Question: When I can’t get outside to ride, what is the percentage of indoor riding that would match the time outside? Also, if I use an elliptical trainer, what is that percentage for riding outside? – Peggy J.
RBR Replies: That’s a hard question to answer because riding indoors is quite a bit different from riding outside due to wind, hills and accelerations out of corners when you’re outside on the road. Then there’s the mental factor. Most riders find it much more difficult psychologically to maintain intensity, not to mention duration, inside. Although smart trainers and the various apps that work with them like Zwift, Sufferfest and Trainer Road have made indoor training much more practical and enjoyable for many riders.
With that said, here’s the short answer:
Equal heart rates for an equal amount of time means you’re getting the same benefit. So if you ride for an hour on the trainer at an average heart rate of 130 bpm, that’s the same as riding outside for an hour at the same average heart rate.
But of course it’s not that simple.
Inside, you’re probably pedaling for the whole hour. There aren’t any downhills for coasting or tailwinds where you can soft pedal. So the general rule is that it’s one third more difficult to ride indoors than outdoors.
An hour inside, then, is equal to 90 minutes on the road.
This formula seems to work well for most riders assuming they ride outside on rolling terrain (not flat, but no long climbs, either).
If you use an elliptical trainer, a treadmill or a rowing machine, the formula works too – with one big exception. On the indoor trainer you’re working the same muscles that you work on the bike outside. On other modes of indoor exercise, the muscles used are different. So while you’re getting a great workout for your cardiovascular system on the elliptical machine, it’s not especially specific to cycling. The carryover value isn’t as great.
However, I’m in favor of mixing up your off-season training. If you have to ride the trainer all winter, you’ll probably have trouble maintaining your enthusiasm. Alternating workouts on the indoor bike with the elliptical trainer, a treadmill, a rowing machine and maybe running, nordic skiing or snowshoeing outside can increase your all-around fitness and make your workouts a lot more fun.
One other thought: Riding indoors on your bike on a trainer means you’re riding with the same position as when you’re outside. On the other hand, on a “spinning” bike you are unlikely to get the same position. That can lead to injury if your saddle height, saddle setback or reach to the bars is different from what you’re accustomed to.
I hope this gives you some food for thought as you’re riding the trainer.