Technology in Physical Therapy

Wireless Sensors and the Sensorimotor Training

A. Thiers

, A. l’Orteye

, K. Orlowski

and T. Schrader

Brandenburg University of Applied Sciences, Department of Informatics and Media, Brandenburg an der Havel, Germany

adtisches Klinikum Brandenburg GmbH Akademisches Lehrkrankenhaus der Charit

Abteilung Medizinische Schule, Brandenburg, Germany

Keywords:

Wireless Sensors, Sensorimotor Training, Proprioception, EMG Data, Motion Data.

Abstract:

The usage of evidence based decision making is supported along the different professions in the health care

system. State of the art in the physiotherapy, especially in the sensorimotor training is that the therapy planning

mainly based on the experiences of the physiotherapist as well as by the information given by the manufacturer

and the literature. The aim of this study is to show, that the wireless sensor s are a beneﬁt in planning as well

as during the execution of the therapy. Therefore different assumptions were veriﬁed. Additionally, a survey

about the acceptance and the beneﬁt of the sensors was made. Ten test persons performed a laterality test

and the sensorimotor training on three different exercisers. During the whole training the muscle activity as

well as the motion data was document by the usage of wireless sensors. Immediately after the training, all

test persons fulﬁlled the survey. The study revealed that is important to investigate the training in more detail.

Nevertheless, most assumptions are seen as basic principles, they could not be veriﬁed. The evaluation of the

surveys ﬁgured out, that the usage of wireless sensors can be seen as an advantage, but the application has to

be optimized.

1 INTRODUCTION

Use of evidence based decision making is promoted

across the different professions along the health care

system. Based on multiple issues, the use of evidence

has become extensively attractive. One of these issues

is the documentation of the great diversity of treat-

ment methods in the management of a variety of dif-

ferent conditions. Additionally, the handling of medi-

cal errors as well as the identiﬁcation of trends in tech-

nology assessment (Jewell, 2010).

The current status of the therapy planning mainly

rests upon theoretical knowledge, observations just

like “trial and error”. The establishment of a special

therapy was supported by the development and dis-

semination by a respected authority (Mangold, 2012).

One treatment, which is established in the preven-

tion, the therapy, the rehabilitation as well as in the

improvement of the athletic performance is the senso-

rimotor training (H

afelinger and Schuba, 2010). In-

duced by the variety of application ﬁelds the training

itself is going to become more and more attractive.

Consequently, the availability of, particularly, special-

ized equipment is steadily increasing. In contrast, the

impact of the training on the body is not yet fully in-

vestigated (R

uhl and Laubach, 2012).

The positive beneﬁt of the training depends on the

correct application of the equipment. Due to the dif-

ferent materials, functions and characteristics of the

exercisers the correct usage might be challenging. In

particular, the therapy planning is still quite incom-

pletely investigated. Hence, the training is based

on the experiences of the individual physiotherapist

and additionally by the given background informa-

tion of the literature as well on the manufacturer’s

data regarding the exercisers characteristics (R

uhl and

Laubach, 2012).

The myofascial chains is one method of treatment

which is often mentioned in the literature. Kabat has

developed a method to integrate weakened muscles

in a special muscle chain to optimize their behav-

ior during the execution of certain motion patterns.

However, this chains cause the activation of the pro-

prioceptive capabilities of the musculoskeletal system

and leads to the strengthening of the weakened mus-

cles. Several different methods derive from the my-

ofascial chains from Kabat. For instance the holistic

model of all muscles chains by Struyff-Denys. The

500

Thiers A., l’Orteye A., Orlowski K. and Schrader T..

Technology in Physical Therapy - Wireless Sensors and the Sensorimotor Training.

DOI: 10.5220/0004913405000505

In Proceedings of the International Conference on Health Informatics (HEALTHINF-2014), pages 500-505

ISBN: 978-989-758-010-9

 2014 SCITEPRESS (Science and Technology Publications, Lda.)

aim of the application of the principle of the myofas-

cial/ muscles chains is to adopt the behavior of mo-

tion from everyday life as well as from sports into the

therapy process. Consequently, up to date the princi-

ple of the myofascial/ muscle chains is still integrated

in the physiotherapists working process (Richter and

Hebgen, 2007; Tittel, 2012).

