A Novel Case Study Approach to the Investigation of Leg Strength Asymmetry and Rugby League Player’s Multidirectional Speed

Leg strength and multidirectional speed qualities have repeatedly been linked with increased performance during Rugby League (RL) match play and associated with career attainment. However, very little of this evidence for strength has been gained through unliteral measurements with no study available that has examined the impact of strength asymmetry, in this population, on speed qualities in RL players. Therefore, this study examined the association between unilateral strength and as a novel development the subject with the most extreme asymmetry was identified for further analysis. 50 RL players undertook the rear foot elevated split squat five repetition maximum, 20 m linear sprint and modified 505 change of direction test. The mean leg strength for the group was 88.92 ±12.59 kg, when divided by body weight the mean relative strength (REL) was 1.03 ±0.17 kg/kg and the mean asymmetry was 3.21 ±5.70 %. The participant with the greatest asymmetry (subject A) had an imbalance of 33% and a mean leg strength of 75 kg (REL = 0.78 kg/kg) and a body mass one standard deviation above the group mean. Analysis of the group’s data and that of subject A did not indicate that leg strength asymmetry was either frequent or harmful, with respect to speed performance. However, relative leg strength was associated with both improved linear and multidirectional speed. Practitioners are recommended to prioritise the development of relative leg strength and disregard the aspiration for between leg performance symmetry.