Balance Perturbation Leads a Stretching Reflexion on Tibialis

Anterior Muscle

Renata Gonçalves Pinheiro Corrêa

, Matheus Lucas Aguiar

, Caluê Papcke¹, Eduardo Borba Neves

Agnelo Denis Vieira

and Eduardo Mendonça Scheeren

Pontifícia Universidade Católica do Paraná, Polytecnic School, Health Tecnology Graduate Program,

Rua Imaculada Conceição 1155, Curitiba, Brazil

Universidade Tecnologica Federal do Paraná, Biomedical Engineering Graduate Program, Curitiba, Brazil

Keywords: Postural Balance, Electromyography, Neural Inhibition.

Abstract: Human posture control is a sophisticated process involving the relationship among multiple joints, muscle

groups and environment. The aim of this study is to show how the balance perturbation (in posterior-

anterior direction) leads to a stretching reflexion on the tibialis anterior (TA) muscle. A case study that

involved a male participant with 23 years old. To disturb the participant's balance, it has been employed a

specially plataform designed with dimensions 1.5 m by 1.5 m with movement of 5 mm of amplitude on a

total time of 3 ms along the axis coinciding with participant's anterior-posterior axis. Soleus (SO) and TA

electromyography signal (EMG) has been recorded. Perturbation in the equilibrium was delivered in the

posterior-anterior direction. The first event observed was the pre-activation of the TA muscle that leads a

reduction in the SO muscle activation, due the stretch reflex at TA.

1 INTRODUCTION

Human posture control is a sophisticated process

involving the relationship among multiple joints,

muscle groups and environment (Horak, 2006).

Theoretically, the passive muscle stiffness can

ensure postural control in upright position under

static conditions (Neves et al., 2013). However in

practice, it is necessary coordinated muscle activity

to ensure balance in daily activities (de Medeiros et

al., 2010). The two main functional goals of postural

control are: postural orientation and balance.

Postural balance involves movement strategies to

stabilize the center of mass within the base of

support due to stability disturbances externally

caused (Gage, 2004; Horak, 2006; Robinson, 2011).

Static balance is guaranteed when the sum of all

external forces and all external torques acting on the

body equals zero, however, under the mechanical

point of view, the body is never in a condition of

perfect balance, as the sum of forces and torques

acting on it are only momentarily zero. Thus, Duarte

and Freitas (2010) propose that the human body is in

constant unbalance and in an endless quest for

balance.

Maintenance of body balance in the environment is

determined by central systems and peripheral

structures responsible for motor execution, whose

functioning depends on the integration of

information from the sensory structures of the

proprioceptive, vestibular and visual systems. These

sensory structures respond in complex and different

ways for each perturbation on the body (Melzer,

Benjuya and Kaplanski, 2004).

For balance control to occur in a harmonious

way the sensory system is used to obtain continuous

and integrated information on position and trajectory

of the body, allowing the issuance of motor

responses arranged to be performed by the

osteomioarticular effector system (Robinson, 2011).

There are three basic strategies for correcting

body balance as responses to postural perturbations:

(a) the strategy of the ankle, where the body moves

as a relatively rigid mass about the ankle, (b) hip

strategy, used when the center of gravity (CG)

moves quickly but with a relatively small

displacement or when the support base is narrow or

unstable and (c) a step strategy used when the GC is

scrolled beyond the limits of stability (Horak et al.,

1989).

324

Gonçalves Pinheiro Corrêa R., Lucas Aguiar M., Papcke C., Borba Neves E., Denis Vieira A. and Mendonça Scheeren E..

Balance Perturbation Leads a Stretching Reﬂexion on Tibialis Anterior Muscle.

DOI: 10.5220/0005283103240328

In Proceedings of the International Conference on Bio-inspired Systems and Signal Processing (BIOSIGNALS-2015), pages 324-328

ISBN: 978-989-758-069-7

 2015 SCITEPRESS (Science and Technology Publications, Lda.)

Between motor responses, are the stretch reflex and

proprioceptive reflex. These reflexes are involuntary

responses to external stimuli in different movements,

automated or forecasting.

