The Harmony of Healthy Hands
Guitar Players are often responsible for adding harmony and structure to a piece of music. Harmony, in essence as we perceive it in music, is a balance of one or more notes within the given musical environment. As we think of this balance in terms of musicality, we often overlook the need for balance in the physicality of playing. Without this awareness we open ourselves up for the dissonance to overthrow the balance of harmony and cause physical discomforts.
"The best prevention is to stretch the hands and fingers before and after practicing or performing"
The most common physical threat to guitarists is RSI or Repetitive Strain Injury. There are many types of RSI (many commonly referred to as Carpel Tunnel, Tennis Elbow, or even Tendinitis) and the name says it all. Repeating particular scales or chords, especially ones that require some fancy finger-work, cause the muscles to overwork in one direction leaving the opposite muscles weak which in turn creates the imbalance which eventually leads to swelling, achiness, and arthritic pain.
RSI is much like spraining a wrist or ankle, but in the case of guitarists the discomfort is usually experienced in either one of the first 3 fingers and or the palm near the thumb. Ignoring the early onset of RSI can cause some long-term difficulties, so it's best to "nip that sucka in the bud" as soon as you feel it, or better yet start implementing some preventative measures now. The best prevention is to stretch the hands and fingers before and after practicing or performing.
There are several great resources for guitarists in regards to hand stretches but I will suggest one that is crucial. As I mention RSI is caused by over-straining the muscles in one direction, so by adding resistance and working the muscles the other way, we can correct this. So we fret pushing our fingers inward towards the neck so to work the opposite muscle group, place a rubber band over your fingertips and thumb (holding them all straight and touching the fingertips together) simply open and close the hand. The resistance of the rubber-band will help build the muscles that will balance out your fret hand (do this for your picking hand as well).
If you're already feeling the pain of RSI then take a few days off from practicing, try to keep the fingers out straight and maybe even use an icepack (or a bag of frozen french fries from your freezer). There are many healthy ways to approach the healing process as well. Keep the joints hydrated by drinking lots of water. Supply the muscles, bones, and joints with all the nutrients they need to be strong.
As a longtime student of the healing arts and dabbling herbalist I would recommend taking a multi-vitamin and mineral supplement and Glucosamine which will greatly help you heal fast and stay healthy. There are also many holistic herbs (ie: Devil's Claw, Black Cohosh, Valerian Root, etc.) that can aide with the swelling and pain. But again, and most importantly be sure to practice proper stretching and exercise. So practice with care and always play it safe. After all, your music is in your hands!