Yuki Ishikawa

Evaluation of wearable gyroscope and accelerometer sensor (PocketIMU2) during walking and sit-to-stand motions

Recently healthcare of the elderly people has become a serious issue in medical and rehabilitation areas. In order to know their functional mobility and provide sufficient medical treatment, it is important to measure their body state precisely and objectively. Therefore we developed a wearable and wireless sensor of gyroscope and accelerometer (PocketIMU2) as an easy and precise measurement of human motions. In the sensor, we employed a small and high accurate LiNbO3 crystal to achieve joint angle computation with simple integration of angular velocity. In the current paper, we evaluate the accuracy of the sensor in two important basic motion, such as a walking and sit-to-stand motions. Computed joint angles of ankle, knee, and hip are compared to the reference data measured from a optical motion capture system in term of coefficients of correlation and root mean square error. As a result, coefficient of correlation showed very high value for all joint angles, and root mean square error was adequately small. This strongly supports the usage of our developed gyroscope and accelerometer sensor for monitoring human body movement for medical usage.

Analysis of muscle synergy contribution on human standing-up motion using a neuro-musculoskeletal model

It is important to understand the mechanism of human standing-up motion to improve the declined physical ability of the elderly people. This study employs the concept of muscle synergies (modular structure of coordinative muscle activation) to understand how humans coordinate their muscles to achieve the standing-up motion. Neuro-musculoskeletal model was developed to represent human body to generate standing-up motion. Using the developed model, forward dynamic simulation was used to analyze how humans utilized the muscle synergies to realize the motion. Results showed that the developed model could generate the standing-up motion with four muscle synergies rather than controlling individual muscles. Moreover, further analysis showed that three different strategies of the standing-up motion could be generated only by changing the start time of the particular muscle synergy.

Generation of human standing-up motion with muscle synergies using forward dynamic simulation

The standing-up motion is one of the most important activities of daily livings. In order to understand the strategy to achieve the standing-up motion, muscle synergy analysis is applied to the measured data during human standing-up motion. In addition, musculoskeletal model which consists of three body segments and nine muscles in lower limb is developed to ensure that the standing-up motion can be generated by muscle synergies. As a result, three muscle synergies have been extracted from the human standing-up motion, and each synergy strongly corresponded to characteristic kinematic events: momentum flexion, momentum transfer, and posture stabilization. Results of forward dynamic simulation show that the standing-up motion can be achieved by controlling time-varying weighting coefficient of three muscle synergies instead of controlling individual nine muscles.

Muscle Synergy Analysis of Human Standing-up Motion Using Forward Dynamic Simulation with Four Body Segment Model

Human motor behavior can be generated by distributed system. In this study, human standing-up motion is focused as an important daily activity. Especially, 13 muscle activation of lower body and trunk measured during human standing-up motion is decomposed into small numbers of modules of synchronized muscle activation called muscle synergy. Moreover human musculoskeletal model is developed with four rigid body segments based on dynamics and anatomical characteristics of human body. Forward dynamic simulation with the developed model showed that four muscle synergies had their own contribution toward body function: bending forward, moving the center of mass forward, extending whole body, and decelerating the center of mass. Results also indicated that combinations of four modules of synchronized muscle activation could generate human standing-up motion rather than controlling individual muscles.

Muscle Synergy Analysis of Human Standing-Up Motion with Different Chair Heights and Different Motion Speeds

Although standing-up motion is an important activity of daily living, it remains unclear how people perform the motion in different situations. As described in this paper, muscle synergy analysis is applied to standing-up motions performed at different circumstances, such as two different heights and at three different speeds. Results elucidated three invariant groups of synchronized muscle activations: The first synergy pulls the ankle and raises the hip. The second synergy extends the upper body. The third synergy stabilizes posture. Results also show that people controlled the activation coefficient of each synergy differently during all motions. The slower the standing-up motion is, the longer each synergy activates to adapt to the slower motion speed. Results of this study show that people use the same group of synchronized muscle activation and only control the activation coefficient to achieve adaptive standing-up motion.

