Bike: Indoor vs. Road

Getting a little brisk outside, so time to pull out the trainer…or 10 pounds of warm clothes to get out the door.  Along the way I’ve read that biking on an indoor trainer is more of a workout than on the road, primarily since there is no ‘glide’ time…and many therefore that ‘count’ an indoor ride as more than an ‘outdoor’ ride. 

In sitting on the trainer for 90 minutes for the first time in the off-season, I had the time to think about it.  As I watched my PowerTap, I couldn’t help but think that a watt is a watt is a watt…I’m in the same position as on the road…I’m just pedaling along…the PowerTap is recording my effort in watts…yes there’s no ‘glide’, but in a steady effort on the road, there’s no ‘glide’ either, so I couldn’t really figure out why it would be different…other than the ‘mental’ side of just sitting there spinning away.

I was left thinking that there may be a perceived difference if someone doesn’t have a power meter, since the speed being displayed can be variable depending on the tension on the wheel, and even the trainer itself and how it operates…and with no ‘glide’, a perception of more effort.  When I downloaded it, I did see that my PowerTap readout on the trainer is almost dead smooth, as compared to the road, where the power readings are a lot more jagged, so there _is_ some type of difference…wondered what it was. 

There are a lot of forums, and articles that give the trainer a higher benefit. Here’s one example from a SlowTwitch forum.

My search lead me to a good article at Carmichael Training, one of the big dogs in cycle training…Lance Armstrong’s coach, etc…and consistent with some other stuff that I read.

In this article by Renee Eastman, CTS Pro Coach, the long and the short of it is that a watt is a watt is a watt.  In part:

Many of my athletes comment that riding the trainer feels harder than riding on the road, and that watts seem harder to generate indoors. Rest assured, it’s not just your imagination.

One key difference between riding the trainer versus the road is how much more constant power production needs to be on the trainer. On the road, there are constant fluctuations in power due to changes in terrain, wind, speed, etc. These changes are expected and natural outdoors, so athletes take them in stride. But trainers offer constant resistance, so fluctuations in power output are almost entirely based on changes in the way the athlete is pedaling. This can be troublesome to athletes because it means nearly constant pedaling instead of the terrain-influenced pedaling style they have outdoors. Basically, in order to achieve your desired workload, you can’t coast or rely on hills to boost your output. Riding on the road is not inherently better; they are just different. I often find that riders who specialize in time trialing experience a smoother transition to riding the trainer because they are used to holding more constant power outputs than other riders.

And while I maintain the concept that a watt is a watt, how you generate the force to produce that watt is somewhat different on the trainer. You can certainly adapt to the slight differences in pedaling style required to maintain more constant power outputs on the trainer (i.e. pushing through the dead spot), it just takes time. Practice makes perfect. The more you ride the trainer, the better you will become at it. With my athletes I often see a wider variance between outdoor and indoor power outputs in the early fall. However, by the end of the winter season, those differences are much smaller.

So, should you have different power ranges indoors compared to outdoors? No. Going back to the concept that a watt is a watt, to be equivalent to your outdoor workouts, your indoor intervals need to be completed at the same power outputs.

We’ve examined a lot of differences between trainer and road workouts…The question can still be asked, are trainer workouts harder? The answer is maybe. There is no coasting. There are no descents or breaks unless you decide to stop pedaling. Indoors, however, you can probably achieve more pedaling time per hour, and thus higher average wattages, by eliminating those seconds spent coasting. This can result in higher total kilojoules of energy used per hour indoors. So you burn up a few more calories per hour while sweating out your workout indoors.

Does this mean you should reduce your workout time on the trainer? A 20% reduction in total workout time (but not interval times) used to be Chris Carmichael’s guideline, but more recently that’s been adjusted to account for different training styles… Most of us have to fit training around work, family, and the weather, so our training time is limited. For Time-Crunched cyclists and athletes riding fewer than about 8-10 hours a week, there’s no reason to reduce your workout times when you move them indoors. If you’re a high-volume trainer who needs to be more careful about balancing even small increases in workload with limited recovery time, then it’s important to monitor the total kilojoules accumulated during your trainer workouts. When you do this, you may find you can reach your kilojoule goal faster on the trainer compared to on the road.

The Bottom Line…

Sadly, it therefore appears, that for a particular workout, there is really no logical basis for taking a scheduled 2 hour bike ride, spending 90 minutes on the trainer and calling it all square.  If someone is not using a power meter, the preceived effort on the trainer is most likely higher, because of the constant effort, and no ‘glide’, but in actual fact, the amount of ‘work’ is the same, as if you used the same steady effort on the road…rats.

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