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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Former Member
A study by Barclay and Weber on mice (rather than humans) found muscle efficiency to be between 13.5% and 13.9%. This is the percentage of the total energy expended by the muscle tissue that results in mechanical work (i.e., a force applied over distance). The rest of the energy is mostly dissipated as heat
Let's assume that human muscle is also about 14% efficient. Suppose I bench press 100 pounds, 10 reps x 3 sets, and my arm extension is 2 feet. That's 6,000 foot-pounds of work. Divide by 0.14 to get 42,857 foot-pounds, the energy cost to the muscle. Finally convert to Calories by multiplying by .000324, to get
a measly
13.89 Calories
from my bench press workout. (This doesn't count the energy expended when the weight is being lowered back to my chest -- not sure how to handle that.)
If I painstakingly calculate the effect of the rest of my weight training routine, I come up with about 75 Calories total -- which is equivalent to a small apple.
A study by Barclay and Weber on mice (rather than humans) found muscle efficiency to be between 13.5% and 13.9%. This is the percentage of the total energy expended by the muscle tissue that results in mechanical work (i.e., a force applied over distance). The rest of the energy is mostly dissipated as heat
Let's assume that human muscle is also about 14% efficient. Suppose I bench press 100 pounds, 10 reps x 3 sets, and my arm extension is 2 feet. That's 6,000 foot-pounds of work. Divide by 0.14 to get 42,857 foot-pounds, the energy cost to the muscle. Finally convert to Calories by multiplying by .000324, to get
a measly
13.89 Calories
from my bench press workout. (This doesn't count the energy expended when the weight is being lowered back to my chest -- not sure how to handle that.)
If I painstakingly calculate the effect of the rest of my weight training routine, I come up with about 75 Calories total -- which is equivalent to a small apple.
