🏋️ Training · 5 min read

Range of motion: why half a repetition is not half the work

What range of motion means

Range of motion describes the distance between the extended and flexed end positions of a joint during an exercise. It is not the same as mobility: mobility is what a joint permits; range of motion is what is actually used in a given exercise.

The distinction matters in practice. Shortening a movement happens either because the joint cannot go further, or because the load is too high, or because the exercise is set up that way. The three cases look similar and have very different consequences.

What the research suggests

In comparisons between full and shortened range of motion, the larger range comes out more favourably for muscle growth in many studies — particularly when the muscle is loaded in the lengthened position. This finding is remarkably consistent across studies, albeit with effects of differing size.

At the same time it is not as simple as it sounds. A larger range almost always means less weight — squatting deeper means loading less. For pure strength performance in a specific position, by contrast, targeted work in exactly that position can make sense; being strong in the upper third of a movement requires training there.

What does not follow: that shortened repetitions are worthless, or that “deeper is always better”. What follows is rather that range of motion should be a deliberate decision instead of a by-product of a weight that is too heavy.

When the range shrinks unintentionally

The most common case is not the deliberate decision but gradual erosion. Over weeks the weight goes up and the movement gets shorter — in the log that looks like progress, in substance it has become a different exercise.

Recording the range alongside the weight helps. It need not be elaborate: a note about the end position, a fixed reference point, a video every few weeks. Without recording the range, two numbers get compared later that do not describe the same thing.

Technique is not aesthetics

Technique is often discussed as if there were exactly one correct execution for each exercise. That holds for the broad lines and not for the details. Body proportions, joint structure and mobility differ; a squat looks different with long thighs than with short ones, without either being wrong.

More useful than an ideal is a set of criteria: does the movement run the same way across several repetitions? Is the end position reached without the rest of the body evading? Is the movement controlled, that is, without momentum taking over the work? If those three hold, the execution is usable for training purposes — even if it departs from an illustration.

Partial repetitions as a deliberate tool

Shortened repetitions have a poor reputation because they usually arise unintentionally. As a decision they are something else. In practice they are used in several places: to add work in a partial range after the last full repetition, to practise a section where the movement regularly stalls, or to load a position that is not reachable through the full range.

Work in the lengthened range has drawn particular attention in recent years — partial repetitions in the lower half of a movement rather than the upper. Several studies suggest this variant comes out more favourably for muscle growth than partials in the shortened range. The number of studies is still modest, the groups are small, and transferability to all exercises is open; an interesting observation has therefore not yet become a general recommendation.

What can be said regardless: anyone using partial repetitions should log them as their own exercise and not write them into the same line as full repetitions. Otherwise exactly the mixing arises that makes comparison across weeks impossible.

When the joint cannot go further

Not every restricted range can be solved with less weight. Joint structure, limb proportions and the mobility of individual segments differ considerably between people. Anyone who cannot take up a particular position even without load will certainly not reach it with load.

In such cases exercise selection is the more obvious lever than forcing an end position. A variant with a different grip, a different stance width, a raised heel or a different machine setting often produces a range that can be controlled cleanly. That is not avoidance but adapting the exercise to the body.

If, by contrast, a movement causes pain — not effort, but pain — it is no longer a question of technique or range. Such complaints belong in a medical assessment before further training variables are adjusted.

What this means for choosing weight

A workable order is: set the range first, then choose the weight that is handled cleanly within it. The other way round — weight first, then as much range as it allows — the exercise shifts with every increase.

That regularly means starting with less weight than would be possible. For the number in the log that is uncomfortable; for comparability across months it is the sounder basis.

Last reviewed: 14.08.2026

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