Having a sturdy and strong body, especially a young man.
It's a positive thing to be strapping. It means you are strong and healthy.
Examples:
He is a strapping young man.
The strapping boy helped me carry the heavy box.
The strapping athlete won the race.
The strapping firefighter lifted the person out of the burning building.
The strapping horse pulled the heavy cart easily.
I felt very safe with the strapping bodyguard around.