You have to travel 100m on perfectly flat concrete, no hills or anything. You walk at a constant rate and when you cycle you pedal constantly (no coasting), reach a constant velocity quickly and stay at that speed. Obviously your body is part of the mechanical chain when you are walking, my first question would be is it when you are cycling? I think it is right? There are no electronics involved i.e how fast you goes depends on how much work you do.

Now we all know that energy expended, distance travelled and time are related. Presumably you'd be making the journey in less time so would be expending more energy right? But are you really?
When you are walking or cycling the work comes from the transition from bodily energy to creating friction between you and the ground, right? Suppose that the bikes tyres and your shoes are made from the same material. Is the mechanical system of the bike more efficient than walking?

Basically what i'm trying to say is, that in todays times of global warming and financial meltdown, if you ride a bike (which we have just established is not as efficient as walking) you are basically culpable for the death of the planet. I feel like it is our duty, as responsible human beings, to lead the most sedantary lifestyle possible. That is the first step anyway.