I can sympathize with you on your back. Splitting wood puts mine into spasms pretty quick.
Barbie saw sounds like it she has had a little work
Reaming is backing the bar out of the kerf as it tightens on the chain and then pushing it back into the same kerf to cut it wider.
The kerf will finally close on itself and serve the same purpose as a wedge and you can continue cutting without reaming.
With a sharp chain it is normally much faster and easier than stopping to set a wedge and then recover it. In fact it becomes second nature and I do it without even thinkin about it.