The development and evaluation of a program for leg-strengthening exercises and balance assessment using Kinect.

[Purpose] In this study, a program was developed for leg-strengthening exercises and balance assessment using Microsoft Kinect. [Subjects and Methods] The program consists of three leg-strengthening exercises (knee flexion, hip flexion, and hip extension) and the one-leg standing test (OLST). The program recognizes the correct exercise posture by comparison with the range of motion of the hip and knee joints and provides a number of correct action examples to improve training. The program measures the duration of the OLST and presents this as the balance-age. The accuracy of the program was analyzed using the data of five male adults. [Results] In terms of the motion recognition accuracy, the sensitivity and specificity were 95.3% and 100%, respectively. For the balance assessment, the time measured using the existing method with a stopwatch had an absolute error of 0.37 sec. [Conclusion] The developed program can be used to enable users to conduct leg-strengthening exercises and balance assessments at home.

Comparison of joint kinematics and pedaling force in the young and the elderly.

[Purpose] Proper pedaling posture can improve muscle strength and cardiopulmonary function. To investigate proper pedaling posture for the elderly, this study compared the pedaling efficiency of the elderly with that of the young by using an index of effectiveness (IE) and kinematic results. [Subjects and Methods] Eight adults in their twenties and eight in their seventies participated in 3-min, 40 rpm cycle pedaling tests, with the same load and cadence. The joint angle, range of motion (ROM), and IE were compared by measuring 3-dimensional motion and 3-axis pedal-reaction force during 4 pedaling phases (Phase 1: 330-30°, Phase 2: 30-150°, Phase 3: 150-210°, and Phase 4: 210-330°). [Results] The knee and ankle ROM, maximum knee extension, and maximum ankle dorsiflexion in the elderly were significantly decreased compared with those in the young. Moreover, there were significant differences in IE for the total phase, Phase 1, and Phase 4 between the elderly and young. IE of the young was greater than that of the elderly, except in Phase 3. [Conclusion] Joint movement in the elderly during pedaling was limited. This study provides information that will facilitate the proposal of an efficient pedaling method for the elderly.

A study on balance assessment according to the levels of difficulty in postural control.

[Purpose] This study aimed to determine appropriate measures for assessing balance ability according to difficulty level during standing tasks. [Subjects and Methods] The subjects were 56 old (>65 years) and 30 young (20-30 years) adults. By using the Berg balance scale, the subjects were divided into three groups: 29 healthy older (Berg score≥52), 27 impaired older (Berg score≥40), and 30 healthy young (Berg score≥55). One inertial measurement unit sensor was attached at the waist, and the subjects performed standing tasks (1 min/task) with six difficulty levels: eyes open and eyes closed on firm ground, one foam, and two foams. Thirty-nine (24 time-domain, 15 frequency-domain) measures were calculated by using acceleration data. The slope of each derived measure was calculated through the least-squares method. [Results] Five (95% ellipse sway area, root mean squares [anterior-posterior and resultant directions], and mean distance [anterior-posterior and resultant directions] in time domain) of the 39 measures showed significant differences among the groups under specific standing conditions. The slopes of derived measures showed significant differences among the groups and significant correlations with the Berg scores. [Conclusion] The slope according to the difficulty level can be used to assess and discriminate standing balance ability.

Fall- and BBS-related differences in muscle strength and postural balance of the elderly.

[Purpose] The purpose of this study was to compare the differences in muscle strength and postural balance between fallers and non-fallers. We also compared the difference between normal and impaired balance groups using the same subjects and the same variables. [Subjects and Methods] Seventy-one healthy elderly females (age: 75.1 ± 75 years; weight: 57.3 ± 57 kg; height: 150.1 ± 15 cm) who had high levels of physical activity participated [25 fallers (FG) vs. 46 non-fallers (NG); and 52 healthy balance group (HBG) and 19 impaired balance group (IBG) subjects]. To compare the groups, the muscle strengths of 9 muscle groups, and 20 variables of the instrumented standing balance assessment (2 area variables, 9 time-domain variables, and 9 frequency-domain variables) were assessed. [Results] The FG and NG could only be categorized based on the frequency-domain variables of the instrumented standing balance assessment. On the other hand, there were significant differences between HBG and IBG in height, 6 muscle strength, and 2 time-domain variables of the instrumented standing balance assessment. [Conclusion] These results suggest that muscle strength and standing balance are reflected in physical balance ability (i.e., BBS); however they are in sufficient for determining the actual occurrence of falls.

