Understanding how your body uses oxygen during exercise is the key to faster times
        by: Amby Burfoot  


All aerobic endurance activities, like running, bicycling, swimming, and cross-country skiing, are essentially contests to see how much oxygen your body can deliver to your exercising muscles. Increase the amount of oxygen, and you can run, bike, swim, or ski faster.

In running, of course, those muscles are in your legs. As you train, two things happen to improve your muscles' ability to use oxygen. First, your heart gets stronger and delivers more oxygen; and second, your leg muscles get better at using the oxygen.

In their laboratory research, scientists frequently measure this delivery and use of oxygen, calling it maximum oxygen uptake or VO2 max. They consider maximum oxygen uptake to be the most basic measure of aerobic fitness, and they've shown that it increases as you train more and harder. I generally reverse the letter order, since max VO2 has a friendlier sound than VO2 max.

As your aerobic capacity increases, you can run farther and faster. All training improves your aerobic capacity, even slow, relaxed jogging. But some workouts improve it more than others.

The best and most efficient way to increase your aerobic capacity is to run slightly faster (10 to 30 seconds per mile) than your 5-K race pace. Faster runners should be closer to the 10-second figure, and slower runners closer to the 30-second figure. For example, if you can race a 5-K at 7:40 per mile, you should run your max VO2 workouts at 7:20 to 7:30 pace. This isn't a pace that you can maintain very long in training. You can run for distance (800 meters) or time (3 to 5 minutes).

After each repeat, jog for four to five minutes, and then do another. The workout is finished when you've completed three to four repeats (for beginning and intermediate runners) or six to eight repeats (for advanced runners).

Many runners do max VO2 workouts on the track as part of their interval training routines because they like to measure the lengths and times of the repeats exactly. That's fine, but it isn't necessary. You can also do max VO2 workouts on a good trail, a grassy field, or any other smooth surface that allows you to run at a fast clip without fear of ankle turns. Use your watch to time the four-minute repeats, and run at a strong and fast (but not all-out) effort.

Don't do these aerobic-capacity workouts more than once a week, and skip them on weeks when you have races. These workouts cover less distance than tempo workouts, but they're more taxing because the pace is considerably harder. If you were to do several max VO2 workouts a week or include one in your training program during the week of a race, you might soon find your race performances deteriorating because you'd be too fatigued to race at full strength.