Force–Length Relationship Modeling of Wrist and Finger Flexor Muscles

Abstract

This study proposes a new method to investigate the force-length relationship by combining ultrasound measurement, musculoskeletal modeling and optimization procedures. The data and relationships provide a new insight into hand biomechanics and muscle function that could be useful for designing hand tools or surgical operations.

Modelling force-length-activation relationships of wrist and finger extensor muscles

“…The methodology developed for hand flexors [33] was adapted to investigate two muscle groups representative of wrist and finger extensors. The ECR group was assumed to represent the global behaviour of both ECRB and ECRL muscles that are extensors and radial deviators of the wrist.…”

“…Adaptations of the protocol previously proposed [33] were required to investigate the extensors especially the tested postures were adjusted to ensure datapoints representative of the force-length portion covered by extensors [4] and limiting the contribution of passive tissues [38].…”

“…Participants performed isometric extension tasks using either the wrist or the four metacarpophalangeal (MCP) joints together in different combinations of flexion/extension angles on an ergometer specially adapted for the hand (Bio2M, Compiègne, France; Figure 1), already presented in previous studies [27,33]. Those extension tasks consisted in progressive isometric ramps guided using a real-time feedback of the EMG activity level of the tested muscle.…”

“…The muscle force ( m F ) generated by the muscle, i.e. EDC or ECR, was estimated as in [33] using a modified version of a previously developed hand musculoskeletal model [1]. The use of such model was required to identify the individual contribution of the targeted muscles in the exertion of the net joint moment measured on the ergometer ( ).…”

“…[23]. Based on protocols previously developed to study the elbow [29,30] and lower limb joints [31,32], Hauraix et al [33] recently developed a new method to evaluate the Force-Length-Activation relationships of hand flexors using non-invasive techniques to assess muscle behaviour and strength among healthy participants. The methodology combined musculoskeletal modelling with in vivo measurements of net joint moments, joint posture, myotendinous displacement and electromyography (EMG).…”