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Low chronic workload and the acute:chronic workload ratio are more predictive of injury than between-match recovery time: a two-season prospective cohort study in elite rugby league players
  1. Billy T Hulin1,2,
  2. Tim J Gabbett3,4,
  3. Peter Caputi5,
  4. Daniel W Lawson6,
  5. John A Sampson1
  1. 1Centre for Human and Applied Physiology, School of Medicine, University of Wollongong, Wollongong, New South Wales, Australia
  2. 2Football Department, St. George Illawarra Dragons Rugby League Football Club, Wollongong, New South Wales, Australia
  3. 3School of Exercise Science, Australian Catholic University, Brisbane, Queensland, Australia
  4. 4School of Human Movement Studies, University of Queensland, Brisbane, Queensland, Australia
  5. 5School of Psychology, University of Wollongong, Wollongong, New South Wales, Australia
  6. 6Baimed Physiotherapy and Sports Injury Clinic, Wollongong, New South Wales, Australia
  1. Correspondence to Billy T Hulin, Football Department, St. George Illawarra Dragons RLFC, 1/5 Burelli Street, Wollongong, NSW 2500, Australia; billyhulin{at}hotmail.com

Abstract

Background Between-match recovery time, and acute and chronic workloads likely affect subsequent match-injury risk in elite rugby league players.

Methods Workloads of 28 players throughout two seasons were calculated during short (<7 days), and long (≥7 days) between-match recovery times. ‘Acute’ workloads (1 week) greater than ‘chronic’ workloads (4-week rolling average acute workload) resulted in acute:chronic workload ratios above 1.

Results No difference was found between the match-injury risk of short and long between-match recovery periods (7.5±2.5% vs 6.8±2.5%). When players had a short recovery between matches, high chronic workloads (18.9–22.0 km) were associated with a smaller risk of match injury than chronic workloads <18.9 km (relative risk (RR) range 0.27–0.32 (CI 0.08 to 0.92); likelihood range 90–95%, likely). Players who had shorter recovery and acute:chronic workload ratios ≥1.6, were 3.4–5.8 times likely to sustain a match injury than players with lower acute:chronic workload ratios (RR range 3.41–5.80 (CI 1.17 to 19.2); likelihood range 96–99%, very likely). Acute:chronic workload ratios between 1.2 and 1.6 during short between-match recovery times demonstrated a greater risk of match injury than ratios between 1.0 and 1.2 (RR=2.88 (CI 0.97 to 8.55); likelihood=92%, likely).

Conclusions Contrary to the philosophy that high workloads and shorter recovery equate to increased injury risk, our data suggest that high and very-high chronic workloads may protect against match injury following shorter between-match recovery periods. Acute:chronic workload ratios ∼1.5 are associated with a greater risk of match injury than lower acute:chonic workload ratios. Importantly, workloads can be manipulated to decrease the match-injury risk associated with shorter recovery time between matches.

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