QUESTION: If this is not too esoteric a question, I'd like to know about muscles, their makeup and generation, etc., specifically about nutrition aspects - J.H.

ANSWER: You have 400 muscles, the tissue of which is 75 percent water, 20 percent protein, the rest made of small amounts of mineral and such substances as glycogen. Muscle is in a continuing state of change. It is, as we say, biologically active. For example, every few days, half of the muscles' protein is turned over.This biological activity within muscles makes it very amenable to outside influences, such as stimulation from exercise. Specifically, a great influence on muscle size is work overload. That means you challenge muscles with new demands on them. This subject is covered so well in almost any exercise book that there is no need to get into it here.

Nutrition is an important aspect of muscle physiology. You don't have to stuff yourself with protein to make muscles grow. You do have to eat a well-balanced diet. You don't have to overdo protein, for example. The emphasis should, in fact, be on complex carbohydrates (starches, pastas, vegetables and fruits). This provides most of the immediate muscle energy.

The average American diet does have plenty of protein in it, but that usually comes along with much too much fat and not enough of those complex carbs. So long as you keep these facts in mind, you should be able to manage any good muscle growth program successfully.

QUESTION: How can a person get specific information on how many calories are burned in various weight exercises? - W.C.

ANSWER: Many training books have pages devoted to this matter. Still, much of my mail contains questions asking about the calorie expenditure from this versus that exercise. So let me recommend a source for your answers. These are specific formulas to gauge various weight-lifting calorie expenditures. These were presented in a recent volume of the Journal of Applied Sport Science Research (Vol. 4, No. 3). There are specific formulas for estimating the calorie cost of the eight most common body building weight exercises.

Generally, you take the amount of weight used, multiply it by the number of reps (times lifted) and multiply that result by a certain factor supplied by the author for each specific kind of lift. Example: If you are bench pressing 200 pounds eight consecutive times (reps), you use this formula: 200 times 8 times .006. That gives you the number of calories (9.6) for the eight reps. Other formulas are used for other lifts.

QUESTION: I am 32 and have a groin hernia. I have been weight training for five years. I have two small hernias (on each side). Surgery is my decision. The pain is great. I don't want the surgery if it means an end to my weightlifting. Can I resume weightlifting later? - B.D.

ANSWER: First of all, if surgery is being recommended, you should have it done. If your present pain is due to the hernias, then repair should end that. And unless yours is a special case, you should be able to resume your lifting. This is particularly true of a man your age. Older persons may not form scar tissue strong enough.

Certainly, you will need specific approval on timing from your doctor. Expect at least a month or two before getting back into a routine. Early lifts will, of course, have to be less than you were accustomed to before your repair. Lots of hernia repair patients have taken up varying degrees of lifting later.

Want to get into shape? Dr. Donohue's pamphlet No. 12, "Introduction to Fitness" offers a fitness program anyone, regardless of age, can adapt. For a copy, send your request to Dr. Donohue/No. 12, P.O. Box 830, Gibbstown, NJ 08027-9909. Enclose a long, self-addressed, stamped (52 cents) envelope and $2.

Dr. Donohue welcomes reader mail but regrets that, due to the tremendous volume received daily, he is unable to answer individual letters. Readers' questions are incorporated in his column whenever possible.