Overview

Flexibility for running is important for two reasons: to prevent injury and to allow for a full range of motion to generate maximum speed. While flexible athletes are not always the fastest runners, inflexible athletes are quite often injured runners. Therefore, it is necessary to maintain at least a minimum amount of flexibility. 

Not surprisingly, lower body flexibility is the key to preventing most running injuries. Runners should work on ankle, calf, hamstring, quadricep, hip, groin, and IT band flexibility. In addition, some occasional upper body flexibility exercises (shoulders, neck, etc.) are not a bad idea to encourage total body conditioning (especially if you are doing an upper body weight program.) 

Ideally, stretching should be done daily. Realistically though, most people do not have the patience to stretch every day. A good goal is to aim for 3 to 4, 15 to 20-minute flexibility sessions per week. Ideally these sessions would occur after a running workout. If this is not convenient, then working a stretching session into a weight workout or stretching while watching t.v. could be attempted. 

Each stretch that you do should be done slowly and held for 5 to 30 seconds. One way of doing this is to hold the stretch at the point of tightness for about 20 seconds and then push beyond this point (i.e. to the point just before discomfort) for 10 extra seconds. 

Like all things, however, stretching can be overdone. Repeatedly stretching far beyond the normal range of motion in a joint can cause injury: either traumatic injury (e.g. tearing a muscle or tendon) or an overuse injury (e.g. excess movement caused by joints which are too loose.) 

In summary, stretching may not make you a faster runner, but some flexibility training should reduce the incidence of injuries.