What Is Training Load, and How Do You Measure It

Training load is an attempt to answer a question that distance and weight lifted cannot: what did that session cost you? The work you did is external load. What it cost is internal load, and it depends on your fitness, your sleep, the heat and everything else you carried into the session. Every number on this page is a way of estimating the second thing.

The two methods, and what each one sees

TRIMP takes the session’s duration, converts your average heart rate into a fraction of your own heart rate reserve, and weights the result exponentially so that intensity counts for more than time. It is objective, needs a monitor, and only knows about your circulation. Full formula and worked example on the TRIMP calculator.

Session RPE takes one 0 to 10 effort rating for the whole session and multiplies it by the minutes. It needs nothing, works for any activity, and folds in muscular fatigue, mood and context — at the cost of depending on an honest, well-instructed rater. See the session RPE calculator.

Both output arbitrary units. Neither is convertible to the other, and neither is comparable between two people.

Where they disagree, with numbers

This is the comparison worth having, because the choice is not cosmetic. In a study of eight trained men who each performed one all-out functional fitness session and one held deliberately at a rating of 6 out of 10:

Method	All-out session	Controlled session	Separated the two?
Session RPE	91.7 ± 30.4 AU	42.6 ± 14.9 AU	Yes, strongly (p = 0.002)
Banister’s TRIMP	61.1 ± 10.6 AU	55.7 ± 12.4 AU	Yes, weakly (p = 0.045)
Edwards’ TRIMP	93.1 ± 9.5 AU	84.9 ± 13.7 AU	No (p = 0.085)

Session RPE was also the only one of the three that correlated with blood lactate 30 minutes after the session. Eight men in one training format is a small study, and the authors say outright that more work is needed on whether session RPE tracks changes in fitness and fatigue over a training block. But the direction is not surprising: heart rate methods were built for continuous aerobic exercise, and a session full of stops is not that.

The reverse case holds too. For steady running or cycling, a heart rate model captures something a single rating cannot — the actual time spent near threshold, weighted properly. Use the method that matches the training, and do not mix the two inside one week’s numbers.

What to do with a weekly total

1. Add up the daily loads across the week, using one method throughout.
2. Compare with previous weeks, not with a target. There is no published number of points a week you should be hitting, because the scale is anchored to your own heart rate range or your own ratings.
3. Check the distribution, not only the total. A week’s total says nothing about whether it arrived as four hard days or as hard-easy alternation — that is what training monotony and strain is for.
4. Watch for the signs the number cannot show: performance sliding, sleep worsening, motivation draining. If those appear while load is climbing steadily, the load was too high for you regardless of what the arithmetic said.

On the honest limits

Increase load gradually is sound advice and is not the same as a validated rule. The commonly repeated percentage caps are conventions, not thresholds derived from evidence that applies to every sport and every athlete. What load monitoring genuinely buys you is much smaller and much more reliable: it makes a jump in volume visible on paper before you feel it in your legs, and it gives you a record to look back on when something goes wrong.

For the effort scale that both methods ultimately rest on, see the Borg RPE scale.

This content is informational and does not replace guidance from a coach or clinician.