Transfer effect of strength and power training to the sprinting kinematics of international rugby players
Lippincott, Williams and Wilkins
Faculty of Health, Engineering and Science
Centre for Exercise and Sports Science Research
Increasing lower-body strength is often considered to be important for improving the sprinting speed of rugby players. This concept was examined in a group (n = 40) of international rugby players in a 2-part study. The players were tested for body mass (BM), 1 repetition maximum power clean (PC), and front squat, as well as triple broad jump and broad jump. In addition, speed over 40 m was tested, with timing gates recording the 0- to 10-m and 30- to 40-m sections to assess acceleration and maximal velocity. Two video cameras recorded the 2 splits for later analysis of sprinting kinematics. The players were divided into a fast group (n = 20) and a slow group (n = 20) for both acceleration and maximal velocity. In the second part of the study, a group (n = 15) of players were tracked over a 1-year period to determine how changes in strength corresponded with changes in sprinting kinematics. The fast groups for both acceleration and maximal velocity showed greater levels of strength (d = 0.5-1.8), lower ground contact times (d = 0.8-2.1), and longer stride lengths (d = 0.5- 1.3). There was a moderate improvement over 1 year in PC/BM (0.08 kg·kg-1, p = 0.008, d = 0.6), and this had a strong relationship with the change in maximal velocity stride length (r = 0.70). Acceleration stride length also had a large improvement over 1 year (0.09 m, p = 0.003, d = 0.81). Although increasing lower-body strength is likely important for increasing sprinting speed of players with low training backgrounds, it may not have the same effect with highly trained players.