Andrew Huberman

And that can be a subtle distinction.

Nonetheless, static stretching involves

both those types of elements, active and passive, but is really about eliminating momentum.

And then there's the PNF, the proprioceptive neuromuscular facilitation.

And proprioception has several different meanings in the context of neuroscience and physiology.

To just keep it really simple for today, proprioception involves both a

knowledge and understanding of where our limbs are in space and relative to our body, typically relative to the midline.

So the brain is often trying to figure out where are our limbs relative to our midline down the center of our body.

And if your goal is to increase your hamstring flexibility and the flexibility and range of motion of other related muscle systems, you might put a strap around your ankle and pull

that muscle, or I should say, excuse me, that limb towards you.

You're not going to pull the muscle towards you.

You're going to pull that limb, your ankle towards you to try and get it sort of back over your head and then progressively relaxing into that, or maybe even putting some additional force to push the end range of motion and then relaxing it.

And then actually trying to stretch that same limb or increase the limb range of motion without the strap.

there's a huge range of PNF protocols.

Those protocols can be done both by oneself, with or without straps, with machines, with actual weights, or with training partners.

So specific exercises to target specific muscle groups aside, we've now established that there are four major categories of stretching, or at least those are the four major categories I'm defining today.

But in terms of increasing limb range of motion in the long term of truly becoming more flexible

as opposed to transiently more flexible, static stretching, which includes PNF, appears to be the best route to go.

So whether or not you want to maintain, reestablish, or gain limb range of motion, static stretching of holds of 30 seconds appear to be best.

Now the question is, how long should you do that?