Load, spikes and the acute:chronic ratio
Why sudden jumps in training load cause more injuries than heavy training itself, and how coaches use load data to build volume up safely.
"Load" is a simple idea with a lot riding on it: roughly how much training a body has done, combining how long a session was with how hard it felt. A tough hour counts for more than an easy hour, and a heavy week counts for more than a light one. Tracked over time, load tells you something a single session never can — whether training is building up steadily, or jumping around in a way a body struggles to keep up with.
Why spikes matter more than volume
It's tempting to think heavy training is what causes injuries. Mostly, it isn't. A body that's built up to a heavy week gradually can handle it well. The same heavy week landing suddenly, after a much lighter patch — a return from a break, an unplanned few easy weeks, or simply a big block starting all at once — is a different story. Tissue that hasn't adapted to that level yet is being asked to cope with it anyway, and that's when things are more likely to go wrong.
This is why coaches watch for the change in load from one week to the next, not just the total. A steady climb is manageable. A sharp spike is the pattern worth catching early.
The acute:chronic ratio, in plain terms
You'll sometimes see this called the acute:chronic ratio — a comparison between a short recent window of training (roughly the last week) and a longer window behind it (roughly the last month). When the recent window is a lot higher than the longer-term average, that's a spike. When they're broadly in line, training is progressing at a pace the body has had a chance to adapt to. Coaches use this as one input among several, not as a rule that overrides everything else — judgement and how an athlete is actually feeling always matter too.
What can also matter besides total volume
It isn't only about how much training there is. A week where the balance shifts sharply towards harder, higher-rate work — even if total time looks similar to the week before — can carry its own load that a simple minutes-added-up total won't show. Coaches build sessions with this in mind, layering intensity in gradually rather than all at once.
What this looks like week to week
In practice, sensible load management just looks like training that builds steadily: volume nudged up a bit at a time rather than in big leaps, a heavier week usually followed by an easier one, and extra care after a break — whether that's an illness, a school-exam period, or simply time off. None of this is about training less. It's about training in a way the body can actually keep up with, which tends to mean fewer setbacks and steadier progress over a season.
Where the data comes from
Load is only as good as what feeds it — the sessions your coach has programmed and what you log against them, plus a quick effort rating an athlete can add after a session. Missing data doesn't get ignored; a week with a lot of unlogged sessions is flagged as less complete, and any pattern spotted from it is treated more cautiously as a result.
Who to talk to
If training is feeling harder than it should for the volume involved, or you've noticed a pattern worth mentioning, your coach is the person to raise it with — they're the one shaping the programme and can adjust it. For anything that feels physical rather than just a hard patch, a physio or your GP is the right next step.
Last updated 2026-09-13