Michael, great question. This one comes up all the time with students. Unless you have smaller hands and cannot comfortably play 5-2 on the c-g I would alternate fingers. Using exclusively 5-1 seems to confuse people's brains and they make more mistakes on which of the two groupings of notes they are supposed to be playing at any given time. At least that's what I have seen from experience.

I cannot think of a single professional player that I have ever seen that uses 5-1. I'm not saying they aren't out there, but I just have never noticed that. However, if students have smaller hands and it's difficult to reach, then I let them do it :-)

To me there is also the added advantage of always using the same fingers over the same keys. For any of the dozen bass lines I use in that same position I always have my second finger over the G and thumb over the A. By now my hand has 'grown into' that position and it feels very natural since there is less hand movement when you use alternating fingers (a third advantage). Since I like to leave my hand in one position over the keys as much as possible, anything I can do to not move is good. With exclusive 5-1 fingering, you are constantly expanding and collapsing your hand. Personally I don't like that feeling for something that I can easily use 2 fingers for and not change hand positions at all.

These comments are for the left hand only, because its job is constant throughout the song. Right hand is changing all the time so I end up having 3 or 4 different fingerings for almost everything I know how to play (although I think I probably only practiced 1 fingering when I first learned each thing).

Hope this helps and is clear.

I will second Arthur's advice. As someone that has used the 5-1 & 5-1 method for years , I have recently (within the past year) been forcing myself to use the 5-2 & 5-1 fingering. I do find that it is easier on the hands and the notes I play are more defined and clear as the tempos get faster. Seems to me that the accents are a little different too as there is a little different hand/wrist motion using these fingers. I just need to stick with it more and break years of old habits so it feels more natural to just drop my index finger on the G.

What about more complex bass lines? I find that for "Boogie Woogie Stomp" or "Down the Road a Piece" type bass lines that use thirds, I use L.H. fingers 1&2 on F&A and 1&3 on E&G on the last 2 beats of the 8 beat figure (in C).These fingers feel very natural to me.Does anybody else use this combination? Am I alone on this one?