Effect of glissade-step on kinetic and kinematic variables of stag ring leaps with and without throw-catch of the ball in rhythmic gymnastics.

This study focuses on certain characteristics of the jump take-offs in rhythmic gymnastics (RG). Rhythmic gymnasts always perform their jumps with the same preferred run-up technique, proceeded by a chassé-step in most of the cases. The overall idea was to analyse other step-techniques that could be performged on one-leg, which could prepare jumps. The aim of this study was to compare kinetic and kinematic variables between three-stag ring leaps with and without throwing-ball, performed using the glissade-step as a preparatory phase for take-off with one-leg these were as follows: glissade stag ring leap without-ball (GSWB), throw-ball glissade stag ring leap (TBGS) and glissade throw-ball stag ring leap (GTBS). Seven members of the Tunisian RG national team took part in this study. The technical elements were recorded in 2D using two-cameras on a specially designed floor carpet where a force-plate was integrated. The results showed that the three-leaps had significant impacts on the performance variables, especially on the force, the velocity and the flexibility. The GTBS was the most effective leap as the throw took place during the jump, which has increased its technicality and the applied physical variables, the vertical force, the rate of force development, the horizontal and vertical velocities and displacements.

Analysis of postural balance between two aquatic sports using vertical vs. horizontal body position.

OBJECTIVE: This study aims to analyze and compare the postural balance between two aquatic sports where vertical vs. horizontal body positions (i.e., windsurfing vs. swimming) are key techniques for both sports. SUBJECTS AND METHODS: Eight volunteer windsurfers and eight swimmers agreed to participate in this study. Each of the assessments was a 2D kinematic analysis of frontal and/or sagittal balance (i.e., in bipedal and/or unipedal stance) of the center of mass velocity on wobble board (Single Plane Balance Board) on hard and/or soft surface. Kinematic analysis was performed in 2D using two action-cams. Data were digitized using the video-based data analysis system SkillSpector. RESULTS: The results showed that the ANOVA, with repeated measures on 1 factor, showed a significant difference (p<0.001) between groups (i.e., swimmers and windsurfers) in all variables and in the interaction between ground (i.e., hard and foam) and group (p<0.01) in all tests in sagittal plane. Furthermore, for the ground*group interaction, a study (i.e., paired t-test) of the difference between balance (i.e., in frontal and/or sagittal plane) on hard and soft ground for each group showed that windsurfers had no difference in body sway in frontal and/or sagittal plane between hard and soft surface in bipedal stance. CONCLUSIONS: We concluded that the windsurfers showed better postural balance performances compared to swimmers in the bipedal posture on hard and soft ground. Also, the windsurfers presented a better stability level compared with the swimmers.

Effect of Plyometric Jump Training on Skeletal Muscle Hypertrophy in Healthy Individuals: A Systematic Review With Multilevel Meta-Analysis.

Objective: To examine the effect of plyometric jump training on skeletal muscle hypertrophy in healthy individuals. Methods: A systematic literature search was conducted in the databases PubMed, SPORTDiscus, Web of Science, and Cochrane Library up to September 2021. Results: Fifteen studies met the inclusion criteria. The main overall finding (44 effect sizes across 15 clusters median = 2, range = 1-15 effects per cluster) indicated that plyometric jump training had small to moderate effects [standardised mean difference (SMD) = 0.47 (95% CIs = 0.23-0.71); p < 0.001] on skeletal muscle hypertrophy. Subgroup analyses for training experience revealed trivial to large effects in non-athletes [SMD = 0.55 (95% CIs = 0.18-0.93); p = 0.007] and trivial to moderate effects in athletes [SMD = 0.33 (95% CIs = 0.16-0.51); p = 0.001]. Regarding muscle groups, results showed moderate effects for the knee extensors [SMD = 0.72 (95% CIs = 0.66-0.78), p < 0.001] and equivocal effects for the plantar flexors [SMD = 0.65 (95% CIs = -0.25-1.55); p = 0.143]. As to the assessment methods of skeletal muscle hypertrophy, findings indicated trivial to small effects for prediction equations [SMD = 0.29 (95% CIs = 0.16-0.42); p < 0.001] and moderate-to-large effects for ultrasound imaging [SMD = 0.74 (95% CIs = 0.59-0.89); p < 0.001]. Meta-regression analysis indicated that the weekly session frequency moderates the effect of plyometric jump training on skeletal muscle hypertrophy, with a higher weekly session frequency inducing larger hypertrophic gains [ß = 0.3233 (95% CIs = 0.2041-0.4425); p < 0.001]. We found no clear evidence that age, sex, total training period, single session duration, or the number of jumps per week moderate the effect of plyometric jump training on skeletal muscle hypertrophy [ß = -0.0133 to 0.0433 (95% CIs = -0.0387 to 0.1215); p = 0.101-0.751]. Conclusion: Plyometric jump training can induce skeletal muscle hypertrophy, regardless of age and sex. There is evidence for relatively larger effects in non-athletes compared with athletes. Further, the weekly session frequency seems to moderate the effect of plyometric jump training on skeletal muscle hypertrophy, whereby more frequent weekly plyometric jump training sessions elicit larger hypertrophic adaptations.