Physical workload during manual and mechanical deboning of poultry

The physical workload after the introduction of new technology, i.e. mechanical versus manual deboning of poultry was studied with respect to force requirements, work postures and repetitive movements of the hand. Thirteen healthy women were studied during manual and mechanical deboning using electromyography (EMG), force recordings, observer based force ratings and electrogoniometers. The muscular activity was significantly higher in Extensor Carpi Ulnaris (ECU), Flexor Carpi Ulnaris (FCU), and Flexor Digitorum Superficialis (FDS) during cutting-the most strenuous task of manual deboning-than during mechanical deboning. Estimated cutting forces were 6.3 and 20.7 N (median and peak levels). Extreme wrist postures were more frequent during cutting, but peak acceleration and repetition-calculated from spectral analysis of the goniometer signal-were higher during mechanical deboning. In general the introduction of new technology, i.e. mechanical deboning had only marginal effects on the risk factors associated with work related musculoskeletal disorders during poultry processing. Mechanical deboning moderately reduced peak forces, but the muscular activity remained high, and in addition higher levels of acceleration and repetition rates were introduced. Observer based estimations of the hand forces correlated in these work tasks well with the mean peak EMG level of the relevant muscles.