The Same Story or a Unique Novel? Within-Participant Principle Component Analysis of Training Load Measures in Professional Rugby Union Skills Training.

PURPOSE: The study aimed to identify which combination of external and internal training load (TL) metrics capture similar or unique information for individual professional players during skills training in rugby union using principal component analysis (PCA). METHOD: TL data were collected from twenty-one male professional rugby union players across a competitive season. This included PlayerLoad™, total distance (TD), and individualised high-speed distance (HSD; >61% maximal velocity; all external TL) obtained from a micro-technology device worn by each player (Optimeye X4, Catapult Innovations, Melbourne, Australia) and the session-rating of perceived exertion (sRPE; internal TL). PCA was conducted on each individual to extract the underlying combinations of the four TL measures that best describe the total information (variance) provided by the measures. TL measures with PC "loadings" (PCL) above 0.7 were deemed to possess well-defined relationships with the extracted PC. RESULTS: The findings show that from the four TL measures, the majority of an individual's TL information (1st PC: 55 to 70%) during skills training can be explained by either sRPE (PCL: 0.72 to 0.95), TD (PCL: 0.86 to 0.98) or PlayerLoad™ (PCL: 0.71 to 0.98). HSD was the only variable to relate to the 2nd PC (PCL: 0.72 to 1.00), which captured additional TL information (+19 to 28%). CONCLUSIONS: Findings suggest practitioners could quantify the TL of rugby union skills training with one of PlayerLoad™, TD, or sRPE plus HSD whilst limiting omitted information of the TL imposed during professional rugby union skills training.