An examination of a modified Yo-Yo test to measure intermittent running performance in rugby players

This is an Accepted Manuscript of an article published by Taylor & Francis in European Journal of Sport Science on 17/06/2018, available online: https://doi.org/10.1080/17461391.2018.1475509This study examined how starting each shuttle in the prone position altered the internal, external and perceptual responses to the Yo-Yo Intermittent Recovery Test Level 1. Using a randomized crossover design, 17 male rugby players completed the Yo-Yo IR1 and prone Yo-Yo IR1 on two separate occasions. External loads (via microtechnology), V ̇O2, heart rate (HR), rating of perceived exertion (RPE) were measured at 160, 280 and 440 m (sub-maximal) and when the test was terminated (peak). The pre-to-post change in blood lactate concentration (∆[La]b) was determined for both tests. All data were analysed using effect sizes and magnitude-based inferences. Between-trial differences (ES 90%CL) indicated total distance was most likely lower (-1.87 0.19), whereas other measures of peak external load were likely to very likely higher during the prone Yo-Yo IR1 (0.62-1.80). Sub-maximal RPE was likely to most likely higher (0.40-0.96) and peak RPE very likely higher (0.63 0.41) in the prone Yo-Yo IR1. The change in [La]b was likely higher after the prone Yo-Yo IRl. Mean HR was possibly lower at 440 m (-0.25 0.29) as was peak HR (-0.26 0.25) in the prone Yo-Yo IR1. "V" ̇E, "V" ̇O2 and "V" ̇CO2 were likely to very likely higher at 280 and 440 m (ES = 0.36-1.22), while peak values were possibly to likely higher (ES = 0.23-0.37) in the prone Yo-Yo IR1. Adopting a prone position during the Yo-Yo IR1 increases the internal, perceptual and external responses, placing greater emphasis on metabolically demanding actions typical of rugby