Primary and secondary gait deviations of stroke survivors and their association with gait performance.

[Purpose] Stroke survivors exhibit abnormal pelvic motion and significantly deteriorated gait performance. Although the gait of stroke survivors has been evaluated at the primary level pertaining to ankle, knee, and hip motions, secondary deviations involving the pelvic motions are strongly related to the primary level. Therefore, the aim of this study was to identify the kinematic differences of the primary and secondary joints and to identify mechanism differences that alter the gait performance of stroke survivors. [Subjects and Methods] Five healthy subjects and five stroke survivors were recruited. All the subjects were instructed to walk at a self-selected speed. The joint kinematics and gait parameters were calculated. [Results] For the stroke survivors, the range of motion of the primary-joint motions were significantly reduced, and the secondary-joint motions were significantly increased. Additionally, for the healthy subjects, the primary joint kinematics were the main factors ensuring gait performance, whereas for the stoke survivors, the secondary-joint motions were the main factors. [Conclusion] The results indicate that while increasing the range of motion of primary-joint movements is the main target to achieve, there is a strong need to constrain and support pelvic motions in order to improve the outcome of gait rehabilitation.

Differences in driving performance due to headway distances and gender: the application of jerk cost function.

Driving is directly controlled by the driver's movement. This study tried to compare differences in gender and headway distances between the DRIVING phase and the SUDDEN STOP phase by using subjects' movement during driving in the simulator. To quantify subjects' movement, the jerk cost function (JC) was used, and conventional vehicle control parameters such as the coefficient of variation of the mediolateral trajectory (MLCV) for lane keeping and the brake time (BT) were also used. As the headway distance increased, MLCV and JC decreased significantly in the DRIVING phase. In the SUDDEN STOP phase, BT was increased and, MLCV and JC were decreased. Differences between genders were detected for both MLCV (males < females) and JC (males > females). The results of this study demonstrate that JC may be used as a variable in evaluating driving performance as influenced by driving conditions and gender.

Effects of low light on the stability of the head and pelvis of the healthy elderly.

[Purpose] The purpose of this study was to evaluate the changes in body stability of the elderly while walking on even surface ground under low light. [Subjects] Ten young males and ten elderly males participated in this experiment. [Methods] Each subject walked along a 7 m walkway five times at their preferred walking speed under normal (>300 lux, NORM) and low light conditions (<5 lux, LOW). To compare the changes in body stability, the root mean square of acceleration (RMSacc) at the head and pelvis was used. [Results] The results show that the body stability of young adults showed a similar RMSacc in all directions at the head and pelvis between the normal and low light walking conditions. In contrast, the RMSacc in all directions at the head and pelvis during low light walking by elderly adults was significantly greater than that of normal light walking. [Conclusion] It was confirmed that, despite walking on even ground, low light condition affects the body stability of the elderly. To clearly evaluate the effect of low light with aging on gait pattern, further study will be necessary to perform additional experiments under various environmental conditions to investigate walking speed, multi-tasking, stairs, and uneven walkway performance.

Driving performance changes of middle-aged experienced taxi drivers due to distraction tasks during unexpected situations.

