This can be a very confusing topic for beginners, and I will talk about what most runners agree on, rather than the minority opinions. Some runners believe stretching and warming up are synonymous. I disagree, as would many other runners. Warming up is simply a transition from your resting heart rate to your training heart rate - slowly. I generally walk or jog for a few minutes to achieve this. Some people also refer to this stage as the 'cardiovascular warm up'. This is very important for people who are unfit and out of shape. (I should also add that if you are out of shape, it may be wise to consult your doctor before taking on any exercise program). Research has shown that a good warm up can help prevent DOMS and improve muscle efficiency. It increases your musclular elasticity and flexibility, which will also help prevent strains. After you have warmed up, it is generally regarded as a good idea to stretch.

Stretching, it's benefits are debatable. Some argue that they have never stretched and have never been injured. On the other hand, some swear they have never been injured because they stretch. Either way, if you do stretch, it should generally occur before your workout but after your warm up. Prehaps you could walk, stretch, jog and then run. I would recommend that you begin stretching just as you begin to sweat. Then you know your muscles are warm and ready for the work. This will help prevent you from damaging/straining your muscles too. When stretching, you should move far enough to reach discomfort, but not pain. Hold the final position for 30 seconds and repeat 3 times. You may also be intrested to know that running will result in inflexability as your muscles will shorten and become tight. Therefore, to maintain a healthy lifestyle, you should stretch as often as possible. If you've thought about it already, prehaps take up yoga. Some friends I know who have begun yoga courses swear by them. There is not much point in me reproducing materials that have been printed many times before, so for some good stretches see here. The first 7 will all aid running.

A part of running that is often neglected is the cool down. It is less time consuming than the warm up and easier too. After running, walk for a few minutes, and then repeat the stretches you did to warm up. If practical, walk for a few more minutes after. If you have done a fast or long run, I would recommend light exercise later in the day to aid recovery as this practice will help carry waste products away from the muscles and keep blood pumping which in turn reduces soreness.

It is understandable that it is not always practical to do these exercises, they can take a lot of time. However, I would stress starting your run slow if you miss out on a warm up or stretching, preferbably for the first 2 miles. However, the cool down is a must. Even if it's just walking for 5 minutes. Stretching and warming up will help prevent injury and improve your running experience, so invest as much time in it as possible.

See also: Leigh.Org