Rocknrollgirl, you are NOT old. Gads.

Chris Carmichael, in his book The Ultimate Ride, talks about transferring strength gains in the weight room by lifting, and then immediately going out on the bike. He admits this makes your biking performance drop, but it is only for a time until you transition into your full biking season and muscle tension workouts on the bike. Just for what it's worth.

Sometimes I get a great back and shoulder workout in the pool by using hand paddles and a pull buoy (no kicking). If you have not used these, it is worth taking it slow and getting some coaching. If your stroke is off, or you are relying more on your arms than your back, you can get overuse injuries fast. But, with a slower, more powerful, mindful stroke, really concentrating on isolating your muscles like you do in the gym, you can get a great workout and build muscular endurance. At least that is my experience.