Why do people say ANTS are the STRONGEST species on the planet?

It's been long proven, "The heavier you are, the harder it is to fight gravity on the surface." Try jumping.. Ok so being as small as an insect, an ant at that... Wouldn't you obviously be able to pick up 3 or whatever times your weight? I understand most animals are built to be stronger than others but it would take a longer time for a leaf to hit the ground than a pebble.