Science File / An exploration of issues and trends affecting science and the environment

Q: What takes the most energy: walking, running or riding a bike up the same hill?

A: Running, according to scientists at San Francisco’s Exploratorium. When you walk, you always have one foot on the ground. When you jog or run, both your feet leave the ground: You expend extra energy leaping into the air with each step. Riding a bicycle is the most energy efficient because your legs don’t have to hold your body up against gravity. Also, your legs spin at a constant speed, which requires less energy than the constant acceleration and deceleration that happens with each stride when you walk or run.