Quite a few players will never be able to meet all of the following standards:
Compromise is necessary, except for this: always keep your hand palm open.
Let your arm hang down at your side with your hand relaxed, palm forward. Bring up the arm keeping the hand in the same relaxed position.
There you have your fretting hand.
Important features:
Place the fingertips, not the pads, on one string halfway the neck at subsequent frets. Keep all fingers curved. Stretching the fingers easily leads to squeezing the hand palm and flexing the wrist. Give special attention to curving the little finger. Stretching the litle finger will encite the thumb to stretch also. You will create tension in the hand palm and in the thumb base joint.
The thumb may be either opposite the middle finger, the index finger or out even more, but it is absolutely essential to
You should be able to play at a reasonable level keeping the thumb away from the neck. Do not squeeze the neck between thumb and fingers. The thumb is to be used only to support the orientation of the fretting hand. Squeezing, especially in combination with an angled wrist, is at the risk of carpal tunnel syndrome. To get more pressure on the strings, some traction by gently pulling the forearm will do. To temporarily get some more pressure from ring finger or little finger, move the elbow out just a little.
Every once in a while, by way of monitoring exercise, do try to play keeping with your thumb away from the neck. If you cannot play at least reasonably that way, your technique is not okay. Notice that if you play with your thumb off the neck, it is impossible to completely flex the wrist.
As shown in the video, gripping exercises are a delicate business. Some people do need to develop some more hand strength. Gripping exercises should always be combined with exercises for extension. If not, you will will impair dexterity. Better than to start on hand grips is to just start on lighter strings and to set action low. Using a short scale bass will give more fingering comfort in the low positions. After a couple of months, step up to heavier strings if you like.
Other players have too much strength in their hands. They should concentrate on exercises to improve dexterity.
As explained above, a correct thumb position prevents flexing the wirst too much. Incidentally flexing the wrist some more is no problem, but constant strain on the carpal tunnel is asking for big problems.
Bending the wrist sideways may cause wrist tendonitis. It may occur in two locations, either below the thumb or below the little finger. Try the following: keep your left hand palm towards you and your wrist straight. Now move the hand sideways from the wrist in both directions, keeping the forearm as it was. Notice that to the right, you have quite some room to move, while to the left, movement is pretty limited. This means the visually straight wrist is NOT the neutral position. The neutral position is, of course, to be found in the middle between the extreme left and right positions you just discovered. This very same position may be found if you let your arm hang down at your side and relax. The hand will not be in line with the wrist, but naturally flexed to the inside just a little. Respect this small inside angle especially when playing in the lower positions!
To avoid problems below the thumb, do not bring out or lift your elbow too much. As explained on the previous page, the elbow is to be kept near the side of the body in a way just allowing it to pass the side to move the hand to the higher positions.
Wrist problems below the little finger may result from keeping the bass' neck too close to the left shoulder. The neck should be moved away from the body to create room to move for the arm, as is explained here.
Should you suspect carpal tunnel syndrome or wrist tendonitis, see a doctor before spending your money on expensive exercise material. Be suspicious of all kinds of products and video courses claiming cure without surgery. Those sellers are playing on fear, showing gross pictures of wrists’ insides with scars or stitches.
Products and exercise courses offering prevention or relief in very mild stages of the syndrome, however, may be very useful, if monitored by a fysiotherapist.
A certain degree of variation in the positioning of your fretting hand is desirable to reduce constant strain. For complex fingerings, the thumb may be either moved to the right, or turned completely sideways to the left or even rest against the lower rim of the fretboard. The latter helps to create more space for the fretting fingers and is commonly seen in fast play above the 12th fret. As long as you do not study in that area constantly, there will be no problem. In easier passages, especially those played in the lower positions, relax by playing with your thumb pointing more to the left, but still keeping the upper thumb pad flat against the neck. Your fingers will be closer to the fretboard, which is no problem for simple stuff. You may even move your thumb pad more towards the upper rim of the fingerboard, extending the wirst for a healthy change of wrist angle. Players with short fingers, but also others, may benefit from adopting a three frets fingering span in the lower positions. You may well skip the ring finger when playing simpler stuff. This will give an overall reduction of strain.