Corporal movements to balance recovery can

trigger reactive fast motor response that leads a

muscle pre-activation, sudden stretch and inhibition

of antagonist muscles. One of these reactive a motor

response is the reciprocal inhibition, which is an

important neurophysiological phenomenon leading

to better coordination of movements and efficiency

(Robinovitch and Murnaghan, 2013). According to

Hortobagyi et al. (2006), the reciprocal inhibition

may decrease with age and contribute to poor

performance of movements in older people, because

it is an important tool in neurophysiological motor

coordination.

Through the disturbance of equilibrium occurs

subsequent order: (a) muscle pre-activation; (b)

sudden muscle stretch; (c) inhibition of the

antagonist muscles. The aim of this study is to show

how the balance perturbation (in posterior-anterior

direction) leads to a stretching reflexion on the

tibialis anterior (TA) muscle.

2 METHOD

A case study was conducted with a 23 years old

male participant, 67kg of body mass and 1.79 m tall,

to show how the balance perturbation leads to a

stretching reflexion on the tibialis anterior muscle.

This study has been approved by Human Research

Ethics Committee of Pontifícia Universidade

Católica do Paraná (PUCPR) under register number

620.735.

2.1 Experimental Protocol

The experimental protocol comprises the

participant's balance perturbation with concurrent

record of balance maintenance muscular action. The

participant has been told to stand still on orthostatic

position on a movable platform keeping 17cm of

feet aperture and 14° of ankle abduction, facing

forward the researcher. Initially the movable

platform has remained still while the participant was

advised that it would start moving. After some

random time, suddenly and without participant's

warning the platform has performed an alternative

movement of 5mm of amplitude on a total time of

3ms on the anterior-posterior direction. Along this

time the (TA) and Soleus (SO) muscular action has

been recorded through a data acquisition system fed

by electromyography signal (EMG). The participant

has kept his eyes open along the experiment. The

platform has started moving from participant's

posterior to anterior side, a perturbation similar as

pulling a carpet intending to cause the participant to

fall sitting. Figure 1 shows the research's participant

standing still on the movable platform.

2.2 Movable Platform

In order to disturb participant's balance it has been

employed a specially designed 1.5m by 1.5 m

platform which is allowed to move up to 0.9 m along

both horizontal orthogonal axes. In this particular

protocol, the platform has been driven by a linear

pneumatic actuator performing an alternative

movement of 5 mm of amplitude on a total time of 3

ms along the axis coinciding with participant's

anterior-posterior axis. Displacement has been

measured with a potentiometric linear transducer.

2.3 Electromyography

Muscular activation has been measured employing a

four channel surface electromyography system.

Site's skin preparation and placement of electrodes

have been in agreement with that stated by SENIAM

project (SENIAM, 2014). Electrodes's site

preparation comprised body hair shaving followed

by skin abrasion employing cotton and alcohol 70°.

It has been employed self-adhesive surface

electrodes in a bipolar configuration (Ag/AgCl

2,2cm) positioned at 1/3 on the line between the

tip of the fibula and the tip of the medial malleolus

in the direction of the line between the tip of the

fibula and the tip of the medial malleolus for TA and

at 2/3 of the line between the medial condyles of the

femur to the medial malleolus in the direction of the

line between the medial condyles to the medial

malleolus for SO. Reference's electrode was placed

around the ankle at the anterior face of Tibia.

2.4 Data Acquisition and Processing

Data acquisition has been performed employing a

National Instruments board, model NI-USB-6009,

and a specially designed software developed on

LabView with a sampling rate of 2KHz with input

analog channels on a differential configuration

resulting in a 14 bits resolution.

Data processing has been performed on Matlab,

comprising the following steps:

i) EMG RMS envelop determination;

ii) Muscular recruitment threshold determination;

BalancePerturbationLeadsaStretchingReflexiononTibialisAnteriorMuscle

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Figure 1: Research's participant standing still on the

movable platform with EMG electrodes on TA and SO

muscles.

iii) Start of muscular recruitment determination;

iv) Time delay between start of balance's

perturbation and start of muscular recruitment

determination;

v) EMG RMS envelop normalization;

Items (i) to (v) have been performed

independently and sequentially from TA to SO

muscles.

EMG RMS envelop determination has been

performed employing function "filtfilt" of Matlab.

This function's input arguments where numerator

and denominator of a 5th order Butter-Worth low-

pass filter with a 20Hz cut-off frequency and 2 kHz

sample frequency obtained by function "butter" of

Matlab. The third input argument of function

"filtfilt" was the absolute value of corresponding

EMG.

