Question

Think about and activity which you can do but old people can't

Answer 1

There are many things that the old cant do but the youngsters due to there extra energy can
Like running, hiking, swimming for long time, lifting heavy weights or doing a back flip 
Some other things are doing stunt on a motor bike jumping off the cliff a parachute 
Or going for a drag race or some other reckless stuff that only youngesters can do at there age

Answer 2

The old people can't do energetic and athletic work. They can not lifts the heavy wights and run as fast as i can . Because their bones and muscles become too weak in the old age.
Old people can't even join a sport like football  team because they are no more fit for that.
Also , they can't do more push-ups and chin ups than me, not even somewhere near .
Additionally they can't climb a mountain so easily the way i can.