Next to the literature of basic principles of the

therapy, a highly important role in the planning of

the treatment is played by the manufacturer’s in-

formation about the exercisers. One popular exer-

ciser is the “Balance Board”. It’s responsibilities in-

clude the strengthen of the musculature of the but-

tocks, the legs, the back and the abdomen (Sport-

Thieme, 2012). Consequently, the following effects

were attributed to the training on the Balance Board.

Firstly, the improvement of the inter- and intramuscu-

lar coordination of the muscles of the feet, the legs,

the lumbar spine, the thoracic spine and the cervical

spine. Secondly, staying with both feed on the Bal-

ance Board, should cause the enhancement of the sta-

bilization in the region of the lumbar spine, the pelvis

and the hip (Bertram and Laube, 2008).

The aim of the current study was to show that there

is a positive beneﬁt when wireless sensors were used

in the sensorimotor training. The usage will lead to

an evidence based therapy planing. Furthermore, the

effects of the training on the body were investigated

in more detail. The research documented the training

of ten subjects of three different exercisers. Addition-

ally, test regarding the laterality were made was well

as inquiries concerning the acceptance of the mea-

surements.

2 MATERIAL & METHODS

2.1 Measurements

The Shimmer

measurements are small and wire-

less sensors. The usage of the Bluetooth technology

allows for online data streaming in real-time (Shim-

mer Research, 2011).

The EMG (Electromyography) daughterboard

provides pre-ampliﬁcation of the EMG-Signal. The

non-invasive method represents the whole activity of

a muscle using either two or three channel data acqui-

sition (Shimmer Research Support, 2012).

The gyroscope module records the angular veloc-

ity of three axis. It consists of a single as well as of a

dual axis angular rate gyroscope (Kuris, 2010).

2.2 Exercisers

For the evaluation of the sensorimotor training the be-

havior of the subjects were documented on three dif-

ferent exercisers.

2.2.1 Balance Board

The Balance Board is an exerciser with a multidimen-

sional instability, ﬁgure 1. Its top is made of stable

and reinforced plastic with a diameter of 40 cm. The

height of the board is 9 cm. The aim of the train-

ing on the Balance Board is in general to strengthen

the musculature of buttocks, legs, back and abdomen

(Sport-Thieme, 2012).

Figure 1: Balance Board.

2.2.2 Rocker Board

One characteristic of the Rocker Board is its one-

dimensional instability, ﬁgure 2. Again, there is a di-

ameter of 40 cm, but in this case a height of 7.5 cm.

The aim of the Rocker Board is to train the coordi-

nation, the stamina, the strength as well as the mo-

tor skills. The Board is either used with a forward-

backward or a left-right deﬂection (Bad-Company,

2013).

Figure 2: Rocker Board.

2.3 Experimental Setup

Supporting the objectives to develop a useroriented

experimental setup and to generate a test procedure,

which can also be executed in patients therapy, the

design of the study was made in cooperation with ex-

perienced physiotherapists of a medical school.

The aim of the study is on the one hand to inves-

tigate the sensorimotor training and on the other hand

to show the beneﬁt of the usage of wireless sensors

in the physiotherapy, especially in the sensorimotor

training. To have a more detailed look at the sensori-

motor training different questions were analyzed:

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• Veriﬁcation of the principle of the myofascial/

muscle chains

• Veriﬁcation of the manufacturer’s data

• Veriﬁcation of the the given information by

the literature, for example exercisers with one-

dimensional instability are easier to handle

than exercisers with multidimensional instability

(Grifka and Dullien, 2008)

• Veriﬁcation of the correlation of laterality and be-

havior on the exercisers

• Acceptance of the measurement units

The study involved ten young and healthy subjects

(seven male and three female). They gave their writ-

ten consent to participate after being informed about

the test procedure. They perform a special test proce-

dure on each of the three exercisers. Furthermore, a

test for the laterality of the hands as well as of the feet

were made. Additionally, a questionnaire about the

acceptance of the wireless sensors had to be fulﬁlled

by the subjects.

