The metabolic cost of in vivo constant muscle force production at zero net mechanical work [RESEARCH ARTICLE]

Tim J. van der Zee, Koen K. Lemaire, and Arthur J. van Soest
The metabolic cost per unit force is generally thought to increase with the mechanical work done by the muscle fibres. It is currently unclear how the metabolic cost of doing alternating positive and negative muscle fibre mechanical work relates to the metabolic cost of doing zero muscle fibre mechanical work at similar muscle force. The current study aimed to investigate this issue by comparing in vivo metabolic power between a dynamic and an isometric near-constant force production task. In both tasks, participants performed periodic movement about the knee joint in the gravitational field. Therefore, net external mechanical work was constrained to be zero. The tasks mainly differed from each other in average positive knee joint mechanical power, which was 4.3±0.5 W per leg during the dynamic task and 0.1±0.1 W per leg during the isometric task. Knee extension torque was near-constant around 15.2±1.7 N m during the dynamic task and around 15.7±1.7 N m during the isometric task. Owing to near-constant knee extension torque, quadriceps tendon length was presumably nearly constant during both tasks. Therefore, knee joint mechanical work was predominantly done by the muscle fibres in both tasks. Average gross metabolic power was 3.22±0.46 W kg–1 during the dynamic task and 2.13±0.36 W kg–1 during the isometric task...

Source: Journal of Experimental Biology - April 16, 2019 Category: Biology Authors: van der Zee, T. J., Lemaire, K. K., van Soest, A. J. Tags: Comparative biomechanics of movement RESEARCH ARTICLE Source Type: research