The effects of in-season, low-volume sprint interval training with and without sport-specific actions on the physical characteristics of elite academy rugby league players.

Purpose: To determine the utility of a running and rugby-specific, in-season sprint interval interventions in professional rugby league players. Methods: Thirty-one professional academy rugby players were assigned to a rugby-specific (SITr/s, n = 16) or running (SITr, n = 15) sprint interval training group. Measures of speed, power, change of direction (CoD) ability, prone Yo-Yo IR1 performance and heart rate recovery (HRR) were taken before and after the 2-week intervention as were sub-maximal responses to the prone Yo-Yo IR1. Internal, external and perceptual responses were collected during SITr/s/SITr, with wellbeing and neuromuscular function assessed before each session. Results: Despite contrasting (possible to most likely) internal, external and perceptual responses to the SIT interventions, possible to most likely within-group improvements in physical characteristics, HRR and sub-maximal responses to the prone Yo-Yo IR1 were observed after both interventions. Between-group analysis favoured the SITr/s intervention (trivial to moderate) for changes in 10 m sprint time, CMJ, change of direction and medicine ball throw as well as sub-maximal (280-440 m) high metabolic power, PlayerLoad™ and acceleratory distance during the prone Yo-Yo IR1. Overall changes in wellbeing or neuromuscular function were unclear. Conclusion: Two-weeks of SITr/s and SITr was effective for improving physical characteristics, HRR and sub-maximal responses to the prone Yo-Yo IR1, with no clear change in wellbeing and neuromuscular function. Between-group analysis favoured the SITr/s group, suggesting that the inclusion of sport-specific actions should be considered for in-season conditioning of rugby league players.