What would working out on a planet with stronger gravitational forces be like?

I'm not quite certain you could survive. But if you did you would definitely build muscle faster, your bones would likely, if anything, become stronger. And technically, yes they would be super-human compared to us on average.

It would be like adding more weights, and you would become more muscular just from doing everyday activities.  However, you would be prone to heart attacks since your heart would constantly be working harder.

I would think you would gain bone density, not lose it. It would be pretty hard for most people if it were a full 2x Earth's. A 200lb man would weigh 400lbs. A little over 1x and we would be OK, it would just be like gaining a few pounds. Maybe some added pressure on the organs but that happens here when people gain and lose weight.

You would build muscle faster eventually yes.  humans who stayed on that planet would eventually change over time after many generations.  They may well be shorter than humans here.  If after many generation they came here they may well be stronger, but they would lose muscle density quickly and suffer effects of lower gravity like we do when we visit the moon or mars.

that is a one nice question indeed !!!!

you will build stronger muscles "but not faster"

no , it will be just your heart and lungs, it will cause you a hell lot of troubles at the beginning till you adapt , it is like gaining twice your weight in one night .

yes they will be super but only here on earth , they will be just normal there , and definitely they will not be the first generation or the second either

Edit : just one more thing , a normal virus there , would be a lethal here on earth , so if you are planning on making some of the super humans live here on earth make sure to bring them home clean and healthy , and don't let then get softer "they will need half amount of food to supply them with the required energy to survive here , and that will make them softer like any other human "

our muscles would have to work harder cause there is more force pulling them to the ground, or we would Develop to float around using the wind to propel us so we do not have to eat to much to grow our muscles.