Accuracy of calories burned while biking

I have a Polar FT 7, which is pretty basic. I came into HRM's and more aggressive bicycling through weight loss. I lost and have kept off for more than a year about 47 pounds.

Here's the news: As you become more conditioned,your calorie burn falls. :( Just ain't fair. But if I understand the physiology correctly, being more physically active kicks up your basal metabolic burn somewhat. You benefit from being more active and less sendentary.

I used the weight loss web site Calorie King and they have estimators for exercise (you can eat back calories burned with exercise). The commonly accepted scuttlebutt was that the estimates were high and the numbers you got with an HRM are "more accurate" and uniformly lower than the estimates. This has tended to be my experience also.

But they are really scientific best guesses, though I think they are not all wrong.

With exercise I have seen my resting heart rate drop. I did an estimation of body fat at my local YMCA (not the gold standard,which is an immersion test).

But with my new bike (did I mention I have new Trek Madone?) my plan is to work on cadence and then I will be interested to see if this kicks up my calorie burn.

Try not to focus on one number. Look at a constellation of data. There is no doubt that the "king" of calorie burn exercise is running. But I like biking. And that beats being a couch potato any day.

Classic MapMyRide has a pretty good calculator for determining one's heart rate zones if you know your maximum heart rate, or you can accept the calculator's formula for maximum heart rate.

http://classic.mapmyride.com/calculate_mhr

There is a good explanation of each zone as pertaining to cycling.

The calculator's formula for calculating the maximum heart rate actually works for me. At my age and based on knowing my heart rate at maximum exertion, I estimated my maximum heart rate to be between 165 and 170, and the calculator states 169, so right in the range I thought it was.

But it looks like all of those just take your MHR (either tested or approximated from the general population), start at 60% and divide into equal portions... Which I know how the 301 got MHR, but it's possible that's what it does for zones 2 through 5, since what it gave me for those are all equal within a beat.

I'm reasonably confident of my MHR. That's what I'll see toward the end of the fourth or fifth of a series of sprint intervals on a really hot day, about the time I'm seeing stars and ready to throw up... :cool: I'm actually more confident of that number than I am of my RHR - I've never bothered to wear a strap while I sleep, so I just took what I'll see when driving to an event, which is in the low 50s as long as traffic isn't crazy, and then just subtracted a couple of beats for the demands of attention and sitting.

But how do you actually test for the zones?

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Originally Posted by OakLeaf

But it looks like all of those just take your MHR (either tested or approximated from the general population), start at 60% and divide into equal portions... Which I know how the 301 got MHR, but it's possible that's what it does for zones 2 through 5, since what it gave me for those are all equal within a beat.

I'm reasonably confident of my MHR. That's what I'll see toward the end of the fourth or fifth of a series of sprint intervals on a really hot day, about the time I'm seeing stars and ready to throw up... :cool: I'm actually more confident of that number than I am of my RHR - I've never bothered to wear a strap while I sleep, so I just took what I'll see when driving to an event, which is in the low 50s as long as traffic isn't crazy, and then just subtracted a couple of beats for the demands of attention and sitting.

But how do you actually test for the zones?

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I agree, is most likely that your MHR is correct as that is the number you can see when dying onr those intervals ;) Calculating your zones from your MHR is good. I would use your anaerobic threshold to calculate your zones as it is a more accurate, anaerobic threshold(Lactate threshold) is the point at which lactic acid starts to accumulate in your muscles, this will be your zone 4 and is between 80% and 90% of your maximum heart rate. You can find out your threshold with a simple test. Find a long climb or a hill that will take about 30minutes to complete when riding all out, if a hill is not available it can be done on a flat or against the wind. Warm up for at least 20 minutes and then ride as hard as you can for 30 minutes, at the 10 minute mark press the lap so it will record the last 30 minutes of you hear rate, this will be your Threshold (Lactate threshold) and you can use this test for running also. Once you get this number all the zones are calculated from that number.

I just wanted to post an update. So this weekend, I changed the battery in my HR strap (even though I didn't think I needed to), picked up a bottle of HR electrode gel and applied it to the HR strap, and took a manual pulse to see if it was close to what my Garmin was showing right before I set off on my ride. My HR was sitting right around 75-78, just futzing around getting on my gloves and so forth...which was right on target with what my manual pulse reading was. So, I established that the HRM seemed to be working properly at the time. I also double-checked my profile on the Garmin, and made sure that all the data was entered correctly - ht 5'6", wt 157lbs, Female, 44yo, activity class = 9.

After 3 consecutive days of riding, the results of my HR/calorie data were the same as before. On Sat, my avg HR was 101; on Sun, 109; and today, 108. Calorie burn was 888 (65 miles), 1,147 (83 miles), and 551 (43 miles) respectively. I don't know, it just seems weird that I cannot seem to get my HR up at all on the bike. I can safely say that I have NEVER even come anywhere close to hitting my MHR while riding. Is it possible that I just have a freakishly low HR? I normally don't wear a HRM at the gym, but now I am curious to see if it's that low during any kind of activity.

Don't know if this matters or not, but I do remember last year during a routine colonoscopy I was hooked up to a monitor and I kept setting off the alarms on it because my HR kept dipping below 40....freaked out the nurses. Maybe I just naturally have a lower HR? I don't know....

