Biology Reference
In-Depth Information
individuals who are poorly fit or extremely fit experience less improvement in
maximal oxygen uptake [36]. Improvement in human performance is a con-
sistent feature of blood transfusions, provided that the amount of red cells
infused is sufficient to increase serum hemoglobin concentration and hemat-
ocrit and thereby deliver more oxygen to working muscles. The improvements
can be shown in race-times, fixed-run times, VO
2 max
, run-times to exhaustion,
and other measures of performance. Accordingly, sport officials search for
ways to deter those athletes who are determined to dope with transfusions or
any other means to increase the delivery of oxygen to muscles.
rHuEPO enhances performance in healthy subjects
It is well known that rHuEPO administered to patients with anemia signifi-
cantly improves fatigue, physical symptoms, and physical performance [38].
(See Chapters 9 and 10 for further information.) In the present context, the
question is whether or not rHuEPO enhances physical performance in healthy
subjects and, particularly, in athletes. Since the release of rHuEPO almost 15
years ago, few studies on have been done with athletes and most of the stud-
ies that have been done have involved its effect on red cell indices and other
markers.
Two placebo-controlled studies have shown that rHuEPO increased VO
2 max
by 6.0% to 7.7% after three to four weeks of subcutaneously administered
rHuEPO (150 U/kg/week) [39, 40]. Typically, the weekly dose is administered
subcutaneously in doses of 150 U/kg/week. At a higher dose (180 to
210 U/kg/week,administered subcutaneously), the VO
2 max
increase was simi-
lar (7%) [41]. These studies, which used recreational athletes, establish that
doses of rHuEPO that are sufficient to increase the hematocrit to nearly 50%
also increase the VO
2 max
up to 7%. Anecdotal reports, however, indicate that
after a few weeks of modest doses (150 U/kg/week), athletes lower the week-
ly dose to approximately 60 U/kg/week. To determine the effect of such a reg-
imen, after three weeks at 150 U/kg/week, investigators [40] decreased the
dose to 60 U/kg/week for an additional five weeks and found that the
improvement in VO
2 max
(4.7% to 9.7%) and increased hematocrits continued.
This study and a similar low-dose study [42] provide support for the anecdot-
al reports from athletes, and confirm that maintenance doses of 60 U/kg/week
are capable of enhancing aerobic performance for at least three weeks after
discontinuation of drug. The question of how long the benefits last after
rHuEPO is discontinued will be discussed.
Adverse effects of rHuEPO in athletes
Unlike studies in patients with anemia, no surveys have been done of the
adverse effects of rHuEPO in athletes. Athletes tend to be healthy and that may
