Is Your FTP Different for Outdoor and Indoor Cycling?
By Zach Nehr
One of the most common questions among indoor cyclists is whether you should adjust your FTP for riding indoors versus riding outdoors. In other words, does your FTP change depending on whether you are indoors or outdoors? It is a great question because FTP is a hot topic in cycling, and everyone wants to know their number.
The thing is, your FTP constantly fluctuates – it is not a constant figure. Depending on how much caffeine you have had, your sleep quality, your work stress, and level of motivation, your FTP could change by a few watts every day. Before we dive into the differences between Indoor FTP and Outdoor FTP, let us make sure you know exactly what we are talking about.
What is Functional Threshold Power (FTP)?
Functional Threshold Power is the maximum average power that you can maintain for an hour, measured in watts. The higher your FTP, the better your aerobic engine and overall fitness level.
Pro cyclists have the highest FTPs in the world, typically between 400-500w. Elite amateurs might have an FTP between 300-350w, while beginner cyclists probably have an FTP between 100-200w. I could talk about FTP forever, but for the purposes of this article, let’s focus on indoor versus outdoor FTP.
Physiologically, your FTP does not change significantly in the short term. But it can certainly feel like your FTP has changed if you are having a rough day on the bike. There are a multitude of factors that can affect your FTP, so let’s take a closer look.
Differences Between Your Outdoor FTP and Indoor FTP
A cyclist typically measures their FTP with a structured power test (you can find three FTP tests on MyWhoosh below), but you can also calculate your FTP using training and racing data. To find your true FTP, I recommend using a structured test, like the MyWhoosh Power Passport Test, because it is simple and repeatable.
Indoors, FTP tests are extremely controllable and consistent. You can ride on the same bike, on the same trainer, with the same fans, at the same temperature and humidity while listening to the same playlist. The small number of variables during an indoor FTP test means that you can directly compare indoor tests to one another.
Outdoor FTP tests, on the other hand, are affected by hundreds of variables, even if you try your best to control them. Perhaps the weather is slightly warmer, the wind is a bit stronger, you are with a group during one test but solo during another…the list of variables goes on and on. That makes it much more difficult to compare outdoor FTP tests to one another.
In addition, your FTP might be inflated from one test versus the other. If you ride out of the saddle on the indoor trainer to maintain a higher power output, your indoor FTP might be significantly higher than your outdoor FTP if you do not use the same pedaling technique outdoors.Conversely, someone who spends 90% of their training time outside might struggle to produce their usual power numbers on the indoor trainer. If your setup is not ideal or you are not accustomed to the feeling of an indoor smart trainer, you might feel weaker on the indoor trainer even though your FTP has not changed.
How to Close the Gap Between Your Outdoor and Indoor FTPs
If you are a cyclist who regularly trains and races both outdoors and indoors, it is important that you use the same FTP for outdoor and indoor workouts. But if you cannot seem to achieve the same workout quality outdoors versus indoors, or vice versa, here are some quick tips for closing the performance gap.
Make your bike setup and riding conditions as consistent as possible between outdoor and indoor riding. Use the same pedaling technique, cadences, and position on the bike. If you are training in the aero position outdoors, perform your indoor bike workouts in the same riding position. Otherwise, you will activate different muscle groups and be left with a performance gap between outdoor and indoor riding.
Testing Your FTP on MyWhoosh
It is important to test your FTP regularly, as often as every 8-12 weeks (about 3 months). The less experience you have, the more often you should test. I recommend that beginner cyclists test their FTP every 8 weeks to monitor their progress.
Experienced cyclists have a much better understanding of their FTP, so they do not need to test often. Instead of testing on a time-based schedule, I recommend that experienced cyclists test their FTP at crucial times in their season. For example, you could test your FTP after the off-season, which helps set up your training zones for the first big block of the year. An experienced cyclist could also test their FTP right before a peak training block (2 to 4-week block completed just their target race).
MyWhoosh has a number of power tests in the TESTING folder, which you can find in the MyWhoosh Workout library.
Power Passport
Description: Three different power tests with full recovery in between. 6 sec sprint, 3 min, and 12 min efforts.
The MyWhoosh Power Passport is the Gold Standard for fitness testing. In less than an hour, you will test your sprint power, anaerobic threshold, and aerobic threshold. With some behind-the-scenes calculations, MyWhoosh will automatically calculate your FTP based on your test results. This is the perfect test for all cyclists.
FTP Test
Description: A fatigued 20 min effort is used to calculate your FTP.
The FTP Test – MyWhoosh is designed to test your limits under fatigue. After an opening 5min effort, you will complete a 10 min endurance block followed by a 20 min power test. This removes the anaerobic contributions of your muscles to the 20 min effort, making it a true test of your aerobic threshold.
Ramp Test
Description: While the power increases every minute, ride as hard as you can for as long as you can. MyWhoosh calculates your FTP by multiplying the final minute of your test by 0.75.
The Ramp Test has been around for decades because it is simple, efficient, and repeatable. This test is designed for all cyclists from absolute beginners to seasoned professionals. There is not an element of pacing; ride for as long as you can while the trainer automatically increases your power. By the end, you will reach complete exhaustion, and MyWhoosh will automatically calculate your FTP.
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About the Author
Zach is a freelance writer, professional cyclist, and the owner of ZNehr Coaching. He writes about everything related to bikes and endurance sports, from product reviews and advertorials to feature articles and pro data analytics. You can find Zach racing the Sunday Race Club on MyWhoosh every weekend.