Calories burned in a ride
 

I think I read once that to burn calories, go longer rather faster. I thought this meant only that there’s a trade off, and going longer makes more difference than going faster. But I recently got numbers from a couple of rides that surprised me.

All metrics supplied by RidewithGPS, Garmin computer, Shimano Dura Ace power meter.

Rides 1 and 2 were the same distance. in Ride 2 I averaged 13 watts harder, so my ride was shorter by 12 minutes. But Ride 1 burned 26 more calories! I’d have thought going harder over same distance would have burned more. But maybe this is an example of going longer rather than harder burning more calories.

I know these calorie estimations are imperfect. But curious for your thoughts.

Did you account for variables such as wind and traffic? Your result is both surprising, because it is unexpected, and also not surprising due to its insignificance - 26 calories is like 13 raisins or a sip of Coke.

If you go hard and fast, then you'll tire and stop riding before you go the mileage you can on a really long ride. So at some point a long ride will always win out on Calorie burn Though for shorter rides the one where you do the most effort on will burn more Calories than a easy ride of the same length.

If you consider what is being used for fuel, fat will be used up at a somewhat consistent rate for either strenuous or easy. Glycogen and energy from serum glucose becomes a larger percentage of those Calories burned when you do high effort riding. And if weight loss is the only main goal, there isn't a point in doing the high effort ride for shorter duration if it's preventing you from riding several hours or more at a time.

Don't use Calories burned as a estimate of power obtained while cycling. Get a PM for that. RWGP"s power estimate are 100 watts over what my PM says I do for the same 22.2 mile route and time.

26 Calories is a trivial amount. Especially if being used for weight loss. I'd think that any tracking of Calories in will be off by way more from actual. So deviations in Calories burned is the wrong thing to focus on.

Since you used a power meter your calories calculation should be fairly accurate. A variable is the type of energy used and that becomes much more complex. High intensity efforts compared to long easy endurance work use different energy systems.


The calculation using power data is based on a direct measure of the work you performed:

• Work (Kilojoules - kJ): Your power meter measures your power output (in Watts) over time. The total amount of work done is expressed in Kilojoules (kJ).
  
  • 1 Watt=1 Joule per second.
    
  • Work (Joules)=Power(Watts)×Time(seconds).
    
• Calorie Conversion: Cycling efficiency for humans is generally assumed to be about 20-25%. This means that for every 1 kJ of mechanical work you put out, your body has to consume approximately 4 to 5 kJ of chemical energy(calories) to produce it.
  
  • Due to the near 1:1 conversion factor from kJ of work to kcal (calories) of energy expenditure for the human body's efficiency, many devices and applications will often report the kilojoules of work as the active calories burned.
    

Active Calories (kcal)≈Work (kJ)This method is considered much more accurate than estimates based only on heart rate, as heart rate can be influenced by many factors (temperature, stress, hydration) that aren't directly proportional to the actual mechanical work you are doing.

I always have kJ shown on my Garmin. Helps with feeding on long rides. I try to consume about half my burn.

Two points:

1. from many sources Shimano power meters are notably inaccurate

2. even without any effort, you are still burning calories, more than 20 Cal in 10 minutes on a bike...

According to Wahoo:
https://support.wahoofitness.com/hc/...s/360020140320

Which I rapidly convert to Calories/ 150 = #beers consumable at break even.

But I never get close to that.

To add a real world example:

Google says that a slice of pumpkin pie is about 350 calories.
Yesterday's 60 min Zwift ride told me that I burned 330 calories.

Today's math problem: Assuming 15mph, how far do I have to ride IRL to burn off next week's Thanksgiving dinner?

Just one meal? Or do you, like some other's of us have to visit and eat with multiple sides of the family during the holiday?

That is the culinary equivalent of interval training.

This year, we are the parents/inlaws moving in for the long weekend, showing the "proper way" to prep the feast etc. So, more like coaching than training. I just hope that the 3 year old doesn't give a turkey leg to the dog.

I think that there are so many different variables involved in this notion of "calories" that it makes it impossible to track calories in/out. But, in general, longer mild to moderate efforts should work best, because among many other things such efforts will reduce cortisol levels and keep your body happy and relaxed whilst burning calories at the same time; think of long (>1h) walks or a 50 km chill bicycle ride.

