I read an interesting article on stretching for exercise that most active people, including runners, would find beneficial. The article listed three basic types of stretching that people do before exercise and to increase flexibility. One is ballistic stretching, a second form is static stretching, and the third was proprioceptive neuromuscular facilitation (PNF). Much of the stretching types centered on the type of activity the athlete was participating in. Some activities need more flexibility than others. Gymnastics needs more flexibility that running. Wrestling needs more flexibility (especially when put into a hold that really pushes the limits of a limbs range of motion) than boxing. Various sports need a specific joint or limb to be more flexible to perform well. Tennis, or a goalie in ice hockey, need hip joint flexibility when stretching for a ball, or trying to stop a fast moving puck.
Runners like to stretch out the legs and low back to help prevent tight muscles during a run. The key point for runners and stretching is it is important to warm the muscle up first. The easiest method for warming up for a runner is to go for a jog around the race area to increase circulation to the leg muscles and to warm the body up. There is some research that recommends the active stretching from running rather than the static type stretching that you see most runners doing before a race. The logic to this is that running warms the muscles used in running and increases the nerve innervation for muscle contraction. Static stretching tends to lengthen the muscle and decreases the ability to contract faster when actually running. Static stretching after the race helps get rid of lactic acid build up from muscle contractions and stretches out the muscles that are tight after a hard run.
The one type of stretching that most trainers do not recommend is the ballistic, or bouncing, form of stretching. When an athlete uses momentum to increase the range of motion there is a good possibility that the movement goes beyond the limits of the muscle and will result in a slight tear of the muscle. A slight bounce might feel good but the danger is when the athlete really increases the momentum to get the extreme range of motion. The result is often a strain, or tear, in the muscle.
Static stretching puts the muscle on a stretch and then holds that position for 30 seconds or more. The key is to put the muscle on an easy stretch. In this case pain is not a good thing. I prefer the stretch for the hamstrings where the athlete sits down, draws the upper thigh tight against the chest, and then tries to lift the foot up as high as it will go. Even if the athlete tries a ‘bounce’ move, or a fast kick, the weight of the foot is so light that the possibility of achieving enough momentum to strain the hamstring muscle group is almost zero. The athlete reaches up as high as the foot will go and then holds that position for 15-30 seconds. It is important to keep the thigh tight against the chest the entire time and not let it move away from the chest. The lower leg, the calf muscle, seems to work well by keeping the heel on the ground as you lean against a support. Remember to do a bent knee stretch for the lower leg as there are two muscles in that region. Bending the knee isolates the soleus muscle.
The PNF form of stretching in some research seems to work the best for increasing a range of motion in a muscle. This form is best done with a partner. As an example for a hamstring stretch, the athlete lays on their back with one leg extended up in the air. The partner pushes the leg until the athlete reaches the range of motion limit. Then the partner holds the leg while the athlete tries to push against the resistance. After 15 seconds, the athlete relaxes the muscle, and the partner will see if they can push the leg a little farther. I used this method when I was a strength and flexibility coach for the NHL Hartford Whalers team. It seemed to help some of the players increase their range of motion.
There is a fourth method of stretching that I see with karate athletes. They put a brace between the legs and it will stretch the inside of the upper leg. The athletes can increase the range of motion limits with a lever. They can increase the limits of stretching, if they can take the discomfort of the extreme range of motion.
Some people think that as you get older you lose flexibility. The only reason you lose flexibility is you stop stretching. Flexibility will remain as long as you keep stretching.