Originally Posted by
svtmike
Whether it's vigorous or not depends on what you put into it. You can turn yourself inside-out on any 5% climb of decent length if you try.
Same goes for the flats.
The issue with hills is you eventually reach a grade where you can't maintain a reasonable cadence with the gearing you have. Plus you can never let up. You can ride harder for awhile, but eventually your muscles burn up.