Then, there is also the notion/theory of energy compensation, where if you are being consistent over time your body will figure out on its own how to match calories in/out, because it is working with an energy budget. And by consistent I mean you are doing roughly the same amount of workout per day and you are eating pretty much the same amount/things (without going to extremes obviously, either at the high or low end).

So who knows, one day I can do a very chill 50 km ride after a superb night of sleep and burn 1000 calories, because my body feels safe, happy, well-fed, and feels like spending some energy due to various hormones signalling that more energy will come in the future, and the next day I can do the same ride pushing for performance and burn 800 calories, because the body goes into preservation mode and starts down-regulating other functions (e.g., protein synthesis, which can cost up to 500 calories).

What device that you're using has an output in calories? Every device that I've used which has an output in calories was inaccurate. My suspicion is that the manufacturers rig their devices to show a good bit more burn that actually happens, making the users happy with their device purchase. Try using a heart rate monitor device which gives an output in calories at the same time you are tracking your power with a device which has a readout in kilojoules.

As noted by Atlas Shrugged, outputs in kilojoules are reliable. The only thing which affects calorie burn is cumulative effort, i.e. kilojoules. That makes it simple for cyclists, too bad there's no way to accurately determine burn in the gym, running, walking, etc.

That said, using a HRM with a calorie output is better than just guessing at what you burned at the gym, walking, etc. Just take the numbers with a grain of salt.

This isn't particularly surprising. Calories burned are close to kilojoules expended, and kJ is just average watts * ride length in seconds / 1000

So you can think of Calories as the product of time * power. Evidently, for your two rides, 12 minutes in time represented a larger percentage decrease in time than an increase of 13 watts was as a percentage of your power. So time decreased (in percentage terms) more than power increased (in percentage terms). So the product of time and power decreased. So Calories burned decreased.

(So, suppose 12 minutes was a decrease in time of 10% but 13 watts was an increase in power of only 9%. Then the 2nd ride would burn fewer Calories).

The weird thing to me is that increased power meant increased speed and power usually increases as the cube of the speed, so WTF. I would have guessed the same as the OP. I guess I'm not understanding something.

Hmm, are you sure you quoted the right person?

I mean, if it is a matter of converting kj to kcal bound to some specific activity, sure, there exist formulas that will give out some number.

But we are not machines in controlled environments; sleep, mood, stress, temperature, food, and many other variables will affect the real number, not just for the duration of the activity, but for the entire day.

We are somewhat complicated chemical devices. The formula however is quite simple: calories burned during aerobic activity = kilojoules of effort expended. It's not complicated and there's really not anything one can do alter that equivalence. Doesn't matter what you ate, are eating, or will eat. Cycling is a special case, in that we can use a device, a power meter, which directly measures power and thus enables us to calculate total kilojoules of effort expended. Note that "effort expended" does not include the calories expended by our metabolism, only the extra effort of cycling is being calculated.

We can't do that with other activities like running and swimming. Whatever one does off the bike will affect one's calorie burn, but no formula for that.

Right, power increases as the cube of speed, but the OP wasn't giving speed -- he was giving elapsed time and average power, but not distance. So we don't know the speed.

Don't know the total weight for each ride either. A difference in the weight will make a difference in the watts needed for a particular time. And if one ride had more and harder accelerations than the other, then that will up the difference in watts or kilojoules of energy too.

As for Calories, on a Garmin device and most other GPS/cyclometers, they are calculating dietary Calories. Which in no way should be attempted to reason with a true power reading from a PM.

I mean, I understand that you can get a somewhat accurate number of calories burned during the duration of a cycling activity, I just don't see any real practical application for it.

Main applications for that are of course weight loss, but also for pro athletes training has become more "scientific", their cooks weight everything they put in their meals, not only to provide the exact quantity of Calories needed, but also proteins, etc...

There are some long routes which I repeat every year if possible. I keep a record of all my rides on TrainingPeaks, so I know my burn in advance. I bring fuel calories equal to 1/2 my burn. I never eat the crap that they put out on sponsored rides. That works for me. Yeah, I'm nuts, but it works. On rides which don't repeat, I watch the kJ accumulate on my Garmin and fuel accordingly.

Another little tip for those interested who happen upon this: I use a HRM strap, so my Garmin shows both power and HR. If my HR is low for my power, I know I need more fuel. If it's high for my HR, I know I'm a little dehydrated.