九州大学 研究者情報
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AN QI(あん ち) データ更新日:2021.06.18

准教授 /  システム情報科学研究院 情報知能工学部門


原著論文
1. Kazunori Yoshida, Qi An, Hiroyuki Hamada, Hiroshi Yamakawa, Yusuke Tamura, Atsushi Yamashita, and Hajime Asama, Artificial Neural Network that Modifies Muscle Activity in Sit-to-Stand Motion Using Sensory Input, Advanced Robotics, 35, 11, 2021.07.
2. Hiroki Kogami, Qi An, Ningjia Yang, Ruoxi Wang, Kazunori Yoshida, Hiroyuki Hamada, Hiroshi Yamakawa, Yusuke Tamura, Shingo Shimoda, Hiroshi Yamasaki, Moeka Sonoo, Fady Alnajjar, Noriaki Hattori, Koji Takahashi, Takanori Fujii, Hironori Otomune, Ichiro Miyai, Atsushi Yamashita, and Hajime Asama, Analysis of muscle synergy and kinematics in sit-to-stand motion of hemiplegic patients in subacute period, Advanced Robotics, 35, 11, 2021.07.
3. Kei Aoyagi, Wen Wen, Qi An, Shunsuke Hamasaki, Hiroshi Yamakawa, Yusuke Tamura, Atsushi Yamashita and Hajime Asama, Modified sensory feedback enhances the sense of agency during continuous body movements in virtual reality, Scientific Reports, https://doi.org/10.1038/s41598-021-82154-y, 11, 2021.01, [URL].
4. Ruoxi Wang, Qi An, Ningjia Yang, Hiroki Kogami, Kazunori Yoshida, Hiroyuki Hamada, Shingo Shimoda, Hiroshi Yamasaki, Moeka Sonoo, Fady Alnajjar, Noriaki Hattori, Kouji Takahashi, Takanori Fujii, Hironori Otomune, Ichiro Miyai, Atsushi Yamashita and Hajime Asama, Muscle Tension Analysis in Stroke Patient Sit-to-Stand Motion by Joint Torque-Based Normalization, 5th International Conference on NeuroRehabilitation (ICNR2020), 2020.11.
5. Ningjia Yang, Qi An, Hiroki Kogami, Hiroshi Yamakawa, Yusuke Tamura, Kouji Takahashi, Makoto Kinomoto, Hiroshi Yamasaki, Matti Itkonen, Fady Shibata-Alnajjar, Shingo Shimoda, Noriaki Hattori, Takanori Fujii, Hironori Otomune, Ichiro Miyai, Atsushi Yamashita and Hajime Asama, Temporal Muscle Synergy Features Estimate Effects of Short-Term Rehabilitation in Sit-to-Stand of Post-Stroke Patients, IEEE Robotics and Automation Letters, 10.1109/LRA.2020.2969942, 5, 2, 1796-1802, 2020.04, [URL], Sit-to-stand (STS) motion is an important daily activity and many post-stroke patients have difficulty in performing the STS motion. Post-stroke patients who can perform STS independently, still utilize four muscle synergies (synchronized muscle activation) as seen in healthy people. In addition, temporal muscle synergy features can reflect motor impairment of post-stroke patients. However, it has been unclear whether post-stroke patients improve their STS movements in short-term rehabilitation and which muscle synergy features can estimate this improvement. Here, we demonstrate that temporal features of muscle synergies which contribute to body extension and balance maintenance can estimate the effect of short-term rehabilitation based on machine learning methods. By analyzing muscle synergies of post-stroke patients (n = 33) before and with the intervention of physical therapists, we found that about half of the patients who were severely impaired, improved activation timing of muscle synergy to raise the hip with the intervention. Additionally, we identified the temporal features that can estimate whether severely impaired post-stroke patients improve. We conclude that temporal features of muscle synergies can estimate the motor recovery in short-term rehabilitation of post-stroke patients. This finding may lead to new rehabilitation strategies for post-stroke patients that focus on improving activation timing of different muscle synergies..
