Slow-Speed Compared With Fast-Speed Eccentric Muscle Actions Are Detrimental to Jump Performance in Elite Soccer Players In-Season.

Purpose: To examine the effect of fast- versus slow-speed eccentric-muscle-action resistance training on lower-body strength, vertical jump height, sprint speed, and change-of-direction performance in elite soccer players during a competitive season.

Methods: Twenty-two elite soccer players, from a single team, were randomly assigned to groups that undertook either 1- (fast speed) or 4-second (slow speed) eccentric resistance training during the in-season period. A 5-week program was conducted during an elite top-division European League soccer season.