Ping Yeap Loh

Effect of wrist angle on median nerve appearance at the proximal carpal tunnel.

This study investigated the effects of wrist angle, sex, and handedness on the changes in the median nerve cross-sectional area (MNCSA) and median nerve diameters, namely longitudinal diameter (D1) and vertical diameter (D2). Ultrasound examination was conducted to examine the median nerve at the proximal carpal tunnel in both dominant and nondominant hands of men (n = 27) and women (n = 26). A total of seven wrist angles were examined: neutral; 15°, 30°, and 45° extension; and 15°, 30°, and 45° flexion. Our results indicated sexual dimorphism and bilateral asymmetry of MNCSA, D1 and D2 measurements. MNCSA was significantly reduced when the wrist angle changed from neutral to flexion or extension positions. At flexion positions, D1 was significantly smaller than that at neutral. In contrast, at extension positions, D2 was significantly smaller than that at neutral. In conclusion, this study showed that MNCSA decreased as the wrist angle changed from neutral to flexion or extension positions in both dominant and nondominant hands of both sexes, whereas deformation of the median nerve differed between wrist flexion and extension.

Median nerve behavior at different wrist positions among older males

The effect of wrist flexion-extension on the median nerve appearance, namely the cross-sectional area (MNCSA) and the longitudinal (D1) and vertical (D2) diameters, was investigated among older adults (N = 34). Ultrasound examination was conducted to examine the median nerve at different wrist angles (neutral; and 15°, 30°, and 45° extension and flexion), in both the dominant and nondominant hand. Median nerve behavior were significantly associated with wrist angle changes. The MNCSA at wrist flexion and extension were significantly smaller (P < .001) compared with the neutral position in both the dominant and nondominant hand. The D1 and D2 were significantly reduced at flexion (P < .001) and extension (P < .001), respectively, in both the dominant and nondominant hand. Our results suggest that a larger flexion-extension angle causes higher compression stress on the median nerve, leading to increased deformation of the MNCSA, D1, and D2 among older adults.

Effects of grip force on median nerve deformation at different wrist angles

The present study investigated the effects of grip on changes in the median nerve cross-sectional area (MNCSA) and median nerve diameter in the radial-ulnar direction (D1) and dorsal-palmar direction (D2) at three wrist angles. Twenty-nine healthy participants (19 men [mean age, 24.2 ± 1.6 years]; 10 women [mean age, 24.0 ± 1.6 years]) were recruited. The median nerve was examined at the proximal carpal tunnel region in three grip conditions, namely finger relaxation, unclenched fist, and clenched fist. Ultrasound examinations were performed in the neutral wrist position (0°), at 30°wrist flexion, and at 30°wrist extension for both wrists. The grip condition and wrist angle showed significant main effects (p < 0.01) on the changes in the MNCSA, D1, and D2. Furthermore, significant interactions (p < 0.01) were found between the grip condition and wrist angle for the MNCSA, D1, and D2. In the neutral wrist position (0°), significant reductions in the MNCSA, D1, and D2 were observed when finger relaxation changed to unclenched fist and clenched fist conditions. Clenched fist condition caused the highest deformations in the median nerve measurements (MNCSA, approximately −25%; D1, −13%; D2, −12%). The MNCSA was significantly lower at 30°wrist flexion and 30°wrist extension than in the neutral wrist position (0°) at unclenched fist and clenched fist conditions. Notably, clenched fist condition at 30°wrist flexion showed the highest reduction of the MNCSA (−29%). In addition, 30°wrist flexion resulted in a lower D1 at clenched fist condition. In contrast, 30°wrist extension resulted in a lower D2 at both unclenched fist and clenched fist conditions. Our results suggest that unclenched fist and clenched fist conditions cause reductions in the MNCSA, D1, and D2. More importantly, unclenched fist and clenched fist conditions at 30°wrist flexion and 30°wrist extension can lead to further deformation of the median nerve.

Impact of keyboard typing on the morphological changes of the median nerve

The primary objective was to investigate the effects of continuous typing on median nerve changes at the carpal tunnel region at two different keyboard slopes (0° and 20°). The secondary objective was to investigate the differences in wrist kinematics and the changes in wrist anthropometric measurements when typing at the two different keyboard slopes.

Deformation of the median nerve at different finger postures and wrist angles

Background The objective of this study was to evaluate the changes of the median nerve cross-sectional area (MNCSA) and diameters of the median nerve at different finger postures and wrist angles. Methods Twenty-five healthy male participants were recruited in this study. The median nerve at wrist crease was examined at six finger postures, and repeated with the wrist in 30° flexion, neutral (0°), and 30° extension. The six finger postures are relaxed, straight finger, hook, full fist, tabletop, and straight fist. Results The main effects of both finger postures and wrist angles are significant (p < 0.05) on changes of the MNCSA. Different finger tendon gliding postures cause a change in the MNCSA. Furthermore, wrist flexion and extension cause higher deformation of the MNCSA at different finger postures. Discussion The median nerve parameters such as MNCSA and diameter were altered by a change in wrist angle and finger posture. The results may help to understand the direct biomechanical stresses on the median nerve by different wrist-finger activities.

