Author(s): KOMM, Y., HELD, S., COMFORT, P., GEISLER, S., AUGSTE, C., Institution: UNIVERSITY OF AUGSBURG, Country: GERMANY, Abstract-ID: 1646

INTRODUCTION:
Resistance training is recognized as a safe and effective modality for enhancing physical performance and health in children and adolescents. While strength gains in youth are largely attributed to neural adaptations, the extent to which resistance training can induce morphological adaptations before the onset of puberty remains unclear. Accordingly, the purpose of this study was to compare the effects of a structured resistance training program on muscle hypertrophy and maximal strength between prepubertal and pubertal adolescents.
METHODS:
Sixty-eight male participants with no prior resistance training experience were classified as prepubertal (n = 39, 11.58 +/- 1.04 years) or pubertal (n = 29, 14.28 +/- 0.88 years) using maturity offset estimates and were subsequently randomly assigned to either a resistance training group or an active control group. The 9-week intervention consisted of two supervised training sessions per week. Strength was assessed using the isometric mid-thigh pull, and muscle thickness of the m. rectus femoris, m. vastus intermedius, and m. vastus lateralis was measured via ultrasound. Data were analyzed using linear mixed-effects models with fixed effects for time, maturity, intervention, and their interactions, and random intercepts for participants.
RESULTS:
The training program did not induce statistically significant hypertrophic adaptations, as no significant Time x Intervention interactions were observed for m. rectus femoris and m. vastus intermedius (F = 1.11, eta-p-sq = 0.01, p = 0.296) or for m. vastus lateralis (F = 0.12, eta-p-sq = 0.00, p = 0.734). In contrast, a significant Time x Intervention interaction (F = 4.23, eta-p-sq = 0.04, p = 0.042) was found for absolute peak force, indicating superior strength improvements in the training group compared with the control group. Importantly, no significant Time x Maturity x Intervention interactions were detected for absolute strength (F = 1.14, eta-p-sq = 0.01, p = 0.289), relative strength (F = 0.31, eta-p-sq = 0.00, p = 0.576), m. rectus femoris and m. vastus intermedius thickness (F = 1.65, eta-p-sq = 0.02, p = 0.203), or m. vastus lateralis thickness (F = 0.82, eta-p-sq = 0.01, p = 0.366), demonstrating that training responses were largely independent of maturational status. For relative peak force, the Time x Intervention interaction was not statistically significant (F = 3.15, eta-p-sq = 0.03, p = 0.079).
CONCLUSION:
These findings demonstrate that twice-weekly resistance training effectively enhances maximal strength in youth, while biological maturation shows no meaningful influence on either strength or hypertrophic adaptations.