  Injuries occur when an athlete performs a greater amount of activity
(workload) than what their body can absorb. To maximize the positive effects of
training while avoiding injuries, athletes and coaches need to determine safe
workload levels. The International Olympic Committee has recommended using the
acute:chronic workload ratio (ACRatio) to monitor injury risk, and has provided
thresholds to minimize risk. However, there are several limitations to the
ACRatio which may impact the validity of current recommendations. In this
review, we discuss previously published and novel challenges with the ACRatio,
and possible strategies to address them. These challenges include 1)
formulating the ACRatio as a proportion rather than a measure of change, 2) its
use of unweighted averages to measure activity loads, 3) inapplicability of the
ACRatio to sports where athletes taper their activity, 4) discretization of the
ACRatio prior to model selection, 5) the establishment of the model using
sparse data, 6) potential bias in the ACRatio of injured athletes, 7)
unmeasured confounding, and 8) application of the ACRatio to subsequent
injuries.
