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DOES INTERVAL TRAINING BURN MORE CALORIES?
For years, I've heard trainers proclaim interval training is the best way to lose weight. Interval training consists of intermittent bursts of increased intensity while doing an aerobic activity. For example, if you're going to walk for 60 minutes and want to incorporate interval training, about every five minutes you would start walking at a much faster pace (e.g., 30 percent increase in intensity) for two minutes or so. Then you'd go back to your regular or beginning pace. 

The theory is that you burn a lot more calories in that time frame than if you were to simply walk without increasing your intensity. "Yes, one could argue that interval training can burn more calories; however, there are also periods after the high intensity is completed during which you might bring your intensity to even lower levels than when you started -- this could counteract any of the extra calories you just burned," explains Walter Thompson, Ph.D., professor of exercise science at Georgia State University in Atlanta.

And even if your "starting" pace remained constant throughout the activity, any increase in caloric expenditure would only be minimal. "In most interval training situations, you might only burn an additional three to five percent," adds Thompson. Let's go back to the example mentioned above: Walking at a moderate pace for an hour burns about 238 calories. If you were to do interval training, by incorporating six, two-minute intervals of brisk walking within your 60-minute walk -- you'll only burn a total of six more calories for all that extra intensity.

At the same time, you're increasing your risk of injury (because of the higher intensity) and you may decrease your ability to adhere to your program. "Interval training isn't really that enjoyable. Taking a great, relaxing walk, versus huffing and puffing -- they're really not comparable. Most people tend to stick to things they like -- it just isn't worth it to burn a few extra calories," says Carl Foster, Ph.D., professor of exercise science at the University of Wisconsin-LaCrosse. 

SHOULD YOU WORK OUT WHEN YOU'RE SICK?
I sometimes work out when I'm sick, but I've wondered if I was actually making things worse. This debate has been going on for years, and after a recent cold, I had to find out what "conventional" wisdom had to say. But to answer this question, you have to ask yourself the following questions: 

Is your heart rate elevated? If so, you should not be exercising. "Your heart can beat as much as 15 beats more per minute when you are sick, and if you add exercise on top of that, you're putting yourself at a higher risk for a heart attack and/or cardiomyopathy [a type of heart disease in which the heart is abnormally enlarged]," says Stephen Rice, M.D., Ph.D., M.P.H., a sports medicine specialist at the Jersey Shore Medical Center in Neptune, N.J. "Not only that, but sometimes we overcompensate when we're sick, and work out even harder, which only increases any potential danger."

Do you have a fever? If so, you should not be exercising, because you could become dehydrated. "Also, your body is fighting the infection and needs energy to keep up that battle, and any exercise is probably not helping your immune system," says Rice.

Do you feel okay to workout? You should listen to your body. Do you have severe muscle aches and pains, or do you just have a runny nose? Keep in mind, if you have any serious respiratory illness, you shouldn't be pounding the pavement or hitting the gym.

But if you feel up to it and you answered "no" to all of the above questions, "Exercise could actually make you feel better and give you a much needed boost," offers Rice.

DOES IT ADD UP? 
Do you have to do continuous cardiovascular training for it to be useful? What if you exercised for 10 minutes three times a day, instead of 30 minutes all at once -- is this really just as effective?

Yes, according to a number of studies, including one published in Medicine and Science in Sports and Exercise, in which 24 sedentary women walked 30 minutes all at once five days a week, while a second group of 24 sedentary women walked three times a day for 10 minutes (also five days a week). The improvements in cardiovascular fitness were virtually identical in both groups. 

In another study published in the International Journal of Obesity, subjects performed continuous exercise three days per week, 30 minutes per session, or exercised intermittently using brisk walking for two, 15-minute sessions, five days per week. There were significant improvements for aerobic capacity for both groups, but the continuous exercise group lost more weight and decreased their percentage of body fat while the intermittent group did not.

"From an overall health perspective, the significant cardiorespiratory fitness and HDL increases are much more important than the small amount of weight lost in the continuous group. You can do aerobic training all at once or break it up into smaller chunks throughout the day. The health and fitness benefits are about the same," explains Steve Farrell, Ph.D., of the Cooper Institute in Dallas, Texas.

The problem is that from a practical perspective, if you go out there and piecemeal your physical activity, there is a tendency to say, "Well, I was moving all day, so I'm getting all the exercise I need." You have to be aware of who you are and what works best for you. Some people do fine increasing their activity in small doses, fitting in 10 minutes here and there; others need to "get it out of the way" all at once. 

DOES EXERCISE MAKE YOU EAT RIGHT?
I only wish this were true. Wouldn't it be nice if you started exercising and some hormone was released that forced you to eat better? Sure, it makes sense that if you start working out, you might want to take better care of yourself and eat less. But that isn't always the case. "The general public believes that they will improve their eating habits automatically when exercising, but this spontaneous healthy change just doesn't happen," says Joseph E. Donnelly, exercise physiologist at the University of Kansas in Lawrence. In fact, the reverse could actually occur. "People tend to think, 'I'm exercising and burning more calories, so I can eat whatever I want,'" says Donnelly. "Exercise is great, but it is not a panacea."

One reason this myth has been perpetuated could be due to workout fanatics. These people typically pay more attention to their eating habits and overall lifestyle choices. "But for the average person just starting out, this doesn't happen -- you need to consciously work on changing both eating and activity habits," adds Donnelly.

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