I'm a big believer in supplemental training like this. For me, the weight training really helps with muscle endurance. I did a lot of weight training before last season and was amazed at the difference in how I felt on the bike. Plus...the more muscle you have the more calories you burn!
I haven't done as much lower body weight training this year but am still doing light upper body to supplement my other lower-body intensive non-biking activities. I had my first century on Sat and was happy with my fitness, though I am not as strong as I was last year at this time. And I started doing plyometrics (the "jumping around" stuff) only about a month ago (but without the ball...I'm not there yet), so I can't report on that yet. It sure works my butt, though. I know what you mean about feeling like you're going to have a heart attack!![]()
Keep it up. Make sure you report back!