Warming Up Hamstring Muscles Bend one leg, put the other leg straight out in front. Bending forwards from the hips, lean on to the bent leg. Feel the stretch in the muscle of the back of the upper part of the straight leg (hamstring). Repeat the stretch for the other leg. Inner Thigh Muscles Sitting on the floor, open legs as wide as comfortable. Lean forward from the hips keeping the back straight to feel the gentle stretch in the inner thighs.