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How fast is your engine running?

Smart Fitness reports on new ways to determine how fast your motor's running.
H. Gentzkow / MSNBC Illustration
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How can you figure out your metabolic rate? And what are some ways to get a little exercise on a long plane ride? Have a fitness question? To e-mail us, click here. We’ll post select answers in future columns.

Q:  Is there a way to determine how fast or slow your metabolism is?

A: Yes, there are several options for determining what's known as your resting metabolic rate (RMR), the number of calories your body burns at rest to carry out typical body functions like breathing and pumping blood. RMR makes up most of your metabolism — the total number of calories you burn in a day.

The traditional way to measure RMR is to use a standardized formula that factors in your sex, weight, height and age. One of those formulas is known as the Harris-Benedict equation:

  • For women, 655 + (9.6 x weight in kilograms) + (1.8 x height in centimeters) - (4.7 x age in years)
  • For men, 66 + (13.7 x weight in kilograms) + (5 x height in centimeters) - (6.8 x age in years)

That's a lot of number-crunching, and when you're all done, the results may not be very accurate for you, particularly if you're overweight. Formulas like this one are based on average people, and all of us aren't average.

"Many equations just provide rough and dirty ballpark estimates," says Cedric Bryant, chief exercise physiologist for the American Council on Exercise in San Diego.

And the formulas simply don't account for the fact that you may pack on pounds faster than someone else, or vice versa. We all know those lucky few who seem to eat whatever they want and never gain an ounce, while others continually battle the bulge.

"There are just some of us who are blessed with higher metabolisms than others," Bryant says.

But now there are other options for determining how fast or slow your engine's running. Two high-tech gadgets available at many health clubs and weight-loss centers promise to give you a more accurate assessment. One is called BodyGem and the other is New Leaf. With both, you breathe into a mouthpiece or face mask that determines your body’s exchange of oxygen and carbon dioxide while at rest. The devices then spit out your individualized RMR, which Bryant and other experts say is more accurate than the mathematical formulas.

The RMR figure can then be used, along with estimates of how much energy you burn each day through physical activity and how many calories you ingest, to tailor-make a fitness and diet plan — how much more you need to exercise and how much less you need to eat —to help you achieve your weight-loss and fitness goals.

The New Leaf system goes a step further: It can be worn during an exercise test on a treadmill or stationary bike to determine how many calories you’re burning during exercise and to calculate your target heart rate. It can also be used over time to determine how much your physical fitness is improving.

The technology behind New Leaf stems from sophisticated devices known as metabolic carts that elite athletes have used for years to gauge their performance over time. Endurance athletes, for instance, like to track the point at which they reach their anaerobic threshold — essentially when they stop burning oxygen efficiently, "hit the wall" and simply can't go any further. Then, the athletes train to push that threshold higher, increasing their overall performance.

A BodyGem assessment costs about $50 while New Leaf can run as much as $200, depending on how much feedback you desire. The companies' Web sites — and — can provide a list of facilities near you that offer the devices.

While these products may provide direction and inspiration, you’re still stuck with the hard part — exercising and eating right.

"In all successful weight-loss programs the key issues are with lifestyle changes, not really with RMR," says Len Kravitz, coordinator of exercise science at the University of New Mexico at Albuquerque.

Q: What's a good way to exercise during a long plane ride?

A: While you can't run laps up and down the aisles of a plane, there are some activities you can do to burn calories and keep your muscles from cramping. An even bigger concern is economy class syndrome, the name associated with potentially deadly blood clots, or deep vein thrombosis, that can develop in the legs of people who sit in a fixed position for extended periods.

Recently, Song airlines debuted In-Flight Fitness, a 15-minute workout program that can be done in your seat. For $8, passengers get a kit that includes a ball, resistance band and a brochure that highlights several exercises aimed at working the major muscle groups.

And JetBlue offers yoga and Pilates. Cards in the seat pockets instruct passengers on how to go about each activity — hopefully without disturbing fellow passengers too much.

But you don't need a specialized program to stay in shape in the skies. The key to avoiding aches and pains in-flight is to remember to move your legs periodically, at least every half hour, experts say. In your seat, stretching and flexing your legs is important for healthy circulation, as is keeping them uncrossed. Roll your ankles. And barring turbulence, get up and take a walk to the lavatory, giving your legs an opportunity to uncurl.

Also, be sure to drink plenty of water and limit caffeine and alcohol, which are dehydrating.