Training Load Calculator

Training load quantifies how much stress your body experiences from exercise. The most practical method is Session RPE (sRPE), developed by Dr. Carl Foster: multiply the session duration (minutes) by the perceived exertion (RPE on a 1–10 scale). The result is in arbitrary units (AU).

The sRPE formula: Session Load = Duration (minutes) × RPE (1–10)

RPE scale reference:

• 1–2: Very easy (warm-up, walking)
• 3–4: Easy (easy run, light swim)
• 5–6: Moderate (tempo, steady-state)
• 7–8: Hard (threshold, intense intervals)
• 9–10: Maximum (race effort, all-out)

Example: A 60-minute run at RPE 7 = 60 × 7 = 420 AU.

Acute:Chronic Workload Ratio (ACWR): Acute load is your last 7 days of training. Chronic load is your average over the past 28 days (or 4 weeks). The ACWR = Acute Load / Chronic Load.

Research suggests:

• ACWR 0.8–1.3: Sweet spot: optimal training stimulus, low injury risk
• ACWR < 0.8: Undertraining: fitness may decline
• ACWR > 1.3: Danger zone: significantly increased injury risk
• ACWR > 1.5: High risk: sharply elevated injury probability

Practical guidance: Increase your weekly training load by no more than 10% per week. After a hard training block, include a recovery week at 60–70% of your peak load. This periodization approach maximizes fitness gains while minimizing injury risk.

What the ACWR does and does not tell you

The ratio is a comparison, not a measurement, and it can move for two opposite reasons. A ratio of 1.6 usually means you have spiked this week, which is the case it was designed to catch. But it also goes up when your chronic load collapses, so coming back from two weeks off with a completely ordinary week can put you in the danger zone on paper while your body is simply detrained.

The honest reading is: a high ACWR means this week is unusual for you. Whether that is because the week is hard or because the last month was easy is a question the number cannot answer, and both are worth being careful about.

Also worth knowing: the ACWR literature is genuinely contested. The 0.8 to 1.3 sweet spot comes largely from Tim Gabbett’s work in team sports, and later reanalyses have questioned how much of the injury signal survives better statistical handling. Treat it as a useful flag for unusual weeks rather than a law.