Understanding stretch shorten cycle capability in adolescence across the different maturational stages
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Stretch-shorten cycle (SSC) capability is fundamental to many sporting activities. To date, there have been numerous studies on the SSC potentiation in adults, however, there are very few studies of SSC potentiation in youths. For youths, the biological maturity may not necessarily coincide with the chronological age. Biological maturity for youths can be classified as either in the pre-puberty, puberty or post-puberty maturation stage. The limited literature to-date has shown that youths at different biological maturity stages have different muscle characteristics and development. This study aims to investigate SSC potentiation at the different biological maturity stages. Such a study will provide evidence as to a possible window of trainability for the development of SSC. Using a force plate, this study measured and compared the countermovement jump and squat jump capability of a total of 209 youths (male, =101, females, =108) aged between 11 to 17 years of age, from the Singapore Sports School. These youth were categorized into the three maturational groups. When compared, gender differences were observed and these differences increased with maturity. Differences in SJ performance across the maturational groups were different as compared to CMJ performance, where no significant maturational differences were observed. It was observed that there was a significant difference in the eccentric utilization ratio for peak force across the maturational stages for both genders. However differences for jump height were not significant. It would seem that concentric force/power capabilities (i.e. SJ performance) are more likely to be influenced by maturation than eccentric force and power. Furthermore it appears that the eccentric capability and thus SSC augmentation is optimal around pubescence and diminishes to some extent with maturity. These changes are most likely best explained by growth related factors (i.e. increase in bone length and loss of tissue extensibility around PHV) as well as maturational factors (i.e. changes in tissue compliance/stiffness). Given these findings it would seem that pre-pubescent athletes would react favorably to plyometric type training given their eccentric force power capability and proposed compliance of their tissues. This study concluded with recommendations for youth coaches to consider. Since vertical stiffness was found to increase with age, a good stretching routine is recommended during this sensitive growth period. Coaches might want to also consider focusing on eccentric training that focuses on full range of motion, correct alignment and stability.