Time Out, everyone! Nicole has a point. Please, just be careful Monica with any type of hand or finger grips. Before anyone injures themselves with finger exercises using hand or finger grips or the like, I thought I'd share a little background...
What we're talking about here is the risk of excessive force and repetitive strain injuries. If anyone has had a wrist problem, please find out the exact nature of the problem and current condition of the wrist before doing any hand or finger grips or any other exercises involving the fingers. Find out if there are any residual effects from a previous injury: calcification, stenosis, inflammation, etc. in the wrist. Even if it means to see a hand specialist. You don't want to injure or re-injure anything. To increase rapidity, as in trills, is not a question of strength, but skill to move fast through the efficiency of movement. It is a matter of technique, not brute strength. I think the story of David and Goliath is a fitting allegory for the notion of brute force and strength vs efficiency and technique. Playing the piano does not require an excess of strength as the weight of the forearm should be ample. "No pain no gain" is not the proper analogy for piano playing, as it's not like sports. When the hand is injured or fatigued, working it harder will not improve the situation, it will make it worse.
The biomechanics of piano playing does not involve strengthening one's grip, as in rock climbing. But rather, we are dealing with achieving individual finger equalization, independence, and versatility of movement. In other words, one of the goals of technique should be to equalize all fingers as much as possible. Obviously, this is not an attainable goal, but rather an ideal to strive for in the pursuit of technique. Besides, certain workouts to increase strength can also limit flexibility which will have a greater affect on playing.
The power in our fingers comes from the muscles which are attached to tendons that terminate in back of the forearm. For pianists, the tendons are the weakest link in the chain. They are different from ligaments, as tendons are collagenous, inelastic, fibrous cords that slide back and forth through the tunnel of the wrist. Some tendons can slide more than 2 inches inside the bony structures in the wrist, or rub against other ligaments. Tendons are enclosed in a synovial sheath that secretes the necessary lubricant for facilitative movement.
However, with the repetitive nature of piano playing can eventually lead to frictional stress and injury of the tendons along bony structures and ligaments. According to Thomas Mark, the threshold of stress injury starts at 1500 repetitions per hour. Let's take a metronome tempo of 120, the rate of repetition for 16th notes over 10 minutes is 4,800, or an hourly rate of 24,000 repetitions. Now you can see the scope of physiologic activity. Clearly, certain ranges of motion can support these rates, however, certain positions will lead to severe injury over time.
Four causes of injury to the tendons for the pianist:
To move a bone in 2 directions, requires 2 sets of muscles - one to move it one way (contraction), and one to move it in the opposite direction (lengthening) to allow for movement. If it doesn't, by both muscles in a state of contraction, then this co-contraction prevents movement and can result in injury. This is most evident when playing with "curled fingers" as opposed to playing with "curved fingers"
2. Extreme positions:
Maximum efficiency and mechanical advantage of the tendon to conduct the force from our fingers is with the wrist in a straight line with the forearm. Deviating from this straight line through awkward angles of the wrist, either sideways, up, or down, can also cause reduced strength, as well as injury. So, posture, bench height are also important.
3. Static muscular activity:
In dynamic muscle activity, the muscle contracts to decrease its length initially, and when the body part moves it lengthens. This results in the healthy flow of blood into the muscle. In static muscular activity, as the muscle contracts, without changing its length as the body part doesn't move. This produces much more stress and prevents the circulation of blood into the muscle, leading to fatigue, and/or injury.
4. Excessive force:
There is a limit to what the muscles, tendons, and supporting structures can withstand. It's not clear how much force will cause injury, but generally, doubling the force produces an exponential increase in the stress on the tendon. Tendons can fray or tear apart with this form of injury.
There are several ways to get acute tendinitis. Tendons may fray or tear apart with constant or excessive stress, which may lead to thickening, formation of nodules along the tendon which can all limit movement. The injury site may also calcify which would could lead to jerky movements. The tendon synovial sheath can also produce excess fluid causing it to swell, even to the point of the tendon becoming stuck in its own sheath within the small space of the carpel tunnel in the wrist. This is Carpel tunnel syndrome as the pressure also exerts on the median nerve, thus producing numbing and tingling on the thumb and 2nd finger. Circulation to the tendons are poor, so if the tendon becomes injured due to stress, the recovery period is very slow. Muscles can also be injured, but since they have a rich blood supply, healing is much faster. Healing can be unpredictable as calcification around the tendon sheath can lead to bumpy movements. Surgery may or may not be an option.
Maintaining a healthy body and proper fitness, sufficient rest, nutrition are very important to prevent injury. Proper hand height, shoulder and back posture are also paramount. It's important to eliminate over repetition, co-contraction, awkward positions, static muscular activity, and excessive force. Remember to maintain proper curvature of the fingers, and don't curl them. When my hands tense up, I like to allow my hands to hang from the shoulders along the side of my body to allow for circulation to reach the hands, but proper rest is the only way to ensure that the tendons recover from fatigue. Injury requires a much longer healing period, and will require modified retraining methods to rehabilitate one's former abilities. But, it may take years....
Disclaimer: Any exercise or product can cause injury, so follow directions, and start small, don't rush to augment the strength routine too fast. Be careful, and you should ask your physician or hand specialist if you're going to be serious about using exercises or hand grips, etc. Here is a unproven list of exercises and products that may be conducive for the pianist to strengthen fingers. Then again the great pianists never used any of these which further debunks the brute force or strength theory. But, for those who want to have another gadget, these look more convincing:
1. Squeezing hand putty
2. These might be good for individual finger strength: http://www.amazon.com/Yellow-Digiflex-E ... B00066FHVU
3. Mostly for rehab, but may work for pianists: http://www.youtube.com/watch?v=WMsxGfACAfo
4. You're on your own on this one... You can also do 2-hand push ups on your finger tips. Start with all 5, 4, then down to 3 fingers. This is the exercise for the tiger claw in martial arts. We're not Bruce Lee, so don't ever do it with less than 3 fingers (he did it with 2). If you don't want to do dynamic push ups, you can simply do stationary push ups by just elevating and suspending your own body your the weight of various fingers, both curved and straight type. Order of increasing difficulty, finger #s: 1,2,3,4,5; 1,2,3,4; 1,3,4,5; 1,2,3; 1,3,4; 1,4,5 (extreme). I won't specify a time, because you're on your own peril here.