Fatigue Index, Explained
Why some players get benched, others get broken, and how Liverpool avoid both
Liverpool, load, and what FI actually means
September is football’s limbo. Half the squad are off posting airport selfies, the other half are stuck doing tight rondos at Kirkby. Then they all drop back within 24 hours and suddenly you’re staring at seven games in twenty days. Burnley on Sunday, Atlético midweek, a derby at lunchtime, the Carabao, Palace, Istanbul, Stamford Bridge. There’s no matchday+1 fairytale here, it’s play, recover, fly, play again.
That’s your reality. The real story is load.
Now the internationals are done, we’ve got a clean sheet to work from. Alisson’s Brazil mileage, Mac Allister’s Argie detour, Konaté’s France minutes, Szoboszlai and Kerkez putting in work, Ekitike doing planned cameos. Rio clocked 60 with the U21s. Everyone’s acute and chronic load is updated, travel tax included.
Look at the squad through the ACWR lens and picking a team stops being “who looks good” and becomes “who won’t break”.
ACRW, in plain Scouse
Think bank account.
Chronic load is the money saved, your last 3–4 weeks of real work. it’s the tissue capacity you’ve built.
Acute load is this week’s spend, what you’ve just asked your body to do.
The Ratio is the gap between the two.
When the spend suddenly dwarfs the savings, roughly acute > 1.3× chronic, injury risk doesn’t creep up, it pops up. That's the core finding popularised by Tim Gabbett (2016, BJSM) across multiple sports. And in elite football specifically, Bradley et al. (2019, BJSM) showed that sudden exposure spikes (total minutes, high-speed running) track with increased soft-tissue injury rates.
Equally important: undercooked is risky too. If your ratio is very low (<~0.7), you look “fresh” but you’re fragile. We’ve all seen it, a player who hasn’t played for weeks gets thrown in for 90 and pulls up at 70. That’s not bad luck; that’s a mismatch.
ACWR doesn’t care where the minutes came from. Kirkby, Wembley, La Paz; it’s that relationship that matters.