Muscle activation patterns in acceleration-based phases during reach-to-grasp movement

Abstract

[Purpose] An earlier study divided reaching activity into characteristic phases based on hand velocity profiles. By synchronizing muscle activities and the acceleration profile, a phasing approach for reaching movement, based on hand acceleration profiles, was attempted in order to elucidate the roles of individual muscle activities in the different phases of the acceleration profile in reaching movements. [Subjects and Methods] Ten healthy volunteer subjects participated in this study. The aim was to electromyographically evaluate muscles around the shoulder, the upper trapezius, the anterior deltoid, the biceps brachii, and the triceps brachii, most of which have been used to evaluate arm motion, as well as the acceleration of the upper limb during simple reaching movement in the reach-to-grasp task. [Results] Analysis showed the kinematic trajectories of the acceleration during a simple biphasic profile of the reaching movement could be divided into four phases: increasing acceleration (IA), decreasing acceleration (DA), increasing deceleration (ID), and decreasing deceleration (DD). Muscles around the shoulder showed different activity patterns, which were closely associated with these acceleration phases. [Conclusion] These results suggest the important role of the four phases, derived from the acceleration trajectory, in the elucidation of the muscular mechanisms which regulate and coordinate the muscles around the shoulder in reaching movements.

Detailed characterization of physiological EMG activations and directional tuning of upper-limb and trunk muscles in point-to-point reaching movements

“…The patterns of phasic muscle activations presented in this study are coherent with precedent findings in literature ( Tokuda et al., 2016 ), ( Sabatini, 2002 ). The activity of deltoid anterior (DA) during the acceleration phase is not surprising; on the contrary, we also found increased activity of the DA in the deceleration phase most likely as a response to the increased activity of the antagonist muscle (posterior deltoid) used to decelerate the limb ( Tokuda et al., 2016 ). This response is most likely a strong co-contraction that is needed for the deceleration phase to stop and stabilize the limb ( Kornecki et al., 2001 ).…”

“…The upper trapezius (UT) presented great activity in the initial phase of the movement but did not cease its contribution in the deceleration phase, acting as a phasic and anti-gravity muscle. This was previously reported in a reach to grasp study where the EMG was obtained by decomposing the movement in phases using the acceleration, highlighting the anti-gravity role of the upper trapezius ( Tokuda et al., 2016 ). While many applications consider DA as the main shoulder elevator, we found that UT play this role in a major extent in the accelerating phase ( Sabatini, 2002 ).…”

Too Much Information Is No Information: How Machine Learning and Feature Selection Could Help in Understanding the Motor Control of Pointing

“…This is in contrast to the experiments conducted by the Flanders group (Buneo et al, 1994, 2008; Flanders et al, 1991, 1992, 1996) where a pointing protocol with elbow rotations was involved. The important role played by the trapezius muscle for modulation in both directions is in agreement with reports by other groups that along with the anterior deltoid, it plays an important role in shoulder orientation for pointing direction (Tokuda et al, 2016; Sabatini et al, 2002). It should be noted that none of the differences in contribution to classification here is due to differences in EMG amplitude as this variable is normalized (see Methods).…”

Deactivation and Collective Phasic Muscular Tuning for Pointing Direction: Insights from Machine Learning

“…In contrast to the two afore-mentioned muscles, the phasic activity of the medial and posterior deltoids are more tuned for downward pointing, showing higher accuracies for distinguishing downward pointing angles. The importance of all these muscles in pointing have been highlighted by various studies [Flanders, 1991, Flanders et al, 1994, Flanders et al, 1996, Mira et al, 2021, Tokuda et al, 2016]. In contrast to the previous studies, the use of classification accuracy allows for a greater ease in comparing and contrasting the roles of individual muscles.…”