6. Ningjia Yang, Qi An, Hiroki Kogami, Hiroshi Yamakawa, Yusuke Tamura, Kouji Takahashi, Makoto Kinomoto, Hiroshi Yamasaki, Matti Itkonen, Fady Shibata-Alnajjar, Shingo Shimoda, Noriaki Hattori, Takanori Fujii, Hironori Otomune, Ichiro Miyai, Atsushi Yamashita, Hajime Asama, Temporal Features of Muscle Synergies in Sit-to-Stand Motion Reflect the Motor Impairment of Post-Stroke Patients, IEEE Transactions on Neural Systems and Rehabilitation Engineering, 10.1109/TNSRE.2019.2939193, 27, 10, 2118-2127, 2019.10, [URL], Sit-to-stand (STS) motion is an important daily activity, and many post-stroke patients have difficulty performing STS motion. Previous studies found that there are four muscle synergies (synchronized muscle activations) in the STS motion of healthy adults. However, for post-stroke patients, it is unclear whether muscle synergies change and which features primarily reflect motor impairment. Here, we use a machine learning method to demonstrate that temporal features in two muscle synergies that contribute to hip rising and balance maintenance motion reflect the motor impairment of post-stroke patients. Analyzing the muscle synergies of age-matched healthy elderly people ( $n = 12$ ) and post-stroke patients ( $n = 33$ ), we found that the same four muscle synergies could account for the muscle activity of post-stroke patients. Also, we were able to distinguish post-stroke patients from healthy people on the basis of the temporal features of these muscle synergies. Furthermore, these temporal features were found to correlate with motor impairment of post-stroke patients. We conclude that post-stroke patients can still utilize the same number of muscle synergies as healthy people, but the temporal structure of muscle synergies changes as a result of motor impairment. This could lead to a new rehabilitation strategy for post-stroke patients that focuses on activation timing of muscle synergies..
7. Hiroshi R. Yamasaki, Qi An, Makoto Kinomoto, Koji Takahashi, Takanori Fujii, Hiroki Kogami, Ningjia Yang, Hiroshi Yamakawa, Yusuke Tamura, Matti Itkonen, Moeka Sonoo, Fady S.K. Alnajjar, Atsushi Yamashita, Hironori Otomune, Noriaki Hattori, Hajime Asama, Ichiro Miyai, Shingo Shimoda, Organization of functional modularity in sitting balance response and gait performance after stroke, Clinical Biomechanics, 10.1016/j.clinbiomech.2019.04.022, 67, 61-69, 2019.07, [URL], Background: Recovery of postural adjustment, especially when seated, is important for performing activities of daily living after stroke. However, conventional clinical measures provide little insight into a common strategy for dynamic sitting balance and gait. We aimed to evaluate functional re-organization of posture and ambulatory performance after stroke. Methods: The subjects of the study included 5 healthy men and 21 post-stroke patients. The spatiotemporal modular organization of ground reaction forces during a balance task in which the leg on the non-affected side was lifted off the ground while seated was quantified by using complex principal component analysis. Findings: A 3% decrease in the temporal strength of the primary module in post-stroke patients was an independent predictor of gait performance in the hospital setting with high sensitivity and specificity. Tuning of the temporal strength was accompanied by the recovery of sitting and ambulation. Interpretation: Our findings suggest that evaluation of the modular characteristics of ground reaction forces during a sitting balance task allows us to predict recovery and functional adaptation through daily physical rehabilitation..
8. Shunsuke Hamasaki, Qi An, Wen Wen, Yusuke Tamura, Hiroshi Yamakawa, Satoshi Unenaka, Satoshi Shibuya, Yukari Ohki, Atsushi Yamashita, Hajime Asama, Changes in body representation of the human upper limb as a function of movement and visual hand position, Journal of Advanced Computational Intelligence and Intelligent Informatics, 10.20965/jaciii.2019.p0196, 23, 2, 196-208, 2019.03, [URL], Several disease presentations are linked to a mismatch between the real body and the body’s internal representation of itself. In order to develop effective rehabilitation therapies, it is necessary to understand the mechanisms underlying changes in body representation. In this study, we focused on changes in body representation of the upper limb as a large part of the body and investigated the conditions under which such changes occur. Participants were presented four conditions which differentially affected their sense of ownership and agency, including a movement condition related to their sense of agency, and a visual hand information condition related to the sense of ownership. In the experiment, participants were asked to move their upper limb forward and backward on a manipulandum. Results of the study showed that visual hand position affected changes in body representation relevant to both conscious and unconscious body parts. In addition, changes in the representation of the unconscious body part occurred with, and were dependent on, active movement..
