The Landing Error Scoring System (LESS) and Lower Limb Power Profiles in Elite Rugby Union Players

Background
The Landing Error Scoring System (LESS) is a clinical test that assesses landing biomechanics during a drop-jump task. Performance measures such as jump height, power, contact time and reactive strength index are used commonly in athletic populations. Comparing results from the LESS against these performance measures has not been reported in elite rugby union.
Purpose
To report i.) normative LESS scores for elite rugby union players ii.) correlations between LESS scores and performance measures and iii.) differences in performance measures between LESS scoring groups. A secondary purpose was to report the intra- and inter-rater reliability of the LESS test when used in elite rugby union players.
Study Design
Cross-sectional design.
Methods
Thirty-six male, elite rugby union players participated. Each participant completed three trials of the LESS and performance measures were recorded concurrently using the OptojumpTM. LESS trials were scored independently by the authors. Statistical analyses were used to confirm reliability, data normality, and between group differences (p<0.05).
Results
The LESS test is a reliable testing tool in elite rugby union players (excellent intra- (ICC=0.96) and inter-rater (ICC=0.94) reliability). One player demonstrated an excellent LESS score, six players had good scores, eight players moderate scores and the majority of the group, 21 players, scored poorly. LESS scores were correlated to contact time (r = -0.461, p = 0.005) only. Participants with moderate to poor LESS scores (a score ≤5) produced greater power (p=0.036, η2 = 0.139), contact time (p=0.002, η2 = 0.268) and reactive strength index (p=0.016, η2 = 0.180). There were no differences in jump height (p=0.842) between players scoring excellent to good and moderate to poor.
Conclusion
The results of the current study demonstrate excellent intra- and inter-rater reliability for the LESS, supporting its use as a clinical assessment tool in elite rugby union players. The majority of players presented with moderate to poor LESS scores, indicating an area of concern in this population. Participants scoring moderate to poor in the LESS recorded significantly higher power and reactive strength index, increased contact time but not jump height. This suggests participants with high-risk landing biomechanics may also produce higher performance measures, but these do not necessarily result in an improved jump height.