I work out with Alison, my personal trainer, two or three times a week. We start each session with a round of dynamic stretching. This is simply stretching while moving. What most of us learned in high school gym class was static stretching, that is stretching while standing or lying still. Here’s an example of dynamic stretching: hold your left arm straight in front of you at shoulder height. Then kick your right foot up to touch your left hand. Then do your right arm and left foot. Repeat 20 times on each side. According to Wikipedia, “Dynamic stretching increases range of movement, blood and oxygen flow to soft tissues prior to exertion.” According to Alison, you perform better when you warm up with dynamic stretching rather than static stretching. At the end of a training session, on the other hand, we often cool down with static stretching.