RESUMO
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.
