Affiliations: School of Occupational and Public Health, Ryerson
University, Toronto, ON, Canada | School of Kinesiology and Health Studies, Queen's
University, Kingston, ON, Canada | Department of Kinesiology, McMaster University,
Hamilton, ON, Canada
Note: [] Corresponding author: Mohammad Abdoli-E, School of Occupational
and Public Health, Ryerson University, 350 Victoria Street, Toronto, ON, M5B
2K3, Canada. Tel.: +1 416 979 5000 ext 7624; E-mail: m.abdoli@ryerson.ca
Abstract: BACKGROUND: In industrial supply companies, the pressure for
productivity can conflict with the ergonomic safety of material handling on the
loading dock, with workers tending to rush through the lifting tasks at the
expense of higher biomechanical loads. OBJECTIVE: The purpose of this investigation was to determine: a)
the potential benefit of introducing an ergonomic safety initiative, which
slows the speed of lifting, and b) the need to use more complex biomechanical
models in work assessments. PARTICIPANTS: One experienced worker and nine university male
students between the ages of 22 and 42 participated in this study; all reported
no recent history of musculoskeletal injuries. METHODS: The investigation involved stacking empty propane
cylinders, one on top of the other, while using a single-handed lift at a
self-selected slow and fast pace, and lifting small, weighted beverage bottles
at a slow, medium and fast pace, this time using a metronome to set the pace.
RESULTS: The results demonstrated a significant main effect for lift
pace for both peak static and dynamic external moments at the shoulder and at
L4/L5, with a larger effect occurring with the lighter loads. A reduction in
peak acceleration with heavier weights partially explained the confounding
influence from load. Significant differences occurred between the peak static
moments according to load, suggesting an accommodation in the lift strategy.
There were also significant differences between the static and dynamic external
moments, which became meaningful when the lift pace was medium or fast,
suggesting that a dynamic analysis is not necessary if the pace is slow. CONCLUSION: This investigation further supports that the pace of
lifting is an important work factor in safe lifting and material handling.
Keywords: Low back, shoulder, biomechanics, lift pace
