No, you wouldn't become a superhuman. Well, at least not for the workout part of this endeavour. Essentially, every mass object would be heavier due to stronger gravitational pull of a larger mass planet than Earth. Say, you use weights to exercise on these gas giants the question you're referring to is inquiring about. And let's, for the sake of argument, pretend you are protected from all the environmental hazards of being on (in?) such planets, and you actually have somewhere to stand (gas giants like Jupiter and Saturn don't really have a solid surface, so you'd be suspended at a point of equal atmospheric density than the average of your own body and whatever you carry on your person, and ice giants like Uranus and Neptune, while they have a solid surface, it is at a depth of a rather uncomfortable atmospheric pressure).
These weights would become heavier by weight, while their mass, of course, stays the same. Something you can do just as well on the good old Earth by simply using heavier weights in the first place. To be more accurate, this gravitational pull wouldn't work on weights only, but on your body as well, so even lifting your arms would involve a lot more effort on its own. You could simulate this by attaching additional weights to your limbs here on Earth, for example. Or doing weight lifting exercises while submerged in water and account for weight difference in displaced water (buoyancy) by using heavier weights.
For example, Jupiter's equatorial surface gravity is 2.528 g.
g stands for g-force, or a measurement of acceleration felt as weight. This means that the 10 kg weights you'd take from Earth with you to the Jupiter would weight there roughly 25 kg. You, the man doing the exercises with these weights however, still have the same physical strength, your bone structure can support same amount of stress (if you didn't spend too much time in zero-g travelling there, and your cardiovascular and respiratory systems can take the added strain and you don't simply collapse due to G-LOC induced hypoxia, heart or lung failure once at the hypergravity environment),...
In short, you would probably feel stronger upon your return (not taking into account your travel back to Earth that would mostly be in zero gravity, negating any such positive effects from before, like muscle atrophy, bone loss, and so on), but that's something you can try e.g. by using a heavy training basketball for a few minutes, and then switching back to a normal one. The normal basketball will appear to "fly" off you as if it was featherweight. Well, for a few minutes at least, until you "recalibrate your senses". Either case, you could practice in becoming a superhuman in a lot safer environment than gas giant outer planets.