When I was 16, I started having problems with my muscles. First, my thumb would shake for several minutes every so often. Then that same year, I briefly used a screwdriver and then my hand was extremely weak to where I couldn't grip anything in the slightest and when I tried to, my hand just shook. That's happened every time I use my hand to grip anything tightly for more than a few seconds, like peeling potatoes and stuff. In boot camp, we had to hold our canteens out in front of us but while everyone else was able to do it for a very long time, it wasn't long before I couldn't move my fingers physically couldn't hold it at all. Later in boot camp, I had to straddle a diagonal rope and climb down upside down but halfway down, my fingers couldn't grip it at all so I had to hang on by my wrists and slide down so I wouldn't fall off. Now I'm 26 and I still have problems gripping after short periods of time.