The relationship between horizontal scrum force and 1RM squat in professional rugby union players

Abstract

Introduction: Horizontal force development plays a large role in rugby union, but gym-based resistance exercises such as the barbell back squat, a vertical force production exercise, is a commonly used key performance indicator of lower body strength for scrummaging. This project employed an instrumented scrumtruk to measure the isometric horizontal scrum specific force compared to the maximal squat.

Methods: Data was collected for one repetition maximum barbell back squat (1RM) and peak (PeakST) and 10-second average (10sAvgST) isometric force on a scrumtruk for 15 professional rugby union forwards across four data collection points throughout a super rugby season. These four points were baseline (start of the pre-season), late pre-season, early in-season and late in-season, with each period separated by approximately six weeks. The analysis involved correlations for the forwards as a whole and the different subgroups of tight forwards, front row, props, and representative props. Standardised differences in 1RM, and PeakST, and 10sAvgST force for these groups across the key data collection points of the season were also determined.

Results: Correlations between 1RM and PeakST force (0.133, small), 1RM and 10sST (0.097, small), PeakST and 10sAvgST force (0.926, strong) were found for all forwards across the season. Better correlations for 1RM were detected with props and representative props. Small and very large magnitude increases were observed during pre-season for 1 RM squat and PeakST and 10sAvgST respectively, followed by significant decreases from pre-season to in-season for all variables. Small increases were shown from early to late in-season. Overall, 1RM decreased, while PeakST and 10sAvgST force showed large and moderate increases from baseline to late in-season.

Conclusion: Surprisingly despite the promotion of heavy squatting for scrummaging there was only a small relationship between 1RM squat and both PeakST and 10sAvgST in professional rugby players across a competitive season. Rugby conditioners should consider including various specific horizontal isometric training options alongside the squat to facilitate optimal scrummaging force development.