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Is it all for naught? What does mathematical coupling mean for acute:chronic workload ratios?
1. Johann Windt1,2,3,
2. Tim J Gabbett4,5
1. 1 Experimental Medicine Program, University of British Columbia, Vancouver, British Columbia, Canada
2. 2 Sports Medicine Division, United States Olympic Committee, Colorado Springs, Colorado, USA
3. 3 US Coalition for the Prevention of Illness and Injury in Sport, Colorado Springs, Colorado, USA
4. 4 Gabbett Performance Solutions, Brisbane, Queensland, Australia
5. 5 Institute for Resilient Regions, University of Southern Queensland, Ipswich, Queensland, Australia
1. Correspondence to Johann Windt, Experimental Medicine Program, University of British Columbia, Vancouver BC V6T 1Z4, Canada; johannwindt{at}gmail.com

## Statistics from Altmetric.com

Traditional calculations of the acute:chronic workload ratio (ACWR) are ‘mathematically coupled’, as the most recent week is included in estimates of both the acute and chronic workloads. As Lolli and colleagues rightly point out, this induces a spurious correlation between the acute and chronic loads of ~0.50 (r=0.52 in their simulated data of 1000 athletes).1 They suggest that the simplest solution is to use uncoupled ACWRs (where the acute load is not part of the chronic load) instead (figure 1).

Figure 1

The distinction between traditional ‘coupled’ and ‘uncoupled’ estimates of the acute:chronic workload ratio. The inclusion or exclusion of the most recent week in ‘chronic load’ calculations is the key distinction.

Notably, at least two studies have already used uncoupled ACWR calculations, both demonstrating that rapid workload increases are associated with higher injury risks.2 3 To this end, Lolli and colleagues’ suggestion warrants consideration—should we use ‘uncoupled’ ACWRs instead of ‘coupled’? We have two aims in this editorial: (1) to further comment on how mathematical coupling affects ACWR estimates and (2) to encourage researchers and practitioners to use a critical approach to load management, wherein ACWRs may play a part.

## Comments on mathematical coupling and ACWRs

### Defining coupled and uncoupled ACWRs

We define mathematical coupling in the same manner as Lolli et al, where a number is represented in both the numerator and denominator of a ratio, contributing to a spurious correlation. In the case of the ACWR, both …

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