For example, if your right forearm begins feeling sore from repetitive gripping motions with a hand tool, try changing hands before you are in pain if you can do it safety. Or talk to your supervisor to see if you can take a break from that process and do something else for a while. Giving those muscles a short rest may be all that is necessary. No one wants you to keep quiet about pain. It only proves to your supervisor that you are not using your head.
Muscles tend to shorten and tighten with overuse.
You can help avoid stiffness and tightness by periodically stretching the muscle in the opposing direction. Be careful not to stretch the muscle too far or to use bouncing motions. Also be sure the muscle is warmed up 3-5 minutes before stretching it. Put it in ice. During the first 24 hours after overworking a muscle, apply an ice pack to the affected area.