Get Energized for Good
How to Use Your Body More Efficiently
The second role of your blood is to deliver oxygen to your muscles and organs, important for helping us pursue the activities we love -- in my case, mountain biking. As a rule, she who can fill her bloodstream with the most oxygen has the best shot at reaching her goal, whether it's surviving a kickboxing class or winning a half-marathon. To improve that capacity, first you need a baseline of how much oxygen your blood can currently transport and deliver to your working muscles.
That's why I'm at the Human Cardiovascular Research Laboratory in the department of kinesiology and applied physiology at the University of Colorado at Boulder, pedaling furiously on a stationary bike. I'm huffing and puffing into a sealed mouthpiece so a sports physician can collect and analyze every milliliter of O2 that I inhale and exhale. The resistance increases steadily and my breathing becomes more rapid until I "go anaerobic," meaning I am no longer taking in enough oxygen to keep up with the demands of my muscles. Translation: burning thighs to the point where I have to stop pedaling. From this test I am able to learn my V02 max, or the maximum milliliters of oxygen per kilogram of body weight that I use in a minute, and my lactate threshold, the point at which the demand for oxygen surpasses my body's ability to take it in and deliver it efficiently to my muscles.
What does this mean in terms of everyday energy use? I send my charts over to Josh O'Brien, an exercise physiologist at the Sports Rehabilitation and Performance Center at the Hospital for Special Surgery in New York City, who works with some of the city's top sports teams.
"Oxygen is the fuel that helps you sustain your efforts in a workout," O'Brien says. The higher the intensity you can sustain before the "burn" gets too intense, the more calories your body will use and the fitter you will become.
Though my VO2 numbers are strong and my lactate threshold is high, O'Brien points out that even if you have a low threshold, you can improve it with proper conditioning. The best way to train your body to use oxygen more effectively: intervals. After a good warm-up on the bike or treadmill, increase your speed and/or resistance until you're working nearly as hard as you can for one minute. Recover at an easy pace for two minutes. Repeat five to 10 times. When you push the intensity to your upper limit for short spurts, your body adapts by pumping out more blood per heartbeat and increasing its ability to take in oxygen and clear lactate. Your fat-burning zone, that coveted point at which you're burning stored fat rather than carbs, becomes bigger, so you can exercise harder and longer before your muscles go into the red.
A final piece of the energy puzzle is muscle mass, O'Brien says. The more your body is made up of muscle instead of fat, the more strength you'll have for daily activity. Though I'm proud of my lean, mean biking-machine body, keeping it that way will only get harder as I get older, O'Brien says, explaining that women are naturally programmed to shed about a half pound of muscle every year after age 30. With it goes potential energy. The good news: You can counteract nature's course with strength-training. For most women that means incorporating twice-weekly weight-training sessions into their cardio routines to gain and maintain active lean tissue. "A leaner body composition also means less fat, so you have less inactive tissue weighing you down," he says. Of course, lean, shapely muscles look better in skinny jeans, too. And that alone is worth the energy.
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