Ask the Expert: Question on Caloric Burn

An instructor asked “One of my students asked me why he burns more calories when he rides outdoors than in Spin class”. This is an important question, and may not be the answer you expected! In fact, this might have each and every one of you paying a little closer attention to your indoor cycling workout… ICA member Nancy sent me this question:


One of my students asked me why he burns more calories when he rides outdoors than he does in Spin class.

This is an excellent question because I think a lot of people have probably wondered something similar!

However, there really isn’t one answer because there are so many variables and so many potential reasons that this is happening. So many that I don’t believe it’s possible to compare energy expenditure indoors to outdoors.

The first question I would have is what is he using to measure caloric expenditure, a heart rate monitor (HRM)? They are notoriously inaccurate.


  1. I took a pretty hard road ride today – but it was straight up for four miles after a short warm-up. And as I mentioned in the article, my intensity for my “warm-up” was higher simply because of the road and the wind (which wasn’t a lot but it was present). However, once on my climb (1-hour long) my HR was hovering close to my threshold most of the way. Not many classes I teach will I push at that intensity for an hour. I never look at my calories so I can’t make any comparisons, and my total ride was longer than any of my classes (though the total climb was an hour), but it did get me thinking about this question a little more deeply…

    As listed in the article, there are so many different variables, but one I didn’t really mention (except to talk about the terrain – such as mostly climbing or mostly flat) was the type of class you are doing. Endurance? Race Day? Mostly hills? Aerobic-focus (endurance)? If I measured the caloric burn of my interval class the other day I bet it would have been higher than a not-climbing-the-whole-time outdoor ride. Some people may see the opposite if in fact they use their outdoor rides for mostly recreational cruising aerobic-intensity rides and their indoor workouts as higher intensity interval or race-day types of workouts.

    So once again….”it depends”! 😉

  2. I have just begun transitioning from indoor cycling to outdoors and I LOVE IT! My calorie burn (via HRM) is always higher outside but I know that I work so much harder outside. As an instructor, my intensity level while teaching is controlled due to having to cue and motivate the class. That is why it is so nice to be able to ride outside and PUSH MYSELF! This is wonderful information! Thank you!

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