But in the best recent controlled studies, stretching has not reduced the incidence of injuries to the lower extremities to a statistically significant degree. On the basis of such studies, many exercise physiologists advise runners not to stretch.
The main problem with this advice and the studies upon which it is based is that they come at stretching from the wrong side of injury. Targeted stretching of abnormally tight muscles and tendons has proven to be an extremely effective means of rehabilitating and preventing the recurrence of specific injuries in runners.
This is because abnormal tightness in specific muscles and tendons is without question a contributing cause of particular running injuries, and stretching can increase the elasticity of muscles and tendons.
Every day, physical therapists prescribe targeted stretching exercises to rehabilitate and prevent recurrence of five different injuries that are frequently associated with tightness in muscles and tendons.
Abnormally tight calves and Achilles tendons contribute to plantar fasciitis, shin splints, Achilles tendinosis, and calf muscle strains. Abnormally tight hamstrings and hip flexors often precipitate strains in these muscles. And an abnormally tight iliotibial band is commonly seen in runners suffering from IT band friction syndrome.
There is no doubt that stretching plays a positive role in the successful rehabilitation of many cases of these injuries, so it only stands to reason that it can also prevent many cases of these same injuries (or at least prevent their recurrence).
For this reason, I recommend that you stretch the above-mentioned muscles and tendons daily.
Another controversial question is the relationship between flexibility and performance. Stretching advocates claim that runners need to be very flexible in order to take long strides. Others believe that runners get all the flexibility they need through the activity of running itself.
In this case both sides are half-right. There are two muscle groups that are unusually flexible in most elite runners: the hips and the shoulders. Non-elite runners can surely benefit from stretching these muscle groups and thereby increasing the range of motion of the shoulders and hips.
But this alone will probably not improve your stride length, because regular stretching exercises increase only passive range of motion, whereas running requires dynamic flexibility, which is the ability to perform sports movements with minimal internal resistance from your own muscles and joints.
This is the distinction that stretching skeptics are trying to get at when they say running itself gives us all the flexibility we need. While the distinction is real, the best way to increase dynamic flexibility is not by running but rather by performing dynamic stretching exercises.
Dynamic stretches are movements that mimic the way your muscles and connective tissues actually stretch during running. An example is the leg swing (described below).
Performing dynamic stretches on a regular basis reduces internal resistance in your running movements and thereby enhances the efficiency of your stride.
These stretches also make for excellent warm-up movements, because they increase dynamic flexibility acutely from resting to active levels by warming, loosening, and lubricating the muscles.
Dynamic stretching warm-up
The following dynamic stretching warm-up will increase your active range of motion for individual workouts and increase your dynamic flexibility generally. Do it 2-3 times per week as a part of your warm-up, following several minutes of easy jogging.<!--insertad-->
Swing your right arm in a giant circle. Do 6 forward rotations and 6 backward rotations and then repeat with your left arm.
Raise your arms straight out to the sides. Twist your torso as far as you can to the right. Without pausing, reverse direction and twist over to the left. Repeat 10 times.
Stand on your left foot and swing your right leg backward and forward in an exaggerated kicking motion. Complete 10 swings and repeat with the left leg.
Side leg swings
Stand facing a wall, lean forward slightly at the waist, and brace your hands against the wall. Lift your right foot off the ground and swing your right leg from side to side (like a pendulum) between your left leg and the wall. Do 10 swings and then switch to the left leg.
Take 10 giant steps forward with each foot, lunging as far forward as you can each time.
Lean forward against a wall with your feet close together and flat on the ground. Raise both heels as high as possible and then "bounce" them off the ground. Repeat 20 times.
Matt Fitzgerald coaches runners and triathletes and is the author of "Triathlete Magazine's Complete Triathlon Book" and "Runner's World Guide to Cross-Training."