A 1s lasting window of the EMG RMS envelop

preceding perturbation's start has been selected on a

monitor's computer plot by visual inspection. The

mean value and the standard deviation of EMG

RMS envelop into this window have been obtained.

Muscular recruitment threshold has been obtained

by the sum of 100% of mean value and 150% of

standard deviation.

Based on visual inspection of a plot, the

researcher has been allowed to select the instant of

time that the value of EMG RMS envelop has

become greater than the muscular recruitment

threshold. This has been considered the start of

muscular recruitment. Time of start of balance's

perturbation was obtained based on displacement's

transducer signal. Subtracting these two time values

has resulted on the time delay between start of

balance's perturbation and start of muscular

recruitment.

EMG RMS envelop normalization has been

performed by subtracting the muscular recruitment

threshold from corresponding EMG RMS envelop

value. Doing so, one may consider that both muscles

have a null normalized muscular recruitment

threshold.

Figure 2: Normalized EMG RMS envelop of TA (blue)

and SO (red); selected start of TA muscular recruitment

(small blue circle); normalized muscular recruitment

threshold (green horizontal line); start of balance's

perturbation (green vertical line).

3 RESULTS

Through the identification of contraction thresholds

of TA and SO muscles and using the normalized

EMG RMS envelop it has been possible to

determine temporal behavior of muscle contraction

(Figure 2). This behavior corresponds to the

situation in which the participant was with eyes open

and with early motion of the platform on the

posterior-anterior direction. The time delay between

start of balance's perturbation and start of muscular

recruitment contraction (muscle contraction delay)

of TA and SO muscles are presented at Table 1.

Table 1: Muscle contraction delay time for TA and SO

muscles.

TA (ms) SO (ms)

Muscle contraction delay 0.0164 0.0462

As the values shown at Table 1, the TA and SO

muscles contracted at different times. This was

expected due to their antagonistic action. Whereas

the balance disorder had higher-anterior direction

and the first muscle to contract was the TA (Table 1

and Figure 2), we believe that the ankle joint,

initially held a plantar flexion. In this movement, the

TA muscle due to its dorsi-flexor action is stretched

and rapidly contracts to maintain the balance.

As the SO muscle performs plantar flexion, and

joint action of the ankle resulting from the balance

disturbance is the same, it was activated later (Table

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1) to the action of the TA muscle for adjusting joint

position after dorsiflexion trend held by TA.

4 DISCUSSION

Despite that the research's participant didn´t know

the exact time of the perturbation, he knew that the

disturbance would happen at any time. In this

situation, Stokes et al. (2000) suggest that pre-

activation occurs in the muscles of the participant

who is subjected to a disturbance of equilibrium,

which is also associated with an increased sensitivity

of the muscle spindle, causing changes in length and

increasing the probability of responding to a sudden

muscle disorder.

Cort et al. (2013) analyzed the contributions of

the muscles of the spine due to balance's disorders,

they concluded that the participants also performed

muscle contractions prior to perturbation. This

enhances the performance of the neuromuscular

system to responses to sudden balance's disorders,

increasing the sensitivity of the receptors responsible

for detecting motion (Cort et al., 2013).

Figure 2 shows that there is an increase in SO

muscle tone prior to perturbation. However, after the

disturbance, the EMG RMS envelop signal

undergoes a sudden attenuation compared to the pre-

perturbation. We believe that this reduction is

associated with transmission's inhibition of the

action potential to the muscle.

Crone et al. (1994), for example, conducted

physical training aimed at increasing the response of

reciprocal inhibition in healthy individuals and in

individuals with musculoskeletal disorders (Geertsen

et al., 2008).

This phenomenon can be explained by the

occurrence of the stretch reflex in the TA muscle

that has the effect of reciprocal inhibition of the

antagonist muscle group to its action.

In a study by Robinovitch and Murnaghan

(2013), using a linear motor connected to a mobile

platform to promote a controlled perturbation, 14

young women were evaluated in three conditions

(forward swing, back swing and static). The results

suggest that the amount of latency (defined as the

time between the onset of the disturbance and the

onset of muscle contraction) in all seven analyzed

muscles (Erector Right Column, Rectus Abdominis,

Soleus, Gastrocnemius, Tibialis Anterior, Rectus

Femoris and Biceps Femoris) seemed to occur

earlier when participants performed a static position.

