Koji Shimatani

Virtual light touch contact: A novel concept for mitigation of body sway

This paper proposes a novel concept called virtual light touch contact (VLTC), which helps to reduce human postural sway in standing and walking states. The VLTC system essentially creates a virtual partition around the user and enables estimation of the virtual force caused when the partition is touched. The resulting force data are fed back to the users fingertips in the form of vibrotactile stimulation, allowing sensation of the virtual partition in any location. To verify the validity of the proposed method, a prototype system was developed using motion-capture technology and a tactile stimulator, and preliminary experiments involving a healthy subject were conducted. The results indicated that the system is capable of helping to reduce the postural sway of the user during tandem (heel-to-toe) standing.

A standing-function evaluation method based on virtual light touch contact

This paper proposes a novel standing-function evaluation method based on virtual light touch contact. In this approach, a virtual partition is first created from measurements of the subjects trunk and finger positions. Random on/off control of virtual forces from the partition enables evaluation of standing function based on the presence or absence of somatic sensory stimulation to the fingers. Evaluation and comparison experiments were conducted with eight young subjects and six elderly subjects. The index values computed from the elderly subjects were standardized based on those of the young subjects. Among the results, values for indices such as the average vector of the center of pressure with elderly subjects were found to be larger than those with young subjects. All index values exhibited significant differences between the subject groups at the 1 or 5% level. The results suggest the validity of quantitative standing-function evaluation based on VLTC.

Effects of methods of descending stairs forwards versus backwards on knee joint force in patients with osteoarthritis of the knee: A clinical controlled study

BackgroundThe aim of this study was to investigate the kinetic characteristics of compensatory backward descending movement performed by patients with osteoarthritis of the knee.MethodsUsing a three-dimensional motion analysis system, we investigated lower extremity joint angles, joint moments, joint force of the support leg in forward and backward descending movements on stairs, and joint force of the leading leg at landing in 7 female patients with osteoarthritis of the knee.ResultsCompared with the forward descending movement, knee joint angle, joint moment and joint force of the support leg all decreased in the backward descending movement. Joint force of the leading leg at landing was also reduced in the backward descending movement. In addition, we confirmed that the center of body mass was mainly controlled by the knee and ankle joints in the forward descending movement, and by the hip joint in the backward descending movement.ConclusionsSince it has been reported that knee flexion angle and extensor muscle strength are decreased in patients with osteoarthritis of the knee, we believe that backward descending movement is an effective method to use the hip joint to compensate forthese functional defects. In addition, due to the decreased knee joint force both in the leading and support legs in backward descending movement, the effectiveness of compensatory motion for pain control and knee joint protection was also suggested.

Supporting Effects on Muscles of a Motion Assistive Wear Depending on the Fixture Position

1.はじめに 老化・疲労の影響により筋力が低下すると,怪 我・事故が発生する可能性が大きくなる.そこで 筋力を補助する役割を果たすサポーターが必要と なる.近年,サポートウェアが盛んに開発されて おり,さまざまな方法でサポート効果の計測が行 われている.従来研究では,トルクや筋電位, 力センサを計測することによりサポートウェアの 評価が行われているが,個人の骨格や筋肉量,体 型が,ウェアのサポート効果にどのように影響し ているのかは分かっていない.そこで本研究では、 動作補助パーツを組み込んだ筋骨格シミュレー ションにより補助効果を定量的に評価し,体型や 取付位置の違いが補助効果に与える影響を評価す るための手法について説明する. 2.動作補助パーツモデル作成 本研究では,ダイヤ工業(株)が市販している 機能性アンダーウェアDARWING における運動補助 効果の検証を行う.DARWING の表層部には伸縮性 素材(動作補助パーツ)が使用されており,バネ のように働くことで装着者の筋負担を軽減する効 果があるとされる.しかし着用する人の体格が変 わると動作補助パーツの身体に対する取付位置が 変わり,筋に対する補助効果に影響が出る可能性 がある.そこで動作補助パーツの性質をモデル化 し,それを様々な体格の筋骨格モデルに取り付け たときに既存の筋肉の活動にどのような影響が出 るのかを調べる. 図1は,荷重に対する動作補助パーツの伸長量 の特性と,計算の簡略化のためその特性を近似し たモデルの特性を示したものである.シミュレー ションによる評価を行うために図2に示す DARWINGの動作補助パーツの形状と特性を模した 動作補助パーツモデルを作成した. 図1 動作補助パーツとモデルの対荷重特性

