How to warm up, and what warming up does

What people are told

That you must warm up to avoid injury, and that warming up means stretching. Hold each stretch for thirty seconds, then begin.

What is actually known

The two halves of that need separating, because they have different answers.

On stretching and injury prevention, the evidence is unusually clear and unusually ignored. A meta-analysis of 25 randomised trials covering 26,610 participants and 3,464 injuries found no beneficial effect for stretching (relative risk 0.963, 95% confidence interval 0.846 to 1.095 — an interval comfortably straddling no effect at all).¹

The same analysis found that strength training reduced injuries to under a third (RR 0.315), and proprioception training helped too. So the intervention with the best evidence for staying uninjured is not stretching before you train — it is training.

On warming up more generally, the picture is different and more favourable. Raising muscle temperature genuinely changes tissue properties and enzyme activity. Rehearsing the movement you are about to do improves coordination and performance — which is the skill point made in what actually changes when you train. Gradually approaching your working load lets you notice how you feel today before it matters.

Those are performance and preparation arguments. They are good arguments. They are not the injury argument, and conflating them is where the confusion comes from.

On static stretching immediately before lifting, there is reasonable evidence of a short-term reduction in force production. The effect is modest and probably irrelevant to most people, but it is another reason it is a strange thing to do first.

What follows from that

Warm up because it helps you train, not because it protects you. The honest reason is the good one.

A sensible warm-up is mostly the movement itself, lighter. Raise your temperature a little, then do progressively heavier sets of what you are about to do. That covers temperature, rehearsal and a check on how you feel, in one thing.

Save static stretching for when you want range, which is a separate goal with its own timeline — and do it after, or on its own.

If injury prevention is the aim, the answer is strength training, which is what the evidence actually points at.

What we still cannot say

Whether warming up prevents injury at all. The stretching question has been studied; "warming up" as a whole is harder to isolate and the evidence is thinner than the confidence around it.

How long or how thorough a warm-up should be. Practice varies enormously and the research does not settle it.

Whether any of this applies to a specific sport with specific demands. The general finding is general.

Sources

1. Lauersen JB, Bertelsen DM, Andersen LB. The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials. British Journal of Sports Medicine 2014; 48(11):871–877. doi:10.1136/bjsports-2013-092538 PMID 24100287 25 trials, 26,610 participants, 3,464 injuries. Stretching showed no beneficial effect (RR 0.963, 95% CI 0.846–1.095). Strength training reduced injuries to under a third (RR 0.315, 95% CI 0.207–0.480) and proprioception training also helped.

Every source here was checked against PubMed rather than recalled. Where this site says something is disputed or unsupported and no source appears, that is deliberate: it means the claim is being conceded rather than cited.