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  1. #1
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    How Much Does HR Data Help with Fine Tuning Diet

    I've been tracking my nutrition daily for over a month using the Livestrong App for keeping track of intake and the calorie numbers estimated by Strava to estimate output. What I'm finding is that even an hour of hard riding can create a big swing in your daily calorie requirements. So large in fact that even a modest error in the calorie deficit created by a ride can prevent you from knowing where you are WRT to you calorie goals.

    For instance, right now, I'm shooting for a basic calorie goal of 1850/day. 90 minutes on the trail and Strava tells me I'm burning something like 1300 calories. So to fuel my ride and make my calorie goal, I need to make some pretty significant changes in intake. But that number does not change a lot even if I feel like I'm riding low intensity vs. a high intensity. That suggests to me that its not tracking well my effort, but is just looking at the trail I covered. If there is a 20% error in that number that burn number, that error margin basically represents the margin that I'm trying to work on to loose a pound or 2 a week.

    I'm just wondering if the calorie burn data I'd get from a Garmin with the HR kit would be substantially better than the Strava data so that I'd have better info for tracking diet.

  2. #2
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    Estimated calories burnt figures are notoriously inaccurate. The Strava figures are likely to be a long way out, and probably overestimate how many calories you're burning.

    Using a heart rate monitor to estimate calories burnt is also not very accurate. The calories burnt figure provided by a Polar or Garmin heart rate monitor can overestimate the number of calories that you actually burnt whilst riding by as much as 30%.

    If you try to closely match calorie expenditure to website or heart rate monitor estimates then you could end up eating more than you intended whilst trying to lose weight. It's something to be wary of. Inaccurate estimates are often worse than having no information at all. It's usually best to assume that any calorie figures that you see are overestimating calories burnt. Stick to a lower figure in order to avoid overeating.

    Actual calories burnt whilst cycling can be fairly accurately calculated with a power meter. You can see wide variations between rides depending upon how hard you're trying. As an example I did a fairly gentle 1h30 ride mountain bike ride the other day and only burned approximately 850 calories. On a hard 1h30 ride I burned approximately 1141 calories in the same length of time.

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    I know power is the best way to generate good data, but a powertap is just not in the budget right now. It would be nice if they could cut the price of those in about 1/3rd.

    I do underestimate the calories that strava gives me. I typically only want to eat about 1/2 of the ride calories. But if you listed to the people that say undereating is as counterproductive as overeating to dieting, that margin of error is still getting you in trouble.

    Tricky business.

  4. #4
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    Those calories burnt figures were just to give an idea of how much it can vary between different rides.

    On the subject of Strava I uploaded a ride file with only speed data (no heart rate or power recorded) and Strava actually seems to have underestimated calories burnt. Strava says 1,041 calories for a 2.5 hour ride but I'd normally expect a similar route and pace to be around 1,500 calories for me.

    You just have to be careful and not take any estimated figures as exact. If you're losing weight at 1-2lbs per week then your diet is probably about right.

  5. #5
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    Quote Originally Posted by Metamorphic View Post
    I know power is the best way to generate good data, but a powertap is just not in the budget right now. It would be nice if they could cut the price of those in about 1/3rd.
    Those are cheaper than these!

    Garmin | Vector™

  6. #6
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    Quote Originally Posted by WR304 View Post
    Those calories burnt figures were just to give an idea of how much it can vary between different rides.

    On the subject of Strava I uploaded a ride file with only speed data (no heart rate or power recorded) and Strava actually seems to have underestimated calories burnt. Strava says 1,041 calories for a 2.5 hour ride but I'd normally expect a similar route and pace to be around 1,500 calories for me.

    You just have to be careful and not take any estimated figures as exact. If you're losing weight at 1-2lbs per week then your diet is probably about right.
    That's very interesting that strava underestimated. What are you using to get your power measurements?

    The concern I have is that when I'm riding a lot I'm loosing more than the 1-2/wk, and when I'm not riding a lot I'm loosing little or nothing. I'm hoping to get better data on the ride end of it so that I can adjust my calorie goal properly. But the on again, off again nature of my ride schedule due to weather makes it tough to get a steady state where you can see cause and effect. I'm also worried that as I loose more it will get harder and so I'll need better data to judge my workout intensity and need for rest days.

  7. #7
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    Quote Originally Posted by nov0798 View Post
    Those are cheaper than these!

    Garmin | Vector™
    Yeah, cheap unobtanium.....

    “After testing our latest advanced prototypes of the Vector system, we are still not satisfied with the results. As you can imagine, Vector is a complex, precision measurement instrument and as of yet, we are unable to ensure that this device will meet the expectations of the cycling community. Presently, we cannot estimate a delivery date but we do not expect the product to be ready in the summer of 2012, as previously targeted. We understand that this is a highly anticipated product within the cycling community, but Garmin’s commitment to quality necessitates this additional delay. We will update our customers when we have additional information to share. Thank you for your understanding.”
    An update on the Vector pedal-based power system
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  8. #8
    gran jefe
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    If you start with a good guess of calories burned and calories consumed, and then just stick with them for a couple of weeks, you can watch to see if you lose or gain weight.

    Pretty much every machine you use to estimate calories burned will probably overestimate.

    Any treadmill that tells calories burned without asking your weight is obviously winging it.

