SammyJ 

Garmen Edge also reads rear wheel. And heart rate, and cadence. Cardiovascular training is real on the trainer, as is leg workout.

RWBlue01

I would count the miles.

Side note:
My Mt. Bike, Road bike, trainer, and the two type of stationary bikes at the gym work me differently. I can't explain it well, but I road miles on the one stationary in the gym and then went back the next week and tried a different type of stationary bike. This second bike killed me. Weather warms up, I get on the mt. bike. I had new pains trying to do the same miles. Mt. bike goes to the shop, on the road bike. New pains, (this one might be 50% fit, but there were also new pains.)

BTW, The easiest miles for me are Mt bike miles.

gforeman 

I count me. For me it a MUCH harder ride on the spinner than outdoors. No coasting on the spinner

InOmaha

I agree. Not all workouts are created equal. To say that a training ride inside is easier than a ride outside throws out all the variables. According to some of the logic 10 miles at 12mph on a flat MUP with a quick donut and coffee break in the middle counts as miles but 1 hour on a trainer at max resistance, a resonably high gear, and a cadence of 85+ doesn't.

You can cheat on the workout inside or out.

As those of us in this section know hill climbing isn't equal either; when you compare someone at 240 vs 175. With so many variables out there, I only try to focus on those health related numbers that matter to me. I track my workouts to attempt to better my time and effort mainly because it leads to better health numbers. At my size, I'm always expending more energy than some 150lb guy whether on a trainer, pushing against the wind, or climbing hills. His miles will probably look better than mine on record.

psalm

Set two goals. An outside mileage goal, and an indoor time goal.

LocoCycle

I say count em. And because I am # crazy. I put a cheap cycle computer on the rear wheel. To capture each rides miles etc. Now I live in an area that the climate is really good most of the time....compared to others. But it does rain and it gets cold...for what I think. So after two plus years of losing some riding time due to rain etc. I decided to get a trainer...just after last xmas. It was the best thing I did. It allowed me to ride when it was raining, or if I was short on time...but still wanted to fit a workout in and get a few miles. You can't beat a trainer workout...no stop lights, truely nothing to stop you. I have even done it a few times this week...as I was pressed for time. Not my trainer is in my garage...and the sun beats on the garage in the afternoon...what a sweat fest.....but I feel good when I am done. And I can have my IPOD and big headphones on...and go for it.....

So have fun....count the miles....if that is what you want to do! Just my opnion