2.3.1 Exerciser-tests

The development of the tests sequences on the ex-

erciser derived from a previous study (Thiers et al.,

2013b; Thiers et al., 2013a).

The measurements on the exercisers requires the

use of two different types of Shimmer

sensors.

The two gyroscope sensors were places centrally on

each exerciser. To verify the different assumption of

the manufacturers and the literature the EMG sen-

sors were placed down the legs. In detail: M. bi-

ceps femoris, M. vastus lateralis, M. tibialis anterior

and M. soleus. Both, the skin preparation as well as

the placement of the Ag/AgCl electrodes follows the

recommendations of the SENIAM Project (SENIAM

project, 2012).

One test sequence comprised of a reference mea-

surement in front of the equipment and the record-

ing on the exerciser. The test sequence had to be per-

formed for each of the three exercisers and the order

of the training equipment was randomized for each

test person. The measurement on the exerciser was

divided into four consecutive phases of changing dif-

ﬁculty and duration, table 1. Another characteristic of

the test procedure was the symmetrical requirement

to both body sides. All recordings have been done

without shoes and were supervised by an experienced

physiotherapist.

2.3.2 Laterality-test

The outcome of previous studies had shown that there

is a dominance body side (Thiers et al., 2013b; Thiers

Table 1: Test procedure.

Phase Task Duration

1 Eyes open 30 s

2 Eyes closed 30 s

3 Throwing a medicine ball 60 s

4 Eyes open 30 s

et al., 2013a). Next to the handedness the phenom-

ena of the laterality is also relevant for other paired

parts of the body (Weineck, 2004). To establish a link

between the laterality and the measured values differ-

ent test were made. On the one hand the handedness

was tested. Additionally, the laterality of the feet was

checked, too.

On the whole, six tests for the handedness and ten

test for the laterality of the feet were made. For a gen-

eral overview a balance test was made, too. Therefore

the subject had to stand on two scales, with each foot

on one scale.

2.3.3 Surveys

To determine the acceptance of the measurement units

a questionnaire was developed. Concerning the con-

tents of restrictions during the execution of the trials

when wearing the sensors, the beneﬁt of the sensors

as well as the transferability of the technology into

physiotherapists everyday life.

The surveys were fulﬁlled by prospective physio-

therapists and students of medical informatics.

2.4 Data Analyzes

The data analyzes process started with the application

of a notch ﬁlter. Additionally, a band-pass ﬁlter was

used (Merletti and Parker, 2004). Afterwards, the nor-

malization of the EMG data took place. Therefore,

the average muscular activity, when staying in front

of the exerciser, was calculated and used as normal-

ization value. Hence, the absolute values were trans-

formed into relative values by using the data of the

reference measurement and were presented percent-

age values of the stance.

Next to the normalization a full-wave rectiﬁca-

tion of the EMG data was made (Merletti and Parker,

2004). To evaluate the recordings in the time domain,

different statistical values were computed as interim

results. Both, the mean as well as the maximum val-

ues were computed over a time window of 512 ms

for the whole signal (Gu et al., 2010). Subsequently,

the course of the maximum values over time was cal-

culated. Furthermore, the mean value of the max-

imum voltage values for each phase as well as for

the complete procedure were computed. In addition

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to the previous parameters the accumulated EMG ac-

tivity (iEMG) was evaluated, too. Firstly, the EMG

was integrated over time. The next step comprised of

the calculation of the area under the EMG for a cho-

sen time period, also known as iEMG (Robertson and

Caldwell, 2004; Medved, 2000). This procedure was

performed on the one hand for each phase and on the

other hand for the complete test procedure. Further-

more, the course of the iEMG was documented for

the whole over time by the summation of the iEMG

during the execution of the exercises.

As a complementary evaluation to the physiologi-

cal data, the motion data was also analyzed. The gy-

roscope data was low-pass ﬁltered and then the direc-

tion of motion as well as the current deﬂection was

computed.

