Thread by @TonyBlazevich

Here's our new invited review on pre-exercise stretching, led by Prof David Behm. Our conclusions might differ from the current viewpoints of many. As it's a long and detailed paper (so please read it all!), here is my summary of our major findings...

https://twitter.com/EJAP_official/status/1329351205898702848

1/8: Prolonged static stretching (SS) may have a detrimental effect on muscle function (force, power, etc.) if stretches relatively long (>60 s), many muscle groups are concurrently stretched, and function is tested soon after SS (~5 – 10 min after, but longer if SS is extreme).

2/8: BUT, increases in force production at longer lengths are usually observed too – there's typically is a shift in the force-length relationship.

3/8. AND, most studies are not designed to determine whether this impacts function in sports or rehab contexts – most are designed to determine whether SS "can" have an effect, not whether it "does" have an effect in most contexts.

4/8: Overall, no substantial changes in function are expected when short/moderate SS durations are used (<60 s), especially when a few minutes are allowed after SS or proper warm-up is done–but there are potential psychological benefits (and others we don’t cover in our paper).

5/8: In the applied context (full warm-up, etc.), dynamic and static stretching show no difference in their effects, so dynamic stretching cannot be assumed to be better.

6/8: A significant decrease in neural drive may explain much of the short-term loss of force with long SS durations, with alterations at the motoneurons themselves the most likely culprit (reduced persistent inward current function; see new paper by Trajano et al in J Exp Biol).

7/8: Changes at the muscle level are also observed, and most likely explain longer force losses that are observed after neural drive returns to normal (e.g. >15 min).

8/8: But there are a lot of gaps in our knowledge of the mechanisms, so we can’t yet form specific testable hypotheses as to how to mitigate force loss in those few instances where it occurs.

My 'practical' conclusion: Stretching may/may not offer benefit. It needs to be tested in each person in each circumstance. It's time to let go of 'stretching is bad'/'stretching is good' narratives and recognise its complexity (seems a common conclusion these days...right?).