Have you ever wondered why you do things a certain way in class? In a good yoga class, everything you do should have clear thinking and a practical rationale behind it. The more you can learn think in that same way, the more informed your home practice can be! I hope these little tidbits help you to think like a yoga teacher.
Why strap there?
For poses using a strap as a support (where the flexibility for the full pose is demanding), putting the strap in different places on your foot can result in a different experience.
When I teach supta padangusthasana (reclined big toe pose), for example, I usually have people put the strap around the ball of the foot–that placement gives a nice opportunity for feedback on calf engagement since you can actively push the ball of your foot into the strap. Since that pose can strain the knee joint by hyperextending the knee, I like to ensure active calves for support: gastrocnemius, the big, two-headed, most-superficial calf muscle flexes the knee (as well as the ankle) and can therefore help to prevent hyperextension when engaged.
Give it a try! Practice the pose with the strap placed differently on your foot and observe the differences.
by Dustin McCallister