NO. 7: STRETCH BEFORE RUNNING
Limbering up has long been a part of the precompetition routine for runners, but research does not back up its usefulness. Study after study has found that increased flexibility actually impairs performance. Static stretching—the kind in which you bend to a position and hold it—decreases the elasticity of muscles and tendons, which causes them to return less energy with each stride. Imagine a Slinky: Each contact with the ground produces more bounce if the Slinky is taut and tightly coiled as opposed to loose and stretched out.