Context: a boxer has just landed a great uppercut with an upward movement. His father describes the punch in this way:
I think here 乗りきる means "to overcome", so my rough translation attempt would be
(After) overcoming his weight, he did a sudden and quick upward/vertical movement
but I am confused by the が after 荷重. Shouldn't it be 荷重を乗りきってから? Is 荷重 the subject? Here you can see the whole page. Thank you for your help!