What is dynamic stretching, and why has everyone turned their backs on the old school stretches I learned in grade school?
Stretching is a really controversial topic right now. For every coach who tells you to stretch before a race, you’ll find one who tells you not to stretch. As a general rule, casual athletes should do some static stretching (where you hold the stretch for 30 seconds), but only after a workout. You don’t want to stretch a cold muscle. Dynamic stretching is when you move through the stretch quickly. Watch Olympic swimmers before a race swing their arms around. That’s dynamic stretching. It’s an effective method of improving flexibility while warming up the muscles. If you’re an elite athlete looking to improve performance, then dynamic stretching will get your muscles warmed up and ready for the quick, fast motions of striding or sprinting. Do a short five-minute warmup, then a simple dynamic stretching routine.
—Scott Murr, professor of exercise science at Furman and Ironman triathlete.

Simple Dynamic Stretch: Leg Swings
While standing, swing your right foot as high as you can in front of your body, then as high as you can behind you, which will stretch your hamstrings and hips. Repeat 10 times, then move to the left foot.

Advanced Dynamic Stretch: The Caterpillar
Start in the push-up position. Drop your hips to the floor to stretch your abs and hips, then walk your feet up towards your hands, keeping your legs straight. When you can’t walk any further, walk your hands away from your feet. Finish with dropping your hips to the ground, and repeat. This will stretch your hamstrings as well as your hips, abs, and shoulders.