I'll start that I used to be a gym rat. I loved going to the gym, and pushing heavy weight around. That is until I found cycling and my road bike.

I follow a "time crunched" plan, and compete in a few races per year. What I've noticed is that the cycling has pretty much cannibalized much of my muscle from my once 175lb body down to about 145lb. I feel almost weak when doing anything besides cycling. I'm also concerned about bone density issues being in my mid 30's and participating in such a low impact sport.

My question is, is there a difference between the "impact" of weight lifting and running? I'm concerned about the damages of running(worn out knees, etc) while interested in the benefits of impact training. Should I do both, or just use weight training as my impact training supplement.

I know more time on the bike will make me a better cyclist, but I know I'm no natural talent, and I feel the benefits of a well rounded training regimen far outweigh the specific training results of a 100% bike training regimen in my case.