Ergonomic Assessment of a Lower-Limb Exoskeleton through Electromyography and Anybody Modeling System.

The aim of this study was to determine the muscle load reduction of the upper extremities and lower extremities associated with wearing an exoskeleton, based on analyses of muscle activity (electromyography: EMG) and the AnyBody Modeling System (AMS). Twenty healthy males in their twenties participated in this study, performing bolting tasks at two working heights (60 and 85 cm). The muscle activities of the upper trapezius (UT), middle deltoid (MD), triceps brachii (TB), biceps brachii (BB), erector spinae (ES), biceps femoris (BF), rectus femoris (RF), and tibialis anterior (TA) were measured by EMG and estimated by AMS, respectively. When working at the 60 cm height with the exoskeleton, the lower extremity muscle (BF, RF, TA) activities of EMG and AMS decreased. When working at the 85 cm height, the lower extremity muscle activity of EMG decreased except for TA, and those of AMS decreased except for RF. The muscle activities analyzed by the two methods showed similar patterns, in that wearing the exoskeleton reduced loads of the lower extremity muscles. Therefore, wearing an exoskeleton can be recommended to prevent an injury. As the results of the two methods show a similar tendency, the AMS can be used.

Evaluation of total grip strength and individual finger forces on opposing (A-type) handles among Koreans.

The present study evaluated the effect of grip span on finger forces and defined the best grip span for maximising total grip strength based on the finger forces and subjective discomfort in a static exertion. Five grip spans (45, 50, 55, 60 and 65 mm) of the opposing (A-type) handle shape were tested in this study to measure total grip strength and individual finger force among Korean population. A total of 30 males who participated in this study were asked to exert a maximum grip force with two repetitions, and to report the subjective discomfort experienced between exertions using the Borg's CR-10 scale. The highest grip strength was obtained at 45 mm and 50 mm grip spans. Results also showed that forces of all fingers, except for the middle finger force, significantly differed over the grip spans. The lowest subjective discomfort was observed in the 50 mm grip span. The results might be used as development guidelines for ergonomic opposing (A-type) hand tools for Korean population.

Effect of finger interaction on individual finger: index finger.

Grip strength is affected by such as enslaving effect, force sharing effect, and force deficit effect relating to the interaction among fingers. The author attempts to analyze index finger strength according to grip span of adjacent middle finger. 6 male graduate students participated as subjects in this experiment. The grip span has been applied from 45 mm to 60mm to investigate the effects of a coordination of grip spans on the index and middle finger strength. Results showed that index finger strength was the smallest in case of index finger grip span of 45 mm. Index finger strength decreased as the middle finger grip span. In general index finger strength shared a decreasing trend when the grip span of the middle finger increased. This study has an implication that the grip span of index and middle fingers influences force sharing effect on index finger.