If you do it right, stretching your muscles makes them stronger. In the Journal of Strength and Conditioning Research, American sports scientists published the results of a study in which subjects increased the strength of both calf muscles – although they had only stretched their right calf muscle.
There's lots of confusion about stretching, and no one is to blame for this. Stretching is a bit like, well... everything really: the deeper you delve, the more complex it becomes.
First of all there's static stretching and dynamic stretching. Dynamic stretching before or during a workout can help enhance your performance. The extent to which it helps depends on the kind of movement. Static stretching before your workout on the other hand is bad for your performance. One theory is that static stretching before a workout worsens your brain's control over the muscles.
Of course you can also stretch your muscles on the days that you don't train them. Some studies show that this leads to a rapid rise in the speed with which the strength training increases your strength. Stretching probably causes minute tears in muscle tissue. When the muscles repair these they become stronger. That's the theory, at least.
The American study referred to here was undertaken to increase understanding of the mechanism behind the effect of stretching. The researchers got a dozen untrained subjects to stretch their right calf muscle for 10 weeks in a row. Three times a week, the subjects stretched their right calf four times for 30 seconds, as shown here.
A control group did not stretch.
At the end of the ten weeks, the range of motion [ROM] in the right ankle of the experimental group had increased by eight percent. In the left ankle there had hardly been any change.
What was more interesting was the effect on the maximal weight that the subjects could lift with their calf muscles [1RM]. This increased by 29 percent in the right leg, according to the table above. And what was even more interesting was that the stretch programme also increased the 1RM in the left calf muscle – even though the subjects hadn't stretched this muscle. The researchers registered an increase of 11 percent.
The findings suggest that the performance-enhancing effect of stretching on muscle strength is to some extent the result of the brain learning to direct the muscles better. Just like imaginary training.
"The results of this study would apply the best to rehabilitation settings", the researchers conclude. "Our results suggest that practitioners wishing to minimize strength loss in immobilized limbs should consider static stretching the mobile limb."
J Strength Cond Res. 2012 Mar;26(3):832-6.