INTRODUCTION: Transient fatigue, defined as a temporary reduction in the ability to maintain high-intensity running, is a common phenomenon in team sports [1]. In rugby league, this transient fatigue is also accompanied by reduced skill quality, which could have important implications for match outcomes [2]. The large match-to-match variability in running metrics in rugby league has meant that simulation protocols are often used to explore changes in performance owing to an intervention. However, to our knowledge, no simulation has attempted to replicate transient fatigue. Accordingly, the aim of this study was to determine if rugby league transient fatigue can be simulated, and whether this fatigue is associated with a reduction in skill. METHODS: Nine sub-elite rugby players consented to participate in the study (age = 21 ± 2 yrs, stature = 178.4 ± 6.8 cm, body mass = 86.2 ± 14 kg). With institutional ethics approval, participants completed two abbreviated (~23 min) versions of the Rugby League Movement Simulation Protocol for Interchanges (RLMSPi) in a randomised cross-over design. One trial involved 4x ~5.7 min blocks of repeated activity (CON), as previously described [3]. In another trial (INT), the second ~5.7 min block was intensified to incorporate six more sprints and three more contacts. Participants wore a 10Hz GPS throughout the protocol, and completed a passing test (comprising 12 passes to different targets) every ~5.8 min. RESULTS: Heart rate (~5.2 b/min), rating of perceived exertion (~2.7), blood lactate (~4.7 mmol/L), distance covered (~115.9 m) and high-intensity running > 14 km/h (~56.1 m) all increased during the intensified ~5.7 min relative to CON (P < 0.05). The intensified period resulted in a decline in high-intensity running in the subsequent ~5.7 min compared to CON (~17.7 m), as well as a greater time to compete the rugby passing test (CON = 51.5 ± 3.6 s, INT = 57 ± 5.7 s; P < 0.05). CONCLUSION: This study has demonstrated that the transient fatigue reported in rugby league matches can be simulated using an adapted rugby league simulation protocol. Furthermore, as with matches, this transient fatigue was accompanied by an impairment in technical performance. Future studies can use this simulation to explore the effects of training and nutritional interventions on transient fatigue in rugby league.
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