Gravity loads and muscle forces estimated by a trunk musculoskeletal (MS) model under twelve static activities were applied to a passive FE model of the L4-L5 segmentoto estimate load sharing among the joint structures (disc, ligaments, and facets) under simulated in vivo loading conditions.
Using the muscle forces estimated by the multisegment finger model, the tendon network model was then used to calculate the forces transmitted along each tendon component.
Masticatory muscle forces were estimated using muscle stress, physiological cross sectional areas and electromyography data collected from the literature.
Muscle forces were estimated based on 200 ms of EMG data recorded immediately before the force release from 12 trunk muscles.
In 14 subjects (seven males, seven females), muscle force and fatigue were estimated by subjective perception (based on Borg scale CR10) and objective indexes extracted from surface electromyogram (EMG).
These findings suggest that computational procedures for estimating muscle force and shoulder joint contact force should be improved in future studies.
The aim of this study was to experimentally determine the most suitable of the currently used sEMG features that can be implemented for machine based sEMG analysis to estimate muscle force and fatigue.
The model is composed of four sub-models that comprise a mathematical as well as graphical three-dimensional representation of the upper extremity: a musculoskeletal model for estimation of muscle tendon lengths and moment arms, a Hill-based muscle force model, a model for estimating optimal muscle lengths, and a model for estimation of muscle activation from EMG signal of the biceps.
Based on estimates of muscle force magnitudes from electromyography studies, the lines of action of resultant force vectors in the apprehension position are more anterior and at their lowest level for glenohumeral stability, explaining why a quick and trivial action involving minimal force such as putting on a T-shirt may lead to repeated dislocations after ASI [ 12, 13].
To produce realistic estimates of bite force we used the total muscle force derived from a dry skull estimate of the cross sectional area of temporalis and masseter plus pterygoideus muscles in the polar bear (18069.6 N - [51]).
