Editors note: Health with Heidi will now appear in letter format. Readers with questions for Heidi can e-mail them to Heidi at email@example.com. Dear Heidi, When I go to the gym I often hear trainers telling their clients to warm up and cool down. What counts for this and why is it so important? Chelsea, Shelburne Dear Chelsea, Warming up before a workout and cooling down after are extremely important. Many people skip these steps and I myself have witnessed the effects of doing so, and it isnt pretty. A good warm up should be performed before any form of exercise, whether it be aerobic exercise or strength training. The main purposes of a warm up are to increase blood flow, oxygen, and energy substrates to the working muscles, as well as to increase core temperature and metabolic rate from resting to exercise levels. A proper warm up consists of approximately 8-12 minutes of a combination of limbering and static stretching. The limbering can be walking on a treadmill for 5 minutes, jumping rope, or riding the stationary bike at a slow pace. The main goal is to get the muscles warm so that they are more pliable and ready for the work you are about to do. Think of it as if you were a blacksmith. You need to heat the metal before you can bend it, right? If you dont, it will just snap. Thus, if we heat our muscles before we put them to work, we prevent the risk of injury. After a good limbering session, it is important to stretch the muscles you are about to work. Static stretching consists of holding a stretch for 17-20 seconds. Focus mainly on the muscles you are about to work to get them ready for the additional workload. Cooling down is equally as important, but for different reasons. Stopping exercise suddenly without a sufficient cool down can cause a sudden drop in blood pressure, which can cause you to feel light headed and nauseous. For people with pre-diagnosed heart concerns, stopping suddenly can actually cause heart arrhythmias, which can be potentially fatal. A proper cool down should consist of a 5-10 minute period of gradually decreasing intensity exercise followed by another session of static stretching. It has been said that stretching after exercise can actually reduce the effects of DOMS (delayed onset muscle soreness). The most common excuse for skipping these two critical steps in an exercise routine is usually lack of time. In my opinion, it is better to cut down on your workout time in your target zone and fit these steps in then to not do them at all. The risks involved with not performing a proper warm up and cool down far outweigh the benefits of an extra 10 minutes on the treadmill at your fastest pace. Besides, if you pass out and cant workout for a few days, you will be gaining those calories back and them some. In short, warming up and cooling down will not only make your workout safer, but because your muscles will be prepared for the work and ready to do it efficiently, you can potentially burn more calories and increase your stamina.