Design and Control of a Polycentric Knee Exoskeleton Using an Electro-Hydraulic Actuator.

An exoskeleton robot helps the wearer with mechanical forces by identifying the wearer's intentions and requires high energy efficiency, sufficient load capacity, and a comfortable fit. However, since it is difficult to implement complex anatomical movements of the human body, most exoskeleton robots are designed simply, unlike the anatomy of real humans. This forces the wearer to accept the robot's stiffness entirely, and to use energy inefficiently from the power source. In this paper, a simple 1 degree of freedom (DoF) structure, which was mainly used in the knees of exoskeleton robots, was designed with a polycentric (multi-axial) structure to minimize the misalignment between wearer and robot, so that torque transfer could be carried out efficiently. In addition, the overall robot system was constructed by using an electro-hydraulic actuator (EHA) to solve the problems of the energy inefficiency of conventional hydraulic actuators and the low load capacity of conventional electric actuators. After the configuration of the hardware system, the sliding mode controller was designed to address the EHA nonlinear models and the uncertainty of the plant design. This was configured as Simulink for the first verification, and the experiment was conducted by applying it to the actual model to demonstrate the performance of the sliding mode control. In this process, an optical rotary encoder was used as the main feedback sensor of the controller. The proposed polycentric knee exoskeleton robot system using the EHA was able to reach the desired target value well despite the presence of many model uncertainties.

The Effect of Geographic Units of Analysis on Measuring Geographic Variation in Medical Services Utilization.

OBJECTIVES: We aimed to evaluate the effect of geographic units of analysis on measuring geographic variation in medical services utilization. For this purpose, we compared geographic variations in the rates of eight major procedures in administrative units (districts) and new areal units organized based on the actual health care use of the population in Korea. METHODS: To compare geographic variation in geographic units of analysis, we calculated the age-sex standardized rates of eight major procedures (coronary artery bypass graft surgery, percutaneous transluminal coronary angioplasty, surgery after hip fracture, knee-replacement surgery, caesarean section, hysterectomy, computed tomography scan, and magnetic resonance imaging scan) from the National Health Insurance database in Korea for the 2013 period. Using the coefficient of variation, the extremal quotient, and the systematic component of variation, we measured geographic variation for these eight procedures in districts and new areal units. RESULTS: Compared with districts, new areal units showed a reduction in geographic variation. Extremal quotients and inter-decile ratios for the eight procedures were lower in new areal units. While the coefficient of variation was lower for most procedures in new areal units, the pattern of change of the systematic component of variation between districts and new areal units differed among procedures. CONCLUSIONS: Geographic variation in medical service utilization could vary according to the geographic unit of analysis. To determine how geographic characteristics such as population size and number of geographic units affect geographic variation, further studies are needed.

Comparison of muscular activities in the abdomen and lower limbs while performing sit-up and leg-raise.

[Purpose] This study compared the muscle activities of sit-up and leg-raise. [Subjects and Methods] The subjects of this study were healthy students in their 20s. For electromyography of sit-ups and leg-raises in the supine position, 5 muscle groups of the abdomen were selected for the attachment of sensors: the upper and lower rectus abdominis, external oblique, rectus femoris, and the iliopsoas. SPSS 20.0 was used for the statistical analysis. One-way ANOVA with repeated measures of all factors was performed to verify the statistical significance of the measurements taken for the muscle activities and follow-up verification was made with the Bonferroni post hoc test. [Results] Sit-up and leg raise showed a significant difference. The eccentric sit-up exercise elicited a significant increase in the activation of the abdominal muscle. The leg raise and eccentric sit-up exercises elicited significant increases in the activation of hip flexor muscle. [Conclusion] The eccentric sit-up had the most outstanding effect on the abdominal muscles involved in stability of the trunk.

Is there an agreement among the items of the Korean physical therapist licensing examination, learning objectives of class subjects, and physical therapists' job descriptions?

