Body Composition, Morphological and Neuromuscular Adaptations to Strength Training in Adolescent Male Athletes

Abstract

Monitoring the effects of maximum strength training programs conducted at various times in the periodized training cycle has been well documented in adult athletes, however, research on adolescent athletes is scarce. PURPOSE: The purpose of this study was to examine the effects of strength training at different periods in the annual training cycle on body composition, muscle morphology and neuromuscular performance in adolescent athletes. METHODS: Fourteen young male athletes (age 16.5 ± 1.1 y, height 171.3 ± 6.3 cm, body mass 65.0 ± 11.2 kg) performed a battery of tests before and after two specific strength training blocks; in-season and preparatory period. Tests included a DEXA whole-body scan, ultrasound of the vastus lateralis (VL), countermovement jump (CMJ), drop jump (DJ), isometric mid-thigh pull (IMTP), 20 m sprint and 3RM back squat. Meaningful differences following each training period were assessed using a magnitude-based inferences approach (effect sizes [ES]) with qualitative descriptors of change also calculated. RESULTS: Body composition showed trivial changes throughout both study periods. VL muscle thickness increased during the preparatory period (7.5% ± 3.3%). The CMJ variables showed no positive effects during the in-season period, however increases were seen in several of these variables during the preparatory period (e.g., jump height = 4.9% ± 3.1%; peak concentric power 5.3% ± 5.9%). Most DJ variables decreased during both training periods whilst IMTP measures showed improvements during the in-season period but remained stable during the preparatory period. Most 20 m sprint variables showed positive effects (e.g., 5 m split = 5.0% ± 4.7%) following the in-season period but no clear changes during the preparatory period. 3RM back squat showed a small increase following in-season training (7.5% ± 4.5%) and an even greater increase during the preparatory period (16.9% ± 5.2%). CONCLUSION: This study found that in adolescent male athletes a specific preparatory period strength program will likely result in greater improvements in dynamic lower body strength/power measures compared to one conducted in-season. In-season strength training may however have a more beneficial impact on sport specific physical performance variables such as sprint speed.