Stretching with chair in Classical Stretch

[daisymae]

Does it bother anyone else to stretch with your foot on the chair? For example: when you put your heel on the chair, point through your toes and lean forward over your leg. This hurts my heel. Actually, any of the stretches where you are supposed to rest your foot on the chair hurt my feet but especially the stretch mentioned above. It also makes my Achilles sore. I can sit on the floor with legs out and stretch my hamstrings just fine but trying to do it on a chair is just very uncomfortable. Would a pad help? Does it get better the more you do it or should I just modify those stretches by sitting on the floor?