Multiple Measures are Needed to Quantify Training Loads in Professional Rugby League

Abstract

This study aims to investigate the effect of training mode (conditioning and skills) on multivariate training load relationships in professional rugby league via principal component analysis. Four measures of training load (internal: heart rate exertion index, session rating of perceived exertion; external: PlayerLoad™, individualised high-speed distance) were collected from 23 professional male rugby league players over the course of one 12 wk preseason period. Training was categorised by mode (skills or conditioning) and then subjected to a principal component analysis. Extraction criteria were set at an eigenvalue of greater than 1. Modes that extracted more than 1 principal component were subject to a varimax rotation. Skills extracted 1 principal component, explaining 57% of the variance. Conditioning extracted 2 principal components (1st: internal; 2nd: external), explaining 85% of the variance. The presence of multiple training load dimensions (principal components) during conditioning training provides further evidence of the influence of training mode on the ability of individual measures of external or internal training load to capture training variance. Consequently, a combination of internal and external training-load measures is required during certain training modes.

The Relationships Between Internal and External Measures of Training Load and Intensity in Team Sports: A Meta-Analysis

“…While some of this could be attributed to individual characteristics or simply noise (either measurement error or biological variation), it may well indicate the omission of potentially valuable information contained both within and between training load measures when using a single item to represent internal or external constructs. We have discussed the implications of our findings in relation to the specific measures used, yet our data could also support the notion that multiple measures are needed to accurately quantify internal and external training loads in team sports [31,32,73]. Since it is already common practice to routinely collect several training load measures [85]-which are often based on perceived clinical or practical importance [26]-a pertinent challenge is understanding the most parsimonious and statistically sound variable selection that best represent 'internal' and 'external' constructs for the differing training modes undertaken by team-sport athletes [31,32].…”

“…These may include, but are not limited to: within- [48] or between-athlete [105] correlations, generalized estimating equations [100], mixed effect linear modelling [106] or dimension reduction techniques (e.g. principal component analysis [31,32]).…”

“…The corresponding authors of studies without the required data or where further clarity was necessary were contacted by email [19,[22][23][24][25][26][29][30][31][32] and we received all relevant information from these studies. Graph digitizer software (DigitizeIt, Brainschweig, Germany) was used to obtain data from two studies where descriptive [28] and correlation [30] data were only available in figures.…”

“…The relationships between internal and external loads in team-sport athletes have received much attention to date, with a myriad of studies reporting correlation magnitudes ranging from trivial to very large [19,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. The dispersion in these effect sizes would suggest that internal-external load relationships are not yet fully understood, which has led some authors to question the validity of specific internal load measures [37,38].…”

“…Abbreviations. %HRmax: percentage of maximum heart rate, AF: Australian Football, BB: Basketball, Banister's: exponentially weighted TRIMP calculated according to Banister [44], CR10: Borg's Category-Ratio 10 (deci-Max) scale [42], CR100: Borg's Category-Ratio 100 (centi-Max) scale [42], Edwards: summated zones TRIMP calculated according to Edwards [45], GPS: global positioning system, MEMS: micro-electrical mechanical system, Modified Edwards: summated zones TRIMP calculated according to Edwards [45], but utilising arbitrary exponential weighting factors [32], RL: Rugby League, SD: standard deviation, SO: Soccer, sRPE: session rating of perceived exertion, sRPE-B: session rating of perceived breathlessness, sRPE-L: session rating of perceived leg muscle exertion, sRPE-TL: session rating of perceived exertion training load, SSG: small-sided games, TRIMP: heart-rate-derived training impulse. Abbreviations.…”