PURPOSE: To determine the agreement among the items of the Korean physical therapist licensing examination, learning objectives of class subjects, and physical therapists' job descriptions. METHODS: The main tasks of physical therapists were classified, and university courses related to the main tasks were also classified. Frequency analysis was used to determine the proportions of credits for the classified courses out of the total credits of major subjects, exam items related to the classified courses out of the total number of exam items, and universities that offer courses related to the Korean physical therapist licensing examination among the surveyed universities. RESULTS: The proportions of credits for clinical decision making and physical therapy diagnosis-related courses out of the total number credits for major subjects at universities were relatively low (2.06% and 2.58%, respectively). Although the main tasks of physical therapists are related to diagnosis and evaluation, the proportion of physiotherapy intervention-related items (35%) was higher than that of examination and evaluation-related items (25%) on the Korean physical therapist licensing examination. The percentages of universities that offer physical therapy diagnosis and clinical decision making-related courses were 58.62% and 68.97%, respectively. CONCLUSION: Both the proportion of physiotherapy diagnosis and evaluation-related items on the Korean physical therapist licensing examination, and the number of subjects related to clinical decision making and physical therapy diagnosis in the physical therapy curriculum, should be increased to ensure that the examination items and physical therapy curriculum reflect the practical tasks of physical therapists.

Activation of back and lower limb muscles during squat exercises with different trunk flexion.

[Purpose] The purpose of this study was to investigate the activation of back and lower limb muscles in subjects who were performing a squat exercise at different angles of trunk flexion. [Subjects and Methods] Twenty healthy subjects (age 21.1± 1.8 years, height 168.7 ± 8.2 cm, weight 66.1 ± 12.3 kg) volunteered. The activation of the erector spinae muscle, rectus femoris muscle, gluteus maximus muscle and biceps femoris muscle was observed while the subjects performed squat exercises with a trunk flexion of 0°, 15°, and 30°. [Results] The erector spinae muscle, gluteus maximus muscle, and biceps femoris muscle were activated more during the squat exercise with the trunk flexion at 30° than the exercise with the trunk flexion at 0°. The rectus femoris muscle showed a tendency to decrease as the truck flexion increased. [Conclusion] Squat exercise be executed while maintaining an erect trunk posture if one wishes to strengthen the quadriceps muscle while reducing the load on the lower back.

Relationships among the Y balance test, Berg Balance Scale, and lower limb strength in middle-aged and older females.

BACKGROUND: Older females have less dynamic postural control and muscle strength than do middle-aged females. Aging-related strength losses may limit balancing performance. OBJECTIVE: The purpose of this study was to investigate the ability of the Y Balance Test (YBT) and lower limb strength to discriminate between females in 2 age groups, the relationship between YBT distance and the Berg Balance Scale (BBS), and the degree to which performance on YBT distance is related to lower limb strength in middle-aged and older females. METHOD: The 40 healthy, independently active females were divided into 2 groups: older and middle-aged. The participants underwent measurements of YBT distance using the YBT, maximal muscular strength of the lower limbs using a handheld dynamometer, and the BBS. RESULTS: The YBT distance in 3 directions and lower limb muscle strength for both lower limbs were significantly lower in the older adults than in the middle-aged group. A moderate correlation but insignificant correlation was found between the YBT composite distance and the BBS score. In the older females, YBT distance was significantly positively correlated with strength of the knee flexor and hip abductor. In the middle-aged group, YBT distance was significantly positively correlated with strength of the knee flexor and hip extensor. CONCLUSIONS: Performance on the YBT was influenced by the strength of lower limb. We suggested that YBT can be used to alternative as a measurement of dynamic balance. Proper training programs for older people could include not only strengthening exercises but also YBT performance to improve balance.

Relationships among the Y balance test, Berg Balance Scale, and lower limb strength in middle-aged and older females

