Hey Mac!
Best advice I can give you is to take a hatha yoga (the easier kind), pilates or stretching class. I'm 46 now and am in good shape with a healthy body. Stretching also relieves the aches and pains from physical work.
However, I've had problems wearing tool belts all day, they make my left side lower back numb. I've solved that problem with wearing bib overalls or work pants that hold just what I need. I am of the strong opinion that you don't need to carry every damn tool on your body! I know the boss doesn't want you to go back and forth for tools, but it saves your body so you can do your work and not call in sick 'cause you have to go to the chiropractor, etc.
Also, very important, don't let anyone intimidate you to do anything unsafe. The first shop I worked for had the JW's wanting you to stand on top of 12' 3 legged red top ladders! I refused.
Lesson here: love your work, but don't kill yourself doing it!
