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30.10.2009


Stretching before training reduces strength

If you stretch your muscles first before starting training, you will reduce the quality of your training session. You'll develop less strength, researchers from Sao Paulo State University write in an article that will be published soon in the Journal of Strength and Conditioning Research.

Stretching before training reduces strength
The researchers did experiments with a couple of dozen women whose average age was 65.The women had started doing fitness training four months before they were subject to measurements, and trained three times a week. In the researchers' exercise laboratory the women had to exercise their legs at maximal strength.

On some occasions the women started with a Standing Unilateral Quadriceps Stretch, shown in the illustration. In this exercise you stretch the muscles with slow movements and hold the stretch for 10-40 seconds. After that the researchers tested the women's maximal strength a couple of times after each other. On the other occasions the women exercised without stretching.

The women developed less maximal strength in their legs as a result of stretching. The table below shows this. MVC is the abbreviation for maximal voluntary contraction, a measurement of strength.


Stretching before training reduces strength


When the researchers attached electrodes to the women's leg muscles, they noticed that the stretching did not reduce the electric activity in the muscles. Control = without stretching. The S-measurements were done at five-minute intervals. VM = vastus medialis, VL = vastus lateralis, BF = biceps femoris.


Stretching before training reduces strength


It's not the first time that sports scientists have recorded the negative effect of stretching before training. One theory that has been put forward to explain the effect is that stretching reduces the connections between the muscles and the nervous system. This study shows that this is not the case. It seems that stretching changes something in the muscle itself.

"If static stretching is used to improve flexibility, then it is recommended that this stretching is not practiced just before the performance of activities that require high levels of muscular force", the researchers conclude. They emphasise that they studied a static form of stretching, and therefore can say nothing about other forms of stretching.

Source:
Journal of Strength and Conditioning Research Oct 2009 23(7) 2149-54.