I ride on rollers instead of a trainer, so I try not to fall off and that keeps my brain active to work on better form to make me a better rider. I think the biggest problem is trying to keep myself motivated over an hour. So I change gears and cadence. I watch my Heart Rate Monitor (HRM), and then I work hard at getting my heart rate up to a percentage that I want and then I slow down and change gearing to reduce my heart rate. My interval times will change depending upon my "attitude" that day. Sometimes I do 5 minutes of hard work with a higher heart rate, then I will slow down for two minutes to reduce my heart rate and then back hard for 5 minutes. I will do this for an hour, or sometimes I will ride slow and easy for 10 minutes and then work my butt off for 3 minutes and then slow for 10 and then hard for 5 and then easy for 10 and then back to 3 hard.
If I am just putting in miles like I did today on my rollers, it was 2 hours at a 21 and higher pace and I have the TV on just for noise. I was watching the weather any time it came on because of snow that was in the forecast. Other times I will throw in a DVD and watch that movie.
__________________
2007 Jamis Ventura Comp
2006 Jamis Explorer 2.0
2000 Specialized Hardrock (bought used)
Swim, Bike, Run and sounds like fun