Stretching and mobility
Evidence: contested
Stretching does not prevent the overuse injuries that affect runners, long static holds before a run can briefly dull performance, and more flexibility is not better. Its real uses are narrow.
Keep it in proportion
This is one of the last few per cent, at most. It pays off only once the basics are already in place: consistent volume, sleep and adequate fuelling. Most runners gain far more from those than from anything on this page.
Stretching is among the most ingrained running habits and one of the most over-claimed. The evidence does not support its two biggest promises, injury prevention and a performance boost, and it cuts against the assumption that more flexibility is always good.
It does not prevent overuse injury
The large strength-training injury meta-analysis found that strength work roughly halves injury risk while stretching showed no such protective effect (Lauersen et al. 2018). Stretching may reduce certain acute muscle strains in explosive, change-of-direction sports, but distance running is a repetitive overuse activity, and there stretching is not a meaningful injury-prevention tool. If the goal is staying healthy, strength training is the intervention with the evidence.
Long static stretching before running can hurt performance
Holding a static stretch for more than about 60 seconds per muscle before exercise can reduce strength and power by roughly 4 to 7.5%; shorter holds cause only a trivial 1 to 2% decrement (stretching reviews). For a warm-up, a dynamic routine, leg swings, drills and easy running building toward pace, is generally preferred, because it raises muscle temperature and primes the nervous system without the brief strength loss that long static holds can cause.
More flexibility is not better
It is intuitive that a “looser” runner is more efficient, but the opposite tends to hold: a degree of stiffness in the muscle-tendon unit stores and returns elastic energy, and static flexibility is largely unrelated, or slightly negatively related, to running economy (stretching reviews). Stretching to become as flexible as possible is not a performance strategy, and may work against the tendon stiffness that economy depends on.
Where it earns a place
Stretching and mobility work are worthwhile for specific, limited reasons: restoring a genuine range-of-motion restriction that affects running form or daily life, easing the feeling of tightness (a real comfort benefit, even if mostly perceptual), and as gentle movement. The reasonable position is to do a dynamic warm-up before running, address specific restrictions rather than chase general flexibility, and not expect stretching to prevent injury or make you faster.