Originally Posted by Randybb

You're not considering how the human body works though. Think of it this way... Let's say you are riding a hand pedaled bicycle. Instead of using your legs, you're using your much smaller and weaker arm muscles (for most people anyway). Now, if you tried to go the same speed as you normally would on a regular bike, you'd find it very difficult and you'd tire more quickly. This is because those smaller weaker muscles will start working anaerobically, which is much less efficient (energy in/out). So, the muscle groups you utilize affects your speed and level of exhaustion. The more muscle mass you use, the less exhausting riding will be at any given speed. If you use only your quads to push down, you'll get more tired going the same pace than if you use quads, hamstrings and glutes, etc