9. Qi An, Yuki Ishikawa, Wen Wen, Shu Ishiguro, Koji Ohata, Hiroshi Yamakawa, Yusuke Tamura, Atsushi Yamashita, Hajime Asama, Skill abstraction of physical therapists in hemiplegia patient rehabilitation using awalking assist robot, International Journal of Automation Technology, 10.20965/ijat.2019.p0271, 13, 2, 271-278, 2019.03, [URL], Improving the walking functions of hemiplegia patients after a stroke or brain injury is an important rehabilitation challenge. Recently, walking assist robots have been introduced in advanced rehabilitation facilities as a way to improve the efficiency of patient rehabilitation and restore their walking functions. Expert therapists can apply this device on different patients; however, such application mainly depends on the therapist’s tacit knowledge. Thus, it is often harder for novice therapists to apply such devices on different types of patients. Consequently, effective use of a walking assist robot has become a new patient rehabilitation skill. Taking rehabilitation as a service provided by medical doctors or therapists to their patients, this study aims to improve the quality of the rehabilitation service. In particular, the objective of this study is to abstract the rehabilitation skill of expert therapists in using a walking assist robot by applying a service science methodology known as skill education. Skill abstraction was performed by interviewing an expert therapist. From this interview, it was found that the expert therapist classified hemiplegia patients into four different classes. Using videos of patients walking, further analysis revealed the expert’s tacit knowledge, which was indicated by differences observed among these four groups in particular phases of the patients’ walking patterns. This study shows that by successfully obtaining explicit knowledge of part of a rehabilitation skill by using a walking assist robot (which until now was a tacit knowledge of experts), and then organizing the acquired explicit knowledge, even non-experts can easily reproduce the skill of experts in new patient rehabilitation..
10. Izumu Hosoi, Etsuko Kobayashi, Song Ho Chang, Takumi Matsumoto, Qi An, Emi Anzai, Yuji Ohta, Ichiro Sakuma, Development of intraoperative plantar pressure measuring system considering weight bearing axis, International Journal of Computer Assisted Radiology and Surgery, 10.1007/s11548-018-1862-z, 14, 2, 385-395, 2019.02, [URL], Purpose: Surgical reconstructions in three dimensions are needed for treatment of foot and ankle deformities. However, surgical results might be influenced by the skill and experience of doctors which complement the limited information for reconstructions in three dimensions. To solve these, studies were carried out to measure plantar pressure distribution during surgery. Though, it was impossible to accurately measure plantar pressure distribution accurately during operation. Therefore, we proposed an intraoperative plantar pressure measurement (IPPM) device that enables proper navigation in the push direction. Methods: For this purpose, first, we investigated how the physiological load axis passes through the human body to identify the pushing direction of the pressure sensor of the device toward the patient’s foot. In particular, we hypothesized that the physiological load axis passes through the femoral head center and we evaluated this in a measurement experiment with nine healthy subjects. Second, based on these results, we developed the IPPM device that has two force sensors to identify the pushing direction toward the femoral head center and a conductive ink sensor to measure plantar pressure distribution. Finally, we conducted the experiments with nine healthy subjects and two users. Results: From the first experimental results, the physiological load axis was found to pass through the femoral head center in normal standing posture. From the evaluation experiment, there are no significant differences statistically in plantar pressure distributions between the conditions of using IPPM device and without using it for both a medical student and a surgeon. However, in some cases the plantar pressure distribution can be reproduced similarly to that of the standing posture, and also from the evaluation experiment concerning the relation between CoP position and NCC, the NCC tends to increase when the position of the CoP is closer to that at the standing posture. Conclusion: The IPPM device has possibility to reproduce the plantar pressure distribution during surgery and prevent the recurrence of surgical complications..
