I was just listening to my recording of Adrian Gonzalez's Q&A at the San Diego Hall of Champions. There was a question about how he maintained his strength through a long season. This was probably his most interesting answer.
One thing that really made an impact in my career: In my second year in the minor leagues I weighed 185 and I went out and hired a strength coach. I went from 185 to 225 in the off-season. I went to practice at San Diego State with Tony Gwynn. He asked me why I gained weight and I told him that it was so that I could hit more home runs. He said "Well weight has nothing to do with hitting home runs, it's your swing. The only good thing about gaining weight is so that you can maintain 162 game season and stay in shape and not wear down. It's more to get you into shape then about gaining muscle".
Interesting that Tony Gwynn would be the one who figured out that weight has nothing to do with hitting home runs. Meanwhile, Tony Gwynn has lost 9.9 lbs in six weeks following his new Wheaties work out schedule.