Katja Orlowski

Cortical activation during balancing on a balance board

BACKGROUND Keeping ones balance is a complex motor task which requires the integration and processing of different sensory information. For this, higher cortical processes are essential. However, in the past research dedicated to the brains involvement in balance control has predominantly used virtual reality paradigms whilst little is known about cortical activation during the challenging balancing on unstable surfaces (e.g. balance board). Hence, the main goal of this study was the simultaneous evaluation of cortical activation patterns and sway parameters during balancing on a balance board. METHODS Ten healthy adults were instructed to balance on a balance board while brain activation in supplementary motor area (SMA), precentral gyrus (PrG) and postcentral gyrus (PoG) was measured with functional near-infrared spectroscopy (fNIRS). Additionally, sway parameters were simultaneously recorded with one inertial sensor. RESULTS Enhanced activation of SMA, PrG and PoG was observed when balancing was compared with still standing. Furthermore, the sway of pelvis (indicated by root mean square) increased in medio-lateral (ML) and anterior-posterior (AP) direction during the balance condition. Notably, a strong negative correlation was found between SMA activation and sway in ML direction during balancing, which was not observed during standing. CONCLUSION Our results underline the important role of sensorimotor cortical areas for balance control. Moreover, the observed correlations suggest a crucial involvement of SMA in online control of sway in ML direction. Further research is needed to understand the contribution of other cortical and subcortcial areas to online balance control.

Examination of the reliability of an inertial sensor-based gait analysis system

Abstract Gait analysis is an important and useful part of the daily therapeutic routine. InvestiGAIT, an inertial sensor-based system, was developed for using in different research projects with a changing number and position of sensors and because commercial systems do not capture the motion of the upper body. The current study is designed to evaluate the reliability of InvestiGAIT consisting of four off-the-shelf inertial sensors and in-house capturing and analysis software. Besides the determination of standard gait parameters, the motion of the upper body (pelvis and spine) can be investigated. Kinematic data of 25 healthy individuals (age: 25.6±3.3 years) were collected using a test-retest design with 1 week between measurement sessions. We calculated different parameters for absolute [e.g. limits of agreement (LoA)] and relative reliability [intraclass correlation coefficients (ICC)]. Our results show excellent ICC values for most of the gait parameters. Midswing height (MH), height difference (HD) of initial contact (IC) and terminal contact (TC) and stride length (SL) are the gait parameters, which did not exhibit acceptable values representing absolute reliability. Moreover, the parameters derived from the motion of the upper body (pelvis and spine) show excellent ICC values or high correlations. Our results indicate that InvestiGAIT is suitable for reliable measurement of almost all the considered gait parameters.

Gait patterns in standard scenarios: Using Xsens MTw inertial measurement units

The paper deals with the determination of 3D gait patterns of the lower limbs and the pelvis as a result of experiments in standardized scenarios. In the experimental setup seven synchronized Xsens MTw inertial measurement units (IMU) are applied to the lower limbs and the pelvis of the subject. The sensors provide filtered and strapped down samples of acceleration, angular velocity and magnetic rate vectors as well as the estimated quaternion of orientation. The data are transferred with a rate of 60 Hz and transformed into an inertial coordinate system. Stable and reliable algorithms processing the gait data and calculating gait features of a single sensor are developed and evaluated. These algorithms are based on precise determination of each gait cycle. In the middle of stance phase the foot is not moving. It stands on the floor and, following, the initial conditions for the calculation of foot velocities and distances by integration are predetermined. The same time intervals are used for calculations of the data of the other sensors fixed to the shank, thigh and pelvis. Investigating the averaged motion of different cohorts in various standard scenarios gait patterns were determined and compared with patterns given by Perry and Murray [1,2].

Model Based Determination of Gait Parameters Using IMU Sensor Data

The paper deals with the determination of gait parameters using inertial measurement units (IMU). An IMU sensor incorporates three microelectromechanical sensors - triple-axis gyroscope, accelerometer and magnetometer. A standard experimental setup for the observation of the locomotion system using seven Xsens MTw sensors was developed. They are applied to the lower limbs and the pelvis of the subject. The synchronization of data from all sensor components (gyroscope, accelerometer and magnetometer) as well as the onboard estimation of the orientation is provided by the Xsens and Adwinda hard-and software. The strapped down data are received with a rate of 60 Hz. The output data of a single IMU sensor allow motion analysis of the sensor unit itself as well as the motion of the limb where the sensor is mounted to. Stable and reliable algorithms processing the gait data and calculating gait features of a single sensor are developed and evaluated. These algorithms are based on precise determination of each gait cycle. In the middle of stance phase the foot is not moving. It stands on the floor and, following, the initial conditions for the calculation of foot velocities and distances by integration are predetermined. Various features of the gait cycle as well as e.g. dependencies in between features or on the gait velocities are investigated. The application of seven sensors to the limbs of the locomotion system provides measurements of their 3D motion observed in an inertial coordinate system. The limbs are parts of skeleton and interconnected by joints. Introducing a skeleton model, the quality of measurements is evaluated and improved. Joint angles, symmetry ratios and other gait parameters are determined. These results can be used for analysis of the gait of any subject as well as of any cohort.