11. Kazunori Yoshida, Qi An, Arito Yozu, Ryosuke Chiba, Kaoru Takakusaki, Hiroshi Yamakawa, Yusuke Tamura, Atsushi Yamashita, Hajime Asama, Visual and vestibular inputs affect muscle synergies responsible for body extension and stabilization in sit-to-stand motion, Frontiers in Neuroscience, 10.3389/fnins.2018.01042, 13, JAN, 2019, [URL], The sit-to-stand motion is a common movement in daily life and understanding the mechanism of the sit-to-stand motion is important. Our previous study shows that four muscle synergies can characterize the sit-to-stand motion, and they have specific roles, such as upper body flexion, rising from a chair, body extension, and posture stabilization. The time-varying weight of these synergies are changed to achieve adaptive movement. However, the relationship between sensory input and the activation of the muscle synergies is not completely understood. In this paper, we aim to clarify how vestibular and visual inputs affect the muscle synergy in sit-to-stand motion. To address this, we conducted experiments as follows. Muscle activity, body kinematics, and ground reaction force were measured for the sit-to-stand motion under three different conditions: control, visual-disturbance, and vestibular-disturbance conditions. Under the control condition, the participants stood without any intervention. Under the visual-disturbance condition, the participants wore convex lens glasses and performed the sit-to-stand motion in a dark room. Under the vestibular-disturbance condition, a caloric test was performed. Muscle synergies were calculated for these three conditions using non-negative matrix factorization. We examined whether the same four muscle synergies were employed under each condition, and the changes in the time-varying coefficients were determined. These experiments were conducted on seven healthy, young participants. It was found that four muscle synergies could explain the muscle activity in the sit-to-stand motion under the three conditions. However, there were significant differences in the time-varying weight coefficients. When the visual input was disturbed, a larger amplitude was found for the muscle synergy that activated mostly in the final posture stabilization phase of the sit-to-stand motion. Under vestibular-disturbance condition, a longer activation was observed for the synergies that extended the entire body and led to posture stabilization. The results implied that during human sit-to-stand motion, visual input has less contribution to alter or correct activation of muscle synergies until the last phase. On the other hand, duration of muscle synergies after the buttocks leave are prolonged in order to adapt to the unstable condition in which sense of verticality is decreased under vestibular-disturbance..
12. Wen Wen, Rin Minohara, Shunsuke Hamasaki, Takaki Maeda, Qi An, Yusuke Tamura, Hiroshi Yamakawa, Atsushi Yamashita, Hajime Asama, The Readiness Potential Reflects the Reliability of Action Consequence, Scientific reports, 10.1038/s41598-018-30410-z, 8, 1, 2018.12, [URL], Humans are capable of associating actions with their respective consequences if there is reliable contingency between them. The present study examined the link between the reliability of action consequence and the readiness potential (RP), which is a negative potential observed from about 1–2 s prior to the onset of an action with electroencephalography. In a condition of constant outcome, the participants’ voluntary action always triggered beep sounds; thus, they were able to perceive the contingency between their action and the sound. In contrast, in a condition of inconstant outcome, the participants’ actions only triggered the sound in half the trials. We found that both the early and late RPs were larger in the condition of constant compared to the condition of inconstant outcome. Our results showed that the RPs preceding the voluntary action reflected the reliability of action consequence. In other words, the action-effect contingency enhanced neural activities prior to the action..
13. Hiroki Kogami, Qi An, Ningjia Yang, Hiroshi Yamakawa, Yusuke Tamura, Atsushi Yamashita, Hajime Asama, Shingo Shimoda, Hiroshi Yamasaki, Matti Itkonen, Fady Shibata-Alnajjar, Noriaki Hattori, Makoto Kinomoto, Kouji Takahashi, Takanori Fujii, Hironori Otomune, Ichiro Miyai, Effect of Physical Therapy on Muscle Synergy Structure during Standing-Up Motion of Hemiplegic Patients, IEEE Robotics and Automation Letters, 10.1109/LRA.2018.2811050, 3, 3, 2229-2236, 2018.07, [URL], Stroke patients suffer from declined physical ability, and it is important to analyze rehabilitation intervention and clarify its effect on the motion of patients. In this study, the effect of intervention on the standing-up motion of stroke patients is investigated. First, the intervention timing of a physical therapist (PT) is analyzed quantitatively from the muscle activity of upper limbs during therapy. Next, the intervention effect is evaluated based on body kinematics and muscle synergy. In this study, twenty trials are conducted, in which the standing-up motion of hemiplegic patients (n=12) is measured with and without the intervention by a PT. The results show that PTs teach hemiplegic patients the timing of lifting their buttocks during standing-up motion. Furthermore, it has been found that this intervention could improve the standing-up motion, although stroke patients had inadequate muscle synergy structure. In particular, some patients had delayed activation of the synergy and they could only stood up after they moved their center of mass toward their feet. However, the intervention by PTs could induce earlier activation of the synergy. Moreover, the intervention could properly shorten the activation duration of muscle synergy for those who had unusually inappropriate longer activation of synergy. These results imply that disordered and inadequate muscle synergy structure can be improved by proper intervention, and this study contributes to the further development of new rehabilitation methodologies..
