The actor posted a video Sunday that shows him strutting his stuff in an anti-gravity treadmill. The reason we know that -- besides just looking at it -- is 'cause JR himself alludes to the fact that he's only using a certain percentage of his body weight as he works his legs.

Watch ... it sounds like he's getting quite a bit of assistance, but it's encouraging to see he's up and moving like this -- especially since the incident went down just a couple months ago.

Jeremy also has had a great caption that further elaborates on how he's doing. He writes, "I now have to find OTHER things to occupy my time so my body can recover from my will."

In other words, he wants to rehab harder than his body might allow at times -- but the fact he's going hard is, frankly, par for the course for him. The dude's a workhorse, and you can clearly see he wants to get back to normal ASAP ... and hopefully will be soon.

Again, it's remarkable how far along he's come since January ... when he was crushed by a massive machine that nearly killed him. Remember, he broke over 30 bones and needed major surgery. Since then, however, he's been on the grind ... documenting his journey as well.