Not sure exactly where it fits in as far as strength vs aerobic fitness but, in my experience, it was RPMs for me that took the biggest hit, due to a layoff (recovery from a revision TKA) and getting'm back (took ~6 months) seems to correspond with a notable increase in performance. I guess the increase in RPMs could have been the result of increased strength and that actually challenged aerobic fitness. Whatever, I was surprised that an increase in speed when it did finally come on, did so rather quickly. Left me thinking there could be some psychology involved too.