Well, in full armor, he's pretty much a combination of attack helicopter and main battle tank. The aerodynamic penalty wouldn't really be as big an issue as if he were in fighter mode.
Anyway, back to the topic at hand. I just noticed, in episode 9, those are some pretty heavy dumbbells that Sheryl's using. Judging by the size, each plate should weigh in at around 2.5 kg meaning that she's lifting around 15 kg which is pretty heavy for someone who's cut but doesn't have much mass.