Preparing your body for a workout by warming up is an excellent way to help prevent injury, just as warming down is important to help reduce DOMs, allows your blood pressure to ease down and prevents cramping. Though warming up and cooling down are very different things. Too often I have seen people stretching before and after their workout, comfortable in the idea that they are both warming up and cooling down effectively. Yet this isn’t the case. Warming up, and cooling down are important considerations to any workout, yet their purposes are very different.
Warming up: The purpose of warming your body up is to kick start your cardiovascular system into pumping extra blood to all the muscles you are about to use. Though this can be achieved with dynamic stretching (such as rolling your shoulders or trunk rotations), it is not done effectively by static stretching (moving into a stretch and holding for a period of time). In fact, static stretching cold muscles can actually have an adverse effect. The idea of a warm up is to move the body vigorously (but not too intensely) and get your heart pumping. For example, a slow jog or skipping rope is an excellent warm up before sprinting or doing a leg session, whereas rowing or star jumps are an excellent way to loosen up your arms and get the blood pumping here before lifting weights.
Warming up before a workout means literally warming yourself up. Moving your body, or at least the areas you are going to be focusing on, in order to get the blood pumping and your muscles warm and ready for a challenge.
Cooling Down: The purpose of cooling down your body after a workout is to allow for gradual recovery and a slowing of your heart rate. For example, if you have been running for 10 km, then an appropriate cool down might be to move into a jog then into a walk for a further 500m or so, to allow your heart rate to slowly return to normal and your muscles to ease off.
Stretching: As I mentioned before, there is a difference between static and dynamic stretching. Though dynamic stretching can be an excellent option to stimulate blood flow to specific muscles as part of a warm-up, static stretches are not. Static stretching, however, can be used after a cool down to help stretch out and relax muscles that you have been working on in order to help reduce stiffness and help avoid DOMs.