Measuring the Effect of Hand Protection on Worker Effort When Moving Small Container Plants

Manual laborers working in various segments of the agriculture industry are subjected, due to the nature of the work, to various job related hazards. The leading causes for these injuries are musculoskeletal disorders (MSD). Generally, these MSDs are categorized into one of several classes; lifting heavy loads, repeated bending/stooping or repetitive hand work. We can find potential causes of these three injury classes in many nursery/greenhouse processes. The manual movement of small container grown plants requires significant stooping and can cause fatigue, specifically in arm and shoulder areas. This study was conducted to ascertain the level at which particular forearm and shoulder muscles were used during small container movement processes while wearing different levels of hand protection. The sizes of containers included in the study were one and three gallon; based on the prevalence of these two common pot sizes at nurseries specializing in small (less than 7 gallon) container production. Typically, these containerized plants are moved multiple times during their life cycle at a nursery. Glove use by workers during these container movement processes is inconsistent and the style of glove chosen varies greatly. Four different levels of hand protection (no glove, thin nitrile, leather and a grip-assist glove) were combined with three different weighted container combinations (single one gallon pot in each hand, single three gal pot in each hand and double one gal pots in each hand). Surface Electromyography (EMG) readings were taken at 12 different muscle locations on the forearms and shoulders of study participants while performing normal container moves. Each container move was made from ground level to a trailer/wagon height at a distance of 20 feet.  Mean and peak EMG readings were compared across the treatments to identify significant differences in muscle activation. Reduced muscle activation would mean that the worker is expending less energy and may correlate with reduced fatigue over time. Post trial psychometric surveys were administered to gage worker preference and perception of glove impact compared to actual EMG readings. Results showed a correlation between glove preference and reduced muscle activity. Study participants generally preferred a thinner or grip-assist glove for most of the container movement scenarios. The thicker glove resulted in muscle use levels aligned with worker perception of an increased effort requirement across most container combinations.