Estimation of knee joint reaction force based on the plantar flexion resistance of an ankle-foot orthosis during gait

[Purpose] The purpose of this study was to investigate the effect of changing the plantar flexion resistance of an ankle-foot orthosis on knee joint reaction and knee muscle forces. Furthermore, the influence of an ankle-foot orthosis with an over-plantar flexion resistance function on knee joint reaction force was verified. [Participants and Methods] Ten healthy adult males walked under the following three conditions: (1) no ankle-foot orthosis, and with ankle-foot orthoses with (2) a strong and (3) a weak plantar flexion resistance (ankle-foot orthosis conditions). The knee flexion angle, quadricep muscle force, hamstring muscle force, and knee joint reaction force during the stance phase were measured using a motion analysis system, musculoskeletal model, and ankle-foot orthosis model. [Results] The peak knee joint reaction force, knee flexion angle, and quadricep muscle force in the early stance phase significantly increased in the strong plantar flexion resistance condition in comparison with the “no ankle-foot orthosis” condition. [Conclusion] Increased knee joint reaction force with over-plantar flexion resistance suggests that over-plantar flexion resistance causes various knee problems such as knee pain and knee osteoarthritis.

Biofeedback for Training Pelvic Floor Muscles with EMG Signals of Synergistic Muscles

Pelvic floor muscle (PFM) training is important in the treatment of stress urinary incontinence. In this study, biofeedback training was performed using electromyographic signals obtained in real time by a surface electrometer attached to the transverse abdominal muscles working in conjunction with the PFM. The low activity of the perineal muscles before training increased by an average of 20% points within 10 min after the start of training. This finding suggests that training of muscles indirectly involved in continence of urine may improve the functioning of the PFM.

A new approach to direct rehabilitation based on functional electrical stimulation and EMG classification

Extensive and focused physiotherapy is needed to help individuals with disabilities, such as hemiplegics, achieve natural physical movement involving the simultaneous use of various muscles. Here the authors outline a new approach to such work involving the use of FES (functional electrical stimulation) and EMG signals to help people with hemiplegia resulting from spinal injuries or cerebrovascular accidents (CVAs) achieve such muscle contraction and to enable related evaluation. The experiment performed as part of the study leveraged exponential functions to clarify the correlation between the current used for stimulation and the joint angles of the forearm. It was found that electrical stimuli and EMG signals can be used to transfer muscle contraction information between individuals.

Simplified Standing Function Evaluation System for Fall Prevention

This paper proposes a simplified standing-function evaluation system based on virtual light touch contact using a Wii balance board and a wearable VLTC device. In this system, a virtual partition by VLTC is first created from measurements of the subjects trunk and finger positions. Random on/off control of virtual forces from the partition enables evaluation of standing function based on the presence or absence of somatic sensory stimulation to the fingers. Evaluation and comparison experiments were conducted with 35 healthy male subjects. The results suggest that the proposed system allows to evaluate the standing function evaluation quantitavively.

A neural network based infant monitoring system to facilitate diagnosis of epileptic seizures

In this paper, we propose an infant monitoring system that automatically detects epileptic seizures in domestic and hospital environments. The proposed system measures the movements and electroencephalogram (EEG) signals of an infant using a video camera and an electroencephalograph. Seizure features are then extracted from the video images and EEG signals, and the evaluation indices based on medical knowledge are calculated from the features. The system employs a probabilistic neural network for the automatic detection of seizures, thereby allowing the choice/combination of evaluation indices appropriate for the environment via network training. We tested the system in simulated domestic and hospital environments. The validity of the proposed system was reinforced by the results of comparisons with clinical diagnoses.