As hunter said, check with your doctor first, but let me ask: are you doing as much menial labour as you used to? Playing sports? Lack of continuuing exercise will cause you to notice weakness when you do actually do some work.
SOme things to look forward to as you age:
1) Recovery time: your body doesn't bounce back from a hard days work like it used to.
2) Stamina: You won't be able to work as long as you used to
3) Stength: Unless you are eating properly, and working out regularly, you won't be as strong as you used to.
4) Reduced flexibility: you'll get the "old man groans" when you bend over or kneel down. My chiropractor told me what happens as we age is our tendons and ligaments tend to get shorter which decreases flexibility. Supposedly up until we're 10, we can bend backwards as far as we can forwards and that starts to diminish after that.
5) You won't be able to do doggy like a jackhammer: Don't laugh, I find that now after a hot session with an sp, my knees tend to ache for a few hours afterwards lol.
Like everything, our bodies wear out. I know of which you speak because in my line of work I'm always working relatively hard and I can't go 12 14 hrs like I used to. I'm pretty much toast by 5 pm.
Not that I'm a doc or anything but losing strenght with your arms over your head could be indicative of a circulatin problem. Your could muscles quivering could be because they are starving for oxygen and just aren't getting it. This could be due to plaque buildup in your arteries due to all those cheeseburgers you ate, high cholesteral, etc etc.
After your physical the doc will prolly say to you: dude, you're getting older! lol
