Often in movies, it is shown that a human body can possess an incredible amount of energy by bio-experiments. However, is there a proved maximum energy limit an average human can possess without any experiments, but just naturally by eating and working out?
If you're referring to energy produced in an environment, like when they did lab experiments having different rankings of cyclists pedal to see how much power they have over an hour, then no, there is no way to test this as a better cyclist may be born every year. Most people have a maximum genetic potential. Whether or not you're an athlete you are limited by what your body can do. This is why we all can't look like professional bodybuilders. In the lab experiment most elite cyclists had about 25 watts per kg while amateurs had about 5-6 watts per kg. These cyclists also don't account for other forms of producing power that don't involve pedaling, etc. I think we are also limited by our anatomy and how quick our body moves, etc., but I assume since the best of the best cyclists all managed to get roughly 25 watts per kg, then this is probably close to what a human cyclist could do at their maximum. Then again, 30 years from now there may be a cyclist that beats this.