I'm working on a bicycling simulation. I'm looking for a formula which relates the energy that a biker spends per time unit to the force on the pedals. I know that power = force * speed, but I'm not sure if this is appropriate here. For example what happens if a biker is on a steep hill with velocity 0? From the formula it follows that power is 0, but the biker still uses energy. What is the relation between this energy use and the force he exercises?