title: Effects of leg contrast strength training on sprint, agility and repeated change of direction performance in male soccer players.
abstract: 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 9-3-6-3-9 m sprint with 180° turns (S180), a 9-3-6-3-9 m 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°, 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.
authors.affiliation: Unit of Research (UR17JS01) &quot;Sport Performance, Health and Society&quot;, Higher Institute of Sport and Physical Education, Ksar Saîd, University of &quot;La Manouba&quot;, Tunis, Tunisia.
authors.forename: Mehréz
authors.initials: M
authors.lastname: Hammami
authors.affiliation: Unit of Research (UR17JS01) &quot;Sport Performance, Health and Society&quot;, Higher Institute of Sport and Physical Education, Ksar Saîd, University of &quot;La Manouba&quot;, Tunis, Tunisia.
authors.forename: Yassine
authors.initials: Y
authors.lastname: Negra
authors.affiliation: Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, ON, Canada.
authors.forename: Roy J
authors.initials: RJ
authors.lastname: Shephard
authors.affiliation: Unit of Research (UR17JS01) &quot;Sport Performance, Health and Society&quot;, Higher Institute of Sport and Physical Education, Ksar Saîd, University of &quot;La Manouba&quot;, Tunis, Tunisia - csouhaiel@yahoo.fr.|Higher Institute of Sport and Physical Education of Ksar Said, University of &quot;La Manouba&quot;, Tunis, Tunisia.
authors.forename: Mohamed-Souhaiel
authors.initials: MS
authors.lastname: Chelly
mesh_terms: D000293:Adolescent; D054874:Athletic Performance / Q000502:physiology*; D016022:Case-Control Studies; D005080:Exercise Test / Q000379:methods; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D011897:Random Allocation; D055070:Resistance Training / Q000379:methods*; D012420:Running / Q000502:physiology; D012916:Soccer / Q000502:physiology*