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Runners have long debated the difference between training on a treadmill and training on solid ground. 鈥淏elt turnover鈥� is commonly cited as a factor that helps to move your foot backwards and thereby makes running on a treadmill easier than running on the road. At constant velocity, is this a real effect? If so, wouldn鈥檛 it be felt on any 鈥渕oving鈥� surface you walk on, such as a train or plane 鈥� or even Earth?

鈥� It is all about who or what supplies the energy and does the work. On a treadmill, the runner does the work of moving their legs through the air, but when a foot is planted on the belt, the treadmill does the work of moving the leg back with respect to their body. The runner鈥檚 body, and centre of mass, doesn鈥檛 move relative to its surroundings. On the road, however, a foot plant is followed by the runner expending the energy required to pull their entire body forward relative to that foot and the road.

So, running on level ground does require more work than running on a level treadmill. It is possible to compensate for this, however, if the treadmill bed can be tilted upward, because then the runner expends additional energy from having to lift their body slightly with each step.

Howard Bobry, Nehalem, Oregon, US

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