Tendon and nerve damage to hands is a common workplace problem seen in many industries today. One of the causes of these hand problems is the repetitive or forceful use of pinch gripping techniques in the workplace. The types of hand problems that can develop over time include Tennis Elbow, tendinitis of the hand and fingers, tendon scar tissue adhesions, and even Carpal Tunnel Syndrome.
Pinch gripping is when you grasp an object between your thumb and fingers, primarily the index and middle fingers. Most people hold a pen or soldering iron with one type of pinch grip, (precision grip) which is why writing or soldering for long periods of time can cause significant fatigue of the hand. Researchers have estimated that a pinch grip can be 3 to 5 times more stressful on the tendons of the hand and fingers than a full hand (cradle) grip or squeeze grip.
The reasons for this include the following:
- The wrist typically bends back (extends) in order to aim the pinch grip and place the thumb in line with the forearm. Wrist extension increases the pressure within the wrist by a factor of 5. It also forces the flexor tendons to bend across the bones on the palm side of the wrist which can microscopically damage the tendons when working repetitively from this bent wrist position. As scar tissue accumulates on these flexor tendons, they take up space within the Carpal tunnel in the wrist and can entrap and press against the median nerve causing it to malfunction. This is Carpal Tunnel Syndrome.
- Much of the grip strength has to come from the thumb in this position, yet the muscles that flex and adduct the thumb are relatively small and relatively weak. This can lead to fatigue and wear and tear damage to the muscles, tendons, and the joint where the thumb joins the rest of the hand.
- Typically the pinch grip occurs with the finger joints extended (locked out in the straight position) while the knuckle joint is the joint that is fully bent. This is not how the hand works optimally to generate force and is a weakened hand position. The hand likes to generate a powerful grip by bending at all of the finger joints and wrapping around an object, known as a Power grip.
Precision grips can be made less stressful by using objects that have between a one and three inch diameter. Smaller or lager than that makes the hand work more stressfully. Looking at the picture on the left, see how small of a pinch grip the left hand uses to hold the wire. A larger diameter solder iron would reduce the stress from holding the soldering iron. Notice the bend of the right wrist.
By changing the way you grasp objects, you can avoid using pinch grips most of the time. Try to use full hand (cradle) grips where your entire hand cradles and supports the object, or power grips where the entire hand wraps around and holds the object.