The Influence of Information Acquisition Strategies on Foot Proprioception and Obstacle Avoidance Pattern in People with Low Vision

The purpose of this study was to understand the influence of various information acquisition strategies on foot proprioception and obstacle avoidance in people with low vision. Ten adult males (41.0 ± 7.1 years) with pigmentary retinal degeneration were recruited for this study. Participants acquired obstacle information (obstacle height: 4 cm and 15 cm) through three different strategies, namely, front (A), downward (B), and tactile (C). Subsequently, the participants performed two different tasks; Task 1: After identification of the obstacles, the participants reproduced the obstacle height by lifting their foot while standing still (10 times). Task 2: Following the acquisition of the obstacle information through conditions B and C, participants performed obstacle step-over from a standing position. In task 1, condition B showed significantly higher toe-rise and coefficient of variance in toe-rise (p < 0.05) than in conditions A and C, which both displayed similar toe-rise. Likewise, in task 2, the highest points of the leading and trailing feet while stepping over the obstacle were significantly higher (p < 0.05) in condition B than in condition C. Additionally, the coefficient of effort in condition B was significantly larger (p < 0.05) than that of condition C. These results suggest that differences in information acquisition strategies have an impact on the foot trajectory during obstacle step-over. Out of the three methods used in this study, information acquisition through the tactile sense may be the best obstacle avoidance feedback method for people with low vision.

Individual differences in contact pressure on the dorsal surface of the foot during gait

The main objective of this study was to examine how contact pressure on the dorsal surface of the foot changes with varying shapes. Ten healthy young men (22.1 ± 0.6 years) with independent walking ability were recruited in this study. We measured the anthropometric characteristics of the foot. Shoe size for the experiment was individually decided based on the obtained anthropometric data. Subsequently, FlexiForce® sensors were attached to the dorsal side of the first metatarsophalangeal joint (P1), intermediate cuneiform (P2), and pternion (P3) to measure the contact pressure during walking. In addition, foot switch sensors were used to determine the gait cycle. At P2, some participants with a higher foot height showed a lower increase in contact pressure during the loading response or pre-swing phases than did participants with a lower foot height. The observed distribution of the contact pressure on the dorsal foot might be caused by the change in the shape of the shoes and the foot joint movement during walking.

Simulation study on the effects of adaptive time for assist considering release of isometric force during elbow flexion

The increasing trend of development of assistive technology allows for the use of assistive robots such as power assist devices to be prevalent in various social domains. Such power assist devices usually provide incidental power to their users, requiring human-machine force interaction. If the power assist device requires users to release their muscular force without considering adaptive time, users might be confused to control the level of their manual performance in response to the external force. This study investigated adaptive time with varying release rates of isometric force during one-arm elbow flexion, focusing on muscle activity and force control. Eight participants conducted graphical force-tracking tasks designed to simulate power-assist condition. Electromyography signals and the tension forces of the biceps brachii and triceps brachii were measured. The results implied that sufficient adaptive time for muscular force release induced better performance level with a smaller difference between the target force and the actual force. However, higher subjective exertion was also accompanied during the longer time for muscular force release. This study suggests that in designing power assist devices, the duration for muscular force release and consequent characteristics should be considered to maintain the precise level of force control.

Motor Control with Assistive Force During Isometric Elbow Flexion

In the modern society, an assistive/powered suit has been developed to enhance the limb and trunk movements by mechanical force. The effective output of assistive products needs cooperation between the users, that is, human beings and the machine. The present study investigated the motor control of external forces that assist with physical exertion. Sixteen adult male participants performed isometric elbow flexion under two conditions of submaximal workload (20% and 40% of the maximal voluntary contraction) and four levels (0%, 33%, 67%, and 100%) of assistive force. The electromyographic (EMG) activity of the agonist and antagonist muscles (biceps and triceps, respectively) and rating of perceived exertion decreased with increased levels of assistive force under both workload conditions. At the lower level of assistance (33%), the EMG amplitude of the biceps was near the expected amplitude, which denotes that the participants made good use of the assistive force. However, at the higher level of assistance (100%), it was far from the expected values at both workload levels. These results suggest that the effectiveness of assistive force changes according to the level of workload and assistive force, and that various human physiological regulations and motor control would be required during cooperative work with assistive force.

Impacts of typing on different keyboard slopes on the deformation ratio of the median nerve

Carpal tunnel syndrome is a symptomatic compression neuropathy of the median nerve as it travels through the wrist. Several factors such as wrist angle and finger posture cause a change of the intra-carpal tunnel pressure. Carpal tunnel syndrome is one of the most commonly reported work-related musculoskeletal disorders. Computer users are at higher risk of upper extremity musculoskeletal symptoms and work-related musculoskeletal disorders, since time spent on the computer is associated with a higher incidence of musculoskeletal disorders. Objective: to investigate the impact of typing at two keyboard slopes (0° and +20°) on the median nerve deformation ratio. Fifteen healthy young men (24.8 ± 2.3 years) were recruited to type using both 0° and +20° inclined keyboards. The participants performed four 30-min blocks of computer typing at 0° and +20° keyboard inclinations. The left wrist median nerve was examined with an ultrasound machine after each 30-min typing block. Two-way repeated analysis of variance was performed to examine any differences in the deformation ratio of the median nerve cross-sectional area. The four time blocks and two keyboard slope conditions (0° and +20° inclination) were used as factors. Continuous typing activity causes a significant increase in the median nerve cross-sectional area deformation ratio (p < 0.05). Ultrasonography examination of the median nerve following computer typing can be used to generate absolute measurements and deformation ratios. These measurements help provide a better understanding of the impact of typing tasks on the median nerve.