Postural Adjustments and Kinematic Index Finger Features in Frail Older Adults under Different Equilibrium Constraints.

Bianca Callegari,France Mourey,César Ferreira Amorim,Bruno Mazziotti Oliveira Alves,Alexandre Kubicki,Ghislain Saunier,Givago Da Silva Souza,Manuela Brito Duarte,Daniela Rosa Garcez,Gizele Cristina Da Silva Almeida

doi:10.3390/healthcare9080921

Abstract

Background: Anticipatory postural adjustments (APAs) are significantly affected by age and may represent restrictions on functional independence. Previous studies in young adults have already highlighted that changing postural stability (i.e., seated vs. upright posture) affects the motor planning and APAs. In frail older adults (FOAs), the effect of these different conditions of postural stability have not yet been established, and the present study aimed to disentangle this issue. Methods: Participants executed an arm-pointing task to reach a diode immediately after it turned on, under different conditions of stability (seated with and without foot support and in an upright posture). A kinematic profile of the index finger and postural electromyographic data were registered in their dominant-side leg muscles: tibialis anterior, soleus, rectus femoris, and semitendinosus. Results: The main finding of this study was that the adopted posture and body stabilization in FOAs did not reflect differences in APAs or kinematic features. In addition, they did not present an optimal APA, since postural muscles are recruited simultaneously with the deltoid. Conclusion: Thus, FOAs seem to use a single non-optimal motor plan to assist with task performance and counterbalance perturbation forces in which they present similar APAs and do not modify their kinematics features under different equilibrium constraints.

Highlights

Anticipatory postural adjustments (APAs) are significantly affected by age and may represent restrictions on functional independence
Self-induced body perturbations are expected by the central nervous system (CNS) and anticipatory strategies are generated [1,2] both to counteract these perturbations and maintain dynamic balance and to create necessary momentums to initiate movements toward the target [3,4,5].These strategies are known as anticipatory postural adjustments (APAs) and are programmed as a feedforward control mechanism, consisting of changes in the activity of postural muscles, 100 to 150 ms prior to the focal muscle [1]
We considered the fraction of movement time required to reach peak velocity, which is known as the ratio of acceleration time to total movement duration (ACC/MD)

Summary

Introduction

Anticipatory postural adjustments (APAs) are significantly affected by age and may represent restrictions on functional independence. Previous studies in young adults have already highlighted that changing postural stability (i.e., seated vs upright posture) affects the motor planning and APAs. In frail older adults (FOAs), the effect of these different conditions of postural stability have not yet been established, and the present study aimed to disentangle this issue. Results: The main finding of this study was that the adopted posture and body stabilization in FOAs did not reflect differences in APAs or kinematic features. They did not present an optimal APA, since postural muscles are recruited simultaneously with the deltoid. Young adults adopt APAs to improve the task performance and kinematic features even with a stabilized body

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Conclusion