Tight hamstrings? You're not alone. Many runners complain about soreness in this group of three muscles in the back of the thigh, especially after intervals of fast running. Stretching helps reduce the risk of aches turning into full–blown injuries. But it can be difficult to get at the hamstrings without stressing the sciatic nerve, which runs parallel to the muscles in the back of the leg. This exercise stretches the hamstrings, not the nerve.

HAMSTRING STEP STRETCH
Put one foot on an eight–inch step. Keep your toes pointed forward and knee slightly bent. Looking straight ahead, lean forward from the hips and pelvis while maintaining an arch in your lower back. Once you feel a stretch in the back of your thigh, hold the position for 15 to 30 seconds. Repeat on the other side. If you feel a stretch in your calf, then you're stretching the nerve. Reposition yourself so the sensation in your calf disappears.

Nikki Kimball, a physical therapist in Bozeman, Montana, is a three–time USATF Ultrarunner of the Year.