A warm-up prepares the body for the activity that is to follow. The two types of warm-ups are general and activity-specific.
Physiologic changes that occur during warm-up include an increase in muscle temperature, blood flow, oxygen delivery to the muscles, and skeletal muscle metabolism. Warm-up benefits include injury prevention and an improvement in performance.
Cold muscles should not stretch, and there is a high chance of injury when stretching is performed without first warming up. Stretching, especially dynamic stretching maybe part of (or follow) a warm-up, but should not exclusively comprise the warm-up.
Stretch only after an adequate warm-up has been performed.
General(or unrelated) warm-up
General(or unrelated) warm-up involves movements eg running in place, jumping jacks, and other calisthenics that is different from or unrelated to the specific activity that is to follow.
This type of warm-up should be performed prior to high-intensity activities eg powerlifting, gymnastics, strength training when immediate participation in the actual activity is likely to result in joint or muscle injuries.
Activity specific warm-up
Activity specific or related warm-up occurs with a low-intensity version of the activity that is to follow. Examples of activity-specific warm-up include a slow jog prior to the long run; slow cycling in preparation for a cycling event; or slow karate moves prior to practice.
A related warm up starts out slowly and progresses to more intense activity. Depending on the activity to be performed, a warm-up of anywhere between 10-30 minutes maybe required-the the greater the intensity of the workout, the longer the warm-up.
All warmups should be of sufficient intensity to elevate body temperature, sweating is a good indication that you are ready to move on to the next phase of your workout.
Both general and activity-specific warm-ups may incorporate some type of stretching, especially if the activity to be performed is one of high intensity and imposes a good chance of acute injury. After a short period of warming up, some pre-exercise stretching should be done.