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#11
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Calories/Hour == Watts?
On Feb 3, 3:06*pm, "(PeteCresswell)" wrote:
I'm trying to convert the calories/hour that a Precor elliptical machine says I'm putting out into watts so I can compare it with commonly-quoted power figures for cyclists. When I use the Precor device for an hour, it says I've burned a little over 1,000 calories. But when I convert 1,000 calories/hour to watts using several different sources (among them ConvertIt.com, which gives a factor of .001163) I keep coming up with a little over one watt. OTOH, my impression is that a cyclist in any kind of condition can put out over 100 watts. But if 100 watts is plausible, 1,000 calories/hour=1 watt doesn't jell because then the 100-watt cyclist would be burning 100,000 calories per hour..... * I can think of a three possibilities right away: -------------------------------------- - Precor's calorie count is way wrong. - My conversion factor is wrong - I'm doing something dumb. -------------------------------------- My money's on #3.... but what? -- PeteCresswell After factoring efficiency, etc., a rate of 1,000 calories per hour yields avg. power for that hour of approx. 278 watts. Best, Bill Black |
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#12
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Calories/Hour == Watts?
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#13
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Calories/Hour == Watts?
Per graham:
What you need to consider working back from calories indicated on your Precore are that these use the term Calories which are in fact kilocalories. The conversion from Calories/hour to watts is 1.163. So your 1000 Calories/hour becomes 1163 watts. This however is the total energy your body is using in propelling your bike but like all other machines its not all that efficient at converting chemical energy into mechanical energy. Typical estimates are in the 20 - 24% range. So your 1163 watts come down to something like 240 watts at the pedals and allowing for transmission losses about 230 watts at the rear wheel. One further complication when working back from gym machines is whether or not they include the Calories your body is also using in powering itself. These are typically 60-70 Calories/hour. If your machine does then these need to be netted off to get the "rear wheel" equivalent watts. That would give you around about 215 watts at the rear wheel. Thanks for the detailed analysis. I think some of the considerations are starting to dawn on me now.... -- PeteCresswell |
#14
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Calories/Hour == Watts?
These machines vary a lot in how they estimate power and thus total energy.
Your mileage may vary. The 25% efficiency factor needs some explanation. Sometimes it's 20%. 25% or a factor of 4 is for incremental energy generated. When you add in the basal rate (what you'd burn sitting on the couch) it becomes 20%. That is you divide by 5 not 4 to get your power output if the energy the machine says you used includes the basal burn rate too. This would get you down to around 200W, still pretty amazing for most of us. Eddy Merxx was measured at 375W for the hour record (if I remember correctly). Most TdF winners are in this range and some of the pros can do 400W for short periods of time. "(PeteCresswell)" wrote in message ... Per : Does the machine allow you to input your weight? Yes, and I do. I suspect I'm gaming the system to a certain extent though. I find consistently higher "calories/min" readings for the same perceived effort level when I set "resistance" to max (i.e. 20) I'm always sneaking glances at the people to my left and right and for the ones that input their weight, their numbers never seem tb over 14-15 calories/min and are often down around 10-12 - while I'm doing 17.5-20. -- PeteCresswell |
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Calories/Hour == Watts?
On Mar 6, 8:48 pm, "Rocky" wrote:
These machines vary a lot in how they estimate power and thus total energy. This would get you down to around 200W, still pretty amazing for most of us. Eddy Merxx was measured at 375W for the hour record (if I remember correctly). 375W - estimated not measured and that was at altitude. A sea-level adjusted power output would put him at around 435W |
#16
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Calories/Hour == Watts?
On 2008-03-06, Rocky wrote:
These machines vary a lot in how they estimate power and thus total energy. Your mileage may vary. The 25% efficiency factor needs some explanation. Sometimes it's 20%. 25% or a factor of 4 is for incremental energy generated. When you add in the basal rate (what you'd burn sitting on the couch) it becomes 20%. That is you divide by 5 not 4 to get your power output if the energy the machine says you used includes the basal burn rate too. This would get you down to around 200W, still pretty amazing for most of us. Eddy Merxx was measured at 375W for the hour record (if I remember correctly). Most TdF winners are in this range and some of the pros can do 400W for short periods of time. A TdF sprinter can put out almost 2kW for a short period of time. |
#17
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Calories/Hour == Watts?
Per Rocky:
This would get you down to around 200W, still pretty amazing for most of us. Further spport for my suspicion that the machine's algorithm is seriously flawed. I'm older than dirt and "real" road riders consistently blow past me at a speed diffs of 3-5 mph. Yes, I'm riding 1.25" slicks on a hardtail MTB... but that can't be good for more than 1 or 1.5 mph. I'd be pleasantly surprised if it turned out that I could sustain 100 actual watts. -- PeteCresswell |
#18
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Calories/Hour == Watts?
In article ,
"Rocky" wrote: Eddy Merxx was measured at 375W for the hour record (if I remember correctly). Most TdF winners are in this range and some of the pros can do 400W for short periods of time. 1200-1300W in the sprints for the very top sprinters. Of course that's for about 10 seconds... |
#19
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Calories/Hour == Watts?
After factoring efficiency, etc., a rate of 1,000 calories per hour yields avg. power for that hour of approx. 278 watts. Best, Bill Black What is interesting is that a human needs an energy equivalent of ~10 power bars to produce these ~200 watts. These 10 powerbars weigh what, a pound? Now, a kilowatt electric battery in a 1kW electric scooter weighs what, 50 pounds? Pretty amazing how the human body can extract energy from "biodiesel". |
#20
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Calories/Hour == Watts?
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