The old rule was to stretch before exercise. The correction, which arrived around 2010 and is now repeated everywhere, is that stretching before exercise makes you weaker and more injury prone, and that the real work belongs after the session. The correction is half right, and the half that is wrong gets repeated with more confidence than the half that is true.
what static stretching before training actually costs
The strength loss is real and it has been measured. Simic, Sarabon, and Markovic pooled 104 studies in a 2013 meta-analysis and found pre exercise static stretching reduced maximal strength by about 5.4 percent and power by about 1.9 percent, with the effect appearing regardless of age, sex, or training status.
Then the numbers were re examined. Behm and colleagues, whose own earlier work drove the anti stretching message, published a 2019 review in Frontiers in Physiology arguing the caveats had been oversold. The deficits concentrate in long duration holds. Static stretching under about 60 seconds per muscle group produces small or trivial effects, and when the stretching sits inside a full warm up that includes dynamic work and activity specific movement, the measurable performance cost largely disappears.
So the practical version is narrower than the internet version. Holding a 90 second hamstring stretch and then testing a one rep max deadlift is a bad idea. Doing 20 seconds of hip flexor stretching inside a 10 minute warm up before a normal training session is not going to cost you anything you could detect.
the rubber band analogy is wrong
The version of this argument that circulated in 2012 compared a cold muscle to a rubber band stretched until it snaps. It is memorable and it misdescribes what happens. Acute strength loss from static stretching is not tissue damage. The proposed mechanisms are neural, including reduced motor unit activation, plus changes in the muscle tendon unit’s stiffness that make force transmission less efficient for a short time. The effect wears off, typically within minutes to an hour depending on how long you held the stretch.
And the injury claim was never well supported in either direction. Reviews of stretching and injury rates in military and athletic populations have generally found weak or inconsistent effects on overall injury risk. Stretching before a run does not appear to protect you, and it does not appear to hurt you either. It is a smaller lever than the arguments about it suggest.
the post workout claim has a problem too
This is the part the corrected advice gets wrong. Stretching after training is widely sold as the thing that prevents soreness and helps you recover. The best available evidence says it barely does anything.
Herbert, de Noronha, and Kamper’s Cochrane review, updated in 2011, pooled randomized trials on stretching and delayed onset muscle soreness and converted all outcomes to a common 100 point scale. Pre exercise stretching reduced day one soreness by about half a point out of 100. Post exercise stretching reduced it by about one point out of 100. Both confidence intervals crossed zero. On a 100 point scale, a one point difference is not something a human being can feel.
| Intervention | Effect on soreness one day later |
|---|---|
| Stretching before exercise | About 0.5 points lower on a 100 point scale |
| Stretching after exercise | About 1 point lower on a 100 point scale |
If you stretch after training because it feels good, that is a legitimate reason and I do it myself. If you stretch after training because you were told it prevents soreness, you were sold something the evidence does not support.
what a warm up is for
The useful idea buried in the old advice is that warming up and stretching are different jobs. A warm up raises muscle temperature, increases blood flow, and rehearses the movement pattern you are about to load. Dynamic stretching, meaning controlled movement through range rather than held positions, tends to either leave performance unchanged or improve it, which is the opposite of the static finding.
A warm up that takes eight minutes and does the job: five minutes of easy cardio until you are breathing harder, then leg swings, walking lunges with a reach, bodyweight squats, and arm circles. Then two progressively heavier sets of the first exercise. If you are squatting, the best squat warm up is squats.
where flexibility work does pay off
Static stretching genuinely increases range of motion, and that is measurable and lasting when you do it regularly rather than once. Long hold stretching also has evidence for improving range in people who are restricted, and range matters if a lack of it is stopping you from reaching a position safely. Someone who cannot get to depth in a squat without the low back rounding has a range problem worth working on.
Do that work when it will not interfere: after the session, on a rest day, or in the evening. Hold 30 to 60 seconds per position, repeat a few times, and accept that visible change takes weeks. Foam rolling belongs in the same category. It reliably makes the area feel better for a while and reliably does not lengthen the tissue, whatever the packaging says.
None of this is a medical opinion about a specific injury. If something hurts in a way that does not resolve, a stretching routine is not the answer to that question.