3 RESULTS

The illustration 3 provides a brief overview of the

complete muscular activity of each muscle on each

exerciser for one test person, a left-hander, during two

different trials. After the ﬁrst execution a short feed-

back was given to the test persons. A few weeks later

the test persons have repeated the whole experimental

trial.

The muscle with the highest strain during each

trial represents the 100 %. The values of the remain-

ing muscles were presented in relation to the 100 %.

The subject achieved the highest values during

trial one with the right M. vastus lateralis as well as

with the right M. tibialis anterior. The highest over-

all strain is documented for the forward-backward

Rocker Board. In contrast, the training on the Balance

Board seems to be the lowest challenge for the sub-

ject. Except the Balance Board, the right body side

is always providing the highest EMG values. Trial

one ﬁgures out the following points: the training on

the exercisers with the one-dimensional instability re-

quired higher EMG activity than the training on the

exerciser with the multidimensional instability. Al-

though, the subject is a left-hander and the laterality

test of the feet shows that in eight out of ten tests the

preferred leg is the left one, mainly the right body side

was dominant. The M. biceps femoris achieved com-

paratively low EMG activity, this reﬂects a contrast

to the assumption of the myofascial/ muscles chains.

In detail, the expected muscle behavior following the

theory of the chains of the supporting and the free leg

was not documented (Tittel, 2012).

After the execution of the ﬁrst trial the test persons

received a feedback to there individual performance

on the exercisers. With a delay of a few weeks the

experimental setup was repeated. The documented

values were illustrated in the lower part of ﬁgure 3.

The major outcome is the new sorting of the EMG ac-

tivity values of the single muscles, which also leads

to different levels of difﬁculty of the exercisers in

comparison to the ﬁrst trail. In this case, the highest

muscle strain is achieved by the right M. tibialis ante-

rior on the left-right Rocker Board. Furthermore, the

EMG values document, that the forward-backward

Rocker Board represents the smallest challenge. An-

other change is shown in the dominance of the right

body side. The second trial documents an increased

occurrence of higher voltage values of the left body

side.

Figure 3: Comparison of two trials of one subject.

The current ﬁgure 4 visualizes the average maximum

voltage values for each muscle when the subject used

the Balance Board.

One ﬁnding of the ﬁgure is, that for all muscles the

lowest values were achieved during the initial phase.

Consequently, this indicates that a slow relaxation

took place because the ﬁrst and ﬁnal phase require an

identical task.

A second ﬁnding is that the highest values were al-

ways achieved by the M. tibialis anterior. Partially the

remaining muscles only had produced voltage values,

which are similar to that during the reference mea-

surement in front of the Balance Board. This obser-

vation speaks against the principle of the myofascial/

muscle chains, again. Additionally, the documented

values do not support the manufacturers information.

The main part for the maintenance of the equilibrium

on the Balance Board is done by the M. tibialis an-

terior. Already the musculature of the thigh is only

slightly involved.

Another outcome of ﬁgure 4 is that in most cases

the higher voltage values were achieved by the mus-

culature of the right body side. Both, the test of the

laterality of the handy as well as the test of the feet re-

sult in the dominance of the right side (hand-six out of

six right dominance, feet- eight out of ten right dom-

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503

inance). Whereas the balance test on the scales docu-

mented a state of equilibrium (29 kg - 30 kg).

Figure 4: Average maximum values: Balance Board.

Figure 5 documents the results of a set of ques-

tions from the survey. Immediately after the execu-

tion of the experimental setup the questionnaires were

fulﬁlled.

The ﬁrst question was about the restrictions during

the training when wearing the sensors. No one of the

ten test persons had documented to feel any restric-

tion. Next to the small form factor of the sensors the

material for the ﬁxation of the measurements is very

important for freedom of movement.

The next question addressed the problem of the

personal feeling when wearing the sensors. The sub-

jects had to decide whether they feel unpleasant or

not. Only one person had reported to feel uncomfort-

able. This was justiﬁed in the temporarily strong ﬁx-

ation of the sensors, which was afterwards optimized.

