The purpose of this study is to clarify the relationship between the center of pressure (COP) and the thickness of the tibialis anterior (TA) muscle during quiet standing by using an ultrasound imaging method. The TA muscle was electrically stimulated, and the displacement of the COP in the anterior－posterior direction was measured using the force plate. The TA muscle thicknesses of the superficial and deep compartments were estimated from the two-dimensional cross-correlation function of the echo images. The muscle thicknesses of the superficial and deep compartments were 11.9－12.7 mm and 22.6－24.2 mm, respectively. The deep compartment was thickened when the COP was posterior to the equilibrium point.

We investigated the nonlinearity of the abductor digiti minimi muscle in voluntary contraction. A healthy young male volunteer participated in the experiment. The electromyogram (EMG) of the abductor digiti minimi muscle was measured during voluntary contraction, and the voluntary contraction force (VCF) was measured with a force sensor. The participant窶冱 hand was fixed on a measurement table made of thermoplastic resin to fit his palm, so that he could move only his digitus minimus. The VCF and the target force were displayed in real time on an LCD display in front of the participant. The participant was instructed to track the target force. Finally, system identification was performed using the Hammerstein model, the input and output of which were the EMG and the VCF, respectively.

Observing cell nuclei in the 3D culture model was still challenging due to the limited penetration depth of lasers from the microscopes. Observation of deformation of cell nuclei is important because it is thought to modulate cellular functions. In this study, we have achieved optical clearing techniques for osteocytic spheroids using OptiPrep. Furthermore, we developed a novel 3D image analysis software to quantify the shape and position of the nuclei in the spheroids. As a result, we found out that the shape of cell nuclei was more sphere-shaped inside the spheroid. The combination of optical clearing and 3D image analysis techniques is expected to become powerful tools in the field of 3D culture models.

A close relationship exists between lesions in the peripheral circulation and angiopathy in the central organs. For the diagnosis of angiopathy, quantitative methods based on the pulse wave transit time, etc., can be used. For lesions in the peripheral circulation, however, few established diagnostic methods exist. According to the Windkessel model, noninvasive measurements can be performed using the radial arterial pressure waveform (RAPW) as the input signal and fingertip photoplethysmography (PPG), which detects changed in the peripheral blood volume, as the output signal. A fast Fourier transform (FFT) is conducted on both the waveforms. By comparing the amplitudes of the measured frequency components, a time constant is then calculated from the frequency transfer characteristics that are thus obtained. Assuming that this time constant can be used as a quantitative index of peripheral circulation, the present study sought to prove the effectiveness in this diagnosis method of angiopathy.

Appropriate pharmacological intervention in the setting of acute heart failure (AHF) presents unique challenges for each patient. Early identification of patients who will not respond to pharmacological therapy alone would be crucial in the clinician窶冱 decision to provide additional therapy such as mechanical support. This paper proposes the concept of drug determined reachability, the maximum range that multiple drug infusions can span cardiovascular parameters. Our approach models how multiple drug infusion affects key cardiovascular parameters, while considering dosage limitations, multi-dependencies of multiple drugs, and nonlinear interaction of drugs to the gradient of the Frank-Starling Curve. The simulation of drug determined reachability sheds light on the effectiveness or limitation of closed-loop therapeutic systems for acute heart failure treatment depending on each patient窶冱 pathophysiological scenario.

In our laboratory, a mathematical model of the decision-making process was constructed and the individual differences of the process in gold trading were represented reasonably, and the learning process was indicated as the convergence of model parameters. However, the learning process in decision-making process has not been identified using a mathematical as far as authors know. Thus, in this research, the learning process was examined using the already constructed model which consist of proposal, integrator, and derivative elements and compared the individual differences in decision-making between in gold trading game and in forex trading game. According to the results, the learning process of all players were represented reasonably. Also, the individual differences in learning process were represented so clearly that the difference of difficulty in learning was grasped between in gold trading and forex trading.

Abstract: In our previous study, low-frequency, short-duration high-intensity interval training (HIIT) was performed for 8-12 weeks in untrained healthy subjects (Once a week, 3 sets, less than 10 minutes total training time), and the results showed that regardless of training intensity, maximal oxygen uptake (VO2max) and exhaustion time during maximal exercise increased by 6-13% and 33-89%. However, it is not clear whether similar results can be obtained in athletes who perform strenuous exercise on a daily basis. The purpose of this study was to investigate the effects of HIIT at different intensities on cardiorespiratory function and exercise performance during maximal exercise in college athletes. The subjects were 13 male college student athletes. The training was determined for each individual using a ramp exercise test to determine the maximum load, divided into 80% (TG80%) or 90% (TG90%) intensity training groups. and conducted once a week for 8 weeks. The training consisted of three bouts of exercises to volitional fatigue at TG80% and TG90% maximum work rate. Regardless different of training intensity, increased VO2max (TG80%: +11%, TG90%: +12%) and maximal work rate during the ramp exercise test (TG80%: +13%, TG90%: +16%) in both groups were observed after HIIT (P <0.01). Maximal exhaustion time during the HIIT (TG80%: +110%, TG90%: +95%) was also significantly prolonged in both groups after training (P < 0.05). In conclusion, low-frequency for short-duration once a week HIIT improves cardiorespiratory function and exercise performance during maximal exercise for athletes, regardless of its training intensity. These findings will contribute to the development of new and optimal exercise programs for various age groups and people, even competitive athletes.

This study estimated the stiffness of the medial gastrocnemius muscle and ankle joint with decreased somatosensory input from the soles due to cooling. Two healthy young male volunteers participated in the experiment. The participants’ soles and the surface of the force plate were iced. Each participant stood quietly on the force plate. Electrical stimulation was applied to the medial gastrocnemius muscle. The center of pressure (COP) was measured with the force plate. The fluctuation of the COP due to electrical stimulation was extracted using a Kalman filter. The transfer function from the stimulation to the fluctuation was calculated using a system identification method. The poles of the transfer function were used to estimate the muscle and joint stiffness. The muscle and joint stiffness was decreased by cooling the soles.

Mathematical models have been used to describe the complex physiological processes of light response in photoreceptors for decades. However, the detailed model has not yet been invented. In this study, we aimed to construct a new photoreceptor model for estimating the chemical and electrical responses to a light stimulus. The proposed model was developed from our previous works (Takeda et at. 2021; Ito et al. 2017; Sato et al. 2017) based on the ionic current model of vertebrate photoreceptor incorporating the classical Goldman-Hodgkin-Katz constant field equation. The novel model successfully describes the biophysical processes of ionic current dynamics during the light responses. Furthermore, the changes in intracellular ion concentrations are in good agreement with theoretical works and experimental data. This study provides an effective framework for future experimental studies and serves as a powerful guideline for better understanding of the pathophysiology of the retina and improving the new treatment studies.