A man pushing a hand-truck of boxes is bending over to pick up a pear.
A man is pushing a hand truck.
'A man is pushing a hand truck' is less detailed rephrasing of 'A man pushing a hand-truck of boxes...', the contents of the hand truck and the man's other actions have been omitted.
A hand-truck is a hand truck.
If the man pushing a hand truck of boxes is bending over, then he is a man pushing a hand truck.