Abstract des Autors

Eight subjects, who were seated with the upper arm supported in a horizontal position, performed a series of elbow flexion and extension movements in which a visual target was provided together with an elbow angle signal by vertically moving horizontal lines on an oscilloscope. Five loading conditions were employed, which differed in the number of steel plates attached to the subject's wrist: 0, 0.65, 1.30, 1.95 and 2.60 kg. The electromyographic /EMG) activity of the bi-articular biceps brachii (BB) was compared with the mono-articular brachioradialis (BR) for each of three EMG components; the first and the second agonist burst (AG1, AG2) duriung flexion movements, and the antagonist burst (ANT) during extension movements. The magnitude relations for each EMG component between the two muscles were evaluated by the BR/BB ratio. The results showed that there were significant differences (p<0.05) among the three EMG components in all the no-loading condition. Further a post-hoc test revealed that there were significant BR/BB differences (p<0.05) between AGI vs. AG2 in 0.65 and 1.3 kg loading conditions and between AG1 vs. ANT in all but the no-loading condition. These results may suggest that different neural processes underlie the activation of mono- and bi-articular muscles in the organization and the control of movements. Verf.-Referat