Effects of long-term volleyball training on multimodal responses in adolescent female athletes: a follow-up study

BACKGROUND: The aim of this study was to examine the effects of long-term (10 months) volleyball training on biochemical responses in adolescent female athletes since the cumulative effects of chronic training on this population are not yet clear. METHODS: Twenty-one adolescent female volleyball players competing at the national level served as the participants. All athletes carried out volleyball training, which consisted of ball handling, specialized drills, and practical game-style exercises, including physical training in the school gymnasium. The average training cycle consisted of 6 days per week, with a total of about 2 to 2.5 hours of volleyball training per day. In order to determine the cumulative effects on autonomic, immune, renal function and bone resorption, salivary and urinary samples were collected before volleyball training on 3 consecutive days (days 1, 3 and 5) at months 0 and 10, respectively. RESULTS: No significant changes in body mass, salivary secretion rate, urinary albumin, L-type fatty acid binding protein and type I collagen cross-linked N-telopeptide concentration were found. In contrast, significant decreases were noted in salivary a-amylase activity (% change:-22.9), total protein (%change:-21.4), and immunoglobulin A concentration (% change:-20.1). CONCLUSIONS: The results of this study imply that the autonomic function after chronic volleyball training in adolescent female athletes may be enhanced due to training adaptation, although the immune function may be attenuated as a result of cumulative overtraining. Moreover, longterm volleyball training in adolescent female athletes appears to suppress bone resorption and not to induce cumulative damage to renal function.