As far as hill sprints and standing starts, they won't strengthen your muscles like lifting weights will. 2 years ago I did a lot of hill sprints and big gear sprints, then started lifting. Even 100lbs felt heavy in the squat when I started. I think all sprinters, maybe even the roadie sprinters should do some total body resistance training, yearround. A good example would be to do just a few heavy sets of 2-3reps in each week: squat/deadlift/step-up, incline weighted sit ups, bench press, bent-over row. It's very unlikely that a total volume this small (5-10reps) will cause any soreness or have any negative effect on your riding or endurance. And remember, you only gain weight when you eat more than calories than you burn.