Investigation of the Sensorimotor Training using Wireless Sensor

Networks

Analyzing Three Different Exerciser

A. Thiers

, L. Meffofok

, K. Orlowski

, K. Schrader

, B. Titze

, A. l’Orteye

and T. Schrader

Brandenburg University of Applied Sciences, Department of Informatics and Media, Brandenburg, Germany

SAfP Spektrum Akademie f

ur Physiotherapie, Berlin, Germany

adtisches Klinikum Brandenburg GmbH Akademisches Lehrkrankenhaus der Charit

Abteilung Medizinische Schule, Brandenburg, Germany

Keywords:

Ankle Injuries, Sensorimotor Training, Proprioception, EMG, ECG.

Abstract:

The sensorimotor training method is more and more applied in therapy, rehabilitation, prevention as well as

to increase performance. The training comprises of the practice of motor action and the improvement of

the proprioception. The increasing demand for training has led to a growing range of training equipment.

However, this can only be achieved when the training equipment is applied correctly. The application of the

training equipment is inﬂuenced by two factors: the indiviual behavior when using the equipment as well as

the subjective impression of effort by each patient, both of which can differ strongly. For the purpose of this

study, 18 healthy test persons were recruited. The test comprised of each person having to use each device

at various levels of difﬁculty. Physiological data measured by EMG and ECG as well as psychological data

were collected. The study revealed that the equipment demands different levels of effort from the individual

depending on the physical abilities. Furthermore, it was shown that changing tasks on the particular exerciser

improved the effort of the test persons.

1 INTRODUCTION

Typical ﬁelds of sensorimotor training are the pre-

vention of ankle sprains, the therapy of instability

of joints, the rehabilitation of cruciate ligament in-

juries and the improvement of the athletic perfor-

mance (H

afelinger and Schuba, 2010).

Reﬂexes, rhythmic and cyclical motion patterns as

well as controlled voluntary movements can be sum-

marized under the term motor activity. Besides the

motor activity, the so-called proprioception, depth

sensitivity, are the main characteristics of a sensori-

motor training (Lukas et al., 2011).

The training’s objectives include the regeneration

and the activation of injured proprioceptors, the in-

crease of their potential force and the reduction of the

response time of the stabilizing musculature. Hence,

the overall goal of the training is the improvement of

the reception and the processing of information. In

addition, the translation of the information into the

targeted movement is necessary to guarantee the op-

timal execution of the movement. The positive health

beneﬁt of this training method has been veriﬁed in

several scientiﬁc studies (Dohm-Acker et al., 2008;

Lukas et al., 2011). Therefore, the market for senso-

rimotor training equipment is still growing.

To maximize training results a correct application

of the equipment is paramount. Due to the different

materials, functions and characteristics of the exer-

cisers correct application might be challenging. An

additional difﬁculty for the therapy planning is repre-

sented in the subjective impressions by the patients.

When facing the same task, different opinions regard-

ing the strain of the exercise tend to be expressed by

the patients. In the following experimental study the

mode of action of three different exercisers was ana-

lyzed. The research involved 18 subjects of different

age and with different experiences.

2 MATERIAL & METHODS

2.1 Measurements

The Shimmer

measurements are wireless sensors

413

Thiers A., Meffofok L., Orlowski K., Schrader K., Titze B., l’Orteye A. and Schrader T..

Investigation of the Sensorimotor Training using Wireless Sensor Networks - Analyzing Three Different Exerciser.

DOI: 10.5220/0004329004130416

In Proceedings of the International Conference on Health Informatics (HEALTHINF-2013), pages 413-416

ISBN: 978-989-8565-37-2

 2013 SCITEPRESS (Science and Technology Publications, Lda.)

with a small form factor. Using Bluetooth allows

for online data streaming in real-time. Providing

pre-ampliﬁcation of EMG-Signal the non-invasive

method represents the whole activity of a muscle us-

ing two or three channel data acquisition. Similar

to the EMG signal, the ECG measures the electri-

cal activity of the heart muscles with a two channel

ECG. As the EMG data, the ECG signal is also pre-

ampliﬁed (Shimmer Research Support, 2012b; Shim-

mer Research Support, 2012a).

2.2 Exercisers

To evaluate different sensorimotor training methods

three different exercisers were chosen and evaluated

under different aspects (ﬁg. 1).

Figure 1: Balance Pad, Balance Board, Ortho Pad.

The Balance Pad offers multifaceted applications

of the sensorimotor training. The Pad is made of a

special foam. One characteristic is its damping prop-

erty. Hence, the destabilization of the lower extremi-

ties is supported (Sport-Thieme, 2012a).

