Have you ever wondered why you get a stitch in your side when you exercise or why you don't sweat more when you work out? Jan Bishop answers many commonly asked questions about exercise in Fitness through Aerobics, 5/e. Here's a sampling . . .

Am I working hard enough if I don't sweat much?

Sweat is not a good measure of exercise intensity. Different people sweat different amounts and in different places. Some sweat profusely before they even cross the training threshold. Others hardly sweat at all. Heart rate is a better indicator of intensity. Men usually sweat more than women because they have more sweat glands and more muscle. When muscle is working, heat is generated--the more muscle the more heat. Sweat is a good thing. The evaporation of sweat cools the body.

Is it good to "go for the burn"?

The burn is the feeling you get when your muscles are working so hard that oxygen cannot be supplied to them fast enough to produce energy. This ischemia (lack of oxygen) and the accumulation of lactic acid make your muscles feel heavy and sometimes cause a burning sensation. If you are trying to work aerobically, the burn is counter-productive because it is a product of heavy anaerobic exercise. Body toning exercises are anaerobic, and it is during these exercises that you are most likely to feel the burn. If you do, you should change the exercise or take a short break to allow blood to circulate through the limb. This will enable you to exercise longer and eventually develop better endurance.

What is cross training, and should I do it?

To cross train is to use two or more types of exercises to train. For example, you can train aerobically using both swimming and aerobic dance exercise. Because each activity uses your muscles differently, you will get a more complete workout. But you do not need to cross train to achieve health-related fitness--each activity by itself provides a good aerobic workout. Cross training can help combat boredom and prevent overuse injury, two reasons that people drop out of programs. Cross train if it appeals to you and if you want to increase your skill and ability in more than one activity.

Will a candy bar before class give me quick energy?

It will give you a short burst of energy and then actually drop your blood sugar. Whenever the blood glucose level gets too high, the liver excretes insulin, which acts to lower the blood sugar. When a lot of sugar is introduced to the system quickly, the liver puts out a lot of insulin. That much insulin ends up dropping the blood sugar below the level it was at prior to the candy. Halfway through class you may suddenly feel very hungry or even sluggish from low blood sugar. You would be better off eating a few crackers or a piece of fruit before class.

How can I tell if I am overtraining?

One way to tell is to monitor your resting heart rate first thing in the morning. If it starts to increase, give yourself a day off. Another sign of overtraining is loss of strength. Strength gains are made only when the muscle has enough time to rebuild between exercise bouts. Chronic injury, lethargy, lack of motivation, and chronic fatigue are all signs of overuse.

I get a side ache (stitch) when I exercise. Why does this happen, and what should I do?

A side ache is usually caused by a bubble of gas caught in your system. Eating too close to the time of exercise or starting your exercise too quickly may cause it. To relieve a side ache, try stretching up with the arm on the side giving you distress. If it continues, slow down your activity and try doing some side and waist stretches.

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