Q: Does inhaling oxygen from canisters improve performance during strenuous exercise?

A: Football players, swimmers, and many other athletes commonly inhale oxygen rich gas at breaks in games or meets, but the practice has little, if any, effect on their performance. If you’re healthy, the hemoglobin in the red blood cells that transport oxygen to the muscles is 95% to 98% oxygen saturated at sea level. For someone weighing 150 pounds, inhaling bottled oxygen can increase the amount of oxygen in the blood by no more than about 10%. ‘This small excess would disappear after a minute or two of breathing normal air. Any slight change in performance could occur only if exercise immediately followed the inhalation of pure oxygen with no intake of normal air. For some athletes, use of oxygen canisters may bea way to get “psyched up” for others it may be a way to encourage deep breathing. Any such benefits, however, have nothing to do with the added oxygen.

Q: Does grunting help you breathe more efficiently when you’re lifting weights?

A: No. The grunts, along with other symptoms of pressure buildup such as bulging veins, come from straining to force air out while your mouth and nose are closed. This potentially dangerous process is called the Valsava manuver. In particular, the stress and strain of lifting a heavy weight or performing isometric exercise (usually done by contracting a muscle against an immovable object) can encourage this type of breathing. The resulting compressed exhalation dramatically increases pressure in the chest area, cutting down the volume of blood returning to the heart so drastically that dizziness or a blackout can result. There’s even a possibility that blood vessels could rupture.

Some coaches tell power lifters to hold their breath, which creates a rigid rib cage and provides support for the upper spine, but this isn’t good for repeated lifts or other

Kinds of strenuous exertion. In those situations, it’s better to breathe out as you strain. And breathe rhythmically. A study of female college students found that those who adopted this tactic avoided the increase in blood pressure experienced by those who held their breath during exertion.

Q Does hyperventilating really increase the time you can stay underwater?

A: Hyperventilation the rapidly repeated intake of air can let you stay underwater a bit longer, but you’re flirting with danger when you do this, You can’t hold your breath indefinitely, in the water or out, because the increased level of carbon dioxide in the blood triggers breathing. But hyperventilation lowers the carbon dioxide level so you’re able to hold your . breath longer. Because you’re not taking in oxygen, however, the oxygen level in your blood falls dangerously low. Thus, you can faint, convulse, or possibly drown, since you can run out of oxygen before rising carbon dioxide level sparks a lifesaving reflex.

Q: Why is it harder to breathe at high altitudes when you’re exercising?

A: Air pressure decreases the higher you rise above sea level. This means that the density of oxygen molecules in the air drops in direct proportion to the fall in pressure. This results in a lower concentration of oxygen in the blood, which alerts the brain’s breathing center to transmit nerve impulses that increase your breathing rate, bringing more air per minute into your lungs when you’re in the mountains than when you’re at sea level. This higher breathing rate is what you experience as difficulty in breathing. Endurance suffers because less oxygen is delivered to the muscles: maximal oxygen consumption declines an estimated 3% for every 1,000 feet of altitude above 5,000 feet. Being in good physical shape can’t inhibit this decline, but it does allow you to use whatever oxygen is in your blood more efficiently than an unconditioned person would, thus making high-altitude skiing or hiking seem somewhat less exhausting.

If you’re going somewhere more than 6,000 or 7,000 feet above sea level, try to plan a night’s layover at a lower altitude. Day trippers or sportsmen who drive up from sea level in a hurry may experience nausea, headache and breathing difficulties. In some people such distress can build to a potentially fatal condition called high-altitude pulmonary edema, in which the lungs fill with fluid. In any case, don’t attempt strenuous activity on your first day out in the mountains. Drink more water to prevent the dehydration that accompanies rapid breathing of dry air at high altitudes; avoid alcohol, which increases dehydration. In general, go easy. Overdoing exercise at high altitudes isn’t worth the risk.

Q: Is it hazardous to exercise in polluted air?

A: Since you breathe faster and more deeply when you exercise, you take in more carbon monoxide, sulfur dioxide and other atmospheric pollutants notably ozone, smog’s major component. Running or cycling during the early afternoon, for instance, when ozone levels tend to be highest, may result in chest pain, coughing, throat irritation, and difficulty in breathing deeply. Though studies haven’t yet made clear whether repeated exposure to pollutants during exercise can result in permanent lung damage, it’s wise to avoid exercising near heavy or even moderate traffic. Your best bet if air pollution is a problem in your locality (and you can’t exercise indoors) is to work out early in the morning before pollution levels peak, or in the evening when levels fall again.

Article extracted from this publication >>  May 12, 1989