The US dairy industry has experienced a rapid transformation from small dairy farms to large operations. In southwest regions the majority of commercial dairy herds are large operations. Current trends are larger herds where a great number of cows are attended for few employees. Reasons for these trends are beyond the scope of this abstract. This transformation has led to significant changes in work tasks and in ergonomic challenges due to the repetitive work nature of the milking process. Despite the improvement in modern equipment and design of milking parlors, it seems that the musculoskeletal workload of dairy workers remains high. Field-based direct measures of physical exposures have been limited in these challenging work environments. To assess quantitatively the posture, muscle activity and muscular fatigue a throughout milking shift, we have recruited 30 milking parlor workers representing large-herd (1000+ head) dairy operations in 3 southwest US states. All participants were Latino males between 21 and 45 years of age, who were free of pain or upper extremities pathologies. Shoulder elevation and the trunk inclination angles, were estimated using wireless triaxial accelerometers. Surface electromyography was continually recorded of the upper trapezius, finger flexors, finger extensors and anterior deltoid muscles, while workers performed milking tasks. These muscles were chosen for their relevance when performing milking tasks. Preliminary findings suggest milking workers may be exposed to awkward postures, high velocity and repetitive movements, high repetition, and high muscle forces. These physical exposures have been often associated with the development of upper limb pathology. These results warrant the need for continued research in these working environments, for development of ergonomic strategies that permit improving work conditions and to reduce the negative effect of postures during the milking routine on the musculoskeletal system, as well as to prevent fatigue that would impair dairy workers performance.