Noted: For decades, researchers have theorized that deceleration starts as energy stored in the muscles is used up. “All mammals engaged in intense exercise, be it a human marathoner, a cheetah trying to catch prey or the prey trying to avoid becoming a meal, rely on energy stored in the body, usually as glycogen,” said Karen Steudel, a professor of zoology at the University of Wisconsin. “Once this is depleted, the human or cheetah is basically out of gas.”
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