The last installment of TTC attempted to debunk the conventional wisdom pertaining to the use of the so-called “hurdler’s stretch” to lengthen the hamstring muscles. Now let’s take a look at another doctrine (one that spurs us to be so conscientious about stretching these muscles) often accepted as gospel. This would be the belief that tight hamstrings lead to injured hamstrings.
Make no mistake, hamstring strains are among the most common injuries suffered by runners. And it may well be true that tight hamstrings possibly increase the risk of injury for sprinters, due to the high-force ballistic motion place these muscles under great strain. The scenario for distance runners, however, may be completely different.
Strain injuries in sprinters are generally macroscopic in nature. That is, the muscle fibers sustain gross tearing which could be seen by the naked eye were the leg opened for inspection. Actually, we can sometimes “see” this, without resorting to such drastic measures, by the ecchymosis (“black and blue” area) which develops in the severely strained/pulled/torn hamstring soon after the injury occurs.
Distance running, however, places a different kind of strain on the hamstrings. The repetitive, low-force motions we find in long, (relatively) slow distance running can, over time, result in injury, but I believe the microscopic tears that occur are due more to tissue failure from overuse (something like metal fatigue in bolts on a vibrating bridge) than forceful rupture of short, tight fibers. This overuse is usually the result of muscle imbalances or gait abnormalities that demand more activity from the hamstrings than is normal. A typical example of this would be when weak external hip rotators in the buttock force excessive, compensatory recruitment of the lateral hamstrings — a secondary hip external rotator.
I make the preceding assertion mostly from an experiential standpoint and admittedly without any hard, scientific evidence to back it up. The most important observation I have made over the years is that maybe only half of runners I have seen with hamstring strains actually have tight hamstrings! In fact, many exhibit inordinate flexibility. Almost all, however, display one or more of the muscle imbalances or gait deviations that would cause the hamstrings to be used excessively.
The bottom line of all this? If this hypothesis is true, does stretching make sense as a treatment for hamstring strains? To put it another way, if you already have fibers that have been torn, even on a microscopic level, and are in a weakened state, do you really want to be pulling those fibers further apart, especially in the acute stage?
Seems to me this is another conventional wisdom that needs to be reviewed.
