Low Calorie readings after long assault bike workout

The problem here if that the watch doesn't have a lot to go on. The only input it receives is heart rate. It doesn't know that you're on an Assault Bike, but can only apply a generic profile for calories from heart rate. 

When I train "on the bike" I use a power meter. If I produce 200W for 90 minutes the watch knows that and can make a very precise calculation of energy production and calories burned. My weight does not matter, nor does my height. These things are irrelevant to the maths, but the calculations are sound. Even my heart rate is irrelevant with a power meter.

So, I can understand why your watch is struggling to produce the correct calories value, whatever that might be. You could try a different profile, like indoor cycling or elliptical trainer and see if you get better results. Also check that your heart rate zones are set correctly, and your activity class too. 

Beyond that I'm not sure. I have seen tables listed for assault style bikes that list Watts or calories per minute or hour at given RPM, but you would need the right listing for your unit. With that data you could make your own calculations to try to come up with the "correct" number for validation purposes.

For my own experience I can burn around 1,000 Cals per hour when racing on the trainer and something around 600 calls per hour for general training. Example data below....

But my heart rate zones may not match yours, nor may my FTP, so its a personal example from one ride, just for illustration. In your case, maybe 700 calories is correct for your workout, maybe 900, maybe 1100, but almost certainly not 1888 at 126 BPM unless you are incredibly fit and powerful (well, relative to me :-)). 

Can i fit a power meter on my assault bike? 

What do you suggest, i get a more professional Assault bike that maybe can give me the reading of a similar power meter?  Sorry if I am asking silly questions since i do not know what i need to do.  I really am asking in the forum since i presume that there are many people having air bikes or assault bikes that they use to track calories with the Fenix 6 watch.

If anyone has any experience with similar bikes that can help me out I would be more than welcome to listen to what they have to suggest.  What you told me in the email does make a lot of sense, but as I said in the original email I posted, I strongly believe that the reading of the bike is way high and fully agree that I am not that fit until now, but I also think that the reading of the watch is way low for one hour and 30 minutes of 63rpm constant pedaling and hand rowing that I could hardly walk after the workout so i think it was effective and on that day i was knackered and went to sleep really early.

I will try different preset maybe like you suggested, elliptical or indoor cycling, but many suggested that cardio is the closest you can go.  I will also search for a table that maybe i can find regarding my airbike watts per hour so maybe i can do a custom preset for my bike.  

I look forward for your response if you can kindly help me and thank you very much for answering back.  

Regards,

Joseph V. Calleja

In afraid I can't provide a solution to fix things for you, only the knowledge to understand better why the problem exists. I also don't speak from experience with your type of bike, only from my thoughts about the practical limitations.

I assumed from the display on your watch that your average heart rate was 126 BPM for the 90 minutes. Maybe it was the figure just at that moment. I'm flying pretty blind here, with guesses, much like the watch has to. 

If you look here.... 

https://i2.wp.com/www.zoarfitness.com/wp-content/uploads/2019/08/WattsRPMsimage2-1.png?w=721&ssl=1

you will see a table of power output at various RPM for a particular brand of assault bike. Maybe you could find an equivalent table for your bike. With this you can then work out the true calories expended during a steady session based on power x time = energy.

If we assume that this table is correct for your bike then 63 RPM would equate to 331W, and to hold that for 90 minutes is pretty hard core, I would think. 

Putting those numbers into a Watts to Cals calculator you actually get 1787 Cals. So the bike is in the right ballpark, if the RPM to power profile matches that table. But does it? The bike seems to think so. 

Unfortunately the watch does not have access to this data. The only thing you can do is to tweak the things I mentioned earlier in the hope of getting a better estimate of calories. 

Sorry I can't be more helpful. Hopefully there are indeed others in your position with a solution to offer. 

By the way, the calculation of power to Calories is described here.... 

https://gearandgrit.com/convert-watts-calories-burned-cycling/

Things like height and weight and speed and heat rate are irrelevant when you can measure power. You can be 1.5m and 50kg or 2m and 100kg, but at 63 RPM you will be producing the same power, no matter who you are and what you're made of.

And I'm not suggesting you try to fit a power meter or upgrade. Just accept the limitations of an imperfect estimation system and do what you can to make the results as true as possible. 

You were very very helpful, believe me, and this is really valid information to me that i do not have and never had. 

I am telling you that I am sure the workouts I do are really hard work and I burn a lot of calories that I cannot track due to the limitations of my airbike.  As I told you in my previous email i think that i am burning much more calories than what the watch is showing me, and this is confirmed because if i do 15 minutes of calisthenics I burn according to the watch on cardio preset with the HR monitor between 150 Cal to 200 Cal and that is why i feel that 700 for an hour 30 minutes of grueling assault bike is way low.

I will try to contact Schwinn maybe they can provide me with a watts to rpm graph that i can calculate approximately what i am burning during a workout.  

Thank you once again for all the help you provided. I really appreciate your time believe me since i have no one ready to help me with my issue here in Malta as no one has ever asked these questions to the supplier of the airbike as he confirmed to me.

Actually, I've just had an idea. Do you do any other cycling indoors or out apart from the assault bike? Do you have an FTP value set in your profile?

If you don't do other types of cycling then try this. Set your FTP to 345W (Just as a starting value) and record your assault bike rides as indoor cycling.

In this way you might be able to force a better estimation of power output vs heart rate and this will in turn give a better calorie estimate. Adjust FTP up or down to increase or decrease calories as necessary. 

This is just an off the cuff idea. I have no idea if it would work, but I like to think that it would. 

Good luck. 

Good advise and i have already setup FTP since apart from the assault bike i never do any other cycling indoors or out, in fact i was considering a MTB to ride outside.

Will test and revert.  Thank you once again for the very valid information you provided.  

I don't know about the Schwinn, but the Assault Fitness AssaultBike measures calories too low.  You can easily convert from power generation in Watts to work in kilocalories (1 kilocalorie = 1.163 Wh).  But that is external work, not internal calorie burn.  Most studies I have seen say that the human body in exercise is around 20-25% efficient.  Which means that the internal calorie burn is between 4x and 5x of the external work done.  In your screenshot above, 168W is 49 RPMs on the AssaultBike, which burns (according the the bike computer) 7.4 calories per minute, which would be 531 total calories (equivalent to 3.07x).  Your estimate above is much closer at 695, which equates to 4.02x.  I usually use 4.25x as a middle estimate.  So my estimate for your workout above would be 735 calories based on average power.  This is 38% higher than would be reported by the AssaultBike for the same workout.