Repetitive Strain Injuries occur from repeated physical movements doing damage to tendons, nerves, muscles, and other soft body tissues. Their are many other related sickness that relate to RSI the most common is Carpal Tunnel Syndrome, this may lead to wrist problem and if worst failure gripping. (my in-law got an surgical operation to correct this problem)
The signs are discomfort, stiffness, soreness or burning in the hands, wrists, fingers, forearms, or elbows, tingling, coldness, or numbness in the hands clumsiness or loss of strength and coordination in the hands, feeling a need to massage your hands, wrists, and arms, pain in the upper back, shoulders, or neck associated with using the computer. (that's to many not to notice)
How do we prevent, take a regular break from what you do, relax, stretch, (yawn ops don't go to seista yet =) and proper posture. There are also gadgets to lessen the risk of RSI.
Once this is notice...consult you doctor immediately...remember prevention is better than cure.
