'Old man' pranks people by lifting heavy weights

Ever been to the gym and thought that you've got things sorted?

You're pushing pretty heavy weights - or you think you're pushing pretty heavy weights, only to be suddenly outdone by a fellow gym member.

Muscle beach is one place you go to train to ensure everyone sees just how muscular you are and to see just what you're capable of pushing.

See: Five reasons why bootcamp is a good way to lose weight

So imagine the shock when an elderly man arrives and challenges the younger guys to a weightlifting challenge.

The younger guys clearly find it a joke and snigger behind the man's back.

But what happens next really differentiates the men from the boys.