BIOMECHANICAL OVERLOAD OF THE WRIST IN MILKING PARLOR WORKERS:RISK PROFILES AND PREVENTION CRITERIA

ABSTRACT The association between biomechanical risks and musculoskeletal disorders in agriculture is well known, but within the dairy industry, the literature is still sparse on the precise exposure. This project, addressed at fulfilling some of the knowledge gaps and at creating exposure and risk Profiles for specific milking parlor activities, has been conducted in order to: a) estimating the effects on wrists of parlors’ workers of repetitive motions, pointing out an ultrasonography approach; b) developing screening tools useful in the periodical health surveillance of dairy workers to detect early wrists’ changes; c) compare the levels of muscle activation in milking work between large herd and small herd operations; d) define preventive criteria addressed at risk control in dairy activities. The project has been carried out in 4 single studies, In the first, 14 parlor workers and 22 controls were studied through a) personal anamnesis collection; b) wrists ultrasonography; c) upper limb clinical evaluation. The study confirmed the wrist as target of biomechanical risk factors and identified the two wrist’s acoustic window characterized by the highest predictive value for wrist’s structure alteration. The second study was conducted on 40 dairy workers, studied with the approach defined in the first study. Main objective was evaluating the levels of concordance between questionnaire results and clinical and ultrasound evidences. The questionnaire showed a high level of specificity (82.15%. C.I.95%: 62.4%-93.2%) if compared with clinical investigation outcomes and/or ultrasound findings. The study allowed us to conclude that 1) the administration of a questionnaire can be predictive of early wrist’s changes. 2) The questionnaire created is adequate for the periodical screening of parlor workers’ wrist. The same population was involved in the third study, addressed to defining risk Profiles of wrist biomechanical overload of parlor workers. Anthropometric measurements, personal and occupational variables, surface electromyography data of dominant upper limb muscles were collected to define activation profiles. Strain Index for each single milking subtask (pre dipping, wiping/stripping, attaching, post dipping) was evaluated. The study defined three main risk profiles: low, medium and high risk. Main risk determinants were: characteristics of the workstation, organization of the work, milking routine. We concluded that organization of the milking routine, and cluster weight not major than 2.4 Kg are useful interventions to be carried out. The fourth study was conducted to compare upper limb muscle activity between US and Italian industrialized Dairy operations. Twenty-nine workers were recruited from large herd US herd (>1000 head) dairies and 39 from small herd Italian dairies. Surface electromyography was used to assess muscle exertion levels of all workers, measuring intensity, expressed as root mean square of the raw signal, amplitude probability distribution function percentiles, and the percent muscular rest of the interested muscles. The statistical analyses indicated significantly greater average muscle activity during milking tasks among large herd versus small herd dairy workers in the biceps brachii (p<0.001), upper trapezius (p=0.002), and the wrist flexors (p<0.001) between the two dairy types. The final study demonstrated that, independently from the size and the country, parlor activities pose significant biomechanical wrist risk.