Mechanical load monitoring in rugby: limitations and future perspectives.

Purpose: Quantifying mechanical work in rugby is essential for improving performance, managing fatigue, and informing load monitoring practices. Traditional metrics that assess acceleration and speed separately fail to capture the interaction between these parameters during gameplay. This study presents an external power approach based on individual acceleration-speed profiles (ASP) to provide an integrated description of players' external work. Methods: Data were collected from 51 professional rugby matches across two seasons. Traditional metrics and external power indicators derived from ASPs were examined to evaluate mechanical demands. This approach combines acceleration and speed into a unified framework, enabling an individualised analysis of high external power actions. Results: Mechanical indicators showed differences between positional groups, with backs exhibiting higher values of high external power actions and external work than forwards. Traditional acceleration thresholds appeared to misclassify some high-demand efforts, particularly those initiated at higher running speeds. The external power approach provided an alternative representation of high-intensity locomotor demands by accounting for the interaction between speed and acceleration. Conclusion: The external power approach represents an additional framework for assessing running-related player-specific mechanical load in rugby, addressing limitations of traditional metrics based on fixed thresholds. It may support a more contextualised interpretation of high-intensity locomotor efforts and should be considered complementary to existing GPS-derived indicators. Future research should investigate its relationship with physiological and performance outcomes, as well as its integration with contact-based demands in rugby.