Regular Breaking Muscle readers will be well versed by now in the ill effects of static stretching on strength. If the concept is new to you, it’s pretty simple: the type of static stretching commonly used in many athletes’ warm ups actually makes you weaker for a short time after stretching. In a study this month published in the Journal of Strength and Conditioning Research, investigators wanted to know if this effect extended to cardio training as well.
While the effects of static stretching on strength are well known, it is only recently that researchers have begun focusing on how it may impact endurance performance. Part of the reason strength and power decrease after static stretching is that it relaxes the muscles and associated tendons. This relaxation reduces the stretch response. Because a muscle and its tendons store energy when being rapidly stretched (often called a countermovement), reducing this stretch response weakens the athlete.
During a run, the relaxation of the muscle and tendons may similarly affect the phase in which you push off of the ground. As your foot makes contact with the ground, it stores energy, which it then uses to drive you into the air. This is why at fast speeds, running is more efficient than walking.
The primary difference in energy output when running is in ground contact time. In all sports that involve running, it’s well known that contact time with the ground limits performance. If the ability to push off the ground is reduced by stretching, then it stands to reason that static stretching might also hinder endurance performance, specifically by decreasing running economy. Essentially, running after static stretching will requires more energy.
The researchers in this study noted that running economy is likely affected by static stretching, but only at the start of endurance exercise, after which the body acclimates and economy improves. They looked at performance over a short run of one mile. The mile test was at a five percent uphill grade, which increased the strength component required to maintain a low contact time. The researchers measured more than just the time it took to complete the mile. If there was a difference in performance, they wanted to know why. So they also looked at ground contact time and also muscle activation via electromyography (EMG).
When the runners stretched, they were indeed slower at running the mile by a full thirteen seconds, which is quite a long time in a one-mile run. The researchers found that muscle activity and ground contact both increased after stretching, indicating it took more effort to complete the run which resulted in the slower times. The researchers did find that flexibility was greater after stretching, which came as no surprise.
This study demonstrated that static stretching does, in fact, reduce endurance performance, at least at the beginning of a run. The effect is probably caused by a reduction in running economy, and while it seems to fade over the course of a long run, it’s significant at the beginning of a run. Enough so that static stretching should be avoided even in long distance runners.
1. Ryan Lowery, et. al., “Effects of Static Stretching on 1-Mile Uphill Run Performance,” Journal of Strength and Conditioning Research, 28(1), 2013.
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