Effects of Lower-Limb Strength Training on Agility, Repeated Sprinting With Changes of Direction, Leg Peak Power, and Neuromuscular Adaptations of Soccer Players.

Hammami, M, Negra, Y, Billaut, F, Hermassi, S, Shephard, RJ, and Chelly, MS. Effects of lower-limb strength training on agility, repeated sprinting with changes of direction, leg peak power, and neuromuscular adaptations of soccer players. J Strength Cond Res 32(1): 37-47, 2018-We examined the effects on explosive muscular performance of incorporating 8 weeks strength training into the preparation of junior male soccer players, allocating subjects between an experimental group (E, n = 19) and a matched control group (C, n = 12). Controls maintained their regular training program, but the experimental group replaced a part of this schedule by strength training. Performance was assessed using running times (5, 10, 20, 30 and 40 m), a sprint test with 180° turns (S180°), a 9-3-6-3-9 m sprint with backward and forward running (SBF), a 4 × 5 m sprint test with turns, repeated shuttle sprinting, repeated changes of direction, squat (SJ) and counter-movement (CMJ) jumping, back half-squatting, and a force-velocity test. Electromyographic (EMG) activity of the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) muscles was recorded during jumping. Two-way ANOVA showed significant gains in E relative to C during the straight sprint (all distances). Scores of E increased substantially (p ≤ 0.01) on S4 × 5 and SBF and moderately on S180°. Leg peak power, SJ, and CMJ were also enhanced, with significant increases in EMG activity. However, repeated-sprint parameters showed no significant changes. We conclude that biweekly strength training improves key components of performance in junior soccer players relative to standard in-season training.