Hamstrings (the muscles in the backs of your thighs)
Anyone who runs — even if it’s just to catch the last commuter train — is subject to tight hamstrings. To loosen them, lie flat on your back with your right foot over your left knee. Grab your right leg just above the knee using both hands, with your fingers pressing into the back of your leg and your thumbs on top by your kneecap (as shown). Run your hands up your thigh, pressing with your fingers as you go. Repeat several times. Finally, press the fingers of either hand into the middle of your hamstring and slowly rub across the leg from side to side. (Use enough pressure so that your fingers don’t slide across your skin.) Move your fingers to work the entire muscle. Avoid putting pressure on the area directly behind the knee, where there are fragile tendons and ligaments. Then work the other leg.