Jonathan Majors isn't sweating Grace Jabbari's lawsuit against him -- but he is working up a sweat ... continuing to train for what sure sounds like a new movie role.
We got the actor out Wednesday in L.A., where he was just leaving a gym session with his trainer -- strength and conditioning guru Jason Best -- and JM was actually willing to chat ... this, of course, while walking out shirtless and looking absolutely ripped.
BTW -- Best is the same guy who got him in peak condition for his bodybuilding role in 'Magazine Dreams' -- and clearly, they're still working together .