ABSTRACT
Introduction ........................................................................................................ 139 Extremes of Human Endurance ...................................................................... 140 e Physiological Basis of Performance Limits and Injury ......................... 144 High Altitude ................................................................................................. 144 High Work Intensity and Energy Balance ................................................. 148 ermal Strain ............................................................................................... 149 Sleep and Fatigue ........................................................................................... 152 Psychological Stress ....................................................................................... 155 Physiological Limits to Risky Behavior........................................................... 156 Psychosocial Modi ers of Environmental Stress and Health ...................... 158 Resilience Modi ers: Exercise and Other Interventions .............................. 162 Conclusions and Recommendations for Future Research ........................... 165 Summary ............................................................................................................. 166 References ............................................................................................................ 166
In appreciation for whatever it is that makes men accomplish the impossible. —Alfred Lansing, Endurance, Shackleton’s Incredible Voyage, 1959
Human physical survival under harsh environmental conditions is fairly well understood and somewhat predictable as a function of known physiological mechanisms. ese essential mechanisms can be seen as analogous to the factors that support or limit machine performance (e.g., fuel levels-energy
availability; combustion requirements-oxygen availability, temperature; physical strain-biomechanical stress; oxidation and rust-oxidative stress from reactive oxygen species). Less well understood is the uniquely human plasticity of responsiveness to environmental challenge that permits exceptional performance in some individuals but not in others who share the same essential physiological attributes. is exibility of response (resilience) to environmental challenge is moderated by factors such as training, acclimatization, behavior, and psychosocial cues.
