Economy of movement
“to improve locomotion (and motion), mechanical work should be limited to just the indispensable type and the muscle efficiency be kept close to its maximum. Thus it is important to avoid: …. using co-contraction (or useless isometric force)”
Minetti, A. E. (2004). Passive tools for enhancing muscle-driven motion and locomotion. J Exp Biol 207, 1265-1272
“At higher levels of competition, it is likely that 'natural selection' tends to eliminate athletes who failed to either inherit or develop characteristics which favour economy”
Anderson T. (1996). Biomechanics and running economy. Sports Med 22, 76-89.