7 Things to Consider When Riding Indoors

Though throwing your bike on a trainer and turning on Zwift are good places to start, there are several other factors to consider if you want to get the most out of your time indoor riding.

Photo: Tim de Waele/Getty Images

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For many triathletes, stay at home has translated into train at home. Combine that with the fact that winter is often a popular time to indoor train anyway, and it feels like we’ve got more people riding inside than ever. While knowing how to properly setup your trainer and log onto Zwift are important, they’re only part of the indoor-cycling success equation. If done properly, indoor cycling can make you a stronger athlete come spring and summer.

One of the big advantages to indoor cycling is the efficiency and focus. Objectives can be met and workout goals can be achieved, all in less time. Gone is the need to find uninterrupted flat roads or perfectly pitched climbs for that day’s scheduled interval. With the ability to structure workouts and monitor progress in programs like Today’s Plan, TrainerRoad, and Training Peaks, indoor cycling can offer any level of triathlete the chance to improve cycling fitness. Also gone are the days of having to stare at the garage wall or grainy VHS tapes of the Tour de France. Gamification programs like Zwift and The Sufferfest can offer workouts, races or just plain rides with other cyclists to keep you competitive and engaged.

Switching from training outside to inside shouldn’t only involve a change of scenery, the how and why should change as well. We checked in with Joe Friel and Jim Rutberg, co-authors of Ride Inside: The Essential Guide to Get the Most Out of Indoor Cycling, Smart Trainers, Classes, and Apps, to find out key elements that should be considered when riding inside.

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How should volume and intensity be adjusted when riding inside?

Friel: Intensity can stay the same as planned for a road ride. The bulk of weekly intensity should be in zones 1 and 2 with a small amount in zones 4 and 5. Workout duration, however, can be somewhat less than planned for the road as there is no coasting indoors. Typically, when riding indoors, the pedals are turning continuously. How then should the duration be changed from what was planned on the road to what will be done indoors? 

The easiest way to determine this is by using Training Stress Score (TSS) on TrainingPeaks.com with a power meter or heart rate monitor. If the workout was planned to be, let’s say, 100 TSS, and the intensity stays the same as planned, then when the target TSS is achieved the workout ends. That will usually make the ride shorter than outdoors. 

If the athlete doesn’t have access to TSS then it’s logical to assume that the ride will be 5% to 15% shorter than planned for the road. It’s hard to be any more specific than that as it depends on the rider and how much he or she may coast on different types of workouts and on different terrain.

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How should indoor cyclists use an FTP test (or any other metric for assessing fitness)?

Friel: If you haven’t performed an outdoor FTP test, and you have a smart trainer with power, an indoor FTP test is important to make the power data meaningful. Without this reference point (FTP) data doesn’t mean much. Keep in mind the rider’s FTP is likely to be somewhat lower indoors than on the road—perhaps 5% to 10%. There are some riders, however, that find there is no difference. The reason for the difference has to do with the type of indoor training device being used. The newer devices make riding more like what happens on the road. 

For example, the newer smart trainers typically have a rather large flywheel that keeps the rear wheel momentum high when the pedals are at 12 and 6 o’clock. With the older trainers that have a small flywheel or none at all, the rear wheel begins to significantly slow down as soon as the downward force briefly stops on the pedals, which happens roughly 180 times per minute. 

Also, the newer trainers allow for a small amount of rocking of the bike while pedaling at high intensity, as when at or near FTP. Most riders don’t realize it, but when at a high power output the bike rocks slightly left-right while the body remains rather steady while seated. The older trainers don’t allow for this rocking. The bike is locked in place so, instead, the rider rocks side to side while the bike remains fixed in place. 

These sorts of things slightly affect the rider’s economy. The greater the loss of economy, the lower the power output will be at FTP. To determine exactly how much, the rider can do two FTP tests of the same type – one indoors and one outdoors. If there is more than a 5% difference, I’d suggest having two sets of zones—one for the road and one for the trainer.

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Should indoor training be augmented with some outdoor riding to work on bike skills?

Friel: Bike handling is one aspect of cycling that gets neglected with a steady diet of indoor cycling. There are four key handling bike skills for triathletes: aero position, cornering, descending, and climbing. The first should be rehearsed by the rider whenever doing a higher intensity or race-like ride indoors. This is critical. 

Too often the indoor rider will sit up in order to produce more power, especially as fatigue begins to set in during a hard effort. That is counterproductive for performance improvement for racing on the road. Cornering can’t be rehearsed at all on an indoor trainer (though that is likely to change as smart trainers and apps make indoor training more realistic). Descending must be practiced, when possible, on the road. 

The only aspect of climbing that can be rehearsed indoors is achieved by elevating the front wheel (there are smart trainers that can do this for you). But it’s still not possible to rehearse gravity with a stationary bike. That is another skill that must be rehearsed when possible on the road.

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Is it best to use a tri bike or road bike when riding indoors?

Friel: It depends on the purpose of the workout. If it’s to be a race-like session, then using a race-like bike is necessary. But if the ride is one of the many weekly rides that are done in zones 1 and 2 then a road bike is fine and may even be preferable since the more relaxed road bike position allows for an easier ride.

How can I make the transition from outdoor to indoor riding?

Rutberg: Athletes would be wise to think about the factors that improve their training or detract from it. In other words, how important is it to maintain the social connections you have riding outdoors? Do you need the accountability of training partners expecting you to join them for indoor group rides? If yes, then an interactive app like Zwift is a good choice. 

Do you do best with fewer distractions for focused workouts, or is your internet connection neither strong enough nor consistent enough to stream content? You would be better off using an app that allows you to download content to use offline—like The Sufferfest—or structured workouts loaded into a cycling computer to control a smart trainer. And if you value simplicity and the need to rely on internal motivation, it’s important to recognize people can train very effectively with fluid trainers, rollers, and other “dumb” trainers. 

The best solution or solutions are the ones that will get you on the bike more often or prevent you from opting out of workouts.

RELATED: How to Set Up Your Indoor Training Arsenal to Take Full Advantage of Zwift

What indoor training gear should I buy?

Rutberg: Whether you can or want to spend a lot or a little money on the trainer, screens, and “pain cave” setup, the most important investments are fans and software that will compile all your training data from indoor and outdoor cycling, as well as the other activities you add to your training. 

Heat is the enemy of endurance performance, and overheating is a common problem for indoor cyclists. One fan is OK, two is good, and three is even better. And a software subscription that aggregates your training data, like TrainingPeaks, is valuable because most athletes will ride indoors and outdoors.

Should I use erg mode? Is it beneficial to work on power control?

Rutberg: Erg mode is great for providing coaches and athletes with perfect looking power files, and that precision can be useful when you want an athlete to accumulate a specific time-at-intensity. It can also be great for those complicated workouts that have a lot of rapid changes in target power; athletes don’t have to reserve some brainpower to keeping count of the intervals or the recovery times and can instead give everything to the efforts. 

On the other end of the spectrum, it can be used to keep an athlete in a lower zone if they have a tendency to go too hard. The biggest problem with erg mode is that there’s a difference between keeping up with the resistance set by the trainer and generating that target power your own–which is what has to happen in real life group rides and races, as well as e-races. 

Coaches also have to consider those perfect power files in context of heart rate and RPE, because that can reveal the way the strain from maintaining that target power is increasing over time, even though power output is staying steady because it’s being controlled by the trainer.

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