    Quote Originally Posted by WR304 View Post
    As an example I did a fairly gentle 1h30 ride mountain bike ride the other day and only burned approximately 850 calories. On a hard 1h30 ride I burned approximately 1141 calories in the same length of time.
    What was your average wattage on those rides, do you remember? I don't have a power meter, but I just started occasionally using an exercise bike with a wattmeter on it, and am wondering how it compares to what you are seeing.

  9. #9
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    Power output on gym exercise bikes is a whole topic on its own. They're usually not calibrated so any power figures you see displayed on a gym exercise bike won't match what you'd see when riding outdoors with a power meter.

    If you're going to a gym try and use the same exercise bike each time. If you use different exercise bikes that are calibrated differently you may find that one exercise bike will display 200 watts for a given effort but the exercise bike alongside it displays 300 watts for the same effort. Although the figures may be wrong using the same exercise bike each time increases the chance that you'll get more consistent readings between sessions, allowing you to track your progress.

    Taken from my Powertap. I weigh 149lb approx.: (Using 1kj = 1 calorie as a rough estimate)
    1h30 Gentle ride - 153 watts average power, 834 calories
    1h30 Hard Ride - 213 watts average power, 1141 calories

    Have a look at the links in this post on the subject of estimating energy expenditure:
    PowerTap Disc

    The two things I found useful when trying to lose weight a few years ago were to not do too long bike rides and also to increase my protein intake. Sticking to regular short but fast rides (only doing 1h30 to 2hrs a day) burns more calories per minute, you can recover from them rapidly and you're less likely to end up feeling the need for "cheat" meals when you get home. It was more successful for me than doing less frequent higher volume rides (5hrs+) at lower intensities. The problem with long rides being that you can't ride as hard and they take longer to recover from so you can't always train as hard the next day.

    Increasing your protein intake (I added extra protein shakes in the morning pre and post ride, along with one before bed) helps support your bodies need to recover and also helps to spare muscle when you're dieting.

    Bodybuilding.com - A Unique Combination Of Science And Experience Based Pre-Contest Advice.

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  10. #10
    gran jefe
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    Quote Originally Posted by WR304 View Post
    Power output on gym exercise bikes is a whole topic on its own. They're usually not calibrated so any power figures you see displayed on a gym exercise bike won't match what you'd see when riding outdoors with a power meter.

    If you're going to a gym try and use the same exercise bike each time.
    This is the bike where you steer yourself through a video game, and we only have one. I'm sure a whole series of sub-rants can be spawned by that sentence. I understand what you are saying. I have played that game myself. Maxed out on this bike = 500 call per hour, that one = 600 cal per hour, the eliptical = 700 cal per hour. Meanwhile, the HRM says 770 cal/hr. I can't trust anyone!
    Quote Originally Posted by WR304 View Post
    Taken from my Powertap. I weigh 149lb approx.: (Using 1kj = 1 calorie as a rough estimate)
    1h30 Gentle ride - 153 watts average power, 834 calories
    1h30 Hard Ride - 213 watts average power, 1141 calories
    Okay, those fit with what this one is showing. For me, I am seeing 185-190 watts at my max sustainable effort (not as strong or conditioned as you), and 153 would be nice and cruisy. Thank you for posting.

  11. #11
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    Quote Originally Posted by WR304 View Post
    Power output on gym exercise bikes is a whole topic on its own. They're usually not calibrated so any power figures you see displayed on a gym exercise bike won't match what you'd see when riding outdoors with a power meter.

    If you're going to a gym try and use the same exercise bike each time. If you use different exercise bikes that are calibrated differently you may find that one exercise bike will display 200 watts for a given effort but the exercise bike alongside it displays 300 watts for the same effort. Although the figures may be wrong using the same exercise bike each time increases the chance that you'll get more consistent readings between sessions, allowing you to track your progress.

    Taken from my Powertap. I weigh 149lb approx.: (Using 1kj = 1 calorie as a rough estimate)
    1h30 Gentle ride - 153 watts average power, 834 calories
    1h30 Hard Ride - 213 watts average power, 1141 calories

    Have a look at the links in this post on the subject of estimating energy expenditure:
    PowerTap Disc

    The two things I found useful when trying to lose weight a few years ago were to not do too long bike rides and also to increase my protein intake. Sticking to regular short but fast rides (only doing 1h30 to 2hrs a day) burns more calories per minute, you can recover from them rapidly and you're less likely to end up feeling the need for "cheat" meals when you get home. It was more successful for me than doing less frequent higher volume rides (5hrs+) at lower intensities. The problem with long rides being that you can't ride as hard and they take longer to recover from so you can't always train as hard the next day.

    Increasing your protein intake (I added extra protein shakes in the morning pre and post ride, along with one before bed) helps support your bodies need to recover and also helps to spare muscle when you're dieting.

    Bodybuilding.com - A Unique Combination Of Science And Experience Based Pre-Contest Advice.

    .
    Your calorie data validates mine to some extent. I'm about a hundred pounds heavier than you so its seems reasonable for my calorie burn for a 90 minute ride to be in the 1300 cal range. My strava calculated wattages range from 200 to 250. So the scaling makes sense.

    You're probably right, I should be including some more protein. Particularly as some of the workout-day make-up calories.

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