Arm lift strength in work space

Abstract

This study was conducted to determine arm strength values for isometric and isokinetic efforts around the human trunk. Thirty-eight normal young adults (20 male and 18 female) performed a total of 19 tasks. These consisted of one self-selected optimum posture with upright stance and elbows bent at 90°, designated as standard posture for isometric test. In addition, isometric testing was done sagittally symmetrical 30° and 60° lateral planes at half-, three-quarters- and full-reach distances at knuckle height. The isokinetic tests were done between knuckle height and shoulder height in postures identical to isometric tests. The sequence of these tasks was randomised. The peak strength in standard posture was invariably lower than the peak strength at half-reach in isometric condition in all three planes for both sexes with the exception of one condition among females (60° lateral plane, half-reach isometric). Peak and average arm lift strengths of males were significantly higher than those of females ( p < 0·01) and ranged between 44% and 71%. For both sexes isometric strength was significantly higher than isokinetic strength ( p < 0·01). The peak and average strengths in the sagittal plane were invariably higher than those of asymmetric postures, with one exception among females. With increasing reach distance the strength declined significantly for all conditions among both genders ( p < 0·01). The ANOVA showed that the gender, mode of lifting, postural symmetry and reach of lifting, in addition to affecting the peak and average strength individually ( p < 0·01), had significant 2-way and 3-way interactions ( p < 0·01). All strength values were inter-correlated ( p < 0·01). The regressions predicting peak and average strengths from anthropometric characteristics and sagittal plane strengths accounted for 63% to 89% of all variance and were highly significant ( p < 0·01).