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Dear
Editor-in-Chief
The
continuing desire to improve performance, particularly at the national
and international levels, has led to the use of ergogenic aids.
Ergogenic aids are defined as "a procedure or agent that provides
the athlete with a competitive edge beyond that obtained via normal
training methods". Random drug testing has been implemented
in an effort to minimize an athlete's ability to gain an unfair
advantage. However, other means of improving performance have been
tried. Blood doping has been used to enhance endurance performance
by improving oxygen delivery to working muscles. As oxygen is carried
in combination with the hemoglobin, it seems logical that increasing
the number of red blood cells (RBC's) in the body would increase
the oxygen carrying capacity to the tissues and result in improved
performance. The first experiments of removing and then reinfusing
blood showed a significant improvement in performance time on the
treadmill (Ekblom et al., 1972).
This process is now known as blood doping.
Of course, this practice is not without risk. The addition of RBC's
results in an increase in hematocrit causing blood viscosity to
rise exponentially (McGuire and Spivak, 1993).
The slowed blood flow resulting from the increased hematocrit is
believed to increase the risks of thromboembolic events. Increased
viscosity also increases vascular resistance requiring an increased
force of cardiac contraction to circulate the blood.
More recently, erythropoietin (EPO) has been used to stimulate RBC
production. However, it is less predictable than RBC infusion and
the amount of RBC production cannot be predicted. This places the
athlete at greater risk for complications from increased blood viscosity.
There has been speculation that EPO administration may have contributed
to several deaths of European cyclists (Woodland, 1991).
Blood doping and the use of EPO have both been banned by the International
and the United States Olympic Committees.
The goal of delivering increased amounts of oxygen to the tissues
may be accomplished in another manner that, while temporary, carries
minimal risk. Hyperbaric oxygenation involves providing a person
with 100% inspired oxygen while in an environment where the pressure
is greater than that at sea level (760 mmHg; 14.7 pounds per square
inch-psi; or one atmosphere absolute-ATA). At a pressure of 2.4
ATA (45 feet of sea water) and breathing 100% oxygen there is an
increase in the arterial partial pressure of oxygen (PaO2)
from 100 mmHg to over 2000 mmHg. The increased pressure causes the
oxygen to dissolve in the plasma leaving the hemoglobin carrying
capacity of the RBC unaltered. Under normal conditions, almost all
oxygen is transported by hemoglobin and very little is dissolved
in the plasma. This sets up a very large gradient at the tissue
level that can raise the tissue oxygen levels to over 300 mmHg (Lambertson
et al., 1953).
It has been speculated that these high levels of oxygen can remain
in the tissues for two to four hours (Bannister et al., 1970).
It would seem logical then that such an elevation of blood and tissue
oxygen tensions could provide a competitive advantage to athletes
competing in aerobic events. In order to test this hypothesis we
had experienced runners predict their times for a 5 km course and
exposed them to hyperbaric oxygenation. Following exposure, they
ran the course and compared actual with predicted times. Nine volunteers
were solicited from the Fort Worth Runners Club and were between
the ages of 18 and 65 years with sufficient running experience to
be able to predict their time on a local 5 km course with which
they were familiar. They reported to the Hyperbaric Medicine Facility
where they received ninety minutes of 100% oxygen in three thirty
minute periods interspersed with two ten minute breaks for air and
liquids. They were pressurized in a multiplace hyperbaric chamber
to 2.2 ATA. All volunteers underwent the exposure without incident.
Upon completion of the hyperbaric oxygenation, the runners were
immediately transported to the 5 km course. The interval between
completion of the exposure and the beginning of running was 30 minutes.
Upon arrival at the course, runners were given an opportunity to
modify their predictions when they personally experienced the weather
conditions. Each runner was provided with a stop watch, started
the course when they felt ready, and kept their own times. On crossing
the finish line a researcher verified and recorded their times.
Four runners had actual times longer than their predicted, four
bested their predicted, and one runner ran the predicted time. The
average predicted time was 12,860 seconds and the average actual
time was 12,904 seconds. A two tailed Student's t test, assuming
equal variances, provided a value of 0.98 (no significant difference).
While the hypothesis seems sound, this small test could not substantiate
it. Some runners in this study predicted a time anticipating a performance
boost rather than their customary time. However, the literature
on this topic is also mixed (Webster et al., 1998;
Cabric et al., 1991).
It would also be interesting to measure serum lactate levels at
several time intervals which have been shown to be affected by exercise
under hyperbaric conditions (Weglicki et al., 1966).
It should also be remembered that statistical validity does not
always coincide with validity in competition when the difference
between gold medals and nothing can be tenths of a second.
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