When I perform anything "strenuous," I experience shaking and extreme trembling. A number of years ago, an infection began a major decline in my health. I'm working on a few things to get back to normal, but I've got an uncontrolled shaking problem when I crouch, squat, or otherwise use my leg and core muscles steadily for an extended period of time. Walking is possible, but it takes a long time and I occasionally need assistance. So, I'm hoping to get some practical thoughts on what might be going on because my GP has a history of misdiagnosis and prescribing dangerous medications, and I may bring this up with my doctor soon.
Just to sprinkle some extra information:
Skeletal muscles: Most of the ones connected to your bones. What folks usually think of when you say "muscle", the ones under your conscious control. (Includes your tongue.)
Smooth muscles: Unlike skeletal muscles, can stay contracted. Commonly found in your arteries, veins, digestive system, etc. widening and narrowing things as needed.
Cardiac Muscles: Your heart, mostly. As you can imagine, it's a bit of a special-case.