Determining best practices for manual pill crushing through evaluation of upper extremity muscle exposures

Nurses in long-term care homes often crush pills into a fine powder using a manual pill crushing device. This study provides novel quantitative data on muscle loading experienced during pill crushing. The influence of surface height, number of pills and device orientation were studied in twelve muscles of the upper extremity. Variations in the work surface height and number of pills crushed resulted in static shoulder and forearm muscle activations that exceeded recommended static limits. In most cases, working at approximately a 50th percentile female's hip height (87 cm) reduced the level of muscle activity, often to below the EMG-based exposure limit, compared to higher heights. A perpendicularly oriented device required substantially lower muscle activity in some shoulder muscles, with marginal differences occurring in muscles of the elbow and wrist. These data can inform practical design and work practice recommendations to reduce muscular activity while performing this important healthcare task.