Why do you suck? Lungs about to burst? Heart about to pop out your mouth? Legs on fire and just can't turn any gear except the weeny one?All 3 are related to overall fitness, esp. 1 & 2 - 3 is maybe more strength. Best way to build strength quickly is in the gym Functional exercises - not leg extensions, leg curls, leg press, etc.Higher rep Squats, deadlifts, etc.Then use this new strength on hills. use a bigger gear for 1 - 2 minthen spin & recoverrepeatbut you can't apply the strength if your fitness isn't there too.