Indoor Vs. Outdoor Power

Turbo season has been well underway for the past few months thanks to a few restrictions. Now we are being allowed back outside, you may see some differences in your numbers. Here is what to expect and why.
Outdoor power will likely be higher than indoor

  • Outdoors we are much more likely to do some out the saddle riding. When this happens we can produce more force thanks to our body weight pushing through the pedals, while indoor we tend not to ride out the saddle and so body weight is largely put through the saddle. This means you should expect to see a higher NP and MAX power when riding outside compared to a similar ride inside.
  • They are called stationary turbo trainers for a reason, they’re stationary. Outside we can move the bike and you will see good riders line them selves up into the perfect power producing position for themselves by rocking the bike. On turbo trainers this rocking cannot happen, so some force is lost due to the movement over the bike to get into a perfect power producing position. This will be prevalent in MAX power efforts.
  • Coasting, a great chance for the legs to rest and regain some energy. Indoors we tend not to coast, a two hour indoor session is said to be like 3 - 4hrs on the road because of this. Unless you are used to riding on pan flat roads (like Al Qudra) the first few times you do longer sessions on the turbo you will really feel them in your legs. Because of the natural breaks we get outdoors we can usually sustain power for longer, so we will see higher power avg and NP compared to indoors. 

Comparing data sets 

  • A huge consideration when comparing indoor to outdoor data is the method of collection. If you ride indoors with a power based trainer, you are likely using that for your data. Outdoors, obviously you must have a different power meter to collect the data. Therefore you are using two different power meters. They will give different readings. If you are getting around a 2.5% difference between your power meters you are doing extremely well. It is common to see a 5 - 10% difference between power meters.
  • You can check the above by performing a test. Record your indoor power data using something like zwift (or similar) alongside recording your ‘outdoor’ data using your power meter and a garmin (or similar). Then compare the two data sets. While this won’t tell you if you are producing more power outdoors, it will tell you how different your indoor to outdoor power readings are. 
  • Don't be alarmed if there is a 10 - 30 W difference between data sets. It doesn’t mean you are not training accurately or correctly it just means to be aware of differences. During your outdoor season, you should try to base your power zones from the outdoor power meter on an outdoor test. During turbo season it is vice/versa. 

Physiological differences

  • If your power meters are coming up flush, then you know the indoor vs outdoor differences in either down to the biomechanics of cycling or something physiological. 
  • The most likely reason is heat. In Dubai, we tend to be able to keep ourselves cooler riding inside compared to outside. For most others in the world it is the opposite. When we heat up, blood is diverted away from the working muscles to the skin to help with cooling, however the muscle are still demanding the same energy output and so the body must reduce the work load to stop itself overheating. You rarely have a choice here, your body will do it automatically. 
  • Indoors we can stay cool via AC, fans and ice cold nutrition. Outdoors in hot conditions this becomes a lot trickier. So if in the UAE and cycling in summer heat, expect to see a lower output than when you are indoors.

The bottom line

  • Expect to see differences but don’t let that put you off using both the indoor trainer and outdoor roads. Being a slave to numbers isn’t why we ride our bike. Understand what your zones feel like. Use the indoor season to gain great muscle efficiency for cycling and look forward to the outdoor season to match it with biomechanical efficiencies. So long as both are being improved at some stage, you are becoming a better cyclist. 
  • If the data differences really bother you, ensure you are doing regular zero resets of your power meters and comparing them every few months.