(Inspired by many other questions that I'm not going to try to list...)
According to most sources I've seen, a "typical adult human" burns around 10-15 kcal/min while doing "strenuous" exercise. (Some sources may go as high as 25 kcal/min. Also, the number can increase depending on mass, so let's say we're talking about someone who masses ~100 kg or less.) However, it seems to me that even a "full body workout", isn't really. (If nothing else, you're usually not using opposing muscles simultaneously.)
If I had some way of causing every cell in the body to spontaneously metabolize as quickly as possible, how much Power could this produce? (Mind that I'm talking about Power in the physics sense, not electricity. Also mind that I'm not asking about burning cells or matter-energy conversion, I'm asking about producing power via normal metabolic processes, i.e. without destroying the body in the process.)
For the purpose of this question, don't worry about waste products or waste heat. I'll ask about those separately. For now, just assume that they are all magically whisked away.
(Note: Yes, this is very similar to this question. Please don't close this as a duplicate, as a) it isn't quite the same, and b) that question doesn't answer this one.)