Your kinda asking the wrong questions. At the moment it seems like your muscles are not adapted to cycling, you can produce a high force for a short period of time, but cycling only requires a small force applied over a very long period of time.

The ability to produce a high power output for a long time is related to being able to use the aerobic system efficiently and being able to get rid of the lactic acid that starts to accumulate as you try increasing power output. Also it is about things like efficient pedaling (in circles not in squares), being comfortable on the bike for longer distances and being able to do the higher cadences of 90-100 RPM.
All of this takes time on the bike. First ride a lot (5-10 hours per week), concentrating on increasing the RPM and at a pace where you can only say a few words between breaths.