Welcome back to "Rock Your Body," The State News fitness and nutrition column. Each week, we hit up our local experts with some questions and pass on their wisdom to you.

But before we get to the goods, we thought we'd tell you a little bit about who'll be giving you advice.

Tom Ostrander: Tom is the owner of Powerhouse Gym, 435 E. Grand River Ave. He is one of Michigan's top amateur bodybuilding competitors. Tom is a personal trainer with experience ranging from professional athletes to stay-at-home moms.

Jim Pivarnik: Jim is a professor of kinesiology and epidemiology. Trained as an exercise physiologist, his specialty is in physical activity and exercise on chronic disease risk. He is also director of MSU's Center for Physical Activity and Health.

This week, we asked:

SN: What are the effects of taking caffeine? Is there a safe amount to ingest?

Jim: Because of its popularity, caffeine is one of the most researched chemicals that we ingest. There does not appear to be convincing evidence that caffeine is a cause of cancer or heart disease, although it may be related to increased stroke risk among individuals who have high blood pressure. Also, some doctors recommend that their pregnant patients not ingest caffeine, just to be safe.

Several years ago, there was a small body of research suggesting that caffeine may be an ergogenic aid - or something that allows a person to eliminate fatigue and increase body and mental labor.

This is due to the well-documented finding that caffeine ingestion can increase free fatty acid release into the blood. The researchers proposed that this might help prevent fatigue by sparing carbohydrate metabolism during endurance exercise. However, as with most other research on caffeine, no firm conclusion could be drawn due to variable results.

It is difficult to make sweeping generalizations whether caffeine intake should be limited. As with most things, moderation (about 300 mg, the amount in two to three cups of coffee) is probably reasonable.

Tom: The main effect caffeine has in the body is a stimulant effect. As with all stimulants, caffeine will raise your body temperature, thus creating a thermogenic or fat-burning effect.

Obviously, caffeine will wake you up and allow for greater intensity during exercise. Caffeine also acts as a diuretic - flushing the body of water. Most stimulant products have the same diuretic response.

I suggest ingesting no more than 200 mg of caffeine at a time - no more than two times per day. For reference purposes, 200 mg of caffeine is the equivalent of two cups of regular coffee or one Vivarin tablet.

SN: Can you overkill on aerobic exercise? How often should you if you are lifting as well?

Jim: Aerobic exercise is the "king" of exercises because of its many benefits. These include weight control, improvement of the cardio-respiratory system and reduction of chronic disease risk. But, like most things in life, just because a moderate amount of exercise is good for you, it does not automatically mean that a lot more is better. It depends on the individual.

For instance, many people on weight reduction programs perform a significant amount of aerobic exercise because of the calories expended. But if you are on a diet with a significantly negative caloric balance, muscle protein will be lost along with the fat.

For instance, upper body musculature will be sacrificed if only aerobic exercise is performed with the legs. In these cases it would be prudent to cut back a bit on the aerobic activity and add some resistance exercise. Research has shown that this will help spare the loss of muscle mass in people losing a lot of weight over time.

Tom: Yes, you can absolutely overdue aerobic exercise. People wishing to burn body fat need not to be so concerned with aerobics as they should weight-training. You can burn far more calories in a hour of weight-training than you will in an hour of cardio.

That is not to say cardio is not important. Simply, it is just not the most important part of the equation. Cardio done in conjunction with weights (after the weight-training session or first thing in the morning on an empty stomach) will supplement a fat-burning program nicely.

How much cardio one needs to do is a very individualized thing. Some people need more, some need less. Generally speaking, I start my clients off at 30 minutes three times per week. From there, we either increase the duration or the frequency as needed.

If you would like to have your questions answered, please e-mail them to msandu@statenews.com.