A son says to his father: 'Dad, would you be willingly to run a marathon with me?

The father, despite his age and a heart disease, says 'YES'.

And they run that marathon, together.

The son asks: 'Dad, can you run another marathon with me?' Again father
says 'YES'.

They run another marathon, together.

One day the son asks his father: ?Dad would please do the Iron Man with me?'

Now just in case you wouldn't know, 'The Iron Man' is the toughest
triathlon in existence; 4km swimming, then 180 km by bike, and finally
another 42 km running, in one stroke.

Again father says 'YES'