Effects of leg contrast strength training on sprint, agility and repeated change of direction performance in male soccer players

BACKGROUND: Contrast training is a popular technique among individuals who are involved in dynamic sports, having as its goal an increase in dynamic muscular performance. It is characterized by the use of high and low loads in the same strength training session. The present investigation aimed to determine the effects of adding 8 weeks of contrast strength training (CSTP) to regular soccer practice in U-17 male soccer players during the competitive season. We hypothesized that CSTP would enhance their performance. METHODS: Subjects were divided randomly between a control group (CG, N.=12) and a contrast strength group (CSG, N.=19). The 2 groups trained together, controls followed the regular soccer program, which was replaced by a contrast strength training program for the experimental group. Performance was assessed before and after training, using 10 measures: 5-10-, 20- 30-. and 40-m sprints, a 4x5 m sprint (S4x5), a 9-36-3-9 in sprint with 180 degrees turns (S180), a 9-3-6-3-9 in sprint with backward and forward running (SBF), a Repeated-Shuttle-Sprint Ability Test (RSSA), and a Repeated Change of Direction Test (RCOD). RESULTS: CSG showed gains relative to controls in 5-m (P<0.000), 10-m (P<0.001), 20-m (P<0.001), 30-m (P<0.05) and 40-m (P<0.05) sprints. There were also significant gains in S180 degrees, SBF, and S4 x 5 agility tests (P<0.01), and all RCOD parameters (P<0.05) except RCOD-FI (P=0.055) but no significant change in any RSSA parameters. CONCLUSIONS: We conclude that biweekly contrast strength training can be commended to U-17 male soccer players as a means of improving many important components of athletic performance relative to standard in-season training.