Motion Analysis of Thumb in Cellular Phone Use

The thumb motion of 10 normal subjects during cellular phone use was measured using a reflective marker detection system to compare the maximum, minimum and range of flexion angles of the interphalangeal (IP), metacarpophalangeal (MP) and carpometacarpal (CM) joints. Two micro-reflective markers 3 mm in diameter were each placed on the dorsal surface of the distal phalanx, basal phalanx and metacarpal bone of the thumb. Three markers were placed on the dorsal hand in order to define the dorsal hand plane. Each subject pushed the 12 keys of a folding cellular phone with an 85-mm-long and 40-mm-wide keypad, sequentially from ‘1’ to ‘#’, and the pushing motion was recorded by six infrared video cameras for 12 seconds, using the VICON 612 system. The mean maximum flexion angle of the MP joint was significantly (p < .05) larger than the CM joint, and the mean minimum flexion angle of the CM joint was significantly (p < .01) smaller than the IP and MP joints. The mean range of motion of the IP joint was significantly (p < .05) larger than the MP and the CM joints. In a comparison of different key-pushing motions, only the CM joint was significantly (p < .05) larger in its range of motion. In conclusion, thumb motion on pushing the keys of the cellular phone was produced mainly by the MP and the CM joints. In addition, the ability to reach keys in different areas of the cellular phone keypad is regulated by changing the flexion angle of the CM joint

The effect of measurement position on brachial-ankle pulse wave velocity

Arterial stiffness measurements are primarily used for the early detection of arteriosclerosis. Methods and devices that can easily measure arterial stiffness at home are in demand. We propose a simple method for measuring brachial-ankle pulse wave velocity (baPWV) at home using a reclining chair and investigate the effects of positioning on baPWV measurement. We measured baPWV in 50 healthy men (21-70 years) in seven different measurement positions, including the supine position, sitting, sitting with the knees flexed at 45°, sitting with the knees flexed at 0°, reclining at 37°, reclining at 50°, and standing. BaPWV was significantly lower in the supine position (P &lt; 0.01) than in the other positions. It was significantly higher in the sitting position (P &lt; 0.01) than in the reclining position (37°). No changes in baPWV were seen changing the knee flexion angle alone while sitting. Strong correlations were also observed between baPWV in the supine position and that in other positions. We showed that baPWV in the supine position can be calculated by making corrections to baPWV measured in the sitting position at a reclining angle. Utilizing this corrected value would allow easy measurement at home using a reclining chair

Measurement of Flexion Angle of the Finger Joint during Cylinder Gripping Using a Three-Dimensional Bone Model Built by X-Ray Computed Tomography

Motion analysis of the thumb and the four fingers during human gripping of a cylindrical object is a prerequisite for designing motion mechanisms in electronic arm prostheses and robotic hands. Conventional measurement methods include the use of angle sensors or multiple video recording of markers. In the present study, we performed X-ray computed tomography (CT) imaging on fingers gripping cylinders of three different diameters (10, 60, and 120 mm) and constructed a bone model based on these CT images to directly measure the flexion angle of each finger joint. We then compared the results with the flexion angles of joints measured using other methods. The subjects comprised 10 Japanese men with no hand injuries or diseases. Our results showed that smaller cylinder diameters were associated with significant increases in the flexion angle of all the joints of the four fingers. When focusing on the distal interphalangeal joint (DIP), there was no significant difference between any of the fingers for each of the cylinders, except between the index and middle fingers for the 10 mm-diameter cylinder. When focusing on the 10 mm-diameter cylinder, the flexion angle of the proximal interphalangeal joint (PIP) of each finger was significantly larger than that of the DIP and metacarpophalangeal joint (MP). However, no such significant difference was noted for the 120 mm-diameter cylinder. The coupling ratio (CR), which is the ratio of the flexion angles of the DIP and PIP, was significantly smaller for the 10 mm-diameter cylinder than for the 60 mm-diameter cylinder. However, there were no significant differences in CR between any of the fingers. A comparison of our study results with those derived using other methods indicated quantitative consistency for the DIP and PIP. However, for the MP, we noted differences that may be explained by the difficulty in determining the longitudinal axis of the metacarpal using other methods