Abstract
The relation between integrated EMG and tension during voluntary isometric contraction was compared in each of the following: M. flexor pollicis brevis, M. biceps brachii, M. rectus femoris, M. biceps femoris and M. tibialis anterior. Also relation between EMG recorded from each muscle and skinfold thickness above that muscle was investigated.Experiments were made on total of 15 young adult females (age 21-22).Integrated surface EMG was recorded during the mid portion of 8 sec. period of sustaining contraction. The exerted force measured at distal phalange of pollex, wrist and ankle was 1, 3, 5, 7 and 10kg. Maximal and 1/2 maximal contraction was also made. Skinfold thickness on the muscle were measured with skinfold caliper. Results are summarized as follows:1) Integrated EMG increased approximately linearly with exerted force in every muscle.The slope of regression lines for various muscles differed markedly. Regression coefficient were decreasing in the followig order:M. flexor pollicis brevis, M. biceps brachii, M. tibialis anterior, M. triceps brachii, M. biceps femoris, M. rectus femoris.2) Analysis was made relationship between the maximum value of integrated EMG (that is EMG obtained during maximal contraction) and skinfold thikness. As regards paticular muscle, individual variation of the skinfold thickness above that muscle showed no systematic variation with integrated EMG. When various muscles are viewed as whole, however, significant negative correlation between integrated EMG and skinfold thickness was found.After logarithmic transformation for integrated EMG (Y, arbitrary unit) and skinfold thickness (X, cm), linear regression line was fitted. The regression coefficient was -0.661, (r=-0.568) showing that original relationship can be expressed by the formula Y=aX-0.661 where a is constant.3) By means of analysis of covariance, the maximum integrated EMG for each subject and for each muscle was adjusted to the skinfold thickness. There still remained significant difference among various muscles concerning the maximal EMG. Examined muscles could be arranged in the following decreasing order with respect to maximal EMG: M. flexor pollicis brevis, M. biceps brachii, M. tibialis anterior, M. triceps brachii, M. biceps femoris, M. rectus femoris.
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