Training Load Calculator

Measuring load through heart rate

Sometimes there is no power meter and no clean pace — hiking, skiing or a gym session. Heart rate is then the remaining measure of effort.

This calculator combines duration and heart rate into a load figure. It is called TRIMP and comes from sports science.

How it is calculated

TRIMP = duration in minutes × HRr × 0.64 × e^(1.92 × HRr) for men, with 1.67 instead of 1.92 for women. HRr is the heart rate reserve: (average HR − resting HR) / (maximum HR − resting HR).

The exponential term comes from Banister: it reflects that lactate rises steeply rather than linearly above threshold, so the same time at a higher heart rate counts disproportionately more.

Example: 60 minutes at 155, resting 50, maximum 185, male. HRr = (155 − 50) / (185 − 50) = 105 / 135 = 0.778. e^(1.92 × 0.778) = e^1.493 = 4.45. TRIMP = 60 × 0.778 × 0.64 × 4.45 = 133.

The rating: below 50 a recovery session, 50 to 99 moderate, 100 to 149 high, 150 and above very high. So 133 is a hard hour, not an extraordinary one.

If you want to calculate training load without a power meter or threshold pace, TRIMP is the one number that comes from heart rate alone.

How to use it

The number alone says little; comparison says a lot. One week against the next, one month against the last.

It matters that resting and maximum heart rate are correct. If they are guessed, so is the result.

Frequently asked questions

How does this differ from TSS?

TSS works from power or pace relative to threshold, TRIMP from heart rate. Where power data is missing, TRIMP is the more usable number.

Where do I get my resting heart rate?

Measure lying down right after waking, across several days. The lowest stable value is a good reference.

Why is my number higher in the heat?

Because heat raises heart rate without the session being harder. That is a known weakness of heart-rate-based measures.