Martial artists, gymnasts and other sportsmen who want to develop flexibility in their lower bodies use leg stretchers. Leg stretchers increase hamstring and adductor or inner thigh flexibility, which is important for high kicks, among other things. Look for leg stretchers at sporting goods stores and martial arts suppliers. They vary in design and cost. The simplest and cheapest leg stretchers consist of a metal tripod and are cost around $20; complicated versions use electric motors and cost $300 or more.
Perform some warm-up activities. Some light cardio exercise elevate your body temperature. Walking, jogging, rowing, cycling and jumping rope are good choices. Once you are warm, perform some light stretches in preparation for the more intense stretching to come.
Get into the starting position. Sit on the floor and adjust the leg stretcher so that your legs are pushed comfortably apart. This is a very mild stretch. Make sure you are sitting tall on your ischium---the bottom bones of your pelvis. Lean forwards at the hips but do not round your back.
Increase the stretch. Depending on the model of leg stretcher you have, either pull the central bar towards you, turn the ratchet handle or press the control button. Increase the stretch as far as comfortable and then hold this position for 30 to 60 seconds. Try to relax and do not hold your breath. Sit up straight or lean slightly forwards at the hips. Do not round your back.
Contract your leg muscles. Without reducing the stretch or holding your breath, try to push your legs together against the resistance of the leg stretcher. Hold this contraction for 10 to 15 seconds. Inhale and then forcefully exhale as you release the contraction. Increase the stretch. You should find that you can increase the stretch significantly as your leg muscles relax. Hold this new, deeper position for 30 to 60 seconds.
Repeat step 4 until you are no longer able to make any further progress. Hold this last position for 60 to 120 seconds and then slowly release the stretch.