VO2 Testing? First, Take a Deep Breath

Welcome to Crew and A, our irregular feature in which we perform French curls with reader questions. This week, Gail Wade of Fairfax asks about an oxygen testing program promoted by her gym, Life Time Fitness. "Does everyone really need this testing and training if they want to be fit?"

Short answer: No. But the test can help you tailor workouts to your fitness level more precisely than you can with only a heart rate monitor. Since the test costs as much as an hour of top-quality psychotherapy (or, in fact, a decent heart rate monitor), let's take a closer look.

Oxygen consumption testing, or VO2max testing, has long been used to determine elite athletes' cardiac fitness. But it can apply to all, says Conrad Earnest, director of the Center for Human Performance and Nutrition Research at the Cooper Institute in Dallas.

Now, a detour to the Moving Crew Science Fair: VO2max is the maximum amount of oxygen, in milliliters, that a person can consume per minute per kilogram of body weight. The test measures both heart rate and the ratio of carbon dioxide released to oxygen consumed. The higher your VO2max, the more efficiently your body handles oxygen -- in other words, the fitter you are.

The test also yields the ideal heart rate zones for cardio training -- warm-up, aerobic, anaerobic and uber-tough intervals. A key number there, which would take another science project to explain, is your anaerobic threshold, the point where your body shifts from burning mostly stored fats as fuel to using mainly glycogen, a sugar stored in muscle tissue. An exercise professional can use the anaerobic threshold and heart rate ranges to design very efficient, customized workouts.

Without a VO2number, your heart rate monitor (or cardio machine) assumes a maximum heart rate based only on your age. This is often wrong by 30 percent or more, given your health status, fitness level and metabolic je ne sais quoi . So if you work out at what your monitor says is 65 percent of your maximum, you may be overworking or underworking by about one-third. A VO2number lets you know what your target should be with nerdly precision.

In laboratory VO2max testing, participants exercise on a treadmill to exhaustion while a mask measures air input and output. Life Time's version takes people only to their anaerobic threshold, says Jeff Zwiefel, senior vice president of Life Time University, the gym chain's training arm, in Minneapolis.

But Earnest is concerned about health club VO2testing. The tester, he says, would need a bachelor's degree in exercise physiology and specialized training, which, he says, you rarely find in mass-market clubs.

Zwiefel says Life Time's fitness staffers undergo "extensive training" including "a certification [involving] a minimum of five tests, where they have to explain how they're determining the anaerobic threshold."

Life Time charges members $129 for the test (non-members, $149); the club sells a single test plus a six-week personalized training program based on the results for $449. Zwiefel suggests clients get retested every six to 12 weeks to measure progress (a rising VO2number reflects improved fitness). But Earnest says the test should be repeated every six months at most, because it takes a long time to see meaningful movement in your VO2numbers.

So, Gail: The test is not necessary -- legions have gotten fit without it. But if you are a fitno-tweak or time-management freak, it can help maximize your fitness and workout time. Plus, exercise sessions could fly by as you nerdily check your heart rate every few minutes.

Check your chat-max threshold at our online chat, Thursday at 11 a.m. at http://www.washingtonpost.com .

-- John Briley