What I do in blending the two is take a tennis ball and place it on the tips of my fingers. With the thumb naturally opposed to the other four fingers I press each finger tip singly into the ball against the pressure of the thumb. This actually builds strength in the tendens of your fingers. Because while lifting weights you are heavily relying on your larger muscle groups, the smaller ones are more involved in working in tandem to get the thrust needed. This exercise I found isolates just those muscle groups needed to play guitar. As a result, for me, it keeps my fingers working independantly and thus able to be limber for fret play.

The reason for the finger tip just below the nail is because it takes more agility to balance the ball while doing this.