[cmurphycode]

This is the stereotypical Asian squat. Interestingly, young children do it by default. I think we lose flexibility as we age. I can't squat back on my heels without straining my shin muscles to keep from falling backwards, but the more I do it, the easier it becomes.

It is certainly a lot healthier for your knees than squatting on the balls of your feet, if only because your knees stay roughly on the same vertical as your toes. This is old powerlifter wisdom, and anyone with a knee injury can tell you first-hand. I can't squat on the balls of my feet without my right knee squealing in pain. Squatting on my heels is, at least, tolerable.

[eitally]

Yep! I was about to post that I learned this from my toddler... and trying to squat (western style) next to him to play.

[eru]

Yes. But the loss of flexibility does not come automatically with age. If you keep moving, you will keep your flexibility. And you can get it back with practice.

[cmurphycode]

I don't think it's as simple as keeping moving. I lost that flexibility fairly early on, certainly in the middle of playing multiple sports through high school, and I'm still very active today.

I know I don't do enough stretching, though. It's just frustrating because my hamstrings never seem to improve, and as soon as I stop stretching, I go back to base (about 12" from touching my toes while standing).