Purpose Individuals exposed to total sleep deprivation
may experience an increased risk of impaired thermoregulation
and physiological strain during prolonged physical
activity in the heat. However, little is known of the impact
of more relevant partial sleep deprivation (PSD). This
randomized counterbalanced study investigated the effect
of PSD on thermal strain during an exercise-heat stress.
Methods Ten healthy individuals performed two stress
tests (45 min running, 70 % _V O2max 33 C, 40 % RH).
Each trial followed three nights of controlled sleep: normal
[479 (SD 2) min sleep night-1; Norm] and PSD [116 (SD
4) min sleep night-1]. Energy balance and hydration state
were controlled throughout the trials. Rectal temperatures
(Tre), mean skin temperature (Tsk), heart rate (HR), RPE,
and thermal sensations (TS) were measured at regular
intervals during each heat stress trial.
Results There was a significant main effect of time
(P\0.05) for all of these variables. However, no differences
(P[0.05) were observed between PSD and Norm,
respectively, for Tre [39.0 (0.5) vs. 39.1 (0.5) C], ;Tsk,
[36.1 (0.6) vs. 36.0 (0.7) C] and HR [181 (13) vs. 182
(13) beats min-1)] at the end of exercise-heat stress. There
were no differences (P[0.05) in Tsk, PSI, RPE, TS and
whole-body sweat rate between PSD versus Norm.
Conclusion Since greater physiological strain during
exercise-heat stress did not follow three nights of PSD, it
appears that sleep loss may have minimal impact upon
thermal strain during exercise in the heat, at least as evaluated within this experiment.