Meaning of 荷重が乗りきる Context: a boxer has just landed a great uppercut with an upward movement. His father describes the punch in this way: > I think here 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 after . Shouldn't it be ? Is the subject? Here you can see the whole page. Thank you for your help!

This is not "to overcome", but a simple combination of + , "(for power/force/etc) to be put/applied/loaded" + "completely/fully". is "after his weight was fully put onto the punch". It can be rephrased as ("after loading/putting his weight fully onto the punch").