Part 2: The REAL skinny on burning Calories in your indoor cycling classes!

Listen to the second half of my discussion with Danielle Foster, Master Trainer for CycleOps and expert on teaching with power. Danielle and I go into kilojoules and calories and power output even deeper. This information is important to all instructors, whether you teach with power meters or not. Remember, just like your heart is beating even if you don’t have a heart rate monitor, you are producing power (or not) even if you don’t have a power meter!

Just because you choose to ignore the facts, doesn’t mean they cease to exist.


  1. Can you provide any information on how we might interpret the watts data provided by the Keiser M3 bikes? We are getting these installed in our gym in the next couple of weeks (yay!). How might the watts number provided by the Keiser M3s relate to the kilojoules number that Danielle talks about getting on the CycleOps bikes? Any tips on how I might help my students understand this data?

  2. Hi MOritz,
    did you see the follow up article I wrote about this?

    This should cover your question. Let me know if it doesn’t and I’ll see if I can go even more into it.

    You can also tell them that if they go into a sauna, their HR will be elevated and they will sweat a lot, but it won’t burn substantial additional calories or make them more fit! So sweating and high HR is not necessarily the indication of work performed. Power is. And only work performed means caloric expenditure.

  3. You probably should provide additional information on why output power is really what is relevant to address following kind of question/doubts from the participants: “my heart rate was high and I was sweating a lot, so why should I not have burnt lots of calories ?” The perceived effort fostered by a high readout of kcal on the HRM display makes participants possibly question the instructor. Instead they might think: “well, perhaps he/she is right that I did not burn X but a little bit less calories, still I feel exhausted and my heart worked hard, hence I have burnt lots of calories” although they had no resistance on the wheel …

  4. Because HR is so variable and affected by so many other things, an elevated HR can be due to many factors besides actual “work”. Your HRM will record that elevated HR as calories burned, even when you didn’t do any work. A power meter wouldn’t measure that; it is only concerned with the force you apply to turn those pedals, not to the stress in your life, the caffeine, the illness, the heat or humidity, the overtraining or excessive fatigue – all those things will register as a higher HR, even though they don’t burn calories to accomplish. It’s the body’s response to the hormonal/chemical stimulus (or environmental) that causes the HR to go up. Also, think about it – when you do a high intensity interval effort, it may take your HR a while to come down. The power meter would show immediately that you reduced resistance and lowered your effort significantly, so calories are not being consumed during that time (at least, not in high amounts). However, your HRM doesn’t know any more that the HR is still high, so it will register that as calories being burned, because that is what it is programmed to register. But it is not the case.

    What Danielle is explaining is that work is equal to the kilojoules, related to the power output. When I ride a bike with a power meter that is measuring actual work, and I compare the number to the calories on my HR monitor, the HRM is always higher, but the power meter is the correct one. Almost all the time, HRM give a caloric burn rate that is too high.

    There is another factor. The calories on your HRM or cardio machine are measuring total calories (and estimated at that), even the ones you would have burned had you been sitting on the couch. The only thing that should matter when looking at calories burned during a workout are the additional calories you had to consume to get the work done – in our case, to turn the pedals. Otherwise, instructors (and those pesky HRMs) are giving people false hope that they are “torching” tons of calories when they take that Spin or Zumba or BodyCombat class. Their watch might say 600 calories (but in reality it was only 300, over and above what they consumed to stay alive). So they go out and get a venti caramel machiatto with 500+ calorie and wipe out any benefit they might have had. If people knew the REAL numbers, they might not get that caloric drink.

    Better yet, if they stopped worrying about numbers and more about effort (and eating right) then there would be more success! ;-

  5. Hi,

    Nice article, but I have some concern that needs to be clarified. In your email newsletter you state: “ignore the calories you see on your HR monitor”.

    When I teach I have everyone wear a HR Monitor and 90% of the students have purchased their own Polar HR monitor (FT7 series). They have entered their user info. (ie: wt, ht, dob, HR limits, etc.), and I too have done the same with my FT80.

    In a 60 min. class I will easily burn 650 – 700 calories, and the majority of my students burn anywhere from 500 – 600. How can you say that I should ignore that number on my HR monitor when I have entered all the vital stats?

    I realize you can’t go by what the media says, but when it comes to HR monitors are they not accurate??? Please clarify.


  6. Glad there was a continuation. thank you and looking forward to my energia magica ride tonight

  7. Thanks for concluding the discussion with Danielle…and reminding instructors about power vs body weight, also interesting to hear that Danielle new CycleOps bike is freewheel. I have been a Master Trainer for a free-wheel bike for 7 years, for all that time it feels like rowing up stream without a paddle – because for most riders a free-wheel bike is too hard and you can not cheat, they can not master the kick and scrape of a pedal stroke so it becomes clunky. They are used to being able to stand up on a fixed wheel bike without much gear. So I wish Danielle all the luck with the transition to free-wheel – your riders will get immense rewards through it though. Thanks Jen. Enjoy NYC!

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