Voluntary maximum isometric grip strength was measured under the conditions of simultaneous bilateral and separate unilateral exertion on 16 male and 8 female subjects. Strengths of each finger and surface electromyograms of finger flexors in the forearm were recorded concurrently with grip strength recording. The Following results were obtained: (1) Grip strength and integrated EMG of both arms were significantly reduced by simultaneous bilateral exertion. (2) The decrease ratio in strength was 5#x2013;14. (3) There was an obvious linear relationship between grip strength and integrated EMG both for original values and for decrease ratios. (4) Parallelism between strength and electrical activity of muscle suggests that neurophysiological mechanisms subserve this strength decrease. (5) The middle finger occupied the largest share of grip strength and the ring, index and little finger followed in decreasing order. (6) The proportion occupied by each finger in decrease ratio of grip strength was largest in the case of the middle finger, followed by other fingers in the same order as strength share, especially for male subjects.
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