The formula

Acute load (A)   = mean of the last 7 days of load
Chronic load (C) = mean of the last 28 days of load
ACWR = A / C

Interpretation zones (Gabbett 2016)

ACWR	Zone	Interpretation
< 0.8	Undertraining	Recent load is well below chronic. Fine briefly; prolonged = detraining
0.8 – 1.3	Sweet spot	Load is matched to fitness — lower injury rates in Gabbett's studies
1.3 – 1.5	Caution	Acute spike — risk elevated but not in danger zone
> 1.5	Danger zone	Significant acute spike — statistically higher injury rates

How to read it

ACWR has been both useful and argued over. Gabbett's first studies found a strong link between a high ratio and injuries in rugby and football. Later reviews pushed back. Some say the plain rolling average can overstate the link, and that an EWMA version tracks risk better. EWMA means an exponentially weighted moving average, which leans on recent days more than old ones.

Most coaches treat ACWR as a flag, not a rule. If your ratio jumps from 1.0 to 1.8 in a week, that is worth a look. Not because you will get hurt, but because the speed of the change is the signal. Plan around it.

ACWR vs. Banister TSB

TSB (from the Banister Form Band model) and ACWR are cousins, but they answer different questions. TSB is fitness minus fatigue, so it reads as how fresh you are. ACWR is acute load ÷ chronic load, so it reads as a risk flag. You can be fresh and still show a high ratio at the same time. That is the race week where you cut volume but did one hard session. Both lines belong in the call.

Track this in Kinoku

The Elite Analytics Recovery tab tracks ACWR for you. It runs across your whole training load: gym, run, and brisk-step. Your data stays on your phone.