External workload patterns of injured elite Rugby League players before and after return to play

Abstract

Introduction: Return to play protocols (RTP) are imperative to ensuring injured athletes are adequately prepared to return to competition without re-injury. This study aimed to characterise the acute and chronic external workloads achieved by injured National Rugby League (NRL) athletes before and after RTP. Methods: Global positioning system (GPS) workload variables were investigated for 10 injured NRL athletes (n= 10, mean age 23.6 years, backs n=5, forwards n=5) two weeks before and after RTP. All athletes had sustained injuries of ≥14-day severity. GPS variables included total (TD) and high to very-high speed running (V-VHSR) distance (≥18km/h), accumulated absolute acceleration (acceleration load), and number of repeat high-intensity efforts (RHIE). Both acute (current week) and chronic (4-week mean) workload was determined for each observation week and analysed using linear mixed models that included time as a fixed effect, mean-centred injury severity as a covariate, and participant as a random effect. Effect magnitude was determined by percentage difference and 95% confidence interval. Results: Mean injury severity was 24 days (range: 14-49 days) and did not significantly moderate any acute (p≥0.614) or chronic (p≥0.272) workload variable. Time significantly affected acute TD, acceleration load, and RHIE (p≤0.038), but not VVHSR distance (p=0.070). Acute workload was highest during the week of RTP for all variables, with an 86 ±51% (TD), 41 ±37% (V-VHSR), 95 ±50% (acceleration load), and 116 ±72% (RHIE) increase compared to the previous rehabilitation week. Time significantly affected chronic RHIE (p=0.038), but not TD (p=0.315), V-VHSR (p=0.931), or acceleration load (p=0.213). Chronic workload was highest during the second week after RTP, with the three previous weeks being decreased by -13 to 17 ±18% (TD), -7 to -8 ±24% (V-VHSR), -14 to -18 ±17% (acceleration load), and -22 to -28 ±19% (RHIE). Discussion: The acute external workloads of injured NRL athletes demonstrated large increases during the RTP week which may increase the likelihood of re-injury. In contrast, chronic workload was relatively stable before and after RTP for all external workload variables except RHIE which was low until 2 weeks after RTP. Greater focus on RHIE workload in the lead up to RTP may be needed to ensure adequate exposure to that aspect of rugby league. Conflict of interest statement: my co-authors and I acknowledge that we have no conflict of interest of relevance to the submission of this abstract.