a 18 m walkway with a force plate embedded in the middle of the walkway. Results showed significant group-by-time interactions for peak impact vertical and lateral ground reaction forces. Training but not control resulted in significantly lower peak impact vertical and lateral ground reaction forces. Significant group-by-time interactions were observed for vastus lateralis activity during the loading phase. Training-induced increases were found for the vastus lateralis in the intervention but not in the control group. This study revealed that the applied exercise program is a suitable means to absorb ground reaction forces (e.g., lower impact vertical and lateral peaks) and increase activities of selected lower limb muscles (e.g., vastus lateralis) when walking on stable ground.
Reference values and validation of the 1-minute sit-to-stand test in healthy 5-16-year-old youth
(2021)
Objectives:
It is essential to have simple, reliable and valid tests to measure children's functional capacity in schools or medical practice. The 1-minute sit-to-stand (STS) test is a quick fitness test requiring little equipment or space that is increasingly used in both healthy populations and those with chronic disease. We aimed to provide age-specific and sex-specific reference values of STS test in healthy children and adolescents and to evaluate its short-term reliability and construct validity.
Design setting and participants:
Cross-sectional convenience sample from six public schools and one science fair in central Europe. Overall, 587 healthy participants aged 5-16 years were recruited and divided into age groups of 3 years each.
Outcomes:
1-minute STS. To evaluate short-term reliability, some children performed the STS test twice. To evaluate construct validity, some children also performed a standing long jump (SLJ) and a maximal incremental exercise test.
Results:
Data from 547 youth aged 5-16 years were finally included in the analyses. The median number of repetitions in 1 min in males (females) ranged from 55 [95% CI: 38 to 72] (53 [95% CI: 35 to 76]) in 14-16-year olds to 59 [95% CI: 41 to 77] (60 [95% CI: 38 to 77]) in 8-10-year olds. Children who repeated STS showed a learning effect of on average 4.8 repetitions more than the first test (95% limits of agreement: -6.7 to 16.4). Moderate correlations were observed between the STS and the SLJ (r=0.48) tests and the maximal exercise test (r=0.43).
Conclusions:
The reported STS reference values can be used to interpret STS test performance in children and adolescents. The STS appears to have good test- retest reliability, but a learning effect of about 10%. The association of STS with other measures of physical fitness should be further explored in a larger study and technical standards for its conduct are needed.
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.