Is it correct to make a brief stretching session even during physical activity, and not just at the end?
Currently, there's no credible studies that show static stretching during exercise is helpful. In fact, as a result of some recent studies, the opposite seems to be true. That is, static stretching before and during a training session can have a negative effect. A study by the Journal of Strength and Conditioning, Chronic Effect of Static Stretching on Strength Performance and Basal Serum IGF-1 Levels found that strength training, performed without any form of stretching before or during, can more effectively increase muscle and basal serum IGF-1 levels (a muscle building hormone).
In the new study, the participants either performed strength training with stretching done before hand, strength training with stretching done during sets (the sort of thing you see all the time in the gym), and strength training alone. They compared the strength results and levels of IGF-1, a muscle building hormone, in each of the three groups after 10 weeks of training.
These findings were supported by a second study that was published in The Scandinavian Journal of Medicine and Science in Sports, leading many to believe that
“stretching before exercise is not only unnecessary, but it may actually be counterproductive, as well.”
The Scandinavian study concluded that...
“We conclude that the usage of SS as the sole activity during warm-up routine should generally be avoided. “
Since these studies were relatively short with a small control group, more research is needed. But, the general consensus is that static stretching is best when performed at the end of your training session.