Does anyone know how efficient human muscle tissue is as a means of converting stored energy into mechanical work? More precisely, how much stored energy (in terms of ATP, fatty acids or glycogen -- say, expressed in calories) must a muscle burn in order to perform one foot-pound of mechanical work? Of course this will depend on a lot of things (age, conditioning, fatigue level,etc.), but just a range or ballpark estimate would be useful.
(I am trying to estimate the energy expenditure of various activities using this approach.)
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Excellent points, Rob. I already mentioned item (1), which I figure might contribute a couple of calories, but not another full 13.89. As for (2) and (3), I suspect that to some extent these effects are reflected in the 14% efficiency. I might not be able to improve on my calculation, however, without having a lot more detailed knowledge.
I've also tried a completely different approach to determining calorie costs. From January until June, I kept a daily log of calories consumed, my body weight, number of minutes swimming, cycling, or weight training. I then ran a least squares estimate (I did some averaging in advance so as to make the computations tractable -- we're talking huge matrices). The results showed that I burn 1950 Calories per day, plus 260 per half hour swimming, 150 per half hour cycling, and 130 per half hour weight training (above and beyond basal metabolism). I believe that the averaging smoothed out the sampling errors (e.g., swimming harder some days); the main confounding variable being changes in body composition (I'm gaining muscle, losing fat), which I do not know how to adjust for.
If you're wondering why I bothered with all this, it's my left-brained control-freak idea of fun.
Excellent points, Rob. I already mentioned item (1), which I figure might contribute a couple of calories, but not another full 13.89. As for (2) and (3), I suspect that to some extent these effects are reflected in the 14% efficiency. I might not be able to improve on my calculation, however, without having a lot more detailed knowledge.
I've also tried a completely different approach to determining calorie costs. From January until June, I kept a daily log of calories consumed, my body weight, number of minutes swimming, cycling, or weight training. I then ran a least squares estimate (I did some averaging in advance so as to make the computations tractable -- we're talking huge matrices). The results showed that I burn 1950 Calories per day, plus 260 per half hour swimming, 150 per half hour cycling, and 130 per half hour weight training (above and beyond basal metabolism). I believe that the averaging smoothed out the sampling errors (e.g., swimming harder some days); the main confounding variable being changes in body composition (I'm gaining muscle, losing fat), which I do not know how to adjust for.
If you're wondering why I bothered with all this, it's my left-brained control-freak idea of fun.
