I have had 4 spinal surgeries, the first in 1999 and the last in 2007. Also shoulder reconstruction in 2011. Riding indoors was a big part of therapy and recovery. I spent so much time, weeks before and post surgery, just laying around being bored and going crazy that I did not need much motivation to do the indoor rides. If just felt so good being active again. I do have issues with riding indoors when healthy and physically able to ride outdoors. For me doing intervals and/or short duration rides numerous times a day helps break up the monotony.