Why can you much more easily ride a bicycle for a mile on level ground than run the same distance? In each case, you transport your own weight for a mile and in the first you must also transport the bicycle and, moreover, do so in a shorter time! (See The Physics Teacher, March 1981, p. 194.)

When a person running down the ground to travel a distance, the man loss some energy to overcome the frictional surface and air resistance. But the person to travel the same distance by riding a bicycle, the energy loss due to the frictional interaction with the level ground is less than the person running down the same distance. That is why you can much more easily ride a bicycle for a mile on a level ground than run the same distance.