Calories Burned - Stationary Bike

While I think this thread is mostly a train wreck at this point, I do think it's interesting to hear people talk about the numbers they can put out, especially power.

I don't have a power meter, so the only power data I have is from the stationary bike I ride at work periodically. Looking back over my workouts, I can do 150w for an hour pretty comfortably... 200w for 30 minutes... 250w for 10 minutes. But I've never really ridden/tested my power output, so those numbers are just from mostly recreational/fitness bike sessions. FWIW, I'm an avid rider who rides a lot but doesn't really train.

DX2JX2 wrote: »

Serious question, forgive me if the answer is obvious.

Why does weight matter when measuring calorie burn on a stationary bike?

In a spin class, at least the ones I take, you spend 1/2 to 3/4s of the time standing, not seated, so you are working against your body weight.

Edited to add, if your bike is measuring watts against a motor or other resistive load, then your body weight really doesn't matter to the bike.

But to some extent, it matters to the formulas that convert HR over time to calories burned. So if the bike or other gear has an ANT+ pickup, measuring your HR, could it be using that data to do some calculations.

Of course, I try to not eat back my workout calories, so this exercise is really just academic.

DX2JX2 wrote: »

Serious question, forgive me if the answer is obvious.

Why does weight matter when measuring calorie burn on a stationary bike?

I don't think it does... not in any meaningful way at least.

jjpptt2 wrote: »

While I think this thread is mostly a train wreck at this point, I do think it's interesting to hear people talk about the numbers they can put out, especially power.

I don't have a power meter, so the only power data I have is from the stationary bike I ride at work periodically. Looking back over my workouts, I can do 150w for an hour pretty comfortably... 200w for 30 minutes... 250w for 10 minutes. But I've never really ridden/tested my power output, so those numbers are just from mostly recreational/fitness bike sessions. FWIW, I'm an avid rider who rides a lot but doesn't really train.

Some of those are like the treadmills for distance - accuracy is based on calibration.
Just as I've never seen a treadmill calibrated in a gym except when a belt is replaced (it's supposed to be done much more often), I've never seen those exercise bikes that measure watts against a motor getting calibrated - but I've looked up manuals of how and when it's supposed to be done.

I've never been in a gym where they used an actual power meter in those types of bikes. And while watts based on the resistance provided by a motor that also runs the display can be accurate - they can also lose it and require that calibration.

HilTri wrote: »

I sync a telementary strap to the bike's computer. I think it is pretty accurate, usually about 650 cal for a 1 hour spin class where my heart rate is in the red zone (max is about 165 BPM) for over 50% of the class. I also happen to wear a Garmin Fenix and the calories burned on that are within 50-100 cals of the bike computer. Gotta enter your stats!

As several have pointed out in this thread - using HR based calc's for calories for anything but the intended steady-state aerobic with HR the same for 2-4 min at a time the calculations are intended for - is just asking for inaccuracy.

Sure someone could purely by coincidence match up well, but how would they know unless they had an an accurate method.

For short rides up to an hour where I did not lift first - I can have HR-based calcs get pretty close to watts-based calc.
But if I lift first - HR is elevated above normal and that is out the window.
If longer than 1 hr, then HR becomes elevated because of dehydration and the effort so far, so again not useful.
If it was interval in nature like a Spin class, like a did a lot of short hills (the only kind I have), elevated again.

The reason why your HR is in the red zone for 50%, is because it takes longer and longer to recover to go below it.
Next time you get a chance - pedal up into that zone for however long you'd normally be there - then stop pedaling totally and just sit there.
How long for HR to drop below that zone?
How long for HR to drop to a HR level that would normally be required for sitting there? (which is what, resting HR?)

NorthCascades wrote: »

heybales wrote: »

jjpptt2 wrote: »

While I think this thread is mostly a train wreck at this point, I do think it's interesting to hear people talk about the numbers they can put out, especially power.

I don't have a power meter, so the only power data I have is from the stationary bike I ride at work periodically. Looking back over my workouts, I can do 150w for an hour pretty comfortably... 200w for 30 minutes... 250w for 10 minutes. But I've never really ridden/tested my power output, so those numbers are just from mostly recreational/fitness bike sessions. FWIW, I'm an avid rider who rides a lot but doesn't really train.

