Just wanted to clarify that when I said cycling was harder than backpacking, I was talking about fully-loaded cycling trips with long and/or steep uphill pulls. Or on an apples-apples comparison, I have done one-day several bike-hikes on the AT i.e. no heavy pack either on bike or hiking. I'd park the car at one trailhead, cycle to the other, and hike back to the car. Not counting the Cumberland Valley which was easy all around, the biking was always harder. One example was the VA roller coaster. The hiking is all up-and-down but so is the biking.
I agree that overnight cycling trips on rail-trails and the C&O are not that difficult. But again using my example of the Great Allegheny Passage's southernmost 23 miles, I defy anyone to claim that backpacking up from Cumberland is harder than cycling it. The grade is gentle enough to hardly notice it hiking but you sure notice it when cycling.