Walking is good for health and longevity
Everyone asked a 100 year-old man for his health secrets: The old man said: "I'll tell you a secret. I've been married for 75 years. Promised my wife when we got married that when two people quarrel, the loser has to walk for 5 kilometers. I've been walking 5 kilometers everyday for 75 years!"
Everyone asked again: "But how come your wife's very healthy as well?"
The old man answered: "I'll tell you another secret: she'd been following me to make sure I really finish the 5 kilometers!"