The authors also concluded that the action of the use

muscles for recovery of the balance are adapted

depending on the nature of the disturbance and the

requested task.

Regarding aging, the work of Piirainen et al.

(2013) monitored EMG signal of muscles SO, TA

and Gastrocnemius of 9 young adults and 10 older

adults in the recovery of postural equilibrium after a

disturbance in the anterior-posterior and posterior-

anterior directions. The authors noted that, due to

aging a decrease in postural control occurs. The

action of SO and TA muscles may not be functional

for maintaining equilibrium in the face of

perturbations in different directions of evaluated

perturbations, indicating a distinct global motor

strategy to balance recovery, and yet, with activation

of antagonistic muscle groups for different

directions of perturbations.

5 CONCLUSIONS

It can be concluded that in the situation of balance

perturbation in posterior-anterior direction, the TA

muscle contracts before the SO, and the SO has pre-

activation, which is inhibited due to the stretch

reflex that occurs in the TA muscle.

REFERENCES

Cort, J. A., Dickey, J. P. & Potvin, J. R. 2013. Trunk

muscle contributions of to L4-5 joint rotational

stiffness following sudden trunk lateral bend

perturbations. J Electromyogr Kinesiol, 23, 1334-42.

De Medeiros, V. M. L., De Lima, F. M. R. & Di Pace, A.

M. 2010. Equilíbrio, controle postural e suas

alterações no idoso.

Duarte, M. & Freitas, S. 2010. Revisão sobre

posturografia baseada em plataforma de força para

avaliação do equilíbrio. Rev bras fisioter, 14, 183-92.

Geertsen, S. S., Lundbye-Jensen, J., Nielsen, J. B., 2008.

Increased central facilitation of antagonist reciprocal

inhibition at the onset of dorsiflexion following

explosive strength training. Journal of appl physiol;

105 (3): 915-22.

Horak, F. B. 2006. Postural orientation and equilibrium:

what do we need to know about neural control of

balance to prevent falls? Age Ageing, 35 Suppl 2, ii7-

ii11.

Horak, F. B., Shupert, C. L. & Mirka, A. 1989.

Components of postural dyscontrol in the elderly: a

review. Neurobiology of aging, 10, 727-738.

Linford, C. W., Hopkins, J. T., Schulthies, S. S., Freland,

B., Draper, D. O. & Hunter, I. 2006. Effects of

neuromuscular training on the reaction time and

electromechanical delay of the peroneus longus

BalancePerturbationLeadsaStretchingReflexiononTibialisAnteriorMuscle

327

muscle. Archives of physical medicine and

rehabilitation, 87, 395-401.

Melzer, I., Benjuya, N., Kaplanski, J., 2004. Postural

stability in the elderly: a comparison between fallers

and non-fallers. Age Ageing, 33 (6): 602-7.

Murnaghan, C. D. & Robinovitch, S. N., 2013. The effects

of initial movement dynamics on human responses to

postural perturbations. Human movement science, 32,

857-865.

Neves, E. B., Krueger, E., Stéphani De Pol, M. C., De

Oliveira, N., Szinke, A. F. & De Oliveira Rosário, M.

2013. Benefícios da Terapia Neuromotora Intensiva

(TNMI) para o Controle do Tronco de Crianças com

Paralisia Cerebral. Rev Neurocienc, 21, 549-555.

Page, P., 2006. Sensorimotor training: A “global”

approach for balance training. Journal of Bodywork

and Movement Therapies, 10, 77-84.

Piirainen, J. M., Linnamo, V., Cronin N. J., Avela J.,

2013. Age-related neuromuscular function and

dynamic balance control during slow and fast balance

perturbations. J Neurophysiology, 110:2557-2562.

Robinson, C. A., Shumway-Cook, A., Ciol, M. A., Kartin,

D., 2011. Participation in community walking

following stroke: subjective versus objective measures

and the impact of personal factors. Phys ther, 91:1865-

1876.

SENIAM, 2014. Surface ElectroMyoGraphy for the Non-

Invasive Assessment of Muscles project.

(http://www.seniam.org).

William H. Gage, W. H., Winter, D. A., Frank, J. S.,

Adkin, A. L., 2004. Kinematic and kinetic validity of

the inverted pendulum model in quiet standing. Gait $

Posture, 19 (2): 124–132.

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