Components of training load: volume, tonnage, TUT and density

August 12, 2026 · 6 min read

Four numbers that come out of the prescription on their own, before you lift anything — and what each one answers.

Every program in PulsoGym has sets, reps, load and rest — the basics for knowing what to do. But the basics do not answer questions like "is this day going to be heavier than yesterday's?" or "how long will this session actually take?". That is what the components of training load are for: four numbers derived from the prescription itself, plus an estimated duration, calculated before you train.

Volumesets × reps

Tonnagetotal lifted, in kg

TUTtime under tension

Densitystimulus : rest

Durationestimated session

Volume — how much work, in reps

It is the sum of sets × reps for every exercise in the day. A regular exercise of 4 sets of 12 contributes 48 reps; a drop set adds every step, and a superset adds every side — the volume of a day with combined methods is always larger than the line count on screen suggests (the article on supersets and drop sets details why). Volume answers: how much work, in reps?

Tonnage — the total moved, in kg

It is the volume multiplied by the load of each set: kilos actually moved in the day. Two days can have the same volume — the same rep count — and very different tonnages if one uses heavier loads than the other. Tonnage answers: how much weight, in total?

Time under tension — how long the muscle stays loaded

It is the sum of the duration of each rep: reps × seconds per rep. When an exercise has a prescribed tempo — the concentric phase plus the eccentric, part of the program's structural variables — the app uses that value. Without a prescribed tempo it assumes a default of 3 seconds per rep, as an estimate. Time under tension answers: for how long was the muscle loaded? — a question volume and tonnage do not answer on their own: two sets of 10 can last 20 seconds or 60, depending on tempo.

Density — the ratio between stimulus and rest

It is time under tension divided by the total rest prescribed for the day, and appears on screen in notation like 1:2 (0.5) — for every 1 unit of stimulus, 2 of rest. A session with a lot of rest between sets has low density; a session with chained sets and little rest — a circuit, for instance — has high density. Density answers: how compact is the stimulus relative to the rest? It is the same variable the product is named after: PulsoGym also measures the pulse between effort and rest.

Estimated duration — how long the session should take

It adds time under tension and total rest, plus a fixed transition time per exercise — changing equipment, adjusting the bench. It is an estimate, not a promise: free tempo assumes the 3-second-per-rep default, and nobody trains with a stopwatch timing every set to the tenth of a second. It is there for one practical decision before you start: does this day fit in the time I have?

These are estimates, and the app does not hide it. The duration of a rep without a prescribed tempo is always an assumption. What matters is not second-level precision — it is giving you, before the first set, a sense of the size of the day that the exercise list alone does not convey.

Prescribed × performed

The components of training load describe what is planned. After a session, the app also stores what was performed — sets completed, reps and load for each one — and shows the two side by side on the day's screen. It is the basis for any reading about progression: without knowing what actually happened in the last session, comparing load between workouts is comparing against memory, not against the record.