Background Risk of overuse injury is often monitored through the acute:chronic workload ratio (ACWR), where workload is the quantity or magnitude of loading cycles. However, weighting the loading magnitude by raising it to a power equal to the slope of the stress-life curve for the tissue may give a better estimate of the damage accumulated due to workload.
Objective To identify differences between injured and uninjured athletes for ACWR based on workload quantity, magnitude, and weighted magnitude.
Design Matched-pair cohort.
Setting Youth basketball.
Participants Fifty (25F, 25M; 16.5 years; 66.2 kg; 173.5 cm) basketball players on four high school teams.
Assessment of Risk Factors A wearable device (VERT® Classic) was used to record jump count and jump height for all participants during practices and games throughout the 17-week season.
Main Outcome Measurements Ten athletes were diagnosed with either patellar or Achilles tendinopathy, and were matched by height and weight with teammates that had no injuries. ACWRs were calculated weekly for three workload types: jump count, jump height, and jump height weighted for tendon damage. Paired t-tests compared mean ACWR of injured and uninjured athletes for each measure of workload.
Results There was no significant effect of injury status for jump count ACWR (injured mean (95% CI): 1.077 (1.011–1.132), uninjured: 1.025 (0.906–1.162); p=0.121) or jump height ACWR (injured: 1.079 (1.015–1.136), uninjured: 1.018 (0.886–1.155); p=0.081). ACWR with jump height weighted for tendon damage was higher for injured (1.075 (0.929–1.243)) compared to uninjured athletes (0.939 (0.729–1.266); p=0.045).
Conclusions Athletes with patellar or Achilles tendinopathy have a greater ACWR than uninjured athletes when workload is calculated as jump height weighted based on tendon properties. This result was not apparent when ACWR was based on the number of loading cycles or the unweighted loading magnitude. Future research into overuse injury prevention should consider the damage accumulation in biological tissue due to repetitive loading.