The third question handled the beneﬁt of the sen-

sors. All test persons have reported to see a beneﬁt of

the usage of the sensors. On the one hand the subjects

documented that one beneﬁt is to see the muscular

activity and to get a feedback. On the other hand the

subjects see the opportunity to get objective results

about the current state of the therapy.

The last discussion point was the transferability

of the sensors into the physiotherapists everyday life.

Nine out of ten test persons thought, that it is possible

to use the wireless sensors in the practice. Neverthe-

less, often one point of criticism was mentioned. The

application of the electrodes had needed a high de-

mand on time. For an effective usage this application

has to be optimized.

4 DISCUSSION

The main ﬁnding in this experimental study is that

wireless sensors can support the sensorimotor train-

ing. On of the most common principles among phys-

iotherapists experts is the method of the myofascial/

Figure 5: Acceptance and beneﬁt of wireless sensors.

muscles chains. Often the therapy planing is based

on this knowledge. However, the EMG patterns of

the two subjects have shown that against the expecta-

tions, already the ischiocrural musculature only has

a limited participation in the sensorimotor training.

This observation was conﬁrmed by the EMG values

of the remaining test persons, too.

Additionally, the statements of the manufacturer‘s

about their products were validated. Again, this as-

sumption could not be veriﬁed. For the character-

ization of an exerciser more detailed information is

needed, for example about its consistency as well as

of its inertia.

One assumption about the therapy planning is, that

the training on an exerciser like the Rocker Board,

which has a one-dimensional instability is easier than

on an exerciser with a multidimensional instability.

The principle behind: the higher the instability the

more the musculature has to stabilize (Grifka and

Dullien, 2008). The comparison of the needed EMG

activity on the individual exercisers has shown, that

the Rocker Board is always requiring the higher par-

ticipation of the muscles. This observation was made

for all of the ten test persons.

Previous studies (Thiers et al., 2013b; Thiers et al.,

2013a) have shown, that there is frequently a domi-

nance of one body side regarding the produced volt-

age values. The analyzes of the motion data has

shown, that there is no correlation to the duration

of the deﬂection to one side. Mostly the deﬂection

values have shown that there is a uniform distribu-

tion regarding the duration of the individual direc-

tions. Hence, there is the assumption, that there is

a correlation to the laterality of the subject. Often

after the laterality-test there was the recognition that

no clear assumption concerning the dominance of the

legs could be taken. Nevertheless, the test persons

mostly have shown a preferred side. This was also

reﬂected by the EMG values. The ambiguity could

maybe caused by the specialization of the test persons

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504

in different sports.

The survey ﬁgured out, that the subjects have seen

a beneﬁt in the usage of wireless sensors in the sen-

sorimotor training. Although, they have critical look

at the transferability into everyday life. Therefore, it

is needed to perform different improvements to opti-

mize the time exposure.

5 CONCLUSIONS

The investigation of the sensorimotor training reveals

that a more detailed look at the therapy planning is

needed. In the current study each test person has

shown different EMG patterns. Consequently, it is

not possible to make general assumptions about the

effects of the exercisers. For an effective usage of the

equipment a personal analyze of the behavior of the

muscles is needed. Therefore the usage of wireless

sensors is a beneﬁt.

Furthermore, the correct application of the equip-

ment would be supported, if the manufactures pub-

lish more information about their exercisers. Data like

the diameter or the height of an exerciser are too gen-

eral to draw reliable conclusions about the effects the

equipment would cause in the training.

All test persons have shown a dominance of one

body side. This observation was invisible to the naked

eye. Using EMG sensors enables physiotherapist to

an objective assessment of the muscle behavior and

to adapt the training to the individual performance of

the patient.

The great diversity of the voltage values of the

muscles of one test person within two trials makes

clear that the behavior of the subject is mainly based

on its individual form of the day. To handle this chal-

lenge the usage of wireless sensor as a real time feed-

back would be possible.

The variety of different EMG patterns of the in-

dividual subjects as well as the differences in the be-

havior of one test person within two trials shows the

necessity of an evidence based treatment in the ther-

apy. This evidence based approach could be realized

by the usage of wireless sensors.

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