Background: Older females have less dynamic postural control and muscle strength than do middle-aged females. Aging-related strength losses may limit balancing performance. Objective: The purpose of this study was to investigate the ability of the Y Balance Test (YBT) and lower limb strength to discriminate between females in 2 age groups, the relationship between YBT distance and the Berg Balance Scale (BBS), and the degree to which performance on YBT distance is related to lower limb strength in middle-aged and older females. Method: The 40 healthy, independently active females were divided into 2 groups: older and middle-aged. The participants underwent measurements of YBT distance using the YBT, maximal muscular strength of the lower limbs using a handheld dynamometer, and the BBS. Results: The YBT distance in 3 directions and lower limb muscle strength for both lower limbs were significantly lower in the older adults than in the middle-aged group. A moderate correlation but insignificant correlation was found between the YBT composite distance and the BBS score. In the older females, YBT distance was significantly positively correlated with strength of the knee flexor and hip abductor. In the middle-aged group, YBT distance was significantly positively correlated with strength of the knee flexor and hip extensor. Conclusions: Performance on the YBT was influenced by the strength of lower limb. We suggested that YBT can be used to alternative as a measurement of dynamic balance. Proper training programs for older people could include not only strengthening exercises but also YBT performance to improve balance. .

The effect of simulating a leg-length discrepancy on pelvic position and spinal posture.

[Purpose] The purpose of this study was to examine how a leg-length discrepancy contributes to the pelvic position and spinal posture. [Subjects and Methods] A total of 20 subjects (10 males, 10 females) were examined during different artificially created leg-length inequalities (0-4 cm) using a platform. The pelvic tilt and torsion and the sagittal deviation of the spine were measured using the rasterstereographic device formetric 4D. [Results] Changes in platform height led to an increase in pelvic tilt and torsion, while no changes in the spinal posture were found with the different simulated leg-length inequalities. [Conclusion] Our study showed that a leg-length discrepancy may cause pelvic deviation and torsion, but may not lead to kyphosis and lordosis. Therefore, we consider that an artificially created leg-length discrepancy has a greater effect on pelvic position than spine position.

The Effects of Diverse Warm-up Exercises on Balance.

[Purpose] To examine how stretching, plyometric, and treadmill exercises influence the dynamic balance necessary for sports activities. [Subjects and Methods] Twenty-two healthy subjects participated in this study. The subjects conducted stretching, plyometric exercises, and treadmill walking for set times over a period of three days. The subjects' dynamic balance was then measured. The measurements were taken prior to the intervention, immediately after the intervention, and 20 minutes after the intervention. All the intervention times were set at 16 minutes, excluding resting times. The data were analyzed with using the two-way ANOVA. [Results] There was no interaction between exercises and time. There were no statistical differences among the exercises and no statistical differences in changes over time. [Conclusion] This study found that warm-up exercises such as plyometric exercises, stretching, and treadmill walking have no effect on the dynamic of balance in healthy subjects.

Effect of Circuit Class Training for Eight Weeks on Changes in Ratios of F-Trp/BCAAs and Depression in People with Poststroke Depression.

[Purpose] The purpose of the present study was to investigate the potential effects of circuit class training (CCT) on poststroke depression through changes in branched-chain amino acids (BCAAs) (isoleucine, leucine, and valine) and free-tryptophan (f-Trp). [Subjects] The study subjects were 40 stroke patients with major depressive disorder. The subjects were group-matched into an experimental and a control group according to sex, age, height, and weight. [Methods] The experimental CCT group performed gradual task-oriented CCT (80 min per session). The control group performed stretching exercises and weight bearing exercises (80 min per session). Both groups performed the exercises three times per week for eight weeks (24 sessions). Blood samples were collected immediately before the exercise (9:10 a.m.) and after the exercise (10:30 a.m.), every two weeks for eight weeks. [Results] The f-Trp/BCAAs ratio in the CCT group showed a significant increase compared to the control group over time. [Conclusion] The results show that the CCT may help to improve depression in people with poststroke depression (PSD).

A function-based framework for understanding biological systems.

Systems biology research is currently dominated by integrative, multidisciplinary approaches. Although important, these strategies lack an overarching systems perspective such as those used in engineering. We describe here the Axiomatic Design approach to system analysis and illustrate its utility in the study of biological systems. Axiomatic Design relates functions at all levels to the behavior of biological molecules and uses a Design Matrix to understand these relationships. Such an analysis reveals that robustness in many biological systems is achieved through the maintenance of functional independence of numerous subsystems. When the interlinking (coupling) of systems is required, biological systems impose a functional period in order to maximize successful operation of the system. Ultimately, the application of Axiomatic Design methods to the study of biological systems will aid in handling cross-scale models, identifying control points, and predicting system-wide effects of pharmacological agents.