14. Qi An, Junki Nakagawa, Junko Yasuda, Wen Wen, Hiroshi Yamakawa, Atsushi Yamashita, Hajime Asama, Skill extraction from nursing care service using sliding sheet, International Journal of Automation Technology, 10.20965/ijat.2018.p0533, 12, 4, 533-541, 2018.07, [URL], Back pain has been a serious problem for novice nurses who care for bedridden patients. To avoid back pain, placing a slippery sliding sheet beneath a patient has been suggested so that nurses can pull it when repositioning the patient rather than lifting the patient. However, inappropriate use of the sheet may not reduce lumbar pain. Therefore, it is important to identify skills required for novice nurses to perform bed care movements using a sliding sheet. This study firstly performed interview to obtain useful knowledge from expert nurses who are skilled in using a sliding sheet. Next, a simulation study was then conducted to determine specific bed care movements that would minimize lumbar joint moment associated with lumbar pain. The simulated and expert movements were compared to validate whether expert movements decreases lumbar joint moment. Finally, a novice participant was taught these expert movements, and the educational effect of using these skills was validated. Our results showed that the experts used characteristic movements, keeping the upper arm and trunk stabilized and utilizing a shift in body weight, when performing bed care movements with the sliding sheet. Additionally, the expert movements and simulated movements were shown to be similar. This result confirmed that expert movements could contribute to reducing lumbar joint moments. Moreover, a novice participant could decrease lumbar moment using skills derived from effective education..
15. Shunsuke Hamasaki, Qi An, Masataka Murabayashi, Yusuke Tamura, Hiroshi Yamakawa, Atsushi Yamashita, Hajime Asama, Evaluation of the effect of prime stimulus on sense of agency in stop operation of the object in circular motion, Journal of Advanced Computational Intelligence and Intelligent Informatics, 10.20965/jaciii.2017.p1161, 21, 7, 1161-1171, 2017.11, [URL], Human cognitive mechanisms have been studied for the design of user-friendly interfaces. One of the key issues is a sense of agency, which is defined as the sense that "I am the one who is causing this action." The user interface is important; it can alter the feeling of sense of agency. In this research, we focus on a prime stimulus and evaluate the effect thereof by experiments with participants. A ball moves in a circle on a monitor at a constant speed and participants stop it by pushing a key. They were given both prime stimulus and feedback stimulus and indicated if they were the agent who stopped the ball, i.e., they felt a sense of agency. From the results of the experiment, we found that the prime stimulus can have both a positive and negative influence on the sense of agency when human prediction is unreliable..
16. Qi An, Hiroshi Yamakawa, Atsushi Yamashita, Hajime Asama, Different Temporal Structure of Muscle Synergy Between Sit-to-Walk and Sit-to-Stand Motions in Human Standing Leg, Biosystems and Biorobotics, 10.1007/978-3-319-46669-9_151, 933-937, 2017.01, [URL], Humans do not only perform individual motion separately, but they transit motions from one to another. It has been widely known that human sit-to-stand and walking motions are composed of four and five muscle synergies, but it is not clarified how humans utilize these muscle synergies to generate sit-to-walk motion. This study conducted a measurement experiment to identify muscle synergy structure in standing leg during the sit-to-walk motion. Results showed that the same muscle synergy of sit-to-stand and walking could explain sit-to-walk motion. Three of four synergies in sit-to-stand was not significant different but the last synergy was adaptively changed in order to shorten the time of postural stabilization to initiate stepping motion..
