Objective.—To study sleep parameters and mood profiles of a female explorer traveling solo and unaided to the South Pole during the winter.

Methods.—During the 44-day expedition, global activity and sleep were assessed using a wrist actigraph (AW) worn on the nondominant wrist. Mood was assessed using an adapted Profile of Mood States questionnaire. Pre- and postexpedition physiologic profiles were conducted to assess body composition, strength and power, and aerobic capacity.

Results.—The AW data revealed decreasing sleep duration throughout the expedition, with an average sleep time of 5 hours (range, 8 hours and 14 minutes to 1 hour and 42 minutes), with sleep times consistently <3 hours during the final third of the expedition. Mood responses indicated a progressive reduction in vigor and increase in fatigue. Sleep time was positively related to vigor and inversely related to depression and fatigue, a finding that is consistent with the notion that positive feelings (high vigor and low fatigue) are linked with sleep.

Conclusions.—This account provides insight to help understand the limits of human tolerance and may be directly applicable when planning future expeditions of this nature.