This study investigated the effects of distraction taskssuch as sending a text message with a cellphone and searching navigation with car navigation system-on the driving performance of 29 highly experienced taxi drivers in their 50s. All participants were instructed to drive using a driving simulator for 2 min. while maintaining a constant distance from the vehicle in front and a constant speed. Participants drove without any distractions for the first minute. For an additional minute, they performed Driving Only or performed a task while driving (Driving + Sending Text Message or Driving + Searching Navigation). An unexpected situation, in which the participant had to stop abruptly due to a sudden stop of the preceding vehicle, occurred during this period. Driving performance during the unexpected situation was evaluated by car control variables, medial-lateral coefficient of variation and brake time, and by motion variables such as the jerk-cost function. Compared to Driving Only, jerk-cost function, medial-lateral coefficient of variation, and brake time increased during Driving + Sending Text Message or Driving + Searching Navigation.

An analysis of the correlation between young males' personal aggression and their skin conductance levels during exposure to aggression images.

This study investigated the correlation between young males' personal aggression and their skin conductance level (SCL) when watching aggression images. SCL increased when participants viewed aggression images as compared to control images. There was a negative correlation between personal aggression score and degree of change in SCL between aggression and control images.

Prioritizing problem features in Korean patients with senile dementia for implementation of monitoring technologies.

The purpose of this study was to investigate the central problem features of Korean patients with senile dementia and to prioritize the features according to risk to the patient with a view to the implementation of remote monitoring technologies. Twenty central problem features were extracted using factorial analysis. The frequency of violent language and confabulation, gathering, and repetition was significantly greater in female than in male patients with senile dementia. All central features, with the exception of abnormal sexual behavior and audiovisual deficits, differed in frequency between the normal elderly and the senile dementia patients and between patients with dementias of different severity. Judgment disorder was the greatest differentiating factor between the normal elderly and the patients with senile dementia. For dementia severity, memory disorder was the greatest differentiating factor of severe versus mild dementia. When risk to the patient was analyzed, problems of perception were identified as the problem features of highest priority.

A simple 5-DoF MR-compatible motion signal measurement system.

The purpose of this study was to develop a simple motion measurement system with magnetic resonance (MR) compatibility and safety. The motion measurement system proposed here can measure 5-DoF motion signals without deteriorating the MR images, and it has no effect on the intense and homogeneous main magnetic field, the temporal-gradient magnetic field (which varies rapidly with time), the transceiver radio frequency (RF) coil, and the RF pulse during MR data acquisition. A three-axis accelerometer and a two-axis gyroscope were used to measure 5-DoF motion signals, and Velcro was used to attach a sensor module to a finger or wrist. To minimize the interference between the MR imaging system and the motion measurement system, nonmagnetic materials were used for all electric circuit components in an MR shield room. To remove the effect of RF pulse, an amplifier, modulation circuit, and power supply were located in a shielded case, which was made of copper and aluminum. The motion signal was modulated to an optic signal using pulse width modulation, and the modulated optic signal was transmitted outside the MR shield room using a high-intensity light-emitting diode and an optic cable. The motion signal was recorded on a PC by demodulating the transmitted optic signal into an electric signal. Various kinematic variables, such as angle, acceleration, velocity, and jerk, can be measured or calculated by using the motion measurement system developed here. This system also enables motion tracking by extracting the position information from the motion signals. It was verified that MR images and motion signals could reliably be measured simultaneously.

Effect of input waveform pattern and large blood vessel existence on destruction of liver tumor using radiofrequency ablation: finite element analysis.

Much research has been directed at improving the effectiveness of the radiofrequency (RF) ablation of hepatocellular carcinomas. In that point of view, this study was performed to provide comprehensive information of the relation between RF waveforms and thermodynamic response of the tissue with the consideration of four different types of RF waveforms (half-sine, half-square, half-exponential, and damped-sine) to maximize the amount of tumor tissue removed while maintaining the advantages of RF ablation. For the aim of this study, finite element models incorporating results from previous numerical models were used and validated with ex vivo experiments. From analyses of the entire results, we concluded that this study may prove valuable as a first step in providing comprehensive information of the relation between various RF waveforms and thermodynamic responses within the tissue during the RF ablation process. This study may also contribute toward studies to determine an optimum RF waveform capable of maximizing the amount of tumor tissue removed while maintaining the advantages of RF ablation.

