The post-workout calorie burn: Do you burn extra calories after a cardio workout? What about strength training? And more of your questions answered here - Fitness Q&A

Shape, April, 2002

Q: Is it true that your body continues to burn extra calories for 12 hours after you've worked out?

A: Yes. "After vigorous exercise, we've seen caloric expenditure increase for up to 48 hours," says exercise physiologist Tom R. Thomas, Ph.D., director of the exercise physiology program at the University of Missouri in Columbia. The longer and harder you work out, the greater the post-workout metabolism increase and the longer it lasts. Subjects in Thomas' research burned 600-700 calories during one hour of running at about 80 percent of their maximum heart rate. During the next 48 hours, they burned about 15 percent more calories -- 90-105 extra -- than they otherwise would have. About 75 percent of the post-workout metabolism increase occurs in the first 1 2 hours after exercise, according to Thomas.

Weight training does not appear to offer as significant a post-workout metabolism increase as intense aerobic exercise, Thomas says, probably because of the rest between sets. A number of studies suggest that, after a 45-minute weight-training session -- three sets of 10 reps per exercise -- resting metabolic rate is increased for 60-90 minutes, burning an extra 20-50 calories. However, keep in mind that strength training is an excellent way to boost your resting metabolic rate (the number of calories your body burns at rest). While aerobics appears to offer more of a post-workout spike in metabolism, strength training enables you to develop muscle mass, which, in turn, increases metabolism overall.

Q: I bought a heart-rate monitor that calculates calories burned during cardio activity. Both the monitor and the treadmill at my gym ask for my age and weight, but there is a huge discrepancy in the calorie information. For example, after exercising on the treadmill for 45 minutes, the machine says I have burned 500 calories. My heart-rate monitor, on the other hand, says I have burned only 350 calories. Which one is more accurate? Why is there such a big difference?

A: The heart-rate monitor is probably more accurate, although both are just estimates. "They're both not taking into account a lot of information," says exercise physiologist Ed Burke, Ph.D., a professor of exercise science at the University of Colorado in Colorado Springs. For instance, the number of calories you burn is related to your body weight. A 150-pound person will burn more calories per minute than a 130-pound person will.

Your heart-rate monitor is likely to be more accurate than the treadmill because it uses personalized information (e.g., your heart rate) about how hard you're working. "The higher your intensity, the more oxygen you're consuming," Burke explains. "And there is a correlation between oxygen consumption and calories burned." The treadmill will provide the same calorie information for two people who weigh the same and run at the same pace. But if one person is more fit and therefore not working as hard to maintain the pace, that person will actually be burning fewer calories.

Another issue with treadmills, Burke says, is that between about 3/2 mph and 41/2 mph, the treadmill can't tell if you're walking or jogging. (Above 41/2 mph, most people jog; below 31/2 mph, most people walk). Oftentimes you can burn more calories jogging than walking, but at fast speeds, such as 51/2 mph, walking burns more.

Q I work each muscle group every other day in the gym. A friend says I will get stronger if I just hit each muscle twice a week. Is he right?

A "The answer depends on whether you are a beginner or more advanced," says Wayne Westcott, Ph.D., research director at the South Shore YMCA in Quincy, Mass. Beginners tend to gain more strength and muscle mass lifting three days a week than twice a week, Westcott's research shows. However, as you gain strength and your muscles require heavier weights to continue making progress, you need more time to recover between workouts. Eventually, twice-a-week training will be more effective. Even if you are a beginner, however, lifting every other day may be too much, Westcott says. Be sure to give yourself two consecutive days off each week.

Q When I do push-ups, my wrists hurt. What am I doing wrong?

A "You may not be doing anything wrong," says trainer Ken Alan. The pain is probably due to weakness in your forearm muscles, which support your wrist joints. In daily life, your wrists don't work very hard, but when you do push-ups, they're suddenly supporting a great amount of weight.

Try these forearm-strengthening exercises: While sitting on a chair or a bench, hold a dumbbell in your hand with an underhand grip and place your forearm on top of your thigh so that your hand hangs over the edge of your knee. Curl your wrist up, then lower the weight back down. Also do reverse wrist curls: Turn your palm down and bend your wrist upward. For each of these exercises, start with a weight that fatigues your wrist after 15-20 repetitions. Do one set, adding another set or two after a few weeks. Gradually increase the weight so that you can perform only 10-12 repetitions.