STRATAACWR explained: catching the spikes before they become injuries
Most non-contact soft-tissue injuries are not bad luck. They are "too much, too soon." The acute:chronic workload ratio is the simplest way to see it coming, and you will not need GPS units or a sports-science degree to use it.
The core idea, backed by a decade of research: it is not high training load that gets athletes hurt, it is the spike. An athlete who has been building steadily can handle a hard week. The one who pulls up lame is the athlete who jumps from a little work to a lot: back from an illness, back from a break, or a fresh transfer thrown straight into two-a-days.
First, how do you measure "load" without hardware?
You do not need wearables for this. The most validated field method is session-RPE: after a session, the athlete rates how hard it felt on a 1 to 10 scale, and you multiply that number by the minutes.
Session load = RPE (1 to 10) × duration (minutes). A 90-minute practice rated a 7 is a load of 630. Add it up across the week and you have that athlete's weekly workload, no GPS required.
Acute vs chronic: fitness vs fatigue
- Acute load is roughly the last 7 days: recent fatigue.
- Chronic load is roughly the last 28 days (a rolling average): fitness, or preparedness.
The ACWR is acute divided by chronic. It asks one simple question: is this week a lot compared to what the athlete is actually ready for?
The sweet spot and the danger zone
| ACWR | What it means |
|---|---|
| Under 0.8 | Undertraining, or detraining. Load has dropped off, and fitness may be slipping, along with the tissue's tolerance for work. |
| 0.8 to 1.3 | The "sweet spot." Load is climbing right in step with what the athlete is prepared for. This is where you want most athletes, most weeks. |
| Above 1.5 | The danger zone: a spike. Research ties this range to a sharply higher soft-tissue injury risk over the next one to two weeks. |
A rule of thumb that keeps you in the sweet spot: ramp weekly load by roughly 10% at a time. The big jumps are what you want to avoid.
Two things ACWR alone misses
Monotony and strain. An athlete can sit inside a "safe" ACWR and still grind the exact same hard load every single day, with no easy days at all. That sameness is its own injury and burnout risk. Monotony (how alike the days are) and strain (load multiplied by monotony) catch what the ratio misses. The best-run programs vary hard days and easy days on purpose.
Modern monitoring also uses an exponentially weighted average rather than a flat one, so yesterday counts for a little more than three weeks back. That reflects how the body actually adapts. The math matters less than the habit: watch the trend, and respect the spike.
A signal, not a diagnosis. ACWR is a flag to look closer, nothing more. Read it next to how the athlete is sleeping, their wellness check-ins, and their injury history. One number never tells the whole story.
Load monitoring without the spreadsheet
Strata turns a one-tap RPE after practice into weekly load, ACWR, and monotony and strain, per athlete, then flags the spikes before they cost you a hamstring. No GPS units required. And because it reads alongside sleep, wellness, and injury history, every flag comes with context.
See it with your school's branding →Frequently asked
Do I need GPS or wearables to track training load?
No. Session-RPE (effort rating × minutes) is a validated, no-hardware method, and it is used everywhere from high school to the pros. Wearables add detail, but you do not need them to get real value from load monitoring.
What ACWR should I aim for?
Most athletes, most weeks, want to sit in the 0.8 to 1.3 "sweet spot." Above about 1.5 is a spike worth acting on. Well under 0.8 points to detraining.
Is high training load bad?
Not by itself. An athlete with a high, well-built chronic load handles hard weeks better than one who is under-prepared. The risk is the rapid change, the spike, not the ceiling.
Sources & further reading
- Gabbett TJ, British Journal of Sports Medicine, the acute:chronic workload ratio and the "training-injury prevention paradox."
- Bourdon et al., Monitoring Athlete Training Loads: consensus statement (International Journal of Sports Physiology and Performance).
- Foster C, monitoring training in athletes, monotony and strain.