Evaluation of Resting and Working Postures from the Viewpoint of Local Muscle Energy Metabolic Rate

Abstract

According to the prediction method of local muscle energy metabolic rate (Yokoyama, 1980), energy metabolic rates of the seven muscle groups were predicted with simultaneous measurements of total energy metabolic rate and bipolar surface EMG during four resting and four working postures. The subjects were 21 Japanese male volunteers aged 22.5±2.7 years. Four resting postures were relaxed standing, sitting on a chair, supine and prone postures. The present working postures were consisted of standing on tiptoes, half rising with knee extension (at 180°), half rising with knees bending at 120° and deep forward bending postures. The seven muscle groups were the muscles of the anterior abdominal wall (M₁), the erector spinae muscles (M₂), the muscles of the buttock (M₃), the posterior femoral (M₄), the anterior femoral (M₅), the posterior crural (M₆), and the anterior crural muscle group (M₇). During standing on tiptoes M₆ had the greatest metabolic rate (mean=21.94kcal/h) among the seven muscle groups, which was also greater than those of M₆ during the other seven postures. During half rising at 180° it was pointed out through t-test (Student-test) that M₂ and M₄ demanded the greater metabolic rates, of which the mean values (n=21) were 29.51 and 6. 87kcal/h respectively. M₅ required 45.78kcal/h during half rising at 120°, which was the greatest mean value in the present study. During deep forward bending posture the greater mean metabolic rates were 11.88kcal/h in M₃ and 10.45kcal/h in M₄. On the other hand, during relaxed standing the metabolic rates were 5.13 in M₁, 7.94 in M₂, 4.88 in M₃, 2.37 in M₄, 5.49 in M₅, 9.61 in M₆ and 0.57kcal/h in M₇. Since each of the seven muscle groups was near to the minimum metabolic rate during the above four working postures, it was considered that relaxed standing has been adopted to the resting posture in standing. The metabolic rates of the seven muscle groups during sitting on a chair were less than those during relaxed standing. Especially it was shown that the metabolic rates of M₄ and M₆ reduced with the significant level p <0.001 and that those of M₂ and M₃ reduced with the significant level p < 0.01. During supine and prone postures the mean energy metabolic rates of the seven muscle groups were the least among the present tested postures, therefore it was interpreted to be reasonable that these postures has been adopted the sleeping postures in human daily life.