TRIMP Calculator (Banister Training Impulse)
Calculate Banister's TRIMP (training impulse) for a workout from its duration and average, resting and maximum heart rate, with the share of heart-rate reserve and the ACSM intensity level.
How it works
ΔHR ratio = (HRavg − HRrest) ÷ (HRmax − HRrest) · TRIMP = minutes × ΔHR ratio × 0.64 × e^(1.92 × ΔHR ratio) for men, × 0.86 × e^(1.67 × ΔHR ratio) for women
Banister's training impulse (1991) turns a session into one load number by weighting time by heart-rate intensity. The exponential factor reflects how blood lactate rises steeply at higher intensities, so an hour at threshold scores far more than an hour of easy jogging. Summed over days, TRIMP feeds fitness–fatigue models and acute:chronic workload ratios.
Worked example
A man trains 60 min at an average of 150 bpm with a resting HR of 55 and a maximum of 190: ratio = 95 ÷ 135 = 0.704, so TRIMP = 60 × 0.704 × 0.64 × e^(1.92 × 0.704) = 60 × 0.704 × 0.64 × 3.86 = 104.4 — a vigorous session.
Sources: Halson SL. Monitoring training load to understand fatigue in athletes. Sports Med 2014 · ACSM — Guidelines for Exercise Testing and Prescription
Frequently asked questions
What is a good TRIMP score?
There is no universal target: an easy 45-minute run is often 40–60, a hard hour 100–150, and a long race 200 or more. Compare against your own weekly totals and increase load gradually.
Why are the coefficients different for women?
Banister weighted intensity by the typical blood-lactate response, which differs between men and women; the female curve (0.86 e^1.67x) rises a little less steeply.
Is TRIMP the same as TSS?
Both measure session load. TRIMP uses heart rate; Training Stress Score uses power or pace relative to threshold. They are on different scales and should not be mixed.
Which maximum heart rate should I use?
A measured maximum from a hard race or test is best. If you must estimate, 208 − 0.7 × age (Tanaka) is more accurate than 220 − age.
Related calculators
This calculator gives an estimate for general fitness and education only. It is not a diagnosis — results from field tests and prediction equations can differ from laboratory measurements, so talk to a doctor or qualified exercise professional before acting on them.