Sock-Type Wearable Sensor for Estimating Lower Leg Muscle Activity Using Distal EMG Signals.

Lower leg muscle activity contributes to body control; thus, monitoring lower leg muscle activity is beneficial to understand the body condition and prevent accidents such as falls. Amplitude features such as the mean absolute values of electromyography (EMG) are used widely for monitoring muscle activity. Garment-type EMG measurement systems use electrodes and they enable us to monitor muscle activity in daily life without any specific knowledge and the installation for electrode placement. However, garment-type measurement systems require a high compression area around the electrodes to prevent electrode displacement. This makes it difficult for users to wear such measurement systems. A less restraining wearable system, wherein the electrodes are placed around the ankle, is realized for target muscles widely distributed around the shank. The signals obtained from around the ankle are propagated biosignals from several muscles, and are referred to as distal EMG signals. Our objective is to develop a sock-type wearable sensor for estimating lower leg muscle activity using distal EMG signals. We propose a signal processing method based on multiple bandpass filters from the perspectives of noise separation and feature augmentation. We conducted an experiment for designing the hardware configuration, and three other experiments for evaluating the estimation accuracy and dependability of muscle activity analysis. Compared to the baseline based on a 20-500 Hz bandpass filter, the results indicated that the proposed system estimates muscle activity with higher accuracy. Experimental results suggest that lower leg muscle activity can be estimated using distal EMG signals.

Posture Feedback System with Wearable Speaker.

Maintaining good posture when using a laptop or a smartphone can prevent computer vision syndrome and text neck syndrome. However, it is difficult to remain aware of posture during an activity. Thus, wearable systems with posture feedback can help maintain good posture during daily activities. In this paper, we propose a posture feedback system that uses a commercial wearable speaker, which has been used for music and video conferencing when working from home. To judge a user's posture as good or poor, we focus on estimating the distance between the user's eyes and the screen when using a laptop and the neck tilt when using a smartphone. To estimate the distance, we use an active sensing method with ultrasound sent from a wearable speaker to a microphone on a laptop or a smartphone. The sound pressure of ultrasound changes depending on the distance between the wearable speaker and the microphone. In addition, an active sensing method can be used to estimate neck tilt because the sound pressure changes depending on the angle between the wearable speaker and the microphone. When the system judges the user's posture as poor, it will provide auditory feedback by applying digital audio effects to audible sounds (i.e., audio being listened to). Audio signal processing is implemented as a web application so users can use our system easily and immediately. We conducted three experiments to verify the feasibility of our proposed method. The sound pressure changed depending on the distance and angle between a wearable speaker and a microphone, and the system could judge posture as good or poor at almost 100 % under the experimental conditions.

Lower Limb Muscle Activity Control by using Jamming Footwear.

To change the lower limb muscle activities while walking, we propose a muscle activity controlling system that dynamically changes shoe insoles. We conducted a preliminary experiment on a prototype system to determine the system's validity. In this experiment, we analyzed how tibialis anterior and gastrocnemius muscle might change their activities depending on each insole condition. The results lead us to conclude that our system may affect changes in the duration percentage of tibialis anterior muscle activation when we change the heel part shape, and that it may change the maximum amplitude of gastrocnemius muscle activation when we change the arch part shape and hardness.