Ergonomic investigation of letter-carrier satchels: part II. Biomechanical laboratory study

A biomechanical investigation of four satchels designed for the purposes of manually carrying and delivering mail was conducted. Twenty United States Postal Service carriers participated in the study. The satchels differed primarily in the presence/absence of a waist belt, the number and design of the shoulder straps, and the number of pouches. The biomechanical analyses were comprised of postural (shoulder and hip) deviation measurements, estimated compressive forces at the L5/S1 joint, soft tissue pressure on the shoulder, spinal torsion during mail retrieval, force distribution between the feet, and an anthropometric evaluation. The results indicated that a satchel with two shoulder straps and two pouches was more desirable than the single-pouch satchels from a biomechanics standpoint.