Abstract
Introduction: Rugby is a contact sport characterised by intermittent high- and low-intensity efforts requiring advanced physical capabilities and strategic decision making. This study aims to determine the strength of the relationships between strength, power and acceleration in professional rugby union players.
Literature Review: Rugby union requires high-intensity accelerative ability as players typically do not sprint beyond 28 metres during maximal efforts. As 10-metre time also correlates with many key performance indicators, it is viewed as an important metric in rugby union. High-intensity accelerative performance has multiple influencing factors, including strength, power, biomechanical and technical aspects of sprinting. Accordingly, strength and power development are often key training targets in part to enhance a player’s ability to accelerate over short distances.
Validation study: Five GPS units were attached to a wheeled trolley system and pulled the units from a stationary start over a 10-metre distance. GPS-derived 10-m times calculated using MATLAB were validated against timing gates and video analysis, demonstrating strong agreement after adjustment (r = 0.98).
Research Design: Acceleration, power and strength were recorded across a Super Rugby season for one Super Rugby team. Strength was assessed four times throughout the season, while standing start GPS 10-metre time (using STATSports Apex 10-Hz), and power (using VALD Force Deck Lite) were measured weekly throughout the season. The relationship between variables were explored using (1) pairwise scatter plots with fitted linear regression lines, (2) change from baseline comparisons to examine how changes in strength and power related to changes in acceleration over time and (3) linear mixed effects models to account for repeated measurements within individuals across the season.
Results: The relationship between acceleration and power showed no relationship (r = 0.19), and neither did the relationship between acceleration and strength (r = 0.11). The delta-delta analysis revealed no correlation between either strength and acceleration (r = 0.05) or power and acceleration (r = 0.04); however, it did reveal a moderate correlation between strength and power (r = 0.43).
Discussion: Measuring acceleration, power and strength across a professional rugby union season provides valuable insights into a population that is seldom studied. Furthermore, understanding that the relationship between strength, power and acceleration identifies that the relationship may be more complex than previously understood. Strength may be important for acceleration up to a certain critical point, and beyond that, strength does not contribute anymore towards acceleration. Additionally, the lack of specificity using a countermovement jump as a predictor for acceleration may indicate that a broad jump could be a slightly better predictor of acceleration.