'Train less and still similarly improve?' Maturational growth is more influential than training engagement on performance indices development in volleyball.

Identifying factors which more or less account for performance improvement during developmental stages is essential for sports science knowledge and coaching practice. Accordingly, this study examined the longitudinal, changing, influences of Volleyball-specific Training Engagement (VTE) and Maturity Status on physical test performance development. Participants were N = 139 Swiss female competitive volleyball players, aged 10-14 years at baseline (M = 12.93, SD = 1.15 years). Annually for 3 years, participants completed the 9-3-6-3-9 Agility Sprint; Standing Long Jump [SLJ] and Jump & Reach test. Linear Mixed Models (LMMs) examined longitudinal independent and interactive relationships between VTE (hours/week) and Maturity Status (YPHV) with test performance indices. LMMs identified both interactive and independent relationships on test indices. Interactions highlighted the influence of VTE generally reduced during peak-post maturational stages (- 0.5-2.5 YPHV), while maturational growth was predominantly more influential on performance development. Findings identified that lowered weekly VTE during maturational peak-post growth periods led to equivalent performance development. With maturational growth more influential, findings highlight the potential to misattribute longitudinal performance development toward training engagement and question the benefit of heightened physiological-focused engagement circa-post PHV stages. However, such questioning may not necessarily apply to skill acquisition or technical-focused training.