This is a fully 3D printed Hand Grip Strengthener, designed with the constraints of current ISM capabilities in mind. While in microgravity, the muscles in an astronaut’s body tend to relax for long periods of time, including those in the hand. With this hand grip strengthener, astronauts can exercise those muscles even while performing activities outside of their scheduled exercise times! It prints as a support-free assembly, and fits on a 6x6x6 inch cubic build platform. Three 3D printed compression springs are equidistant from each other in the rectangular body, and a circular viewing window makes it easy to tell when the springs are fully compressed. The completed assembly fits well in the hand at default size, but because it is completely printable it is also completely scalable, and size can be adjusted for any astronaut.

I recommend that this be printed in ABS. It works in for a while in PLA, but nowhere near as well.

http://giphy.com/gifs/LgbnuZ2x...