Jakub Parak 1; Lucie Talacková 1; Jan Havlik 1; Lenka Lhotska 2
Deparment of Circuit Theory, Faculty of Electrical Engineering, CTU in Prague
1; Deparment of Cybernetics, Faculty of Electrical Engineering, CTU in Prague
Lékař a technika - Clinician and Technology No. 2, 2012, 42, 65-68
Conference YBERC 2012
In this article, the use of accelerometers for rehabilitation of patients is described. The appropriate rehabilitation process is a key approach to treat a broad range of different diagnoses. The main problem of rehabilitation processes is a subsequent evaluation of their quality to achieve best results. This initial study describes a possibility of using accelerometers for objective evaluation of quality and monitoring the results. The first measurements with accelerometers were conducted on several exercises which are part of the Tinetti balance assessment tool. For these measurements, the 3D MEMS accelerometer implemented in the STM32-Primer2 development kit was used. After the assessment of results obtained on healthy persons, the clinical tests on senior patients will follow.
The rehabilitation of patients is commonly used
therapy after traumas or commas. Moreover the
rehabilitation is used for the patients who have various
problems with a musculoskeletal system.
The main problem of rehabilitations is an objective
evaluation of the quality and progress. It means that
today the physiotherapist or doctor evaluates the results
of rehabilitation only watching the patient. Every
physiotherapist or doctor evaluates the progress and
results on his way and there is no objective aspect. It
means that two conclusions from two doctors can be
The other problem is that the patients do not have
any feedback from therapy process. It means that the
patients cannot monitor the progress independently
without physiotherapist or doctor.
The use of accelerometers in the rehabilitation
process can improve the evaluation of results and make
the rehabilitation process more efficient. Based on
measured signals, the quality and progress of
rehabilitation therapy can be established. A detailed
analysis of using the accelerometers in rehabilitation of
patients is described in .
The diagnostic method which is used mainly in
rehabilitation is called the postugraphy. This method is
used for used to quantify the postural control in upright
stance in either static or dynamic conditions. The
objective evaluation of results of postugraphy method
is based on accelerometer data during postugraphy
The rehabilitation training of a patient with elbow
ligament injury was improved by the supplementary
monitoring system. This system is based on the
wireless accelerometer network and integrates remote
monitoring and intelligent crossplatform terminal .
The accelerometers are used for monitoring the
rehabilitation training of the hemiplegic patients as
Another usage of the accelerometer is upper
extremity rehabilitation of the children with the
cerebral palsy. In this rehabilitation is used feedback
from trunk wearable accelerometer during playing the
game on the multitouch display .
In addition the signal from accelerometers is used for
physical activity detection. The personal mobility
monitoring is very important for patients with physical
disabilities or chronic cardiac diseases. This type of
monitoring is a part of rehabilitation process for these
patients [6, 7].
Several possible solutions and related works which
implements accelerometers in rehabilitation process are
In this article the application of the accelerometers in
diagnostic rehabilitation process is described. This
initial study is focused on exercises from Tinetti
balance assessment tool enhanced with measurements
on the accelerometers. The acquired signals show the
possibility of using accelerometers for objective quality
and results evaluation in this diagnostic method.
The measurement system consists of two main parts:
the development kit with integrated accelerometer and
the PC application for data acquisition.
The development kit STM32-Primer2 was selected
for this project. The kit is product of France Company
Raisonance. The kit contains 32-bit microprocessor
ARM CORTEX STM32F103BVET with maximal
clock frequency 72 MHz. The device uses especially
these kit components: LCD display, accelerometer,
joystick button and external USB connector.
In the development kit there is integrated three-axial
MEMS accelerometer LIS3LV02DL. This inertial
sensor has a user selectable full scale of ± 2g, ± 6g and
it is capable of measuring acceleration over a
bandwidth of 640 Hz for all axes. The device
bandwidth may be selected accordingly to the
application requirements .
The precision and accuracy of the accelerometer in
the development kit was analyzed on the several
measurements with pendulum and gramophone.
