Comparison of upper limb muscle activity among workers in large-herd U.S. and small-herd Italian dairies.

Objectives: Commercial cow milking tasks, regardless of dairy size, have been documented in many regions of the world as strenuous work requiring high muscular effort, awkward positions, and task repetition. Large-herd dairies are common in the United States, while Europe historically has mostly small-herd dairies. The objective of this study was to compare the upper limb muscle activity during milking tasks between workers at large-herd U.S. dairies and small-herd Italian dairies. This is the first study international directly comparing upper limb muscle activity among dairy workers from different countries using identical methods. Methods: Data was collected at 6 large-herd dairies in the U.S. region of Colorado and at 21 small-herd Italian dairies in the Lombardy region. Surface electromyography (sEMG) from the trapezius, anterior deltoid, biceps brachii, wrist flexors and wrist extensors muscles were recorded from all participating workers (N=65). Electromyography data was normalized to functional maximum voluntary contractions. Anthropometric measurements were also recorded. Results: Upper limb muscle activity was generally greater among workers in the large-herd U.S. dairies compared to small-herd Italian dairies. The amount of muscular rest as a percent of the work time was significantly greater among large-herd U.S. dairy workers. Conclusions: The differences revealed in sEMG and percent muscular rest among workers from the U.S. and Italy are likely due in part to differences in work processes adopted by fast paced industrialized large-herd dairies compared to the slower but sustained work processes performed at small-herd diaries.