Abstract
The effect of 60 h without sleep upon maximal oxygen intake was examined in 12 young
women, using a cycle ergometer protocol. The arousal of the subjects was maintained
by requiring the performance of a sequence of cognitive tasks throughout the experimental
period. Well-defined oxygen intake plateaus were obtained both before and after sleep
deprivation, and no change of maximal oxygen intake was observed immediately following
sleep deprivation. The endurance time for exhausting exercise also remained unchanged,
as did such markers of aerobic performance as peak exercise ventilation, peak heart
rate, peak respiratory gas exchange ratio, and peak blood lactate. However, as in
an earlier study of sleep deprivation with male subjects (in which a decrease of treadmill
maximal oxygen intake was observed), the formula of Dill and Costill (4) indicated
the development of a substantial (11.6%) increase of estimated plasma volume percentage
with corresponding decreases in hematocrit and red cell count. Possible factors sustaining
maximal oxygen intake under the conditions of the present experiment include (1) maintained
arousal of the subjects with no decrease in peak exercise ventilation or the related
respiratory work and (2) use of a cycle ergometer rather than a treadmill test with
possible concurrent differences in the impact of hematocrit levels and plasma volume
expansion upon peak cardiac output and thus oxygen delivery to the working muscles.
Key words
maximal oxygen intake - sleep deprivation - aerobic power - blood volume - hematocrit
