Isometric stretching is a form of passive stretching similar to PNF, but the contractions are held for a longer period of time. Isometric stretching places high demands on the stretched muscles and is not recommended for children or adolescents who are still growing.
Other recommendations include allowing at least 48 hours’ rest between isometric stretching sessions and performing only one isometric stretching exercise per muscle group in a session.
A classic example of how isometric stretching is used is the standing ‘push-the-wall’ calf stretch, where the participant stands upright, leans forward against a wall, and then places one foot as far from the wall as is comfortable while making sure that the heel remains on the ground. In this position, the participant then contracts the calf muscles as if trying to push the wall down.
To perform an isometric stretch, assume the position of the passive stretch and then contract the stretched muscle for 10–15 seconds. Be sure that all movement of the limb is restricted. Then relax the muscle for at least 20 seconds. This procedure should be repeated 2–5 times.