Accurately showing weight in animation can be one of the hardest things to do. This is a shining example of how to do it right!
The whole body here is under the bar. Something so heavy is held close to our centre of gravity. Notice also how the stance has widened to prepare for the heave!
There is a very slow progression from this above frame to the one below, perfectly shows the weight and strain.
Watch throughout the weight of his body gradually moves up his body.
(Above) the elbows pop out to push up the weight and (below) the arms are straight and locked pushing the weight up.
What I like is the arms come down slightly after the initial push up showing the weight applying force on the body. This follow through then precedes by a further slight push upwards as the weight becomes comfortable on his shoulders!
Slapstick surprise ending. Unexpected is often key to being funny!