Key takeaways: Exercise doesn’t just train your muscles; it also trains specific brain circuits that support endurance and adaptation. In mice, repeated workouts changed activity in a cluster of hypothalamus neurons that stayed active even after the run ended. Blocking these neurons after exercise erased endurance gains, suggesting the recovery window is critical for how the body adapts to training. Most people think of exercise as something that mainly changes the body—building stronger muscles, improving stamina, and making each workout feel a little easier over time. But new research suggests a big part of that improvement comes from changes in...

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