Fitness by the Numbers
Folks don't know their full potential until they know their VO2max.

Exercise performance physician Massimo Testa, M.D., is one of the foremost experts on VO2max in the world. He explains that your cardiovascular fitness score tells you how efficiently your oxygen carrying system is delivering oxygen to your working muscles, using the combined performance of your heart, lungs and blood. VO2max is one of the best indicators of your aerobic fitness.

Knowing your VO2max is not entirely necessary for starting an exercise program, but Testa says that it's great for anyone who wants to measure progress over time.

Testa says that you can get a VO2max test at a lab, or you can estimate it using a simple walking test. No matter your fitness level, the walking test is ideal because you can walk at any pace that's comfortable for you - perfect for folks who have not been exercising regularly and who should not push themselves to exhaustion.

Choose a location for your test: a flat stretch of road or trail with mile markers, or using a pedometer on a treadmill or at a mall, or at a local high school or college track. (Four laps equal one mile.)

First and foremost, get cleared by your physician for walking a mile if you have a known medical condition. Beforehand, drink water but avoid a big meal or any caffeinated drinks - these can lower your score by raising your heart rate. Wear good walking shoes and comfortable clothing, and bring a watch that measures time in seconds.

Warm up for a few minutes with easy walking. Practice taking your pulse on your wrist or at one side of your windpipe using two fingertips. (Never simultaneously press both sides of your neck when you take your pulse; this can cause a drop in heart rate and blood pressure.) When you feel your pulse, look at your watch and count the number of beats you feel in 10 seconds. Multiply this number by six. This is your heart rate. So 20 beats multiplied by six equals a heart rate of 120. Or use a heart rate monitor. Then start:
  • Note your start time.
  • Walk your mile at a comfortable pace.
  • Note your ending time.
  • Immediately upon finishing, take your pulse.
You have two numbers now: the time it took you to walk the mile and your ending heart rate. No matter your pace, the combination of these two numbers will reveal your aerobic capacity. For example, if you are really fit but you don't want to push yourself, you might walk the mile in 20 minutes, but then your pulse might be only 100 (the lower the heart rate, the lower the effort for you). If you give everything to walk the mile and it takes 14 minutes, your pulse at the finish might be 170, revealing greater effort.

To arrive at your estimated VO2max, plug your two numbers into the following formula (For your gender, use 1 if you're male and 0 if you're female):

VO2max = 132.853 - (0.0769 × weight in pounds) - (0.3877 × age) + (6.315 × gender) - (3.2649 × time) - (0.1565 × heart rate)

This method is a good option for people who don't have access to a lab. However, this formula only yields your estimated VO2max. You can't use it to compare yourself to another person because it may overestimate your VO2max or underestimate it. But you can use it repeatedly to track your own improvement over time because the margin of error will be consistent.

And remember your number - in next week's column, we'll look at the sports best suited to different VO2max levels.