The rowing machine was easy to break down, it was just bolted together to begin with, so disassembly was just a matter of loosening the bolts. That took about 15 minutes.
The hard part was the treadmill. Several of the pieces were extremely long (4-5 feet) or welded together, and many of the screws had rusted. I'd brought a portable bandsaw home from work to cut through some of the pieces, but discovered there wasn't a blade for it! So I had to do it the old fashioned way, with a hacksaw. Fortunately the material the treadmill was made of was very soft, so the hacksaw made quick work of it. Still, it was quite exhausting. I was able to break down most of the machine, but the heaviest piece of all, the particleboard platform, still needs to be broken up. Since the garbage can was getting full and quite heavy, and I'd already spent an hour working on the treadmill, I'll have to wait until next week to do anything with the last piece.