Deviation in height of Zhan Zhuang
1. At high Zhuang: for health purposes:
2. At low Zhuang: for martial artists.
The lowest one can go down by bending the knees at 90 degrees has the stronger legs. The knees will take all the stressful punishment without even having them pass the toes.
If one can anchor the feet to the ground with the bending angles at 90 degree of ankles and knees, then one can be classified as a Shaolin warrior monk.
PS....
My delusion of authority has been certified by Steve...........