Heiliane de Brito Fontana1, Seong-Won Han2, Andrew Sawatsky2, Walter Herzog2. 1. Department of Morphological Sciences, School of Biological Sciences, Federal University of Santa Catarina, Florianópolis, Santa Catarina, Brazil; Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada. Electronic address: heiliane.fontana@ufsc.br. 2. Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.
Abstract
INTRODUCTION: In this study, we tested two assumptions that have been made in experimental studies on muscle mechanics: (i) that the torque-angle properties are similar among agonistic muscles crossing a joint, and (ii) that the sum of the torque capacity of individual muscles adds up to the torque capacity of the agonist group. METHODS: Maximum isometric torque measurements were made using a specifically designed animal knee extension dynamometer for the intact rabbit quadriceps muscles (n = 10) for knee angles between 60 and 120°. The nerve branches of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) muscles were carefully dissected, and a custom made nerve cuff electrode was implanted on each branch. Knee extensor torques were measured for four maximal activation conditions at each knee angle: VL activation, VM activation, RF activation, and activation of all three muscles together. RESULTS: With the exception of VL, the torque-angle relationships of the individual muscles did not have the shape of the torque-angle relationship obtained when all muscles were activated simultaneously. Furthermore, the maximum torque capacity obtained by adding the individual torque capacities of VL, VM and RF was approximately 20% higher than the torques produced when the three muscles were activated simultaneously. DISCUSSION: These results bring into question our understanding of in-vivo muscle contraction and challenge assumptions that are sometimes made in human and animal muscle force analyses.
INTRODUCTION: In this study, we tested two assumptions that have been made in experimental studies on muscle mechanics: (i) that the torque-angle properties are similar among agonistic muscles crossing a joint, and (ii) that the sum of the torque capacity of individual muscles adds up to the torque capacity of the agonist group. METHODS: Maximum isometric torque measurements were made using a specifically designed animal knee extension dynamometer for the intact rabbit quadriceps muscles (n = 10) for knee angles between 60 and 120°. The nerve branches of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) muscles were carefully dissected, and a custom made nerve cuff electrode was implanted on each branch. Knee extensor torques were measured for four maximal activation conditions at each knee angle: VL activation, VM activation, RF activation, and activation of all three muscles together. RESULTS: With the exception of VL, the torque-angle relationships of the individual muscles did not have the shape of the torque-angle relationship obtained when all muscles were activated simultaneously. Furthermore, the maximum torque capacity obtained by adding the individual torque capacities of VL, VM and RF was approximately 20% higher than the torques produced when the three muscles were activated simultaneously. DISCUSSION: These results bring into question our understanding of in-vivo muscle contraction and challenge assumptions that are sometimes made in human and animal muscle force analyses.
Authors: David S Ryan; Sebastián Domínguez; Stephanie A Ross; Nilima Nigam; James M Wakeling Journal: Front Physiol Date: 2020-11-12 Impact factor: 4.566
Authors: Daiani de Campos; Lucas B R Orssatto; Gabriel S Trajano; Walter Herzog; Heiliane de Brito Fontana Journal: J Sport Health Sci Date: 2021-05-29 Impact factor: 7.179