Author(s): CHANEL, B., BABAULT, N., COMETTI, C., Institution: SPORT SCIENCE FACULTY, UNIVERSITY OF BOURGOGNE-FRANCHE-COMTÉ, Country: FRANCE, Abstract-ID: 1082

INTRODUCTION:
The current literature suggests that prepubertal children experience less fatigue than adults following neuromuscular exercises. This is particularly supported by studies reporting a smaller decrease in maximal force production in children compared to adults (1). However, many sport-specific actions rely on the stretch-shortening cycle rather than solely on maximal force production. (2) Therefore, the main aim of this study was to examine how an ecological fatiguing exercise composed of repeated jumps affects the function of the stretch-shortening cycle during a plyometric jump in prepubertal children.
METHODS:
Eight children and eight adults participated in a single experimental session, including a fatiguing exercise composed of five sets of 20 maximal repeated vertical jumps. Pre tests included maximal voluntary isometric contraction of the knee extensors (MVIC) with measurements of the torque and the electromyographic activity of vastus lateralis (RMS VL). Two drop jumps were also performed in tests, with measurements of the reactive strength index (RSI), jump height, contact time (CT), and braking and propulsion phases durations. These tests were repeated immediately after the exercise. All these variables were analyzed using a three-way analysis of variances, with main effects of time (Pre vs. Post), age (children vs. adults), and sex (females vs. males).
RESULTS:
A significant time ́ age interaction was observed for MVIC Torque (p = 0.008), highlighting a decrease for adults (p = 0.002), while no change was observed for children (p = 0.780). No significant time effect was observed for RMS VL (p = 0.444). A significant time effect was observed for DJ RSI (p = 0.006), indicating a decrease, independently of the age group. This decline in RSI was associated with a decrease in DJ height (p = 0.045), and an increase in DJ CT (p = 0.013). Moreover, braking phase duration increased (p = 0.014), whereas no change was observed in propulsion phase duration (p = 0.436). All these modifications were observed independently of age or sex.
CONCLUSION:
Consistent with previous literature, children exhibited a smaller decrease in maximal force production capacity than adults. However, they showed a decrease in jumping performance, suggesting that in children, the stretch-shortening cycle may be more affected by fatigue induced by repeated jumping exercises than maximal force capacity.

REFERENCES:
1 Patikas, Williams, & Ratel, Exercise-induced fatigue in young people: advances and future perspectives, 2018
2 Komi, Stretch-shortening cycle: a powerful model to study normal and fatigued muscle, 2000