My joints feel...sludgy?

Without knowing your age or of any physical issues you may have, do you do any hand exercises before you pick up your bass? I've found that in itself really helps me a lot. Another suggestion is to drink plenty of water to keep yourself hydrated.

 

Try drinking more water.

 

Turn the amp up a bit more and play lighter. You'll have to pay more attention to muting but you'll retain more energy and put your fingers under less stress.

 

try rolling them tighter and storing in a low humidity environment. maybe try smoking left handed......

 

Exactly. That's why you're all tensed up. A little trip aboard the Marrakesh Express is in order.

 

Ask your doc? Without knowing what your medical issues are, we are shooting in the dark.