Velocity-Based Strength Assessment in Youth Athletes: Effects of Maturation Stage and Repeated Testing on Reliability

Moraga-Maureira, E, González, JA, and García-Ramos, A. Velocity-based strength assessment in youth athletes: Effects of maturation stage and repeated testing on reliability. J Strength Cond Res 40(4): 406-413, 2026-Resistance training in youth, once clouded by misconceptions about safety and development, is now widely endorsed for its role in enhancing health, motor performance, and athletic skills-highlighting the need for reliable assessment protocols to guide its implementation. This study aimed to evaluate the reliability of velocity-based strength assessment protocols in youth athletes and to examine how testing frequency (1 to 4 sessions) and maturation stage (pre-/circa- vs. postpeak height velocity [PHV]) influence their consistency. Thirty-four young male athletes-16 pre-/circa-PHV (age = 13.2 ± 0.8 years) and 18 post-PHV (age = 15.1 ± 1.0 years)-completed 1 familiarization session followed by 4 identical testing sessions. The testing protocol involved 4 incremental loading conditions during the squat exercise. Velocity values at fixed absolute loads showed acceptable absolute (coefficient of variation [CV] ≈ 7.0%) and moderate relative reliability (intraclass correlation coefficient [ICC] ≈ 0.67), whereas load-velocity relationship variables demonstrated acceptable absolute (CV ≈ 9.1%) and good relative reliability (ICC ≈ 0.75). Younger athletes (CV ≈ 7.6%) demonstrated reliability indices comparable with those observed in post-PHV athletes (CV ≈ 8.3%). Although reliability was acceptable from the first session (CV ≈ 9.5%), progressive improvements were observed in subsequent sessions (CV ≈ 8.8 and 6.2%). These findings support the use of both velocity at fixed loads and load-velocity profiling in youth athletes, suggesting that these protocols can be reliably implemented from as early as 12 years of age, provided that athletes are adequately familiarized with the procedures.