Kinematic and kinetic changes in cycling during an exhausting steady-rate ride

Abstract

A personal lift assist device (PLAD) was designed with passive elastic elements that act with a similar line of action to the spine muscles and reduce the extension moment experienced during lifting activities. The purpose of this paper was to evaluate the device's ability to reduce fatigue during a repetitive lifting task. Women (n = 12) lifted a box load representing 20% maximal extensor strength repetitively (12 lift/lowers per minute) for 45 min while electromyography (EMG) was recorded from the lumbar and thoracic erector spinae, and cardiovascular measures were monitored. Subjects were also tested on strength and endurance tests prior to, and after lifting. The increase in EMG RMS amplitude from the start until the end of the lifting session was significantly lower when wearing the PLAD for the TES (91% vs 3%) and the LES (104% vs 16%). The median frequency (MF) drop was also significantly lower when wearing the PLAD for TES and LES. The PLAD delayed the onset of fatigue in women by requiring less muscular effort.Relevance to industryThere are numerous industries that still require repetitive manual materials handling tasks to be performed by humans. Repetitive lifting fatigues the musculature involved and may lead to an increased risk of injury. The PLAD reduced fatigue on several measures. This device appears to have potential for industries where women perform repetitive, fatiguing lifts.