Safety and Comfort

If you gently tap a pencil once on the palm of your hand it doesn't hurt. If you tap it the same way once a second for an hour you will get a blister.

If you tap your palm with a pencil every day for 4 hours then after a week you will begin to get a callus. If you do this for a few months you will wear down the pencil and get a tattoo!

When a thing happens over and over it is "repeating" or "repetitive". "Repetitive Stress Injury" happens when the same little injury happens over and over. Sometimes the damage is permanent. Sometimes the person needs an operation.