We always figured that stretching made us more flexible by loosening up our muscles and joints. Some of us, ahem, might have even tried to fall asleep in our middle splits to get our stubbornly stiff inner thighs to let go.
But it turns out that might not actually be how stretching works.
A new review published in the Scandinavian Journal of Science & Medicine in Sports suggests that increased flexibility actually comes from your brain growing more used to the tension.
Former Scottish Ballet dancer Eve Mutso. Photo by Quinn Wharton
Researchers investigated two competing ideas about how stretching increases your range of motion:
The Mechanical Theory: Regular stretching physically alters the muscles, joints and tendons by lengthening them or making them less stiff.
The Sensory Theory: Regular stretching teaches your body to tolerate more of the tension that's caused by stretching.
After looking at the results of 26 studies lasting between three and eight weeks in which participants stretched a couple times a week, researchers found that participants were able to handle moving in a greater range of motion, but there were only small physical changes noticed in their muscles, joints and tendons. Which seems to support the sensory theory rather than the mechanical one.
Of course, it's possible that physical changes may simply take longer than the neuromuscular ones—we'd love to see a study that looks at what happens in the body after a year's worth of stretching. But it's fascinating to find out that at least part of what's going on every time you inch your nose closer to your knee is a change in your brain.