Differences in reproducibility of gait variability and fractal dynamics according to walking duration.

BACKGROUND: Gait variability and fractal dynamics may be affected by the walking duration. OBJECTIVE: The purpose of this study is to examine the reproducibility of stride time while walking on a self-paced treadmill. METHODS: Fifteen young and healthy subjects walked on the treadmill for 10 minutes. Three to eight minutes duration of the data were used to compare the trial-to-trial and day-to-day reproducibility of the average, variability, and fractal dynamics of stride time. RESULTS: The results show that all variables had high trial-to-trial reproducibility. In the day-to-day results, the average walking speed and mean stride time showed reproducibility without regard for duration, but the variability and gait fractal dynamics showed differences in reproducibility according to duration. The variability and fractal dynamics showed better reproducibility in less than 5 minutes and over time, respectively. However, both variables generally showed improved reproducibility when average data from two to three rounds were used. CONCLUSION: Based on the results of this study, it is proposed that variability should be examined using data of 5 min or less, and fractal dynamics should be examined using 5 min or more of repeated data when performing walking tests from a gait dynamics perspective.

Development of a magnetic resonance-compatible galvanic skin response measurement system using optic signal.

The purpose of the current study is to develop a magnetic resonance (MR)-compatible galvanic skin response (GSR) measurement system that can measure the GSR signal during MR image acquisition. If GSR signals are measured simultaneously with the acquisition of MR images, there can be a mutual interference effect. The present system was designed to block noises caused by the main magnetic field, the gradient magnetic field, and the radio frequency (RF) pulse when MR images are acquired. To minimize the distortion of MR images, the GSR measurement system was shielded. Especially, this system used analog, not digital, elements in order to remove any possible effects on MR images. An RF-interference-free optical data link using the pulse-width modulation technique was adopted in order to transmit GSR signals measured inside the MR room. The experiment verified that a reliable GSR signal can be obtained without deteriorating the MR image. It is expected that this system can be used for diverse medical and neuroscience studies.

A study on the cerebral sizes of Koreans in their 20S and 40S.

The purpose of this study was to measure the cerebral sizes of Korean adults in their third (20s) and fifth decades (40s) of life using Talairach-Nowinski reference points to determine the effect of sex and age on cerebral size and asymmetry. Magnetic resonance images of the brain of 94 adults between 20 and 29 years of age (43 males and 51 females) and 99 adults between 40 and 49 years of age (38 males and 61 females) were measured. The distance between reference points and cerebral size of males was greater than those of females. Cerebral width and the size of the left cerebrum of those in their 40s decreased more than those in their 20s. The effect of age on left cerebral atrophy of males was greater than that of females. Left cerebral size was greater than right cerebral size. There was no difference in cerebral asymmetry between the genders. Cerebral asymmetry of those in their 40s was smaller than of those in their 20s and the decrease of cerebral asymmetry of males due to age was greater than that of females. A positive relationship existed between cerebral height, and body height and weight for males in their 20s.

A study on the effects of 40% oxygen on addition task performance in three levels of difficulty and physiological signals.

This study investigated the effect of 40% oxygen administration on addition task performance in three levels of difficulty and physiological signals, such as blood oxygen saturation and heart rate. The accuracy rates of the addition tasks were enhanced with 40% oxygen administration compared to 21% oxygen. As the difficulty level increased, the difference in the accuracy rate between 40% and 21% oxygen administration increased. When 40% concentration oxygen was supplied, blood oxygen saturation was increased and heart rate was decreased compared to that with 21% oxygen administration. A positive correlation was found between task performance and oxygen saturation level during the Task3 phase. This result suggests that 40% oxygen administration would lead to increases in addition task performance.

Physiological mechanism underlying the improvement in visuospatial performance due to 30% oxygen inhalation.