The top of the Balance Board is made of stable

and reinforced plastic with a diameter of 40 cm. Here

the aim is to strengthen the musculature of buttocks,

legs, back and abdomen (Sport-Thieme, 2012c).

The Ortho Pad is a speciﬁc type of a teeter board. Its

special construction offers a multi-axial balance train-

ing, as the patient has to handle a balance shift in at

least four directions (Sport-Thieme, 2012b).

2.3 Experimental Setup

18 healthy subjects from the university and the medi-

cal school took part in the study. They gave their writ-

ten consent to participate after being informed about

the test procedure. Based on age and skills, a divi-

sion into three groups was made. One group consisted

of young students with no experiences in sensorimo-

tor training. Group two comprised of students with

comprehensive experience in balance training. Group

three included all subjects over the age of 40 years

irrespective of their experience with the exercisers.

During the research, two different types of

Shimmer

sensors were used. For stress documen-

tation the ECG sensor was placed on the anterior tho-

rax for measuring the chest leads. During the data

analysis, primary attention was paid to the muscular

activity. The ECG was of secondary importance. To

examine the muscular activity, sensors were placed

on the right and on the left lower extremities and but-

tocks. The placement of the sensors was chosen due

to the fact that injuries of the ankle joint are often

treated with proprioceptive training and it is therefore

of interest to look at the behavior of the M. tibialis an-

terior. This muscle supports dorsal ﬂexion, supination

and adduction of the foot (SENIAM project, 2012).

To proof the assumption that the upper body areas par-

ticipate in balancing motions, the EMGs of the right

and the left M. gluteus maximus were also measured.

All subjects had to perform the same test pro-

cedure for all exercisers. The order of the training

equipment was randomized for each test person. One

test sequence comprised of a reference measurement

(30 s) and the measurement while on the test equip-

ment (210 s). The reference measurement was made

on the ﬂoor while the subject was in rest. Immedi-

ately afterwards, the measurement on the exerciser

took place. The test scenario consisted of ﬁve phases

of varying difﬁculty. Each of the ﬁrst two phases

(standing on the exerciser with eyes open and eyes

closed) lasted 30 s. The following phases, throwing

a medicine ball and doing a cable pullover, had a du-

ration of 60 s each. The ﬁnal phase is identical to

the ﬁrst one regarding the task as well as the duration.

After ﬁnishing the procedure on one exerciser the test

persons were asked different questions regarding the

handling of the equipment in general and which phase

was the most exhausting one. All questions used an

eleven-point answer scale (0 equals “no effort” to 10

equals “very high effort”) except for the one inquiring

about the most exhausting phase.

2.4 Data Analysis

The data analysis process startet with the normaliza-

tion of the EMG data. The absolute values were trans-

formed into relative values by using the data of the

reference measurement. A notch ﬁlter with a block-

ing frequency of 50 Hz and a band-pass ﬁlter from 15

to 500 Hz were applied to the raw EMG (Merletti and

Parker, 2004). In the next step, EMG signal process-

ing required the full-wave rectiﬁcation of the signal.

In order to analyze the data in the time domain, differ-

ent statistical parameters, such as mean and maximum

were calculated. On one hand, the parameters were

computed over an interval of three seconds. On the

other hand, the parameters in each of the phases were

calculated. Similar to the processing of the EMG sig-

nal, the ECG was also bandpass (0.05 Hz - 30 Hz )

and notch ﬁltered (Husar, 2010). The properties of

the notch ﬁlter were identical to those of the EMG.

Analyzing the ECG in time domain includes the cal-

culation of the heart rate itself as well as the compu-

HEALTHINF2013-InternationalConferenceonHealthInformatics

414

tation of statistical parameters of the heart rate.

3 RESULTS

The aim of the sensorimotor training is to improve

the motor action and the proprioception. The train-

ing process should lead to a targeted use of the mus-

cles. Therefore, it is to be expected that trained sub-

jects have both, a smaller total amount and a shorter

time in muscle activity. This effect is visualized in

ﬁgure 2, comparing one untrained subject from group

one with one trained subject from group two. Already

in the phase “Eyes Open” the difference between the

trained and untrained subjects is clearly illustrated.

The trained person has lower voltage values across

all phases. In addition it is visible that the subject of

group two restored its balance faster and was able to

keep the balance much better because there was tem-

porarily nearly no muscle activity. Especially in the

phases “Eyes Open” and ”Cable Pullover” the com-

parison of the individual EMG courses show a clear

difference in the patterns. For example, in the phase

“Cable Pullover”, the untrained subject has to apply

more than double the muscle activity. A similar effect

can be seen in the ﬁrst ans last phase. In summary,

ﬁgure 2 supports the assumption that trained persons

can better preserve their balance and are also able to

restore their equilibrium faster.

