BJMB

Brazilian Journal of Motor Behavior

Current Opinion

Hortobágyi et al.

2020

VOL.14

N.1

https://doi.org/10.20338/bjmb.v14i01.176

1 of 3

Is standing sway an accurate measure of fall risk and predictor of future falls in older

adults?

TIBOR HORTOBÁGYI

| LUIS A. TEIXEIRA

| JACQUES DUYSENS

| URS GRANACHER

| JAAP VAN DIEËN

RENATO MORAES

Center for Human Movement Sciences, University Medical Center Groningen, The University of Groningen, Groningen, The Netherlands

Human Motor Systems Laboratory, School of Physical Education and Sport, University of São Paulo, São Paulo, Brazil

Motor Control Laboratory, Movement Control and Neuroplasticity Research Group KU Leuven, Leuven, Belgium

Division of Training and Movement Sciences, Research Focus Cognition Sciences, University of Potsdam, Potsdam, Germany

Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, The Netherlands

Biomechanics and Motor Control Laboratory, School of Physical Education and Sport of Ribeirão Preto, University of São Paulo, São Paulo, Brazil

Correspondence to: Tibor Hortobágyi, Center for Human Movement Sciences, University Medical Center Groningen, The University of Groningen, Groningen, The

Netherlands.

email: t.hortobagyi@umcg.nl

https://doi.org/10.20338/bjmb.v14i01.176

PUBLICATION DATA

Received 28 03 2020

Accepted 30 03 2020

Published 01 04 2020

ABBREVIATIONS

CoM center of mass

CoP center of pressure

In 1836, English physician Marshall Hall in his lectures on the nervous system

posited that proprioception, vestibular function, and vision underlie postural control. In 1851,

German physician Moritz Heinrich Romberg observed that patients suffering from tabes

dorsalis lost their balance when they stood with eyes closed, giving rise to the Romberg test.

In the 1880s, American neurologist Silas Weir Mitchell developed the first standing sway

meter. This rudimentary device and the clinical observations over 180 years ago formed the

neuromechanical basis of today’s postural sway measurements during quiet standing tasks

on a force platform used to ‘measure’ fall risk and ‘predict’ future falls.

Annually, 30-50% of adults age 65-90 experience a fall. Falls are the leading cause

of fatal and non-fatal injuries and will result in 3M injuries, 27,000 deaths, and incur medical

and social costs of ~$67B in 2020 in the USA. In Brazil and in many other countries, including

the Netherlands, public healthcare reports reveal a trend toward increasing rates of fall-

related morbidity and mortality among older adults. The most frequently declared causes of

falls among the elderly being tripping, slipping, dizziness, and uneven flooring

. A massive

international research effort is underway to identify accurate measures of fall risks and

predict future falls. Such data could inform therapists to develop targeted interventions to

reduce fall risks and delay a first-ever fall in older adults.

While the measurement of postural sway is relatively straightforward, it is

challenging to establish a mechanistic link between the magnitude and velocity of postural

sway and fall risk as well as future falls. Fundamental inconsistencies between studies

complicate our current understanding and perhaps even the validity of postural sway during

balancing tasks as a predictor of fall risk and future falls. In standing, muscles generate

corrective moments to counteract gravity’s pull but a putative role has been also assigned

to the availability and accuracy of sensory information, sensory weighting, delays and gains

of control loops, and system noise. Muscle moments shift the center of pressure (CoP) and

BJMB! ! ! ! ! ! ! ! Current Opinion!

Brazilian(Journal(of(Motor(Behavior!

Hortobágyi et al.

2020

VOL.14

N.1

https://doi.org/10.20338/bjmb.v14i01.176

2 of 3

control center of mass (CoM) movements, which, if ‘too large’ or ‘variable’, are presumably

undesirable and should be limited by feedforward or feedback mechanisms. Like Romberg’s

ill patients with a lesioned dorsal column, healthy older adults also increase sway magnitude

in standing with eyes closed. Nevertheless, older adults with a history of falls are able to

modulate and reduce their postural sway when performing a visual-cognitive task (the

adapted visual Stroop test)

. Heightening the conflicting data further are the observations

that Parkinsonians often show less sway than healthy controls but are more fall prone. Then,

there is no clear understanding of the source and meaning of postural sway. Some authors

posit that sway is not even a valid measure of postural control with respect to fall prediction

because metabolic costs increase with decreasing sway. From this perspective, the variable

neuromuscular system optimizes in standing would not be CoP or CoM sway magnitude and

variability but metabolic cost. It is also not possible to make inferences on the functionality

of postural responses to perturbations because we cannot tell if the motor actions observed

accelerate the CoM towards or away from the target state

. There is, then, the view assigning

a beneficial, ‘exploratory’ role to a ‘certain magnitude’ of sway

. Thus, we cannot tell how

much of sway is ‘good’ or ‘bad’ for estimating balance stability or its association with fall

prevention. Our opinion resonates with the conclusion that the fall risk assessment tools,

including standing sway CoP metrics, currently in use to test older adults, do not have

sufficiently high predictive validity for differentiating high and low fall risks and to predict

future falls on an individual level

. Falls also often occur in dynamic situations and rarely

during quiet standing.

The future perspective is that age-related increase in balance sway magnitude could

be a valid risk factor for falls and predict future falls if we could verify that sway magnitude

or velocity in unperturbed standing were markers of neural and mechanical dysfunctions that

also fail at the time of a fall. That is, we need to link sway outcomes, measured during

standing under sensory challenges, to dysfunctions at the time of a fall. Until we have such

data, it remains indeed difficult to explain why standing trials with eyes opened instead of

eyes closed predicted future falls more accurately in 1,877 community-dwelling adults age

and why inexplicably both anterior-posterior and mediolateral CoP velocity predicted

future falls

7,8

. We need to develop innovative experiments to understand the relationship

between sensory acuity, sensory processing, sensory and motor noise, contractile

properties of key muscles and standing sway and see if changes in these outcomes would

reduce fall risks and prevent future falls

. There is also a need to complement the static CoP

measures with dynamic ones, provided by moving platforms

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2020

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Citation: Hortobágyi T, Teixeira LA, Duysens J, Granacher U, Van Dieën J, Moraes R. Is standing sway an accurate

measure of fall risk and predictor of future falls in older adults?. BJMB. 2020: 14(1): 1-3.

Editors: Dr Fabio Augusto Barbieri - São Paulo State University (UNESP), Bauru, SP, Brazil; Dr José Angelo Barela -

São Paulo State University (UNESP), Rio Claro, SP, Brazil; Dr Natalia Madalena Rinaldi - Federal University of

Espírito Santo (UFES), Vitória, ES, Brazil.

Section Editors (Current Opinion): Dr Luis Augusto Teixeira - University of São Paulo (USP), São Paulo, SP, Brazil;

Dr Tibor Hortobágyi - University of Groningen, The Netherlands; Dr Renato de Moraes - University of São Paulo

(USP), Ribeirão Preto, SP, Brazil.

access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0

International License which permits unrestricted use, distribution, and reproduction in any medium, provided the

original author and source are credited.

Funding: There was no funding for this study.

Competing interests: The authors have declared that no competing interests exist.

DOI:!https://doi.org/!10.20338/bjmb.v14i01.176