This study investigated the effect of 30% oxygen inhalation on visuospatial cognitive performance, blood oxygen saturation, and heart rate. Six male (25.8(mean)+/-1.0(SD) years) and six female (23.8+/-1.9 years) college students participated in this experiment. Two psychological tests were developed to measure the performance level of visuospatial cognition. The experiment consisted of two runs: one was a visuospatial cognition task under normal air (21% oxygen) condition and the other under hyperoxic air (30% oxygen) condition. The experimental sequence in each run consisted of four phases, that were Rest1 (1min), Control (1min), Task (4min), and Rest2 (4min). Blood oxygen saturation and heart rate were measured throughout the course of four phases. The analysis of behavioral performance with 30% oxygen administration when compared to 21% oxygen revealed that the mean performance was improved. When supplied 30% oxygen in the air, the blood oxygen saturation was increased while the heart rate was decreased compared to those under 21% oxygen condition. We conclude that 30% oxygen inhalation enhanced visuospatial performance by the increased the oxygen saturation in the blood.

A comparison of the mean signal change method and the voxel count method to evaluate the sensitivity of individual variability in visuospatial performance.

This study compared the mean signal change method and the voxel count method in evaluating the sensitivity of individual variability in visuospatial performance using functional Magnetic Resonance Imaging (fMRI). Sixteen right-handed male college students (mean age 23.2 years) participated in this study as subjects. Functional brain images were scanned with a 3T MRI single-shot EPI method during a visuospatial task. No correlation was found between visuospatial performance and the number of activated voxels in the activated brain areas. Significant positive correlations, however, were found between visuospatial performance and the mean signal changes of activated voxels in the parietal, frontal and other areas. In conclusion, the mean signal change is more sensitive to individual variability in visuospatial performance than the number of activated voxels.

Effects of high concentration oxygen administration on n-back task performance and physiological signals.

This study investigated the effect of 40% oxygen administration on n-back task performance, blood oxygen saturation and heart rate. Five male (25.8 +/- 1.3 years) and five female (23.0 +/- 1.0 years) college students were selected as the subjects for this study. The experiment consisted of two runs: one was an n-back task with normal air (21% oxygen) administered and the other was with hyperoxic air (40% oxygen) administered. The experimental sequence in each run consisted of Rest1 (1 min), 0-back task (1 min), 2-back task (2 min) and Rest2 (4 min). Blood oxygen saturation and heart rate were measured throughout the four phases. The results of the n-back behavioural analysis reveal that accuracy rates were enhanced with 40% oxygen administration compared to 21% oxygen. When 40% oxygen was supplied, blood oxygen saturation was increased and heart rate was decreased compared to that with 21% oxygen administration. It is suggested that 40% oxygen can stimulate brain activation by increasing actual blood oxygen concentration in the process of cognitive performance, and hyperoxia makes heart rate decrease. This result supports the hypothesis that 40% oxygen administration would lead to increases in n-back task performance.

Fractal fluctuations in spatiotemporal variables when walking on a self-paced treadmill.

This study investigated the fractal dynamic properties of stride time (ST), stride length (SL) and stride speed (SS) during walking on a self-paced treadmill (STM) in which the belt speed is automatically controlled by the walking speed. Twelve healthy young subjects participated in the study. The subjects walked at their preferred walking speed under four conditions: STM, STM with a metronome (STM+met), fixed-speed (conventional) treadmill (FTM), and FTM with a metronome (FTM+met). To compare the fractal dynamics between conditions, the mean, variability, and fractal dynamics of ST, SL, and SS were compared. Moreover, the relationship among the variables was examined under each walking condition using three types of surrogates. The mean values of all variables did not differ between the two treadmills, and the variability of all variables was generally larger for STM than for FTM. The use of a metronome resulted in a decrease in variability in ST and SS for all conditions. The fractal dynamic characteristics of SS were maintained with STM, in contrast to FTM, and only the fractal dynamic characteristics of ST disappeared when using a metronome. In addition, the fractal dynamic patterns of the cross-correlated surrogate results were identical to those of all variables for the two treadmills. In terms of the fractal dynamic properties, STM walking was generally closer to overground walking than FTM walking. Although further research is needed, the present results will be useful in research on gait fractal dynamics and rehabilitation.