Vertical jump development in elite adolescent volleyball players: Effects of sex and age

Double-Leg and Single-Leg Jump Test Reference Values for Athletes With and Without Anterior Cruciate Ligament Reconstruction Who Play Popular Pivoting Sports, Including Soccer and Basketball: A Scoping Review

OBJECTIVE: To synthesize and present reference values for double-leg and single-leg jump tests in healthy athletes who play pivoting sports, and athletes with anterior cruciate ligament reconstruction (ACLR) who play pivoting sports. DESIGN: Scoping review. LITERATURE SEARCH: We searched PubMed, the Cochrane Library, MEDLINE, Embase, and Web of Science until April 7, 2023. STUDY SELECTION CRITERIA: We included reference values in 2 different categories: (1) double-leg and/or single-leg jump test outcomes in pivoting-sport athletes with ACLR at a specific time point during rehabilitation, and (2) double-leg and/or single-leg jump test outcomes in healthy pivoting-sport athletes. DATA SYNTHESIS: We performed data synthesis for reference values from double-leg jump tests (squat jump and countermovement jump) and single-leg jump tests (vertical hop, single hop for distance, triple hop for distance, crossover hop for distance, medial triple hop for distance, lateral triple hop for distance, 6-m timed hop, side hop, drop jump, and 10-second repeated hop) that were performed according to a standardized test description. We summarized the data for type of sport, sex, sport participation level, and age group. RESULTS: Of the 27 included studies, nine reported reference values from healthy soccer players, six from healthy basketball players, and eleven from other healthy pivoting-sport athletes. LSI dominant/nondominant (LSI-D/ND) ranged between 97% and 106% for healthy soccer players, and between 99% and 120% for healthy basketball players. Four studies reported reference values from pivoting-sport athletes with ACLR from 7 to 10 months postsurgery. CONCLUSION: This scoping review summarizes double-leg and single-leg jump test reference values for athletes who play common pivoting sports, including soccer and basketball. J Orthop Sports Phys Ther 2024;54(6):1-14. Epub 20 March 2024. doi:10.2519/jospt.2024.12374.

Effects of Stroboscopic Vision on Depth Jump Motor Control: A Biomechanical Analysis

Researchers commonly use the 'free-fall' paradigm to investigate motor control during landing impacts, particularly in drop landings and depth jumps (DJ). While recent studies have focused on the impact of vision on landing motor control, previous research fully removed continuous visual input, limiting ecological validity. The aim of this investigation was to evaluate the effects of stroboscopic vision on depth jump (DJ) motor control. Ground reaction forces (GRF) and lower-extremity surface electromyography (EMG) were collected for 20 young adults (11 male; 9 female) performing six depth jumps (0.51 m drop height) in each of two visual conditions (full vision vs. 3 Hz stroboscopic vision). Muscle activation magnitude was estimated from EMG signals using root-mean-square amplitudes (RMS) over specific time intervals (150 ms pre-impact; 30-60 ms, 60-85 ms, and 85-120 ms post-impact). The main effects of and interactions between vision and trial number were assessed using two-way within-subjects repeated measures analyses of variance. Peak GRF was 6.4% greater, on average, for DJs performed with stroboscopic vision compared to full vision (p = 0.042). Tibialis anterior RMS EMG during the 60-85 ms post-impact time interval was 14.1% lower for DJs performed with stroboscopic vision (p = 0.020). Vastus lateralis RMS EMG during the 85-120 ms post-impact time interval was 11.8% lower for DJs performed with stroboscopic vision (p = 0.017). Stroboscopic vision altered DJ landing mechanics and lower-extremity muscle activation. The observed increase in peak GRF and reduction in RMS EMG of the tibialis anterior and vastus lateralis post-landing may signify a higher magnitude of lower-extremity musculotendinous stiffness developed pre-landing. The results indicate measurable sensorimotor disruption for DJs performed with stroboscopic vision, warranting further research and supporting the potential use of stroboscopic vision as a sensorimotor training aid in exercise and rehabilitation. Stroboscopic vision could induce beneficial adaptations in multisensory integration, applicable to restoring sensorimotor function after injury and preventing injuries in populations experiencing landing impacts at night (e.g., military personnel).

Changes in Body Composition and Motor Fitness of Young Female Volleyball Players in an Annual Training Cycle

BACKGROUND

Modern volleyball requires a high level of motor preparation, specific body build and optimal body composition.

OBJECTIVES

The aim of this study was to determine changes in body build, body composition and motor skills in young volleyball female players during an annual training cycle.

METHODS

The research group was comprised of 36 female athletes aged 14-16 years, who were monitored throughout a whole season using a longitudinal study design. Body composition was estimated by bioelectrical impedance analysis. Motor fitness was assessed with the following tests: vertical jumping tests (based on one-handed and two-handed reach, standing vertical jump and running vertical jump), standing long jump and 2 kg medicine ball throw. Measurements were carried out at the beginning of the preparatory period, after its completion, in the middle of the start period, at the end of the start period and during transition periods.

RESULTS

The study showed significant changes in body composition and motor fitness level during the annual training cycle. These changes differ in subsequent periods of the macrocycle. The most pronounced changes occurred after the preparatory period and concerned increases in fat-free mass, total water content and cell mass. A significant reduction in fat content was also noted at this point.

CONCLUSIONS

Systematic monitoring of morpho-functional changes in young female volleyball players over extended periods provides them a chance to maintain their optimal fitness level.