The measurement and prediction of isometric lifting strength in symmetrical and asymmetrical postures

Abstract

Static lifting strengths of nine men and nine women were measured at six heights from just above the floor to just above the head, at two horizontal reaches from the mid-ankles (equal to the elbow to grip and acromium to grip distances), in the sagittal plane and also at 45° and 90° to the right for two-handed exertions and at 45° and 90° to each side for one-handed exertions, making a total of 96 postures. A second and different group of 18 subjects (nine men and nine women) were studied in 20 two-handed and 40 one-handed postures intermediate to those of the first group. A third group of 16 subjects (eight men and eight women), with six drawn from the other groups, were used to determine maximum possible reach (at which lifting strength is zero) at the same heights and planes as those for the first group. When strength was expressed as a fraction of body weight and height and reach were expressed as fractions of stature, predictive equations of static lifting strength were obtained which were gender free. The predictive equations may be used to generate isodyne contours for an individual in any chosen planes. Individuals exist whose strengths are consistently greater or less than the prediction. The possibility of identifying such persons in a process of worker selection is discussed.

Keywords:

• Asymmetry
• Lifting
• Posture
• Strength