A biomechanical evaluation of lifting speed using work- and moment-related measures

Abstract

A biomechanical evaluation of lifting speed was conducted in the laboratory. The study investigated the effects of lifting speed on several predetermined biomechanical cost functions. The lifting tasks consisted of five lifting speeds labelled as the slowest, slow, normal, fast and fastest, and three weights, 50, 65 and 80% of their maximum acceptable weight of lift. The speed at each level was determined individually by each subject according to their capability. The study found that work-related measures, including the total net muscle work, total absolute net muscle work and work done to the load, decreased significantly as the lifting speed increased (p<0.05, <0.001 and <0.001, respectively). The time integral of sum of squared ratio of joint moment and strength also decreased significantly (p<0.001). This indicates that lifting at a faster speed tends to reduce the work the body has to do. The peak speed of load occurred at 70% of total lifting time for the slowest lifts, but at 30% of total lifting time for other lifting speeds. Performing lifts at the minimum speeds changed the usual speed coordination technique the subjects used.