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13.02.2013

Static muscle stretching before training reduces maximal strength

There's nothing wrong with stretching your muscle groups: it prevents injury and may even speed up muscle growth. But you're better off avoiding static stretches before starting a training session. Even if you've been training for years, you'll reduce your strength, write researchers at the Universidade Nove de Julho in Brazil in an article soon to be published in the Journal of Strength and Conditioning Research.

You can stretch muscles 'dynamically' and 'statically'. Dynamic stretching involves 'pumping': you adopt a stretch pose, then keep on stretching to the point where you feel the stretch in your muscle, and then release it so that the muscle returns quickly to its original length. Then you repeat the procedure. Dynamic stretching boosts performance when done before an sprint training session or during rests between sets.

Static stretching is done by stretching until you feel the stretch in the muscle, and then maintaining that position for a longer amount of time. This way of stretching is safer than dynamic stretching, but if you use it just before a weights or running session then your performance will suffer. The Brazilians examined this aspect in their study.

Most human studies on the effect of stretching used untrained students as the test subjects. But do men and women with years of weight training experience react in the same way? To answer this question the Brazilians performed a small study using 9 untrained [UT] and 11 trained [RT] males in their twenties. The trained men had been doing weight training for six months.

The researchers got their subjects to do static stretches for their chest muscles, upper back muscles, biceps and thigh muscles. They then measured how many kg the men were able to shift just once using these muscle groups, for the bench press, lat pull-down, biceps curl and leg press.

As the table below shows static stretching reduced maximal strength.

The figure above compares loss of maximal strength in the untrained men and the trained men. Although there's a tendency for the negative effect of static stretching to be lower in the trained men, it's clear that static stretching does reduce maximal strength by several percent in trained individuals.

"A passive static stretching program prior to resistance training is detrimental to maximum muscle strength development", the Brazilians conclude. "From a practical standpoint for coaches and trainers, it seems inappropriate to encourage static stretching before athletic events or physical activities that require high levels of muscle strength."

Source:
J Strength Cond Res. 2012 Nov 30. [Epub ahead of print].

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