Lost motion assemblies are basically valve springs for the VTEC followers in your valvetrain. The normal intake/exhaust followers have valves and valve springs to press against so they're not flopping around all the time, but the VTEC followers don't. The LMAs help to control their movement. I took some pictures a year ago when I was swapping out my LMAs. I went ahead and marked one of them up real quick so you can see exactly where the LMAs sit and what they look like: The picture is of a B16 head with the cams removed. You can clearly see the cam journals and the retainers on top of the valve springs. The rubber banded items are the cam followers. The center one is the VTEC follower, and the ridge in the middle is what bounces on top of the lost motion assembly.