Endurance training: Surviving the Tour


1. Torture de France

2. Breathing training

3. Incredible eating machine

4. Exercise: Healthy for you and me?

The diaphragm, shown in the exhale position, expands and compresses the lungs; although many muscles affect breathing, the diaphragm is the biggest blowhard of them all! Graphic: NIH

Leg muscles get tired. Why not lung muscles?

The primary role of air resistance is evident as the US Postal team wins the Tour's team time trial in 2003. Equally obvious is the enormous amount of training required to reach this peak of physical condition. Photo by Graham Watson, courtesy Trek Bicycle

Heavy breathing ahead
Athletic performance is all about oxygen. Muscle cells need oxygen to burn sugar or fat to produce ATP, the chemical that causes the muscle contractions that move your bones. The more oxygen your muscles receive, and the quicker they can dump carbon dioxide, the better your performance. That's one reason why the performance capacity of endurance athletes is often measured in "VO2 max," the maximum volume of oxygen taken into the blood per minute.

Graphic of human ribcage and diaphragm muscle exhaling. Lungs deliver oxygen to the blood. And since lungs are filled by the breathing muscles, you might think it obvious that squeezing the last ounce of performance from a pair of lungs would depend on strong, tenacious breathing muscles. But Ralph Fregosi, a professor of physiology at the University of Arizona, says misleading measurements long caused researchers to believe that endurance athletes were not breathing at maximum during competition. "Performance [in the studies] was not limited by the capacity of the respiratory muscles to ventilate the lungs," he says, "because when asked to do so athletes can voluntarily increase their ventilation during maximal exercise, but only for a very short time."

If endurance athletes were not breathing their hardest, breathing could not be a limiting factor, and there was no point in training the breathing muscles for strength or endurance. (As an aside, exercises for some lung-disease patients do aim to strengthen respiratory muscles, but not to improve their endurance -- see "Controlled Breathing and Dyspnea..." and "Maintenance of Inspiratory Muscle..." in the bibliography).

Fregosi says the earlier measurements focused on sprinting sports, and didn't prove whether the breathing muscles could simply grow tired in endurance sports. To answer the question, Fregosi's grad student, Paige Holm, asked 20 amateur bike racers to serve as Lycra-clad guinea pigs.

After all, bikers train their leg muscles to improve endurance. Would it help to train the breathing muscles?

For four weeks, 10 of the guinea pigs did heavy breathing through a computer-controlled apparatus for 30 minutes a day, five days a week. By inhaling through a long tube, the pigs breathed their own exhalations, eliminating the chance of hyperventilation.

Even though heavy breathing is part of all serious races, the pigs described the heavy breathing as a chore. "They found that the training was extremely vigorous; it made them very tired," says Fregosi.

Cyclist team in blue racing gear pushes forward.

Proof in the pudding
At the end of the experiment, the riders rode a simulated 40-kilometer race on a computerized exercise bike. While neither control group improved, the experimental group rode 4.7 percent faster. That's a huge improvement in a sport where a five-hour race may be decided by seconds.

Oddly, the trained guinea pigs didn't find breathing more difficult, Fregosi says, even though they were breathing more. Apparently the obvious was happening: The respiratory muscles didn't tire, so they filled and emptied the lungs more often. More oxygen reached the blood.

More important, says Fregosi, more carbon dioxide was dumped to the atmosphere. "Because oxygen does not normally limit exercise capacity in healthy subjects," he says, "the performance gain is likely due to the enhanced elimination of carbon dioxide, which makes the blood slightly less acidic. Moreover, the fact that the athletes could breathe more with no change in breathing effort is an important finding because most people stop exercising because of severe shortness of breath."

If we can minimize the feeling of breathlessness, athletes can go faster.

He adds that researchers have found that patients with emphysema and other lung diseases often stop exercising due to an overwhelming shortness of breath, and that respiratory muscle training reduces their feelings of breathlessness during exercise.

"We think it's the same with healthy, fit people. If we can minimize that feeling of breathlessness," athletes can ride faster.

What are you going to gobble on a 2,082-mile road race?

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