Exercise bike calories burnt, accurate?

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  • NorthCascades
    NorthCascades Posts: 10,968 Member
    @MeganMoroz89

    If you go for a jog, your weight is an important part of how many calories you burned, because you used your muscles to move your body weight.

    If you ride your (outdoor) bike up a hill, your weight is also an important part of how many calories you burned, because you used your leg muscles to move your body weight against gravity.

    For both of those, if you wear a backpack with 10 lbs of water, you'll burn even more calories. I'm not telling you anything you don't already know.

    But if you sit on a bike that's bolted to the floor and not moving, your weight is almost not important at all for calories. Because you're not moving your body weight. You're sitting down, resting your weight on a saddle. You're using your muscles to turn the pedals and to move your legs, but not the rest of you. Imagine being on a spin bike with or without a backpack - almost no difference for calories because it's turning the pedals that burns the calories, and your backpack doesn't play into that.

    Exercise bikes have something called "resistance" that you can turn up or down. Outdoor bikes don't have that, the amount of resistance is set for you by what gear you're in, and how hard you push; how hard you push is dictated by your weight and the conditions (hills, wind, etc).
  • kcjchang
    kcjchang Posts: 709 Member
    aliem wrote: »
    I believe that power meters are really good for performance. I agree that power meters can be very good if you are trying to become a serious cyclist. However, the power meters only are output based. It does not calculate the body's metabolic response to the workout. It assumes that the response is constant throughout the workout, which is almost never the case.
    Power meter measure the work being done. It does not care what the cost is keeping you alive and seating on the bike but what it is required to "spin the wheels". To relate to the true metabolic cost, you need to know your metabolic efficiency. Lucky most people falls between 22% - 27% and 25% is a good middle ground and provides an easy conversion of roughly 1:1 between a kilojoules and a kilocalories. And, your metabolic efficiency don't jump around that much between the three pathways. One is very limited and available fuel is only good to about 30-90 seconds at best. The second is limited to around 20 kj give and take depending on your fitness. The third is virtually limitless and duration of use is also fitness depended. It's the most accurate means of estimating metabolic cost short of analyzing your oxygen intake and carbon dioxide output.
    aliem wrote: »
    It will be most accurate if you are serious cyclist and know what you are doing, but for the average person, I would make the case that a good heart rate monitor can be more accurate.
    Heart rate monitor measures your heart rate, period. HRM estimates are derived from small sample size that may or may not be doing what you are doing or build like you. It's fit is also limited. For example, your work output is not limited by your maximum heart rate and yet the fit end there. To use it for serious training, yes, PM requires some basic knowledge and it's a bit of an art to interpret. It's more so with HRM and limited to a narrow steady-state bandwidth.
    aliem wrote: »
    Now, if you wanted the most accurate, you would need both. I guess I should not have used the "only way".
    No need for HRM, period. For training, maybe, as a secondary correlation to track fatigue. But, that touches the "art" of interpolating the data and having a sufficient data set.
    aliem wrote: »
    There are studies that say each is better in their own way. Each study has its merits and pitfalls. So it is really up to the educated consumer to decide for themselves. For me, I like heart rate monitors because they are more accurate than relying on the machines (which tend to be way off, depending on the brand) and are more multi-purpose. However, to each his own.
    Machine estimate of work done? If it based on measurement of work done using strain gauges to measure torque and angular velocity, it's a power meter. Otherwise it could be as accurate or inaccurate as a HRM. It just depends on the sample size and composition of the fit.

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