Rampage was just goofing around, as always. What he says here does not reflect at all on how he will train for Forrest. Keep in mind that just a few seconds before he said he "I think I'm smarter than Forrest", he said "Everybody know Forrest ain't that bright... but I ain't no smarter, so...". The whole thing was just him being a silly mofo, I laughed my ass off.
His helmet was stifling, it narrowed his vision. And he must see far. His shield was heavy. It threw him off balance. And his target is far away.