Why do medical employees always exercise?

These guys work 60-100 hour weeks during residency and they still exercise every day before, in between, or after their shift. My family doctor is at least 60 and booked a trip to climb one of the tallest mountains in the world with his son, and he used to climb the CN tower every year to raise money for charity. I know another doctor who bikes uphill for 60 kilometres a day to raise money for charity, and his wife bikes next to him. Do they do it to sharpen their minds?

Why do medical employees always exercise?
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