Inertial Measurement Units in Gait Analysis Applications - Questions, Suggestions and Answers

The paper deals with inertial measurement units (IMU) and their application in gait analysis in the wide range from movement monitoring through rehabilitation feedback to sports improvement. An IMU sensor incorporates three microelectromechanical sensors triple-axis gyroscope, accelerometer, magnetometer – and, optionally, a barometer. The outputs of all sensors are processed by an on-board microprocessor and sent over a serial interface using wired or wireless communication channels. The on-board processing may include sensor conditioning, compensations, strap-down integration as well as determination of orientation. The sensor output is sent to applications working on standard PC, tablets or smart phones using different sampling rates. The output data of one IMU sensor allow motion analysis of the sensor unit itself as well as the motion of the limb where the sensor is mounted to. Using a combination of two or more sensors the movement of limbs/legs can be compared; their relative motion can be investigated; angles can be calculated. In general, in motion and gait analysis, we like to get primary information about the position of all interesting points, the orientation of the limbs and the joint angles at each moment of time as well as derived averaged and summarized characteristics about the motion and the gait. Based on our own investigations the paper discusses how much information is really necessary to determine gait events and gait features for

Analyzing the Transfemoral Amputee Gait using Inertial Sensors - Identifying Gait Parameters for Investigating the Symmetry of Gait - A Pilot Study

The amputation of a lower limb is a drastic event and it completely changes the life of the person. Current development of prosthesis is already advanced, but most of the affected persons suffer from changes in the gait which are visible to the general public. The gait of transfemoral amputees was investigated in the laboratory environment and is called asymmetric due to different facts: shorter step length, smaller velocity and smaller cadence. The use of mobile inertial sensors can be supportive in the rehabilitation process of these patients. That is why a pilot study is conducted to evaluate the gait of transfemoral amputees and compare their gait parameters with those of the healthy subjects. The purpose of the investigation is to identify gait parameters showing the asymmetric properties of the amputees gait. Eight parameters seem to be distinctive

A Pilot Study to Examine the Activity of Primary Plantar Flexor Muscles using an Electric Motorized Treadmill in Comparison to Overground Walking.

The gait during overground (OG) and treadmill (TM) walking was already investigated by different scientific groups. Differences in the muscle activation and in the kinetics were found. The aim of the present examination was to find conditions for a comparable or higher activation of the plantar flexor muscles during TM walking in order to give recommendations for training and rehabilitation. A pilot study with different conditions (e.g. with and without inclination) was done. Furthermore, the aspect of different walking velocities in OG and TM walking was investigated. The self selected speed was reduced during TM walking (1.1 km/h). Regarding the muscle activation, it is recognizable that the primary plantar flexor muscles react similarly. The activation is reduced during TM walking. Based on the inclination of 1.5 %, a little larger activity during TM walking is observed for the muscles M. gastrocnemius medialis and lateralis. Our results confirm that there are differences between OG and TM walking in the activation of the primary plantar flexor muscles. The results indicate that there is an effect of different, adjustable conditions (speed and inclination). Further examinations are planned to find detailed information about the different conditions and their impact on the

Estimation of the Average Gait Velocity based on Statistical Stride Parameters of Foot Sensor Data

The paper deals with the estimation of gait parameters based on data acquired by inertial measurement units (IMU) placed at the middle foot (metatarsus). The developed method described in (Loose and Orlowski, 2015) is robust against a wide spectrum of the gait speed. The gait parameters (stride duration, length, velocity, distance) are calculated stride by stride with excellent quality. This paper is focused on experimental data acquired during walking on treadmill with a speed profile. First the robustness of the method is shown and quantified using statistical characteristics of each speed level and the whole walking distance. Second the determined speed profiles are evaluated against the adjusted speed profile and an alternative camera based measurement. Third the influence of the walking speed on various physical and statistical stride parameters is discussed. Fourth a model to estimate the walking speed as a function of the root mean square of the magnitude of the angular velocity vector is proposed and evaluated. The rms is calculated for the acquired sensor data after stride detection for the whole stride. The proposed method is applicable to any IMU applied to the metatarsus.

Technology in Physical Therapy

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. Therefor 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.

Analyzes of Influencing Factors to the Sensorimotor Training - Technical Support Systems in the Physiotherapy

The popularity of the sensorimotor training is still growing. Nonetheless, the training is not yet fully investigated. Information given by the manufacturers, in the literature and the experience of physiotherapists will form the basis of physiotherapeutic interventions. For an integration of evidence based decision making a change in the approach of the therapy planning is needed. This can be achieved by the use of technical support systems. Therefore, the behavior of 32 test persons was investigated. Within two different setups several investigation scopes were analyzed. One scope was the influence of the laterality to the muscular activity during the training on the exerciser. Furthermore, the effects of the different equipment with regard to the information of the literature and the manufacturers were analyzed. Additionally, a detailed investigation of the muscular activity during the realization of tasks given by the physiotherapist was made. Also, a survey regarding the muscular strain during the training as well as the acceptance of the sensors was fulfilled. Finally, factors which have an influence on the progress of the training were identified and analyzed. The benefit and the necessity of technical support systems in the sensorimotor training was shown.