Linda

The only other thing I can think of is your cycling position, can it be moving the chest strap away from contacting with your flesh? I can't wear a chest strap on the spin bike at the gym because some of the positions interfere with the chest strap, and maybe it is the same for you on your bike.

Regarding the low heart rate, the people I know with low heart rates during cardio exercise are on heart medications. I also chatted with a female cyclist a few years ago, who had transtioned to the bike from long distance running, and she couldn't get her heart rate anywhere near her max rate on the bike, but I am sure her average rate was over 120. So if you are not on heart meds, maybe you are super fit from another sport and the bike is too easy for you, or perhaps you need to do more miles of steep climbing?

Yesterday I biked an event metric. I looked at the Garmin data of a training group friend who did the metric too. When climbing the nasty hill, his heart rate was around 180; my heart rate was around 140, and that is a huge difference, though my max is only 165-170. But when I looked at the other data, his cadence was 80 and my cadence was 60, his speed up the steep hill was 8 mph and my speed was only 6 mph. He was able to push harder because he is a male or more fit, and got a higher heart rate due to more exertion. On the other hand, at the top of the hill was this one male cyclist who was younger than everyone in my group, and he was off his bike gulping in air like a landed fish, looking like climbing that hill just about killed him.

If your heart rate remains low when climbing real steep grades and you are exerting yourself fully, then my suggestion is see your doctor and make sure you are heart healthy. If your heart is fine, then guess you shouldn't worry about it.

Too many possibilities. You can also have depressed heart rates from fatigue and overtraining. (As well as elevated rates--can go either way).

A good time to measure your resting heart rate is while you are still in bed, right after waking up.

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Originally Posted by DarcyInOregon

The only other thing I can think of is your cycling position, can it be moving the chest strap away from contacting with your flesh? I can't wear a chest strap on the spin bike at the gym because some of the positions interfere with the chest strap, and maybe it is the same for you on your bike.

Regarding the low heart rate, the people I know with low heart rates during cardio exercise are on heart medications. I also chatted with a female cyclist a few years ago, who had transtioned to the bike from long distance running, and she couldn't get her heart rate anywhere near her max rate on the bike, but I am sure her average rate was over 120. So if you are not on heart meds, maybe you are super fit from another sport and the bike is too easy for you, or perhaps you need to do more miles of steep climbing?

Yesterday I biked an event metric. I looked at the Garmin data of a training group friend who did the metric too. When climbing the nasty hill, his heart rate was around 180; my heart rate was around 140, and that is a huge difference, though my max is only 165-170. But when I looked at the other data, his cadence was 80 and my cadence was 60, his speed up the steep hill was 8 mph and my speed was only 6 mph. He was able to push harder because he is a male or more fit, and got a higher heart rate due to more exertion. On the other hand, at the top of the hill was this one male cyclist who was younger than everyone in my group, and he was off his bike gulping in air like a landed fish, looking like climbing that hill just about killed him.

If your heart rate remains low when climbing real steep grades and you are exerting yourself fully, then my suggestion is see your doctor and make sure you are heart healthy. If your heart is fine, then guess you shouldn't worry about it.

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I did a steep but short climb on my ride this morning. I was monitoring my HR throughout the climb...my HR peaked at 131 (which also happens to be my max HR for this ride), and this is a very challenging hill for me. I have to ride in my absolute lowest gear...my speed up this hill is about 7mph, if that, so cadence is sure to be low as well. As for the possibility of my strap being moved while riding...I think it's unlikely. I generally have to "peel" the thing off me when I'm done, so it pretty much stays put once I put it on.

ETA - not on any heart meds

Linda, I just caught this thread but wanted you to know that I have a Garmin 500 and I have been having the same issue. We time trial on Tuesday evenings and without the hrm the Garmin says I burn around 550 calories in a 10 mile hilly tt with an 18 mph average (which I think is close to accurate); with the hrm the Garmin says I burn 225--usually cuts it in half. DH has a Garmin Edge 305 and his heart rate records in the 500-600 range for the same tt. I think it has something to do with the Garmin 500.

I do not have a Garmin but have heard from others that the Garmin 500 does seem to be prone to reporting lower heart rates and under-estimating calorie useage.

I'd suggest stopping at the top of that killer hill and taking a manual pulse.

To original poster: Why do you want this information? Training purposes? To gauge how much to eat? Just for kicks? Numbers nerd? I'm curious.

I use a Polar FT40 to see my calorie burn for every activity (fitness) I do. I don't eat more or less based on calorie burn. For me it just ensures that I get consistent calorie burn each week for fitness.

Linda,

It appears that your zones are off on the Garmin and is as you are always riding zone 1. As OakLeaf sudjested measure your pulse at the top of that hill and compare the 2 if they agree set your zones and MHR to that number.

What do people do after they have lost weight and measured calories during the weight loss process? Do you still do it this carefully?

Hopefully some people reach a point that they know instinctively how much and what to eat works for them in accordance to a rough guessestimate of their exercising activity.

For me, it's still a guessing game- I stayed even for a while, gained a few pounds, dropped all but one and stayed there for a couple months, but the next time I seem I went up, I seem to have found an equilibrium that is 3 lbs above my goal. So I'm riding 100 miles a week but can't seem to get these 3 lbs off. It's all about counting and tracking and I think I haven't been as good at that.

Interesting how the Garmin gave a more realistic result w/o the HRM.

nscrbug - did you ever try contacting Garmin to ask them about the discrepancy? My DH did not have any other ideas...