Some of those are like the treadmills for distance - accuracy is based on calibration.
Just as I've never seen a treadmill calibrated in a gym except when a belt is replaced (it's supposed to be done much more often), I've never seen those exercise bikes that measure watts against a motor getting calibrated - but I've looked up manuals of how and when it's supposed to be done.

I've never been in a gym where they used an actual power meter in those types of bikes. And while watts based on the resistance provided by a motor that also runs the display can be accurate - they can also lose it and require that calibration.

This is true outdoors as well. You need to "calibrate" (zero) a power meter before every ride.

Ya, my 310XT is set on auto, and for a while I checked about 5 min in (for temp changes), and compared existing to new and never had a difference - so I've gotten out of the habit of checking and running through manual.
Need to start again to confirm auto is still working as expected.

0ysterboy wrote: »

tbright1965 wrote: »

I left the MyZone at home, so I don't have the HR information from it.

However, what I found interesting from my GPS equipped FitBit Surge is that for about the first 2/3rds of the ride, the calculation was a fixed 22 calories/minute.

It was only about the last 1/3rd that it then claimed I was burning 11 calories/minute.

Certainly not setting any records as I was stopping and waiting for some slower riders in the group several times.

Finally averaged about 18.1 MPH the last 10-11 miles according to my MapMyRide data from my iPhone.

But they both estimated over 3000 calories on a 38 mile ride. I didn't start the Fitbit tracking until after we rode from the parking area to the registration table, so it has a lower total ride distance.

Jeez, I always poo-pooed the 1200+ kcal burns my computer/HRM would record on a 90-105 min (26-30 mile) ride, but maybe my burn rate is that high...

I was going to suggest the opposite. I worked hardest the last 10-11 Miles when I left the group and rode in at an average of 18.1 mph instead of the around 14 mph with the group.

At that point, the FitBit claimed I was burning 11-12 calories/ minute instead of 22. Leading me to believe the real number is in the 600-750 calories per hour range.

heybales wrote: »

Since Fitbit is going by HR for calorie burn - could it have been misreading your HR since at higher intensity?
Many find that, it either keeps cutting out when HR is higher, or it just plain stops going higher at certain HR.

Since you were getting higher calorie burn, I'd guess it's not the latter, but the former, higher interspersed with a bunch if inaccurate lower readings.

From your reading though - it appears the first block of time where the calorie burn is a straight line despite the moving HR, I'd suggest the first block is screwed up.
Did something sync a calorie burn over to whatever is displaying that?

I have no idea? I had my phone and my fitbit both with me the whole time, as the phone was running MapMyRide?

I considered cellular data service, but you would think if it were data, I'd have the same rate of burn at the beginning as the end when I was likely using the same cell towers, etc.

I rode on the hoods the entire way, so it wasn't like I moved from hoods to drops or something of that nature that would change how my heart rate was being measured.

Also, my higher intensity was at the end, not the beginning, and that was when I had the lowest rate of burn. I wasn't working nearly as hard riding with the group.

Just goes to show that you just cannot really trust the numbers. Need to check them against reality to see if they make sense.

34xx calories doesn't make sense. Now 1500-1700 might make sense.

I've seen other estimates, that I realize are rough indicating 40 calories/mile, which would be just over 1500 calories if I've done the math in my head correctly.

aeloine wrote: »

Good afternoon!

I go to spin class and it gives me kcal and kj burned but I don't input my height/gender/weight.

My question is, are those burn numbers absolute or are they weight relative? For reference, I'm roughly 220 lbs and I've been "burning" around 300 kcal/hour which seems a little low.

Don't get me wrong, I'm definitely not putting out very high watts yet (there's been a lot of improvement in my averages over the last couple of months in terms of watts/miles "ridden" per hour) but if 1 mile run/jog is ~100 calories and I can do 4+/hour, and I feel like I'm exerting significantly more weight effort on the bike, shouldn't my burn be higher?

I guess I'm hoping that I'm burning more due to my (relatively) higher mass. Plus, my little HR enabled FitBit is giving me higher calorie burns. FitBit has always overestimated, but rarely triples what any other "calories out" meters estimate.

