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Indoor vs Outdoor Threshold Testing

Indoor vs Outdoor Threshold Testing

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Knowledge Level: Intermediate

All of the British Cycling Training Plans give you the option of indoor trainer workouts and, especially for the shorter and higher intensity midweek sessions, this option can be the most convenient and effective to take. Here is more information on buying an indoor trainer and getting the most out of your indoor training.  However, if you are going to be following the Training Plans both inside and outside and are training using heart rate or power, you should conduct Threshold Tests and set Training Zones for both.

Why would my zones be different?

If you conduct a Threshold Test on an indoor trainer, most riders will find that the average heart rate they attain is significantly lower than on the road, even though they will feel that they rode as hard. There are three main reasons for this. On most indoor trainers, rollers being the exception, you don’t need to engage or recruit as much stabilising and upper body musculature. Without a cooling headwind, your core temperature will rise more on an indoor trainer and increase your perceived level of exertion. Finally riding on an indoor trainer is more of a psychological challenge as you have to overcome the monotony and unrelenting nature of the experience.

Does it really matter?

Yes. If you test yourself indoors and then apply those heart rate zones to the road, they will be skewed too low. This can make sticking to lower endurance zones impossible, and also mean that you will be under performing on higher intensity efforts. Similarly, if you try to apply heart rate zones set using an outdoor threshold test to indoor training, you may struggle to attain and sustain the levels prescribed.

Does this apply to power as well as heart rate?

Both the motivational and higher body temperature factors can also potentially impact a Threshold test conducted on an indoor trainer. Many riders will produce less power for an indoor test compared to one conducted outdoors. Also, if you are using a different power measurement system for indoor training, you can’t use the same zones for different devices and should test for both.

A cool and well ventilated room and a powerful fan can make a big diffrence and, for motivation, using a Zwift race rather than a dedicated test can help.

How can I schedule in the additional test?

Prioritise the test which applies to the most riding you do, for most cyclists, this will be an outdoors test. For the second test, as long as you take a full rest day beforehand, it can be scheduled in as a midweek indoor trainer workout. Don’t forget that a Threshold Test is a challenging and effective training session and not just a test.

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