Effect of reduced force requirements on neuromuscular inputs and movement patterns in manual materials handling tasks

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Lifting is the one of the most common tasks performed in manual materials handling jobs and is the most frequently reported cause of injury.  Mechanical off-body lifting aids (i.e., hoists or trolleys) reduce joint loading and increase efficiency, especially when lifting and moving heavy loads and manipulating awkward objects that are beyond human capability.   However, when loads are within human lifting capacity, there is a tendency for workers to lift manually since most mechanical hoists and lifting devices cannot be operated quickly and force workers to slow down.  Although one solution is to make faster 'off-body' lift assists, another solution is to design 'on-body' lifting assists.  The purpose of this application is to examine the safety and effectiveness of a new dynamic 'on-body' personal lift assistive device (PLAD) on the trunk and leg muscle activity and forces and moments on the spine and the resulting movement patterns in manual materials handling tasks.  More specifically, I am particularly interested in how workers lift loads when wearing a dynamic assistive device and whether it is a safe and effective device to use.  To accomplish this objective, there will be four studies.  The first study will examine the effects of no ergonomic lifting aid (no-PLAD) and wearing a dynamic lift assist (PLAD) on cumulative loading on the spine in terms of: a) the impact on cumulative moments at L4/L5 disc; b) cumulative EMG as processed in amplitude and frequency domains; c) changes to technique as a result of the device; d) changes in lifting technique between subjects from beginning to end of the lift; and, e) subjective and heart rate differences by condition.  The second study will examine the effect of the PLAD on trunk stability during both static holding and dynamic tasks at different trunk postural angles with different elastic element tensions.  In the third study, these experiments will be repeated for men and women to determine the differential effect of sex. The final study will determine if such a dynamic assistive device when worn over an eight week period in an industrial situation will cause de-conditioning of muscles and/or alterations in movement patterns.