🏋️ Training · 5 min read

Warming up: what it does and what it does not

What happens in the body during a warm-up

Warming up is first of all a question of temperature. As muscle temperature rises, enzymatic processes in the muscle run faster, tissue viscosity falls, and nerve conduction as well as muscle contraction become somewhat quicker. This is not a trivial matter: a cold muscle works measurably more sluggishly than a warmed one.

Added to that is the adjustment of the circulatory system. Heart rate and stroke volume rise, blood flow to the working muscles increases, breathing adapts. This adjustment takes minutes, not seconds — and it happens anyway, whether it is prepared for or not. The difference is whether it takes place during the first working set or before it.

The third part is the least visible: coordination. Movements that do not occur in everyday life — a deep squat, an overhead press — run more cleanly after a few preparatory sets than on the first attempt of the day. That is a process of learning and recall rather than warming in the narrow sense, and it is one of the most concrete reasons not to go into the first heavy set cold.

General and specific

Training theory usually distinguishes a general and a specific part. The general part gets the circulation going — several minutes of easy, cyclical movement in which breathing rises noticeably but not uncomfortably. Cycling, rowing, brisk walking, skipping: the choice is largely interchangeable, because what matters here is temperature and blood flow, not the exercise to come.

The specific part is the more important one and is skipped most often. It consists of the same movement that is about to be trained, at increasing load. Anyone intending to squat heavy squats first without load, then with light, then with moderate. Each of these sets is short and ends well before any fatigue; its purpose is to groove the movement, not to do work.

How many such preparatory sets make sense depends on the gap between starting point and target weight, on the complexity of the exercise and on the day. There is no single figure that fits everyone — and prescriptions naming such a figure describe a habit, not a measured value.

Static stretching before strength training

The idea of stretching statically and at length before training persists stubbornly. Research over the past twenty years paints a different picture: prolonged static stretching immediately before a strength or power effort is, in many studies, associated with slightly reduced performance afterwards. The effect is usually small and appears smaller with short holds than with long ones.

The qualification matters: “small performance drop” does not mean “harmful”, nor does it mean stretching is useless in general. It only means that extensive static stretching is not a suitable warm-up for a strength effort that follows. Anyone wanting to work on mobility can do so at another time — after training or on another day.

For preparation, moving work has established itself instead: taking movements through their range without holding the end position for long. Whether that has an independent benefit beyond the plain warming effect is less clear than the concept’s popularity suggests.

What warming up does not do

The most common expectation of a warm-up is protection against injury. Here the evidence is considerably weaker than everyday belief suggests. Studies on this are methodologically difficult: injuries are comparatively rare events, training groups differ in many respects at once, and what counts as an injury varies between studies. Blanket statements about a protective effect cannot be substantiated at that level of generality.

What can be substantiated is more modest: warming up improves the performance that immediately follows in many cases, and it makes the first repetitions technically cleaner. That is a good reason to do it — even without the injury argument.

Nor does warming up substitute for a load matched to the person. Anyone working with a weight they do not technically control carries that risk warm as well as cold. And persistent pain cannot be warmed away: it is a reason for medical assessment, not a training variable.

How long, and when less is enough

A warm-up is meant to prepare, not to tire. Anyone already strained after warming up has brought part of the session forward. In practice it therefore usually comes down to a few minutes of general movement plus several ascending preparatory sets.

The extent may vary. A heavy session with multi-joint exercises needs more preparation than a light machine session. Training in the morning or arriving from the cold generally takes longer than starting in the afternoon after an active day. And the second exercise of a session needs less than the first, because circulation and temperature are already up — there a short, specific lead-in usually suffices.

And afterwards?

For its counterpart, the cool-down, the evidence is thinner. Easy tapering after intense effort is frequently recommended and is unobjectionable; that it measurably speeds recovery before the next session or reduces muscle soreness has, however, not been convincingly shown in research.

That is no argument against doing it — it is an argument against expecting more from it than is established. Anyone who keeps moving gently for a few minutes after training because it feels more pleasant has reason enough.

Last reviewed: 14.08.2026

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