A model of open-loop control of equilibrium position and stiffness of the human elbow joint

According to the equilibrium point theory, the control of posture and movement involves the setting of equilibrium joint positions (EP) and the independent modulation of stiffness. One model of EP control, the α-model, posits that stable EPs and stiffness are set open-loop, i.e. without the aid of feedback. The purpose of the present study was to explore for the elbow joint the range over which stable EPs can be set open-loop and to investigate the effect of co-contraction on intrinsic low-frequency elbow joint stiffness (

A Biomechanical Musculoskeletal Model of Human Upper Limb for Dynamic Simulation

. In this paper, we provide the biomechanical model of human upper limb we have designed and applied to the three-dimensional left human arm reconstructed from the Visible Human imaging Dataset. This model includes the mechanical properties for bones, joints and muscles lines of action. This work has been done as a part of the European Esprit Project CHARM. Its objective is to develop a Comprehensive Human Animation Resource Model allowing the dynamic simulation of complex musculoskeletal systems, including finite element deformation of soft-tissues and muscular contraction. In our approach, simplifications have been done so as to ensure the feasibility of the project while preserving the biomechanical validity of the model. Animations: http://ligwww.epfl.ch/~maurel/EGCAS96.html 1 Introduction The European Esprit Project CHARM involving several universities proposes the development of a comprehensive human resource data base, allowing the dynamic simulation of complex muscu..

Common input to different regions of biceps brachii long head

The purpose of the experiment was to compare the level of synchronization exhibited by pairs of motor units located within and between functionally distinct regions of the biceps brachii muscle. Pairs of single motor units were recorded from seven subjects using separate electrodes located in the lateral and medial aspects of the long head of biceps brachii. Participants were required to exert a combination of flexion and supination torques so that both motor units discharged at approximately 10 pps for >/=200 s and the level of motor unit synchronization could be quantified. When motor unit recordings were sufficiently stable at the completion of this synchrony task, a series of ramp contractions with multiple combinations of flexion and supination torques were performed to characterize the recruitment thresholds of the motor units. Common input strength (CIS) was significantly greater (P < 0.01) for the within-region pairs of motor units (0.28 extra sync. imps/s, n = 26) than for the between-region pairs (0.13 extra sync. imps/s, n = 18), but did not differ significantly for the 12 within-region pairs from the lateral head and 14 from the medial head (0.27 vs. 0.29 extra sync. imps/s; P = 0.83). Recruitment thresholds were measured for 33 motor units, but there was only a weak association between CIS and the respective recruitment patterns for motor unit pairs (n = 9). The present investigation provides evidence of a differential distribution of synaptic input across the biceps brachii motor neuron pool, but this appears to have minimal association with the recruitment patterns for individual motor units