How Can Energy Be Used Without Performing Work?

[znicolaou]

im kinda confused with some concepts with work, specifically using energy without doing any work. for example, when a person exerts a large force on an object without moving it, he obviously does no work on the object, yet he burns a sufficient number of calories. if all this were converted to heat, its seems as if one could substantially raise their body temperature by applying a force over a time. this much heat does not appear to be produced, although the body does cool itself and i may be mistaken. if all is not converted to heat, how is the rest of the energy used? the only thing i can think of is that your muscles contract and retract very quickly when you apply a constant force, but i cannot really tell if this is the case. some clarification would be nice. thanks

 

[whozum]

Alot of it is to keep you planted on the ground.

 

[znicolaou]

ya, but i guess i described the situation I am thinking of poorly. really, i want to know where energy is used if you just flex a muscle for an extended period.

 

[James R]

When you flex a muscle, the individual muscle fibres repeatedly contract and expand. The movements in those fibres do work on the fibres, which produces heat. Chemical energy in the muscle cells is converted to heat, and sometimes useful work, too.