Showing posts with label Oxygen. Show all posts
Showing posts with label Oxygen. Show all posts

Thursday, February 7, 2013

Why supplemental oxygen is not considered a performance-enhancing drug

You often see a football player on the sidelines breathing oxygen after running a long distance or having worked hard during a long series of plays.

Have you ever wondered if it works? Does breathing a high concentration of oxygen help an athlete recover from exertion faster?

The answer is a resounding “No,” and here’s why.

In healthy people, such as college and professional football players, nearly all of the oxygen in the blood is carried by hemoglobin. Only a very small percentage is dissolved in blood. Saturation defines the oxygen that is attached to hemoglobin and partial pressure of oxygen is that which is dissolved in blood.

Definitions: SaO2 = arterial oxygen saturation, Hb = hemoglobin, 1.34 mL is the amount of oxygen a fully saturated gram of hemoglobin can carry, Pa02 = partial pressure of oxygen or the amount of oxygen dissolved in blood

If an athlete has a normal Hb level of 15 gm, a SaO2 of 100% and a PaO2 of 100 mmHg, the formula used to calculate his blood oxygen content is

[Hb X 1.34 X (SaO2/100)] + 0.003 X PaO2 or
[15 X 1.34 X 100/100] + 0.003 X 100
20.1 + 0.3 = 20.4 mL/100 mL of blood

So, only about 1.5% of the oxygen content of blood is dissolved.

If an athlete raises his PaO2 to 400 mmHg by breathing pure oxygen the calculation is

[Hb X 1.34 X (SaO2/100)] + 0.003 X PaO2 or
[15 X 1.34 X 100/100] + 0.003 X 400
20.1 + 1.2 = 21.3 mL/100 mL of blood

Even at a PaO2 of 400 mmHg, only 5.6% of the oxygen content of blood is dissolved. Note that hemoglobin cannot be more than 100% saturated with oxygen.

Very soon after the athlete stops breathing the pure oxygen, its minimal effect disappears. It’s simply not enough to affect recovery or performance.

Possibly because the basic science is well-understood, there have not been too many papers on this subject.

Here’s one from JAMA that looked at 12 soccer players given 100% oxygen or placebo after exertion. Then they had to exercise again. “The administration of enriched oxygen during the recovery period had no effect on plasma lactate levels [an objective measure of recovery] or on performance during the second period of exercise. The subjects were unable to identify which gas they received.”

A similar study of 13 athletes from Medicine & Science in Sports & Exercise concluded “These findings offer no support for the use of supplemental oxygen in athletic events requiring short intervals of submaximal or maximal exertion.”

Another from the European Journal of Applied Physiology found that giving athletes supplemental oxygen during the recovery periods of interval-based exercise improves the recovery time of SpO2 [equivalent to SaO2] but did not improve post-exercise markers of reactive oxygen species or inflammatory responses because the improvement in saturation was clinically insignificant.

The situation is explained in simple terms in an excerpt from the book Exercise Physiology: Integrating Theory and Application. It concludes that supplemental oxygen may have a placebo effect, but there is “no real physiologic benefit.”

If you Google “supplemental oxygen and athletes,” you will find a number of websites touting the supposed benefits of inhaled oxygen. They are almost all supported by companies that sell oxygen.

Bottom line: Supplemental oxygen is not considered a performance-enhancing drug because it doesn’t work.

Thanks to  Dr. Joel Topf ( ) for suggesting this topic.