Training Load Calculator (TRIMP)

TRIMP (TRaining IMPulse) is a method developed by Dr. Eric Banister in 1991 to quantify the physiological stress of a workout using heart rate data. It combines session duration with heart rate intensity into a single numerical score, allowing athletes and coaches to track and compare training loads across different sessions and time periods.

Banister's exponential TRIMP formula uses a sex-specific weighting factor in the exponent: 1.92 for males and 1.67 for females. This difference reflects research showing that women have a different heart rate response to exercise intensity compared to men, particularly at higher intensity levels. Using the correct value ensures your TRIMP score accurately reflects your physiological stress.

TRIMP scores vary widely depending on fitness level and session type. As a rough guide: an easy recovery session might score 30–60, a moderate aerobic session 60–120, a hard threshold workout 120–200, and a very long or intense session above 200. The absolute numbers matter less than tracking your personal trends over time to manage weekly load.

The ACWR compares your recent training load (acute, typically the past 7 days) to your longer-term average load (chronic, typically the past 28 days). A ratio between 0.8 and 1.3 is generally considered the 'sweet spot' for performance with low injury risk. Ratios above 1.5 ('spike zone') are associated with significantly increased injury risk.

Both TRIMP and TSS quantify training load, but TSS is primarily used in cycling and is based on power output (normalized power and functional threshold power), while TRIMP uses heart rate data. TRIMP is more accessible for sports where power meters aren't used, such as running, swimming, and rowing. TSS scores of 100 represent roughly one hour at threshold effort, while TRIMP scores don't have a fixed reference point.

Yes. Session RPE (Rating of Perceived Exertion) load is calculated as duration (minutes) multiplied by RPE on a 1–10 scale, giving an AU (arbitrary units) score. It's a valid and widely-researched alternative when heart rate data isn't available. Research by Foster et al. has shown strong correlations between session RPE load and TRIMP, making it a useful backup metric.

TRIMP captures cardiovascular stress well but doesn't account for the neuromuscular load of activities like heavy strength training or high-impact plyometrics. Heart rate lag during high-intensity intervals can also underestimate true stress. Additionally, factors like heat, illness, caffeine, and emotional stress can elevate heart rate without corresponding increases in mechanical workload, potentially inflating TRIMP scores.

Track your TRIMP for every session and sum it weekly to get a weekly training load. Aim to increase your weekly load by no more than 10–15% from week to week to avoid overtraining. Periodically review your acute (7-day) and chronic (28-day) averages to calculate your ACWR and ensure you're building fitness without excessive injury risk.