The human body was designed by the forces of evolution to preserve energy wherever possible. The more energy that is preserved by a performer, the longer their muscles and brain can operate at optimal levels.
To conserve energy, most forms of human movement are RHYTHMICAL. The body has large amounts of elastic tissue imbedded into the end of range of each joint, so that one side of a rhythmic movement can bounce into the next and thus minimise energy expenditure. [At maximal efficiency a human body when walking can reuse over 90% of the energy of one stride for the next].