Ask The Coach QnA: difference in trainer and outdoors; trainer power and road speed

Coach Atul Godbole answers your training related questions…

Q. Pranali asks “Is time on bike trainer equivalent to riding out on the road for the same amount of time?”

A. Yes, there is a bit of difference – on the trainer, you have to pedal continuously, whereas on the roads you get some respite every now and then when you coasting due to declines, traffic, etc. Also the lack of air movement when riding indoors on the trainer make for some stuffy and hot conditions. Be sure to use a big fan to help with this, a table fan placed directly in front of you is ideal, if not, a ceiling fan will work good enough.

All said and done, you can use the rule of thumb that 50 minutes of riding on the trainer is equivalent to 60 minutes of riding outdoors. So you can make this adjustment, especially for long rides of 2 hours or more.

Q. Sudhir asks “The power I am able to hold on the trainer does not correspond to the speed I was hoping to get on the roads. What gives?”

A. Firstly, there is a difference between riding on the trainer and riding outdoors, the major factors being air resistance/wind and inclines, plus other factors like traffic, potholes, etc.

Secondly, even if your trainer is properly calibrated, the power measured by your trainer will not have an exact correlation to the theoretical speeds you should get on the road for that power, even accounting for above factors of wind, incline, etc. Measure fitness progress on the trainer separately using the power given by trainer, and measure fitness progress on the roads separately during other metrics like speed or HR. Or buy a power meter for your bike!

Thirdly, your weight also comes in the picture, especially if you are riding on routes with climbs. So rather than absolute power, the power to weight ratio will be a better metric.



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