Stretching is not warming up! It is, however, a very important part of warming up. Warming up is quite literally the process of "warming up" (i.e., raising your core body temperature). A proper warm-up should raise your body temperature by one or two degrees Celsius (1.4 to 2.8 degrees Fahrenheit) and is divided into three phases:
It is very important that you perform the general warm-up before you stretch. It is not a good idea to attempt to stretch before your muscles are warm (something which the general warm-up accomplishes).
Warming up can do more than just loosen stiff muscles; when done properly, it can actually improve performance. On the other hand, an improper warm-up, or no warm-up at all, can greatly increase your risk of injury from engaging in athletic activities.
It is important to note that active stretches and isometric stretches should not be part of your warm-up because they are often counterproductive. The goals of the warm-up are (according to Kurz): "an increased awareness, improved coordination, improved elasticity and contractibility of muscles, and a greater efficiency of the respiratory and cardiovascular systems." Active stretches and isometric stretches do not help achieve these goals because they are likely to cause the stretched muscles to be too tired to properly perform the athletic activity for which you are preparing your body.
The general warm-up is divided into two parts:
1. joint rotations
2. aerobic activity
These two activities should be performed in the order specified above.
The general warm-up should begin with joint-rotations, starting either from your toes and working your way up, or from your fingers and working your way down. This facilitates joint motion by lubricating the entire joint with synovial fluid. Such lubrication permits your joints to function more easily when called upon to participate in your athletic activity. You should perform slow circular movements, both clockwise and counter-clockwise, until the joint seems to move smoothly. You should rotate the following (in the order given, or in the reverse order):
After you have performed the joint rotations, you should engage in at least five minutes of aerobic activity such as jogging, jumping rope, or any other activity that will cause a similar increase in your cardiovascular output (i.e., get your blood pumping). The purpose of this is to raise your core body temperature and get your blood flowing. Increased blood flow in the muscles improves muscle performance and flexibility and reduces the likelihood of injury.
The stretching phase of your warmup should consist of two parts:
1. static stretching
2. dynamic stretching
It is important that static stretches be performed before any dynamic stretches in your warm-up. Dynamic stretching can often result in overstretching, which dam ages the muscles (see section Overstretching). Performing static stretches first will help reduce this risk of injury.
Once the general warm-up has been completed, the muscles are warmer and more elastic. Immediately following your general warm-up, you should engage in some slow, relaxed, static stretching (see section Static Stretching). You should start with your back, followed by your upper body and lower body, stretching your muscles in the following order (see section Exercise Order):
Some good static stretches for these various muscles may be found in most books about stretching. See section References on Stretching. Unfortunately, not everyone has the time to stretch all these muscles before a workout. If you are one such person, you should at least take the time to stretch all the muscles that will be heavily used during your workout.
Once you have performed your static stretches, you should engage in some light dynamic stretching: leg-raises, and arm-swings in all directions (see section Dynamic Stretching). According to Kurz, you should do "as many sets as it takes to reach your maximum range of motion in any given direction", but do not work your muscles to the point of fatigue. Remember -- this is just a warm-up, the real workout comes later.
Some people are surprised to find that dynamic stretching has a place in the warm-up. But think about it: you are "warming up" for a workout that is (usually) going to involve a lot of dynamic activity. It makes sense that you should perform some dynamic exercises to increase your dynamic flexibility.
The last part of your warm-up should be devoted to performing movements that are a "watered-down" version of the movements that you will be performing during your athletic activity. HFLTA says that the last phase of a warm-up should consist of the same movements that will be used during the athletic event but at a reduced intensity. Such sport-specific activity is beneficial because it improves coordination, balance, strength, and response time, and may reduce the risk of injury.