Real world fatigue testing in professional rugby union: A systematic review and meta-analysis

Background: Professional rugby union is a high-intensity contact sport with position specific high training and match volumes across a season that may lead to periods of fatigue if above a typically experienced threshold. This study assesses the influence of match-play and/or training on fatigue levels in rugby union players. Objective: To perform a systematic review and meta-analysis of measures used to assess fatigue status in male professional rugby union players. Methods: Using electronic databases (PubMed, SPORTDiscus, Web of Science, Cochrane Library, EMBASE, and MEDLINE), a systematic review of fatigue testing in rugby union was conducted on 1) neuromuscular, 2) subjective self-report, 3) biochemical and 4) heart rate derived measures. Results: Thirty-seven articles were included in this systematic review, of which 14 were further included in a meta-analyses. The results of the meta-analysis revealed small, yet not significant, decreases in countermovement jump height immediately after (ES = -0.29; 95% CIs = -0.64 to 0.06), 24 hours (ES = -0.43; 95% CIs = -3.99 to 3.21), and 48 hours (ES = -0.22; 95% CIs = -0.47 to 0.02) after exposure to rugby union match-play or training. Reported wellness (ES = -0.33; 95% CIs = -1.70 to 1.04) and tiredness (ES = -0.14; 95% CIs = -1.30 to 1.03) declined over a period of a few weeks (however, the results were not-statistically significant), meanwhile muscle soreness increased (ES = 0.91; 95% CIs = 0.06 to 1.75) within the 96 hours after the exposure to rugby union match-play or training. Finally, while cortisol concentrations (ES = 1.87; 95% CIs = -1.54 to 5.29) increased, testosterone declined (ES = -1.54; 95% CIs = -7.16 to 4.08) within the 24 hours after the exposure. However, these results were not-statistically significant. Conclusions: Subjective measures of muscle soreness can be used to assess fatigue after match play and training in rugby union players. Within and between-study variability for countermovement jump height, biochemical markers and heart-rate derived measures means the utility (practical application) of these measures to assess fatigue in professional rugby union players after matches and training is unclear