Best Time to use Dynamic Stretching. One of the main purposes of dynamic stretching is to prepare the body for activity or sport, which is why dynamic stretching is so effective as part of a warm up routine. Please note though, that dynamic stretching is not THE warm up, is it only PART OF a warm up. A proper warm up has a number of very important key elements. These elements, or parts, should all work together to prepare the individual for physical activity and minimize the likelihood of sports injury.