TRIMP

What it is

TRIMP, short for training impulse, comes from Eric Banister’s work modelling how training turns into fitness and fatigue. It combines how long you trained with how hard your heart was working, relative to your resting and maximum heart rate. A weighting factor makes time at high heart rates count for much more than time at low heart rates.

Several variations exist. Some, like intervals.icu’s HRSS, scale a TRIMP-style score so that an hour at threshold heart rate comes out at about 100. That makes it roughly comparable with power-based scores.

Why it matters for training decisions

TRIMP lets you put a number on load for any session where you wear a heart rate monitor, without a power meter. Totals over a week, and the 42-day and 7-day averages built from them (see CTL and ATL), are what most load charts are based on.

Limits

• It depends on correct resting, maximum and threshold heart rates. If those are out of date, every score shifts.
• Heart rate lags behind effort, so short intervals, sprints, sled pushes and heavy lifting can be under-counted.
• Heat, dehydration and fatigue raise heart rate for the same work, which inflates TRIMP on those days.

How P247 uses it

P247 calculates its own load score, HRSS, from workout heart rate. It’s Banister’s TRIMP, scaled so that an hour at a set threshold heart rate scores 100. A workout only gets no load score if it has no heart rate data at all. A Strava average heart rate is enough for a partial score.

This glossary is general information to help you understand your training data. It isn't medical advice, diagnosis or treatment. For injury, illness, medication, blood test results or any health concern, speak to a qualified health professional.

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