Its too late to make an effective difference physically. At best you can stretch and warm up before moving stuff on the day, but it won't drastically increase your endurance or capacity.
However but you do have time to go buy or borrow some lifting equipment. A sackbarrow and a sampson (flat platform with 4 wheels) would be good, and get a light truck with a hydraulic tail lifter.
Your risks are being tired and throwing yourself into a lift (gung ho) rather than slowing down and taking your time. Stairwells and second floors are also risky locations.
If you hire a truck with movers, they can do the big items. Don't try to emulate their lifts though! I've seen two movers easily move a piano that was a struggle for 6 normal-size adults to move.
Another thought is to make sure all the stuff is boxed up ready to go. You don't want a box heavier than 20 kilos maximum, and ideally should be under 10 kilos. If you're packing books, more+smaller boxes is wise. It helps if boxes are all regular-sized; which is why banana boxes are valued for moves.