What i am going to suggest may seen un-conventional but its based in fact. There will be many that will have some, if not all of these positions in their playing. There will be many more that don't.
These are the bare facts, the research backs it up in more ways than not.
Many will cite famous players and that their technique is trouble free, that is of no importance. What is important that you read, understand and make your own decisions on what your thumbs do. Incorrect use of the thumbs and the positions they occupy if under stress will lead to problems in later life.
There are many reasons for hand problems that are not related to bass playing in any way, but if you have one (how would you know) bad positions will compound the condition. What you are doing now by typing is one such example.
So when playing your bass your thumbs should be in a neutral position.
To show you that position, turn your palms round and look at them.
Keeping your fingers together point your thumbs out to the side.
This is a neutral position.
If you look to the base of your palm you will see it is flat in respects that it has no ridges or valleys in its shape.
Now bring your thumbs in and put it in front of your forefingers.
Notice the valley starting to form at the base of the thumb pad in the centre at the base of the palm.
As you move to you little finger notice how this valley deepens, this is where hand trouble starts in respect of compressing the median nerve. The Median nerve runs through a narrow pathway of bone and ligament in the palm of your hand.
Repeated use of the thumb with this valley present will in the long run give you hand and finger problems.
Long run is defined as between now and the day you die, as in repeatedly smoking cigarettes will give you lung disease in the long run.
When adopting a technique to use when playing have your thumbs of both hands point to the head stock.
Try and keep you wrists as straight as you can.
All techniques allow this from floating thumb to fixed thumb, from slap to classical, all allow for this if you examine you own technique and try it. It may be unfamiliar but a few hours to a few days will see it become better, making it natural you will have to work at.
As for the fretting hand ask yourself how often can i straighten my wrist? How often can i use my fingers? How often can i move my hand rather than stretching from a fixed position? And most important of all how often do i really need the top of my thumb directly behind the neck in front of my forefinger? The thumb is should be able to move from the neutral position for support when needed, not stay fixed in one position.
Let your thumb come over the top of the neck if need be, by doing so you let the pad at the bottom of the thumb and palm of the hand take the strain it is designed to handleand let the fingers do the work with a straight wrist.
Look at you hand with the thumb directly behind the neck in front of the forefinger, now point it towards the neck. You will notice the carpal tunnel area flattens allowing the whole of the base of the palm to take the strain.
Ask yourself this if i asked you to crush a tin can, would it be more effective to do it with the base of the palms or the tip of your thumbs, well any part of the thumbs really?
As i said this is the information, take it to you doctor, surgeon, osteopath, physio, specialist and ask them the benifits.
By the way i smoke so i know it will kill me... i have the facts and i know the risk..thats my decision.
To find out more, rather than me give you links, search out on searches of your own and try
Carpal tunnel injuries,
RSI injuries,
Hand Injuries,
How the hands work,
De Quervains Tensynovitis
Computer game hand injuries
Bass playing related injuries,
Injuries common to musicians,
are just a few to give you an idea. Search out your own job or trade and any hand related injuries, and remember you found them yourselves i did not point you to prefered sites.
Any questions, if relevent, i will be happy to answer if i can. Check the link out for more info.
http://blogs.myspace.com/index.cfm?f...ndId=233492636