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Definition: "An ergogenic aid is any substance or phenomenon that enhances performance "

10.02.2010

Dynamic stretching between sprints better than rest

You recover more quickly between short explosive bursts of exercise if you do dynamic muscle stretches rather than resting or exercising gently. Physiologists at the Picardie Jules Verne University in France reach this conclusion in the Journal of Strength & Conditioning Research. Their study is based on trials they did with 10 soccer players aged 25.

The researchers wanted to know which of three well-known recovery techniques work best when doing intensive exercise: dynamic stretching [RS], passive recovery [PR] or active recovery [AR]. Dynamic stretching refers to stretching your muscles with a pumping action. As you stretch you repeatedly go for the point where you feel that your muscles are extending. Passive recovery means doing nothing, and active recovery involves continuing the movement you were doing, but at a low level of intensity.

The researchers got their subjects to sprint on the bike at 120 percent of their maximal aerobic capacity. That's a rate at which you use 20 percent more oxygen than your body is capable of taking in. You can only do this for very short bursts.

First the test subjects sprinted for 30 seconds, 4 times. Between sprints they rested for 30 seconds. At the end of the series they did a 4-minute recovery, using RS, PR or AR. Then the subjects repeated the whole procedure. And after that, they had to cycle for as long as they could at 120 percent of their maximal aerobic capacity.

When the subjects used stretches to recover – they stretched their quads and hamstrings – they were able to cycle for longer during the test.

Dynamic muscle stretching, and to a lesser extent active recovery, enable the heart to beat faster so the body can take in more oxygen. But perhaps the most important mechanism involved in both recovery methods is that they reduce the concentration of lactic acid in the blood, the researchers discovered.

The researchers base their explanation on a theory that's been around for a while. Lactic acid inhibits the formation of glycogen in the muscle cells, goes the theory. Get rid of the lactic acid and performance improves.

An alternative explanation may be that lactic acid actually provides muscle cells with energy. And that would seem to go faster if you don't rest completely between exercise bursts, but stretch your muscles instead.

Source:
J Strength Cond Res. 2010 Jan 21. [Epub ahead of print].