My son is sbout 40 years old so he is already adult.But I still worry about him. As he worked too hard in his company, I advised to have physical excercise for his good health often.When he called me on the phone yeasterday, I asked him how did do in these days. He answered He enjoys running evry moening 16km. It takes one and half hour. He said it's very confortable. I unconsciously said not to do too hard. A father always worry his childern for ever.