REGULATION OF LOCAL SWEATING IN SLEEP-DEPRIVED EXERCISING HUMANS

Thermoregulatory sweating [total body (m(sw,b)), chest (m(sw,c)) and t high (m(sw,t)) sweating], body temperatures [oesophageal (T(oes)) and mean skin temperature (T(sk)BAR)] and heart rate were investigated in five sleep-deprived subjects (kept awake for 27 h) while exercising on a cycle (45 min at approximately 50% maximal oxygen consumption) in m oderate heat (T(air) and T(wall) at 35-degrees-C). The m(sw,c) and m(s w,t) were measured under local thermal clamp (T(sk,l)), set at 35.5-de grees-C. After sleep deprivation, neither the levels of body temperatu res (T(oes) T(sk)BAR) nor the levels Of m(sw,b), m(sw,c) or m(sw,t) di ffered from control at rest or during exercise steady state. During th e transient phase of exercise (when T(sk)BAR and T(sk,l) were unvaryin g), the m(sw,c) and m(sw,t) changes were positively correlated with th ose of T(oes). The slopes of the m(sw,c) versus T(oes) or m(sw,t) vers us T(oes) relationships remained unchanged between control and sleep-l oss experiments. Thus the slopes of the local sweating versus T(oes), relationships (m(sw,c) and m(sw,t) sweating data pooled which reached 1.05 (SEM 0.14) mg . cm-2 . min-1 . degrees-C-1 and 1.14 (SEM 0.18) mg . cm-2 . min-1 . degrees-C-1 before and after sleep deprivation) resp ectively did not differ. However, in our experiment, sleep deprivation significantly increased the T(oes) threshold for the onset of both m( sw,c) and m(sw,t) (+ 0.30-degrees-C, P < 0.001). From our investigatio ns it would seem that the delayed core temperature for sweating onset in sleep-deprived humans, while exercising moderately in the heat, is likely to have been due to alterations occurring at the central level.