Thanks in advance!

My goodness, OP, we've come far - very far, indeed - from your original question!

heybales wrote: »

tbright1965 wrote: »

heybales wrote: »

Since Fitbit is going by HR for calorie burn - could it have been misreading your HR since at higher intensity?
Many find that, it either keeps cutting out when HR is higher, or it just plain stops going higher at certain HR.

Since you were getting higher calorie burn, I'd guess it's not the latter, but the former, higher interspersed with a bunch if inaccurate lower readings.

From your reading though - it appears the first block of time where the calorie burn is a straight line despite the moving HR, I'd suggest the first block is screwed up.
Did something sync a calorie burn over to whatever is displaying that?

I have no idea? I had my phone and my fitbit both with me the whole time, as the phone was running MapMyRide?

I considered cellular data service, but you would think if it were data, I'd have the same rate of burn at the beginning as the end when I was likely using the same cell towers, etc.

I rode on the hoods the entire way, so it wasn't like I moved from hoods to drops or something of that nature that would change how my heart rate was being measured.

Also, my higher intensity was at the end, not the beginning, and that was when I had the lowest rate of burn. I wasn't working nearly as hard riding with the group.

Just goes to show that you just cannot really trust the numbers. Need to check them against reality to see if they make sense.

34xx calories doesn't make sense. Now 1500-1700 might make sense.

I've seen other estimates, that I realize are rough indicating 40 calories/mile, which would be just over 1500 calories if I've done the math in my head correctly.

When a block like that shows up - makes me think something else synced in a workout of X calories, Fitbit merely has means to show per 15 min block burns, so it merely divides it out.

That could be MMR syncing to MFP, then MFP to Fitbit.

And for whatever reason, duration was short, so it left untouched the end of the ride.

Unless the difference is 1 hr, in which case something may not be on DST, and the start time is off.

Besides being elevated.

My start times were off because I didn't start the FitBit until I left the registration table. I did start MMR when I left the parking lot, which explains the start time difference and the greater distance.

However, when I got to the finish, I stopped both of them within a minute or two of each other. So why is the last ~45 minutes so different from the first ~105 minutes?

Let me look at another ride captured by my FitBit????

The OP is using a bike with a power meter. The fact that Fitbit makes goofy estimates had no relevance here.

NorthCascades wrote: »

The OP is using a bike with a power meter. The fact that Fitbit makes goofy estimates had no relevance here.

I agree - of course the question is, has the power meter on the bike been calibrated recently (or at all - though if it hasn't been recently it wouldn't matter)? Shane Miller did an interesting review of the ELITE Arion Digital Smart B+ Rollers (stay with me - this becomes relevant quickly). While he calibrated them the first time he didn't on his second ride on them (which was a few weeks later) when he was testing them on Alpe du Zwift and comparing the power readings with his Favero Assioma pedals (which are dual sided power meters). Needless to say, at one point the rollers were reporting that he was putting out 80 watts more than the pedals were saying. His previous test (in which he calibrated the rollers correctly) showed readings that were much closer together, even with the rollers warm.

Alpe du Zwift is an extreme test given the limitations of those specific rollers, but even when the rollers weren't really hot, there were large differences in the power reported. Significantly larger differences than when the rollers had been calibrated correctly.

For what it's worth, Stages PMs are slightly less accurate than some others. Because they use accelerometers instead of reed switches to measure cadence (RPMs). Which makes them slightly slower to respond to change, like in a standing start.

Stages PMs do a better job of holding their calibration though.

At the end of the day, they have a maximum error of 2%. There's really no point in sections guessing what it said without a good reason to.

SeaG1ant wrote: »

I would recommend that you believe your feelings, because measuring devices can fail. If we talk about me, I recently started training on a spin bike that I ordered here https://spinbikeexpert.net/. And I felt as if I was doing something wrong and my legs were greatly enlarged in volume. I already wanted to return the simulator back to the seller , but decided to consult with a specialist first. And he told me that I didn't train correctly and showed me where to find information about training on a spinbike. It turns out that it's very important to know exactly what to do. Because otherwise you can harm yourself and your health.

Do these guys provide discounts?