I had to take about a year off from playing bass, now that I am getting back into it my hands no longer have the strength or dexterity they once had. Any specific exercises to help combat this problem?
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Do a quick Google search for "bass permutation" (or guitar). Permutation exercises are for the fretting hand, and essentially involve using each finger once in all the different possible combinations (there are 24 total), starting with the first (index) finger. Do all 24 permutation exercises on each string (e.g. 96 total on a 4 string bass).

For the plucking/picking hand, if you have a smart phone, download a free metronome app. Set the metronome to a number of beats per minute that you can begin doing 8th notes for 1 minute on each string (4 minutes total on a 4 string bass). When you can do this easily, change to 16th notes and repeat on all strings. When you can do this easily, increase the beats per minute on the metronome.

There are other exercises but these will definitely help.