In the firmware application for development kit there
was implemented USB HID device driver for
accelerometer data transmission. An acceleration
sampling frequency was set to 50 Hz.
The development kit is shown in the Figure 1.
The PC application for data acquisition from
development kit is based on USB HID Component
for C# . The application allows saving raw data
from the development kit into a file in real-time. The
Realtime Chart and Graph component is integrated in
the application for visualization of receiving data .
The application screenshot is shown in the Figure 2.
Signal processing was designed and implemented in
At the beginning the dynamic acceleration is non
linear filtered from raw signal. The signal is decimated
to 10 Hz sample frequency firstly. Then the median
10th order filter is applied on the signal. Finally, the
signal is interpolated back to 50 Hz sample frequency.
After this filtration the signal contains only the static
acceleration. This acceleration is dependent on
direction of gravitational acceleration. Further the static
acceleration is used for computing tilt of sensor.
The sensor tilt angle in particular axis can be
computed by using formula (1). In this formula φx is
the tilt angle in the axis X, ax is the actual measured
acceleration in X axis depended on tilt angle and gx is
is measured acceleration of gravity in axis X. The
analogously same formula can be applied for other two
axes. Although the formula is very simple it is not used
for determination of the tilt angle.
The other way how to calculate sensor tilt angle is to
measure the acceleration of gravity in two specific
plane of Cartesian system. This method is explained in the Figure 3. For computing the angle in XY plane was
used the formula (2). In this formula α is tilt angle in
plane XY, ax is acceleration in X axis and ay is
acceleration in Y axis.
The formula (3) was used for computing the angle in
XZ plane (1). In this formula β is tilt angle in plane
XZ, ax is acceleration in X axis and ay is acceleration in
The experimental measurements have been
composed of three exercises which are a part of Tinneti
balance assessment tool. These exercises are listed in
In this first study the exercises are practiced by
healthy persons. The measured person tries to simulate
health problem during the exercise according to the
description in Tinnet’s test. The description and the
results of the performed measurements are in the next
Measurement of person who rises from a chair and
sits down back
During this experiment the device was set on the side
of the tight. The computed tilt angles of the healthy person who rises from a chair and sits down back are
displayed in the Figure 4.
In the Figure 5 there are displayed the computed tilt
angles of measured healthy person who simulates
problem with rising from a chair and sitting down.
A person stands up with the aid of hands.
The computed tilt angles of the healthy person who
simulates trying to stand up without success is shown
in the Figure 6.
Measurement of person balance with opened and
The sensor was attached on the side of the belt
during this measurement. In the Figure 7 there are
displayed tilt angles computed during simulation of the
balance problems with opened eyes. The simulation of
the same problem with closed eyes has similar results.
The simple measurement system with accelerometer
was developed for evaluation of the quality and
progress of the rehabilitation. The system can be very
easily extended and adapted for other measurements
during rehabilitation using the development kit.
Based on experimental measurements applied on
exercises from Tinetti balance assessment tool it may
be argued that accelerometer can provide suitable
information about rehabilitation process.
The proposed method of computing the sensor tilt
provides better results than using information only
about acceleration in the one specific axis.
The study will be extended with clinical tests on the
geriatric department. The exercises from Tinetti
assessment tool simulated by healthy people will be
measured on real geriatric patients. The data will be
acquired periodically during the whole rehabilitation
process in order to watch the rehabilitation progress
and its quality.
Another parallel research will apply this knowledge
in rehabilitation of patients with artificial hip joint
This work and the participation in the conference
have been supported by the Foundation of Stanislav
Hanzl CTU in Prague.
This work has been also supported by the research
program No. MSM 6840770012 of the Czech Technical University in Prague (sponsored by the
Ministry of Education, Youth and Sports of the Czech
Ing. Jakub Parak
Department of Circuit Theory
Faculty of Electrical Engineering
Czech Technical University in Prague
Technicka 2, 166 27, Prague,
Phone: +420 224 355 86
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