This is a 3D printable muscle roller I made. I tend to use it on my legs, but it can be used on any muscles.
A roller requires 2 handles (of either variety), a bar, and 3 nubs. The connection is a friction fit so you have to force the smaller end of the handle into the bar. The "ShorterHandle" is .5 inch shorter than the "Handle", so there is not that much of a difference.
To assemble: Connect a handle to the bar. Slide the 3 nubs onto the bar. Force the other handle onto the open side.
The handles and bar should be printed in ABS, as the shrinkage contributes to the friction fit. ABS is also stronger than PLA, so it should not break while using it. The nubs can be printed in any material. I plan on purchasing more materials and testing them out, as well as changing the size of the handle to work with materials with less shrinkage.
I tend to print this at 3 perimeters and 5% infill, but I would recommend using 4+ perimeters and 10%+ infill, so there is much less chance of it breaking. I used makergeeks ABS to print mine. There is a 8.5mm diameter gap that runs through the center of this design that is ~26.7cm, which a metal rod could be placed to imporve the strength of the roller.
I plan on making more nubs for this roller.
Thanks and have fun with your new roller!