I don't like to anthropomorphize things like bikes (they hate that), but if you ride a fixed-gear in the hills, you're probably investing more energy to manage the thing than the other folks on geared bikes. The alternative would be to get off and walk.

[MENTION=432261]drlogik[/MENTION], I wonder if your gearing might be higher than optimal. My fixed-gear at 71" keeps me in better shape for spinning than my geared bikes, since I can't shift into higher gears when going fast.