When I used to go to the gym before it became too expensive($40+ a month for a student membership) I used to love leg day honestly as it was really the only day were I could embarrass all my gym buddies. Being 5'5" and 150lb I got some extremely odd looks when I would have to almost gather up all the 45lb plates I could manage to do leg presses. Normally I would do a set of 10x540lbs, 10x 630lbs, 10x720lbs and one time attempted a max lift of around 1080lbs. Now being one of the slower members of the swim team a few of them got so ashamed that they decided to attempted my max set of 720lbs even after warning them and came close to getting crushed by the sled when their legs buckled. Personally if I would skip any day it would be upper body or arms as I hate doing bench presses, curls, hangs, or any other upper body exercises as it seems pointless for my usage which is cycling.

Anyone wanting to skip leg say will be missing out on the gains in sprint and top end speed you can easily gain vs doing intervals. Since I have stopped going to the gym these are 2 areas I have noticed it is harder to get gains in and I still am not back to my lifting sprint capability.