Affiliations: Department of Human Kinetics and Ergonomics, Rhodes
University, Grahamstown, South Africa
Note: [] Address for correspondence: Andrew Todd, Department of Human
Kinetics and Ergonomics, PO Box 94, Rhodes University, Grahamstown, 6140 South
Africa. Tel.: +27 466 038 469; Fax: +27 466 038 934; E-mail:
[email protected]
Abstract: Objective: Increasing awareness of the high physical cost associated
with lifting has led to the redesign of these tasks, incorporating manual
handling devices and consequently pushing and pulling. Little research has
focused on muscle activity responses to pushing and pulling, the current study
therefore investigated these responses to further the understanding of risk of
injury, informing ergonomics intervention strategies. Methods: A laboratory study was undertaken to determine the effect
of three push/pull techniques and two loads (250 and 500 kg) on muscle
activation in nine muscles, distributed through the upper and lower body.
Unloaded forward and backward walking were used as control conditions for lower
limb muscle activation. Participants: Thirty-six healthy male volunteers participated in the
study. Subjects were required to manoeuvre a loaded pallet jack at a velocity
of 0.45–0.55 statures. Results: The muscles of the shoulders and upper extremity were
affected to a greater degree by technique and load changes than those of the
lower limbs. Further, high levels of erector spinae activation were recorded
across all six experimental conditions. Conclusions: Each technique displayed a unique muscle activation
profile, indicating that alternating between techniques may reduce early onset
of fatigue. Further understanding of muscle activation during pushing and
pulling is necessary.
