As the saying goes: Six to one, half-a-dozen to the other. A bike trainer is a great tool for improving your cycling skills and overall fitness level, regardless of what the weather's like outside. Because it has constant resistance, the trainer has the potential to deliver an even more efficient workout than you'd get outside—but you may have to make it hurt more to get a comparable workout.
The first thing you'll notice when you hop on a trainer: No hills to coast down. That makes a significant difference in actual time spent pedaling, says sport scientist and cycling coach Neal Henderson, owner of Apex Coaching and Consulting. "When you're outdoors, even in time trials and racing scenarios, it's normal to coast 10, 15, even 20 percent of the time," he says. "But when you're on a trainer, you can pretty much go non-stop the whole time."
That can make your workout more targeted and allow you to practice things you wouldn't be able to outdoors, like holding a 100-RPM cadence for ten minutes straight, or focusing on evening out your pedal stroke. It also means you can get as good a workout in a shorter amount of time.
"Most schools of thought say your an outdoor workout should be 25 to 35 percent longer than a comparable indoor one," says triathlon coach Robert Pennino, founder of Terrier Tri and T2 NYC. "So an hour on the trainer would be roughly equivalent to an hour and 15 minutes on the open road."
Here's the catch: Your trainer workout may be more efficient, but it's also going to feel harder. If it doesn't, you're probably not working hard enough.
Take this recent study from the University of Nebraska at Omaha. In it, researchers asked cyclists to ride 40 kilometers on two separate days—one inside on a trainer, and one outside on flat, open roads. Participants wore the same clothes (including helmets) for both rides, and temperatures and humidity levels were similar as well.
The cyclists were told to complete both rides at the same level of perceived exertion. But what felt like similar efforts were actually quite different: they rode 30 percent harder outdoors.
This makes sense, says Pennino. It's easier to be distracted outdoors—things like keeping your balance, watching for cars, and taking in the scenery can all take your mind off your workout's intensity level. Also, the study authors point out, indoor cyclists may get hotter, and therefore have a higher heart rate, because there's no wind to cool their skin. (The fix: ride with a fan pointed at you.)
Because of these combined factors, the authors concluded, "cyclists may want to ride at a higher perceived exertion in indoor settings to acquire the same benefit as they would from an outdoor ride."
You can avoid slacking off on the trainer by paying closer attention to stats like your cadence, gearing, and power output, says Pennino, and by always having a plan when you sit down to ride. "Don't just tune out to Netflix without a workout in mind," he says. "Do drills you don't have the ability to do outdoors, and keep track of your progress from workout to workout so you know that you're improving."
If that sounds boring, it doesn't have to be. Riding with other people—at an indoor cycling studio, for example—can help boost motivation and make hard workouts less daunting, says Henderson. So can video programs that sync with electronic trainers (or, less effectively, with "regular" fluid or magnetic trainers) and pit you against virtual riders.
Bottom Line: An indoor trainer can provide an excellent workout, especially for short, high-intensity sessions—as long as you're willing to put in a high level of effort. You may not want to axe the trainer altogether come spring, either. "We work with athletes who, even in the summer, do a trainer workout once a week because it's so convenient and time-efficient," says Henderson. "You can get in a warm-up, 20 to 30 minutes of intervals, and a cool-down without worrying about getting out to an open road."