Stretching Too Long may be Bad for Muscle Growth
Just about every fitness book, magazine, article recommends to stretch before, during, and after exercise but have also been told to stretch before, during, and after workouts to stretch the connective tissue surrounding muscle cells to prevent injury. Stretching is thought to expand the muscle sheaths, which will allow the connective tissue to expand and allow for more growth of the muscle bellies. Researchers put the stretching theory to the test and examined muscle IGF-1 responses. Thirty people were randomly assigned into one of three training groups: a) static stretching before strength training, b) static stretching before each training set, and c) no stretching before or during exercise. Strength and IGF-1 levels were collected at the beginning (pre-test) and end (post-test) of the entire experimental procedure. The outcome was not positive for stretching before exercise. The group that did not stretch showed a significant increase in strength with all exercises, whereas the groups that stretched before or during exercise had increases in strength for only certain exercises. Researchers found that the group that did not stretch showed higher values of IGF-1 when compared with the other groups. It has been concluded that not stretching can more effectively increase muscle strength as well as basal serum IGF-1 levels. So despite what you have been taught for years, stretching is not good before or during exercise. If you decide to stretch, make sure it’s afterward.
Borges Bastos CL, Miranda H, Vale RG, Portal Mde N, Gomes MT, Novaes Jda S,
Winchester JB. Chronic effect of static stretching on strength performance and
basal serum IGF-1 levels. J Strength Cond Res. 2013 Sep;27(9):2465-72.