Yoichiro Sato

Relationship between Muscle Fiber Conduction Velocity and the Force-time Curve during Muscle Twitches.

[Purpose] The aim of this study was to clarify the relationship between the muscle fiber conduction velocity (MFCV) obtained during muscle twitches from evoked potentials and the dynamic characteristics of muscular tension (muscle dynamic characteristics) by manipulating deep temperature. [Subjects] Subjects were 10 healthy adult men. Their mean age was 23.0 ± 3.9 years. [Methods] Measurement items were MFCV of the right tibialis anterior muscle and the force-time curve of right ankle dorsiflexion (muscle twitch). Measurements were made under conditions of ordinary (room) temperature, hot and cold. The rate of change in maximum torque was calculated from the force-time curve. [Results] In all subjects, MFCV increased significantly with heating and decreased significantly with cooling. A strong correlation was seen between MFCV and deep temperature. A strong correlation was also seen between MFCV and the rate of change in maximum torque. Stronger correlations were seen in the present results than in previous studies that conducted investigations using voluntary contractions. [Conclusion] The present results were not affected by psychological or other such factors, and are valuable as data with high physiological reliability. In conclusion, this study was able to clarify the relationship between MFCV from evoked potentials and muscle dynamic characteristics.

Four-Quadrant Phase Mask Coronagraph with a Jacquinot-Lyot Stop

We report numerical simulations and laboratory demonstrations of a four-quadrant phase mask (FQPM) coronagraph equipped with a Jacquinot pupil as a Lyot stop. We demonstrate that the Jacquinot-Lyot stop can effectively suppress the residual stellar intensity due to tip-tilt errors for unresolved stars. We also show that the achievable contrast with the Jacquinot-Lyot stop depends on the direction of the tip-tilt errors, which suggests that the contrast can be improved if the direction of these errors is monitored simultaneously with the data acquisition. Furthermore, we conduct laboratory experiments with a polarization differential imager in which the Jacquinot-Lyot stop is introduced into a four-quadrant polarization mask (FQPoM) coronagraph. In these experiments we also demonstrate two image processing techniques, a cross-correlation technique and a polarization-degree analysis, to extract planetary signal from residual stellar speckle noise.

Objective spectrometer for exoplanets based on nulling polarization interferometry

The light from exoplanets is expected to be partially polalized and the image intensity becomes different with the polarization direction. Based on this expectation we have reported the laboratory experiment of two-channel nulling stellar coronagraph for direct imaging of exoplanets, where a differential imaging with respect to mutually orthogonally polarized light is conducted. We show that this differential technique is also useful for obtaining objective spectra of exoplanets. Several experimental results on the differential objective spectrometer are reported.

Interlimb Coordination of Ground Reaction Forces during Double Stance Phase at Fast Walking Speed

To better understand interlimb coordination during the double stance phase at fast walking speeds, we analyzed ground reaction forces generated by the leading and trailing limbs during the double stance phase at multiple speeds. Ground reaction forces were recorded during the double stance phase at slow, self-selected, and fast walking speeds in eleven healthy volunteers. We calculated the instantaneous phase of the ground reaction forces for the vertical and anterior-posterior components, and then calculated the relative phase between the leading and trailing limbs for each component. For the vertical component, the relative phase showed a significantly lower value in the fast condition than in the other two conditions in the early-double stance phase (fast vs. self-selected, p < 0.01; fast vs. slow, p < 0.001). For the anterior-posterior component, the relative phases in the early- and late-double stance phases in all speed conditions were significantly smaller than those in the mid-double stance phase. These findings suggest that interlimb coordination of the forces exerted by the leading and trailing limbs in the early-double stance phase would be an important factor for walking at fast speed.

Analysis of Differences in the Scores of Inside and Outside Examiners in the Examination Prior to Clinical Practice

[Purpose] An examination that evaluates students’ clinical skills in a situation similar to clinical practice (i.e. evaluation of patients) is held prior to clinical practice. To improve the validity of the scores of this examination, the differences in the scores of inside and outside examiners were analyzed. [Subjects and Methods] The subjects were 49, 3rd-year physical therapy students of Hokkaido University of Science (21.0 ± 1.7 years old). The students were split into two groups one of which and took a test of the musculoskeletal system and the other of the central nervous system. Each student was evaluated by an inside and outside examiner, and the differences in the examiners’ scores were analyzed. A questionnaire survey of the inside examiners was conducted about the results. [Results] There were significant differences between inside and outside examiners’ scores for history taking, anthropometric measurement of the musculoskeletal system, and deep tendon reflex of the central nervous system. Regarding the factors of the differences, there were survey answers indicating disagreements over the evaluation standard among examiners. [Conclusion] To raise the validity of the examination scores, improvement of the questions and standards will be required.

Mechanical properties of water alter temporal parameters of human walking

Abstract Background: Walking in water is an effective rehabilitation exercise for patients with various diseases. However, how the mechanical properties of water alter the temporal parameters of human walking is still

Temporal coordination between ground reaction forces generated by leading and trailing limbs for propulsion during double stance phase in human walking

Although it was reported that ground reaction forces (GRFs) are generated simultaneously by the leading and trailing limbs during the double stance phase, the finding was not examined by temporal analyses. Therefore, the purpose of the present study is to clarify how GRFs can act to propel the body in a forward direction during the double stance phase. GRFs were recorded during the double stance phase in eleven healthy volunteers. We calculated the instantaneous phase of the GRFs for vertical and anterior-posterior (AP) components, and then calculated the relative phase between the leading and trailing limbs for each component. The relative phase of the vertical component was approximately 180° (i.e., anti-phase), indicating that the lower limb transfers weight smoothly from the trailing limb to the leading limb. The relative phase of the AP component ranged from 40 to 55°, indicating that the AP component of the forces do not occur simultaneously, but instead has a lag. This finding suggests that the forces exerted by the leading and trailing limbs would temporally coordinate to propel the body in the forward direction.