How flexible should runners be?

I heard Kipchoge can't touch his toes.

A physio told me don't stretch, it will not lengthen any muscles.

And the bouncy and stiff muscles is necessary to be able to be fast. Might be different for sprinters.

Does lack of flexibility not have a correlation, and possibly causation with injury though?

I don't have all the answers, but the range of motion required for distance running isn't much, so I don't see how being able to touch your toes will provide any benefit. I think you need to be flexible enough to handle the stresses of running and most of that can come from actual running and other exercises.

Flexibility is a bit more than just flexibility. A few examples:

- Someone who does nothing but stretch and yoga. They're not very strong, but boy can they bend. They couldn't jump or sprint to save their life. Probably not getting injured for stepping off a curb anytime soon.

- Someone who only lifts through a very short range of motion, never stretches. Might be able to jump through the roof, likely at a higher chance of injury.

- Someone who squats very deep, jumps from deep squats, etc. Someone like an Olympic lifter, they have very good flexibility but have no issue being explosive.

So the yoga person wouldn't make a good runner, and the second person might make a good runner but anything "unexpected" could pose a risk of injury, something as simple as losing balance while jumping.

The reality is, you can be flexible and springy, you just have to train it. You probably don't need to be as stretchy as a gymnast, but they seem to have no problem jumping very high.

Thanks for the insight!

If you do a quick google search there are lots of studies indicating that running economy is inversely proportional to flexibility and there is no difference in injury risk. Personally I have found stretching to be occasionally good for minor pain relief but if your only goal is running performance I wouldn't stretch very much and any time you'd use for stretching could instead be used for core/hip strengthening, plyos ect.

I think the simple answer is you need to be flexible enough to not get hurt in training and flexible enough to go through the running gait without issues.

Based on what I've read and personal experience being too inflexible can be an injury issue. But as FatKing69 alluded to, there needs to be corresponding strength through the flexibility range.

Responding to BeepBeep: I could be wrong but I think those studies usually say muscle or tendon "tension" not flexibility. Sprinters have lots of tension but are also flexible.

To the OP, I would say it depends on your age. When you’re young, say under 30, some flexibility is natural, especially if you do regular easy stretching. It’s probably not too important.

But as you age, your flexibility will naturally start to decrease as your muscles aren’t growing and become less pliable. Now at 55+, I can feel how much flexibility I’ve lost in 10 years, and that’s with steady running.

I would recommend more “active warmups” and adding a variety of other movements or activities to keep your flexibility in key areas like hamstrings, glutes, and lumbar.

You should be flexible enough to fit into a carry-on suitcase on flights.