17. Yuki Ishikawa, Qi An, Junki Nakagawa, Hiroyuki Oka, Tetsuro Yasui, Michio Tojima, Haruhi Inokuchi, Nobuhiko Haga, Hiroshi Yamakawa, Yusuke Tamura, Atsushi Yamashita, Hajime Asama, Gait analysis of patients with knee osteoarthritis by using elevation angle
confirmation of the planar law and analysis of angular difference in the approximate plane, Advanced Robotics, 10.1080/01691864.2016.1229217, 31, 1-2, 68-79, 2017.01, [URL], Evaluating knee osteoarthritis is an important issue. Gait pattern has been suggested to be related to the progression of knee osteoarthritis; however, there are only a few studies elucidating the motion features associated with knee osteoarthritis. Therefore, our objective is to analyze the elevation angle of patients with knee osteoarthritis during gait and to clarify the movement features by an approximate plane of the elevation angle. As a result, the same planar law could be applied to patients with knee osteoarthritis as well as to healthy people. The patients have approximate plane slopes that differ from that of healthy people. Our validation results have shown that these angular differences can distinguish between the patients and healthy people..
18. Ningjia Yang, Qi An, Hiroshi Yamakawa, Yusuke Tamura, Atsushi Yamashita, Hajime Asama, Muscle synergy structure using different strategies in human standing-up motion, Advanced Robotics, 10.1080/01691864.2016.1238781, 31, 1-2, 40-54, 2017.01, [URL], Standing-up motion is an important daily activity. It has been known that humans can employ different strategies to stand up from a chair, but it was not clear how people control their redundant muscles to achieve different strategies. This study employs the concept of muscle synergy which suggests that humans utilize the small number of modules (called muscle synergy) to generate the movements. This study uses two approaches to understand how humans generate different movements. Firstly, measurement experiment was performed to investigate the muscle synergy structure during different strategies.Next, the finding from themeasurement experiment is validated through the forward dynamic simulation using our developed neuromusculoskeletal model. Both of our results from simulation study and measurement experiment showed that four muscle synergies could generate standing-up motion. However, they adaptively changed the start time of a certain synergy to achieve different strategies..
19. Wen Wen, Katsutoshi Muramatsu, Shunsuke Hamasaki, Qi An, Hiroshi Yamakawa, Yusuke Tamura, Atsushi Yamashita, Hajime Asama, Goal-directed movement enhances body representation updating, Frontiers in Human Neuroscience, 10.3389/fnhum.2016.00329, 10, 2016.06, [URL], Body representation refers to perception, memory, and cognition related to the body and is updated continuously by sensory input. The present study examined the influence of goals on body representation updating with two experiments of the rubber hand paradigm. In the experiments, participants moved their hidden left hands forward and backward either in response to instruction to touch a virtual object or without any specific goal, while a virtual left hand was presented 250 mm above the real hand and moved in synchrony with the real hand. Participants then provided information concerning the perceived heights of their real left hands and rated their sense of agency and ownership of the virtual hand. Results of Experiment 1 showed that when participants moved their hands with the goal of touching a virtual object and received feedback indicating goal attainment, the perceived positions of their real hands shifted more toward that of the virtual hand relative to that in the condition without a goal, indicating that their body representations underwent greater modification. Furthermore, results of Experiment 2 showed that the effect of goal-directed movement occurred in the active condition, in which participants moved their own hands, but did not occur in the passive condition, in which participants’ hands were moved by the experimenter. Therefore, we concluded that the sense of agency probably contributed to the updating of body representation involving goal-directed movement..
20. 安琪, 柳井香史朗, 中川純希, 温文, 山川博司, 山下淳, 淺間一, 実映像と筋活動の重畳表示によるローイング動作教育システム, 日本機械学会論文集, 2016.02.
21. Kohei Hanatani, Hiroshi Yamakawa, Yuki Ishikawa, Qi An, Atsushi Yamashita, Hajime Asama, Development of stress measurement system during human stand-up motion using accurate shape knee joint model, Seimitsu Kogaku Kaishi/Journal of the Japan Society for Precision Engineering, 10.2493/jjspe.81.99, 81, 1, 99-104, 2015.01, [URL], Recently, the knee osteoarthritis (OA) patients are increasing, and their qualities of life would be worsen. In order to cope with this, clarifying the mechanism of the knee OA is important, so it is needed to inspect knee joints for understanding of the disease. In this study, the new experiment system was developed to measure knee femur-tibia joint contact pressure distribution during human stand-up motion using knee joint model. Accurate shape knee joint model was fabricated from high polymer material with the use of 3D printer based on human medical images. Knee joint kinematics and joint force during human stand-up motion were reproduced respectively by a robot manipulator and air cylinders. Pressure distribution of knee joint model was measured statically and dynamically, and it was found that medial pressure on the tibial plateau was higher than lateral one, which corresponds with the clinical observation. Therefore, the new proposed method is feasible to investigate knee joints..