Analysis of contribution of muscle synergies on sit-to-stand motion using musculoskeletal model

Recently, declining physical ability of elderly people has become an extremely important social issue. To improve their daily living activities, the standing-up motion is emphasized in this study as an important daily motion. Synergy analysis is applied to the standing-up motion to extract four important groups of muscle activations (synergies). Furthermore, the effect of synergies on body movement is calculated based on a musculoskeletal model of the human body. Results suggest that the first synergy works as preparation of the motion by pulling the ankle and flexing the hip. The second synergy controls the joint moment of the hip and knee joints to raise the hip and move the center of mass forward. The third synergy controls the ankle joint according to movement of the center of mass. The last synergy stabilizes the posture change from a seated to a standing position. Our findings imply that it is important to train those functional muscle activity to enhance the ability of standing-up motion.

Extraction and Evaluation of Proficiency in Bed Care Motion for Education Service of Nursing Skill

In the areas of care nursing, conventional physical skill education which has been conducted face-to-face prevents both experts and beginners from realizing the effects of their education and practice. In order to solve this problem, we aim to develop an effective skill education service of bed care motion with slide sheet which can prevent the outbreak of lumbago. In this study, we calculated the lumbar burden with measured body joint trajectory, foot reaction force, and muscle activities in the motion of experts and non-experts. Based on these analysis results, nursing skill was extracted and evaluated for skill education service.

Design and optimization of support structures for tactile feedback

Vibration motors are often used to generate tactile feedback to enhance human-machine interactions and provide information about the environment. We are interested in using these motors to enhance user feedback when wearing below-knee prostheses by providing informational cues via vibrations on the thigh. Our initial designs to hold the motors against the thigh resulted in a weak perception of vibration. We took an engineering approach to improve sensation by modeling the system and designing a new device that maximized skin displacement. Our results show the new suspended design increased skin displacement for both types of vibrational motors.

Analysis of Joint Correlation between Arm and Lower Body in Dart Throwing Motion

As the population continues to age, the number of elderly people requiring healthcare is increasing. In order to improve their physical function, they need to get physical training. There are activities which require integrated arm movements and lower body movements. However there are no quantitative testing methods of the degree of recovery for the coordination between arm movements and lower body movements. In this study, we focus on dart throwing motion as arm movements in lower body movements and suggest the quantitative evaluation of the coordination between arm movements and lower body movements in dart throwing motion. Normalized correlation coefficient (NCC) between arm and lower body was computed at different throwing distances. In addition the standard deviation of the NCC was computed in order to investigate the stability of the joint correlation evaluation. This analysis shows that the correlation between elbow and ankle, or between elbow and knee, are increased at throwing long distance. We suggest that the NCC between elbow angle and right knee angle may be used for the evaluation of the joint correlation between arm movements and lower body movements in dart throwing motion.

Linear chain aldehydes evoke calcium responses in B16 melanoma cells

Oxidative stress is involved in various physiological impairing stages, such as aging, diabetes, atherosclerosis, cirrhosis, and neurological disorders. Recent research indicates that aldehyde compounds derived from oxidized lipids increase in cancer patients compared to healthy individuals. Among of them, hexanal, a six-carbon liner chain aldehyde, is commonly found in cancer patients. Lipid oxidation products including aldehydes are in general chemically unstable and react with biological molecules such as proteins. The purpose of this study is to investigate effects of lipid-derived aldehydes and the related compounds on intracellular Ca2+ responses in B16 melanoma cells. Hexanal-induced [Ca2+]i elevation is observed in B16 cells in a dose dependent manner, but [Ca2+]i changes were observed neither in 3T3-L1 cells nor Caco-2 cells. Propanal, a chain length analogue of hexanal, elicited no change in [Ca2+]i, but nonanal initiated [Ca2+]i increases. Analogue compounds of hexanal failed to induce [Ca2+]i elevation. Furthermore, unsaturated aldehydes known as TRPA1 channel agonists also failed to alter [Ca2+]i levels in B16 melanoma cells. Pharmacological spectra using inhibitors against intracellular Ca2+ signaling suggest that hexanal-induced [Ca2+]i responses in B16 cells might be involved in TRP channels other than TRPA1. Our results suggest that saturated aliphatic chain aldehydes would be novel compounds for initiating [Ca2+]i increases through very strict recognitions of chain saturation, aldehydic base structures, and chain lengths in B16 melanoma cells. B16 cells would have sensing mechanisms for oxidative status and/or metabolic activities in their growth environment.