Repeat Stitch Injury
RSI is also known as Repetitive Stress Injuries but we stitchers know the true cause. The repeated motion of stitching can irritate an already present condition or develop a new one in either or both your dominant and non-dominant hand. If you hold your hoop or frame in your non-dominant hand it can cause stress on your wrist and the back of your hand. The repetitiveness of putting your needle through the fabric can cause stress in your dominant hand.
One way to alleviate the stress in your non-dominant hand is to use a lap or floor stand to hold your frame. Using a floor stand will leave both of your hands free to stitch. Use your non-dominant hand to put your needle through from the front of your fabric; return the needle to the front of your fabric using your dominant hand (yes this feels awkward at first). By pulling the floss straight through with either hand-do not bend your wrist when you do this--you can lessen the stress felt by your hand muscles. You may even want to try the double tipped needle. This needle has the eye in the centre of the needle, lessening the need to turn your needle with every stitch. A bonus here is less twisting and tangling of the floss. This method also takes some getting used to. These methods use the stab method more than the sewing method of stitching, which is much easier on your wrists.
You could also look into a product called Hand-Eze. This wrist supporting half-glove is made from a material that will massage your hand and keep the blood flowing. I have not personally tried it, but other stitchers I know don't sew without it.
Little details to pay attention to are your posture and taking breaks. Give your hand a rest every 20 minutes or so, gently open and close your hands to relax the muscles. Make sure your lap or floor stand is at the correct height-no slouching! Try to keep your body relaxed; muscle tension adds to RSI.
If your hands or wrists feel numb or painful and you are having trouble controlling your needle, chances are you either have RSI or are headed in that direction. You should discuss this and any possible tests or medical remedies with your health provider. If your hands are painful, you should (oh no!!) stop stitching for one or two days until your hands feel better.
Remember that RSI is not caused just by stitching. Other causes include housework (just kidding) typing, other crafts and the playing of many musical instruments. Pay attention to your posture and the ergonomics of your furniture, mouse pad, and keyboard. Make sure that your chair is the right height for your desk, and that your monitor is at the right level for you. Take breaks when you have lots of typing to do and don't hit the keys hard with your fingers, this irritates the situation. Stretch your finger, hand and wrist muscles before you start-you may not be running a marathon, but if you stitch like I do, your hands are.