22. Junki Nakagawa, Qi An, Yuki Ishikawa, Hiroyuki Oka, Kaoru Takakusaki, Hiroshi Yamakawa, Atsushi Yamashita and Hajime Asama, Analysis of Human Motor Skill in Dart Throwing Motion at Different Distance, SICE Journal of Control, Measurement, and System Integration, 2015.01.
23. Qi An, Yuki Ishikawa, Junki Nakagawa, Hiroyuki Oka, Hiroshi Yamakawa, Atsushi Yamashita, Hajime Asama, Measurement of just noticeable difference of hip joint for implementation of self-efficacy
In active and passive sensation and in different speed, Advanced Robotics, 10.1080/01691864.2013.876938, 28, 7, 505-511, 2014.04, [URL], Self-efficacy, which is a belief to achieve a goal, is important for sufficient enhancement of physical ability of elderly people. For implementation of self-efficacy to assistive systems, it is necessary to subliminally change reference trajectories of the system within the range at which people cannot recognize the difference (just-noticeable difference: JND). This study clarified that elderly people have weaker position sense rather than young people when they are moved passively in relatively fast speed. New reference hip trajectories are computed to gradually extend hip flexion of human standing-up motion based on the measured JND..
24. 安琪, 石川雄己, 舩戸徹郎, 青井伸也, 岡敬之, 山川博司, 山下淳, 淺間一, 座面高と速度の異なるヒト起立動作における筋シナジー解析, 計測自動制御学会論文集, 2014.08, In order to understand human motor function, it is necessary to clarify how humans achieve adaptive motions regarding to external environment or their own purpose. This study analyzes human standing-up motion in different chair seat heights and motion speeds using muscle synergy analysis to find important modules to achieve the movement. Muscle synergy is determined from measured eight muscle activations (n=10), and relationship between muscle synergy and body kinematics is clarified. As a result, invariant three muscle synergies were found in human standing-up motion regardless of different seat heights and motion speeds. On the other hand, amplitude and duration of time-varying activation of muscle synergies were properly adujusted to enviromental change. Moreover, it was observed that time-varying activations were strongly corresponded to characteristic kinematic event of standing-up motion. This result implies that humans can achieve the adaptive standing-up motion mainly by controlling time-varying activation of three muscle synergies..
25. Qi An, Yusuke Ikemoto, Hajime Asama, Muscle synergy analysis between young and elderly people in standing-up motion, Journal of Robotics and Mechatronics, 10.20965/jrm.2013.p1038, 25, 6, 1038-1049, 2013.12, [URL], Standing up is fundamental to daily activities of the elderly. It is necessary both to enhance muscle strength and to strengthen muscle coordination for improvement of their motor function. In this paper, we extract important data related to muscle coordination, called synergy, to perform standing motion by young and elderly participants. The contribution of muscle synergy to body kinematics is calculated through neural networks that estimate joint torque and body kinematics. To explain deficient motor function in elderly persons, extracted synergy is classified into 4 clusters based on how synergy contribute to body kinematics. Cluster analysis explains that elderly participants have weaker synergy than young persons in bending their backs to generate momentum. Compared to younger persons, older persons require additional muscle coordination to stabilize posture after standing-up in order to avoid falling..
26. Cara E. Stepp, Qi An, Yoky Matsuoka, Repeated training with augmentative vibrotactile feedback increases object manipulation performance, PloS one, 10.1371/journal.pone.0032743, 7, 2, 2012.02, [URL], Most users of prosthetic hands must rely on visual feedback alone, which requires visual attention and cognitive resources. Providing haptic feedback of variables relevant to manipulation, such as contact force, may thus improve the usability of prosthetic hands for tasks of daily living. Vibrotactile stimulation was explored as a feedback modality in ten unimpaired participants across eight sessions in a two-week period. Participants used their right index finger to perform a virtual object manipulation task with both visual and augmentative vibrotactile feedback related to force. Through repeated training, participants were able to learn to use the vibrotactile feedback to significantly improve object manipulation. Removal of vibrotactile feedback in session 8 significantly reduced task performance. These results suggest that vibrotactile feedback paired with training may enhance the manipulation ability of prosthetic hand users without the need for more invasive strategies..

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