Dear Forum, Please advice. I have a project where I'll be implementing a device that helps with Bicep Curls, adding resistance to it. So I have an idea with 2 pieces of guards, one on the forearm and one on the biceps, it will be conjoined through a latch in the middle which will rest in between the forearm and bicep. This is easy and all but my issue is, I'd like to know what kinds of springs can I use? Is there any ways where I can implement springs into my device, where I can adjust the stiffness to give different level of resistance to the user? My initial idea is to have a huge flat spring or torsion spring go through both the pieces, and there will be a slider in the pieces so that at different length where it's pushing on the spring it will provide different resistance, but I don't know whether I'm going in the right direction. Please advice, Thank you!