Running to catch the bus might be the only exercise some of us get during the day, but your leg muscles aren't the only muscles getting an unexpected workout. Christina Spengler explains that our respiratory systems also have to rise to the challenge. But when an endurance athlete runs for the bus at the same speed, they hardly get out of breath, because they breathe less. Spengler also knew that the athlete's peripheral chemosensory system, the system which constantly monitors the body's levels of key metabolites as well as carbon dioxide and oxygen, is less sensitive than untrained people's. Spengler wondered if it was the act of exercising the whole body that reset the chemoreceptors, or could heavy breathing alone reduce the chemoreceptors'sensitivity? Working with her team, she tested how endurance athletes'respiratory systems responded to six weeks of heavy breathing training, and was astonished to find that the breathing exercises alone had somehow reduced the athlete's chemoreceptor's sensitivity()!
But training by hyperventilating isn't straightforward, because heavy breathing makes you dizzy. Spengler explains that when we are sitting still,we exhale as much carbon dioxide as our low metabolism generates, keeping the carbon dioxide levels in the body at about 5%. But as soon as you begin breathing heavily, without exercising, the body's carbon dioxide level falls,causing a sudden dizzy spell. Over the last ten years, Spengler and her colleague Urs Boutellier have overcome this problem by developing a portable rebreathing system that can be used by athletes to top-up the amount of carbon dioxide that an individual inhales, keeping their carbon dioxide levels high enough to prevent a dizzy spell.
Spengler and her team recruited ten fit young men to begin the unorthodox training regime. First they measured the length of time each athlete could cycle at a speed close to their top speed. Then the athletes began half hour respiratory training periods, using the partial rebreathing device. After six weeks of ventilatory training, Spengler's team tested the cyclist's performance, and found that the athletes could cycle longer at high speed, and their breathing had not changed.
Next, Spengler compared the athlete's chemoreceptors' sensitivity, before and after the six weeks of respiratory training. She was amazed to find that by simply breathing hard, the athlete's had reduced the receptors'sensitivity, although she adds that how the receptors get reset is a mystery.
Spengler explains that she had wondered if resetting the athlete's chemoreceptors would reset their breathing, but as the athlete's breathing had not changed after six weeks of heavy breathing, she knew that the change in the chemoreceptor's sensitivity could not have changed the athlete's breathing. So trained athletes, who breathe less than other more unfit mortals, seem to breathe less for some reason other then a reset chemosensory system.
And has respiratory training contributed to any famous sporting victories?Apparently some successful athletes have used the rebreathing device as part of their training program, but the chances of it getting the rest of us fit enough to take to the Olympic starting blocks isn't high.
