title: Muscular strains in different modes of load handling.
abstract: The influence of posture on the ability of a person to hold loads was evaluated from a study on six healthy, young males. The muscle activities in terms of isometric strength and electromyographic (EMG) characteristics of the trunk and lower limb were determined in ten load-holding postures. The postures were comprised of trunk, knee and elbow in different straight and bent positions to include load heights (LH) of 32, 44, 85 and 125cm from the ground and subject-load distance (SLD) of 12 and 32cm. The pull-up maximum voluntary contraction (MVC) was significantly influenced by the SLD. The MVC values were consistently high with the increase in LH, when the SLD was 12 cm but the opposite was the case for SLD of 32 cm. The trunk-bent/knee-straight postures had higher MVC values (31 ± 8 to 34 ± 2·5 kgf) than those in knee-bent/trunk-straight postures (21 ± 3 to 28 ± 5 kgf). The trunk muscles behaved differently in trunk-straight and in bent postures. The hamstrings and quadriceps were counter-balanced in sharing loads during knee-bent or straight postures. It was observed that the load-holding operations were performed better in trunk-bent/knee-straight postures, and when the load was closer to the body at heights ranging from 32 to 44 cm. Whereas, in trunk and knee-straight postures, the pulling of the load was more convenient from waist height.
authors.affiliation: Occupational Physiology Division, National Institute of Occupational Health, Ahmedabad 380 016, India.
authors.forename: S N
authors.initials: SN
authors.lastname: Ghosh
authors.forename: P K
authors.initials: PK
authors.lastname: Nag