Mj. Ashenden et al., Simulated moderate altitude elevates serum erythropoietin but does not increase reticulocyte production in well-trained runners, EUR J A PHY, 81(5), 2000, pp. 428-435
The purpose of this study was to investigate whether the modest increases i
n serum erythropoietin (sEpo) experienced after brief sojourns at simulated
altitude are sufficient to stimulate reticulocyte production. Six well-tra
ined middle-distance runners (HIGH, mean maximum oxygen uptake, (V) over do
t O-2max = 70.2 ml . kg(-1) . min(-1)) spent 8-11 h per night for 5 nights
in a nitrogen house that simulated an altitude of 2650 m. Five squad member
s (CONTROL, mean (V) over dot O-2max = 68.9 ml . kg(-1) . min(-1)) undertoo
k the same training, which was conducted under near-sea-level conditions (6
00 m altitude), and slept in dormitory-style accommodation also at 600 m al
titude. For both groups, this 5-night protocol was undertaken on three occa
sions, with a 3-night interim between successive exposures. Venous blood sa
mples were measured for sEpo after 1 and 5 nights of hypoxia on each occasi
on. The percentage of reticulocytes was measured, along with a range of ret
iculocyte parameters that are sensitive to changes in erythropoiesis. Mean
serum erythropoietin levels increased significantly (P < 0.01) above baseli
ne values [mean (SD) 7.9 (2.4) mU . ml(-1)] in the HIGH group after the 1st
night [11.8 (1.9) mU . ml(-1), 57%], and were also higher on the 5th night
[10.7 (2.2) mU . ml(-1), 42%] compared with the CONTROL group, whose eryth
ropoietin levels did not change. After athletes spent 3 nights at near sea
level, the change in sEpo during subsequent hypoxic exposures was markedly
attenuated (13% and -4% change during the second exposure, 26% and 14% chan
ge during the third exposure; Ist and 5th nights of each block, respectivel
y). The increase in sEpo was insufficient to stimulate reticulocyte product
ion at any time point. We conclude that when daily training loads are contr
olled, the modest increases in sEpo known to occur following brief exposure
to a simulated altitude of 2650 m are insufficient to stimulate reticulocy
te production.