Yes, you hurt more on the trainer than outside because you don't move around in the saddle as much as you do when you're outside. It's a very similar thing as riding on the back of the tandem. I try to sit still on the tandem so it is easier for Rowan to handle, and there is a lot more sitbone pain on the tandem than on a single bicycle.

Solution on the trainer ...
-- take a break and get off the trainer once every hour.
-- during the break, do some stretching. I especially have to stretch the lower back and hamstrings.
-- while on the trainer I spend some time riding on the drops, some time riding on the top of the handlebars, and some time sitting bolt upright.

Solution on the tandem ...
-- we stand and stretch about every 15 minutes.
-- get off the tandem more frequently than we do on our singles.
-- during the break off the tandem, do some stretching. I especially have to stretch the lower back and hamstrings.


They aren't perfect solutions, but they help. As does just getting on and riding more and toughening up the butt.