Strahorn, J, Serpell, BG, McKune, A, and Pumpa, KL. Effect of physical and psychosocial interventions on hormone and performance outcomes in professional rugby union players: a systematic review. J Strength Cond Res 31(11): 3158–3169, 2017—This systematic review investigates the acute effects of physical or psychosocial interventions on testosterone and cortisol responses in elite male rugby union players, and the subsequent association with physical performance areas (e.g., strength, power, sprint performance) or key performance indicators (e.g., coach-identified skills). Medline (via EBSCO), SPORTDiscus, Web of Science, InformIT, ProQuest, Cochrane, and Scopus were searched for relevant articles. Nine articles met the inclusion criteria, with 6 articles examining the effect of speed, strength or power training, and the remaining 3 psychosocial interventions. Quality assessment of the articles as determined by their PEDro score was either 6 or 7 out of 11. This review found that both physical and psychosocial interventions can alter testosterone and cortisol, and physical performance areas important for rugby union are affected by these changes. The limited literature in the field supports the notion that physical interventions of short duration and high intensity, and psychosocial interventions that create a positive environment may elicit a hormonal response that is associated with favorable performance outcomes. Studies that reported psychosocial interventions suggest that testosterone and cortisol may be altered in elite rugby players without metabolic stress, something of great interest to elite athletes and coaches who are looking to elicit a performance advantage without increasing athlete load. Overall, this review identified that when the testosterone responses to an intervention are notably greater than that of cortisol, favorable outcomes are likely. Further research is required to improve our understanding on how to best manipulate training to induce these favorable changes.