A Pokeball functions by taking a creature and converting 90% of its mass into energy.
...Heavy Pokemon like Geodude and Onix are always carried by a large and muscular Hikers. Of course, the weight of those balls adds up, so most people are only capable of carrying three or four Pokeballs at a time, if that many. Gym leaders, being in a static location, don't have to carry their Pokemon, hence they can usually get away with using up to five. Red and Blue, being genetically engineered superhumans, have the strength to carry up to six Pokeballs at a time.
Geodude, which you label a heavy pokémon, weighs 44 pounds. If after going into a pokéball a pokémon weighs 10% of what it would otherwise, this means that a heavy pokémon weighs 4.4 pounds inside a pokéball. In my view it shouldn't take a superhuman to be able to carry around 26.4 pounds, and apparently this is on the high end.