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Human athletic achievement is impressive. Elite marathoners sustain ~75–85% VO₂ max [the maximum rate of oxygen consumption during peak exercise] for hours. Humans can outrun horses in extreme heat and over distance. But evolution has optimized humans for endurance efficiency rather than for maximum oxygen flux. How do we compare to other animals and what can we learn about physiology from their adaptations?
Every March, teams of sled dogs depart Willow, Alaska on the Iditarod: a 938 mile race to Nome, run in legs totaling roughly 16 hours of effort per day, over 8–11 days (the current record is 7 days, 14 hours). The dogs run in temperatures that can drop below −40°C, consuming 10,000–12,000 kcal per day. They do not develop the rhabdomyolysis [destruction of striated muscle cells] that would destroy a human athlete attempting equivalent work.