Figure 2: Comparison of one representative of group one

and two.

Figure 3 documents the muscle activity of an un-

trained young subject on the various equipments. It is

obvious that the three exercisers lead to different mus-

cle activity patterns. Comparing the same phases with

the three pieces of equipment revealed that each exer-

ciser required different skills of the subject. Both, the

Balance Board and the Ortho Pad demanded a high ef-

fort during the “Eyes Closed” phase. On the contrary,

the comparison of the sum of the voltage values of the

Balance Pad in this phase showed relatively low val-

ues. The third and the fourth phase illustrated regular

muscle activity. At the start of both phases the volt-

age values were relatively high and long-lasting. The

muscle activity correlated with the catching/throwing

of the medicine ball and the pulling of the load in

the phase “Cable pullover”. The comparison of the

measured values of the Balance Pad and Board dur-

ing the third phase showed that the average values for

this subject were higher when using the Pad. How-

ever, the recorded impression of the subject showed

the highest effort during the second phase. The cate-

gorization based on ﬁgure 3 generated the following

ranking for the level of difﬁculty (lowest ﬁrst): Bal-

ance Pad - Balance Board - Ortho Pad.

Figure 3: Comparison of the three exercisers.

The heart rate is used as an indicator for stress.

Figure 4 shows the average heart rate during the ﬁve

phases for each of the three groups. The test persons

of group one have the lowest heart rate. In contrast

to the other groups, the subjects of group one were

familiar with the measuring instruments. The higher

heart rate during the initial phase could have been

caused by the tension of the subjects. This assump-

tion is supported by the course of the heart rate of

group two which is lower during the last phase than

in the ﬁrst one. The recorded course of the heart rate

for group one follows a similar pattern than the one

for group three, both increasing during the ﬁrst four

phases. In contrast, the heart rate for group two al-

ready decreases after the second phase. This conﬁrms

that training causes a learning effect and leads to the

subjects starting to feel comfortable after an initial

phase of adaptation.

The test persons’ subjective impressions when us-

ing the “Ortho Pad” are documented in ﬁgure 5.

When analyzing the heart rate, the lowest stress level

was recorded for group two while group 3 had the

highest one. Comparing the test persons’ subjective

impressions (ﬁgure 5) with the measured heart rate

InvestigationoftheSensorimotorTrainingusingWirelessSensorNetworks-AnalyzingThreeDifferentExerciser

415

Figure 4: Comparison of the heart rate at the Ortho Pad.

Figure 5: Subjective impressions after using the Ortho Pad.

(ﬁgure 4), only group three showed a direct link be-

tween the two.

4 DISCUSSION

The main ﬁnding of this study is that the correct appli-

cation of an exerciser depends on several factors. The

analysis of the EMG patterns from one subject using

the three exercisers shows that the patterns are dif-

ferent with respect to the produced voltage values as

well as the activation duration of each muscle. Hence,

the analysis of the individual exerciser could be a tool

for the optimal therapy planning. Despite identical

tasks, the muscle activity patterns of the individual

subjects differ strongly. This implies that the course

of the muscle activity is also depending on the sub-

jects’ skills. Therefore, it is recommended to analyze

the individual behavior of a patient at the various ex-

ercisers in order to plan his or her therapy effectively.

One possible application for the sensorimotor

training is the fall prevention, especially for older pa-

tients. Depending on the physical ﬁtness of these pa-

tients, a veriﬁcation of the general effort could be use-

ful.

The study further revealed a limited correlation

between the subjective impressions of the test per-

sons and the measured values. Therefore, the thera-

pist should critically review the patient’s comments.

5 CONCLUSIONS

The evaluation of the exercisers showed that differ-

ent subjects can have different courses of movement

when using the same equipment. Hence, mobile sen-

sors could greatly improve the study of the individ-

ual interaction between a subject and the equipment

in use. Furthermore, the sensors can assist with ther-

apy documentation in general as well as the progress

recording of a particular muscle.

A possible continuation of this study could be the

measurement and analysis of the gyroscope data. In

combination with the muscle activity pattern, the data

can offer additional information about the way a pa-

tient is reacting to movements of the exerciser. Within

this context, the calculation of the reaction time of the

muscle could also be considered. Hence, it is possi-

ble to characterize the individual muscles needed to

improve for example the instability of a joint.

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