EFFECTS OF SYRINGE SIZE AND HAND CONDITION ON THUMB LOADING AND MUSCLE ACTIVITY DURING PIPETTING TASKS

ABSTRACT

Plunger operated syringes are typically used by laboratory staff to dispense precise quantities of liquid. Such workers commonly complain of discomfort in the upper extremities as a result of prolonged repetitive actions over the course of their workday. A pipetting task was designed to quantify thumb loading and muscle activity measured by pinch strength and surface electromyography (EMG). The root mean square (RMS) EMG was recorded for the abductor pollicis brevis, extensor pollicis brevis and flexor pollicis longus. Analytical results indicate that pinch strength decreased significantly by 20.9% after pipetting tasks. Females had higher reduction rates in maximum pinch force (31.5%) than males (14.8%). User of a large syringe had negative significant effects on thumb loading and muscle activities; however, no statistically significant difference existed between hand conditions, and no interactive effects existed between syringe size and hand condition. We conclude that syringe size influences applied thumb force and muscle activity.

Keywords:

• syringe size
• pipetting task
• muscle activity
• electromyography