title: Effects of milking unit design on upper extremity muscle activity during attachment among U.S. large-herd parlor workers.
abstract: BACKGROUND
  Large-herd dairy parlor workers experience a high prevalence of musculoskeletal symptoms in the upper extremity. The purpose of this study was to evaluate the effect of milking unit design on upper extremity muscle activity during milking unit attachment.
  
  
  METHODS
  Upper extremity muscle activity was recorded among U.S. large-herd parlor workers (n=11) using surface electromyography. Participants performed several milking unit attachment cycles with each of six milking unit designs. Muscle activity levels were then compared between unit designs.
  
  
  RESULTS
  Mean muscle activity levels (in %MVE) across milking units ranged from 6.8 to 8.2 for the upper trapezius, 8.2 to 10.3 for the anterior deltoid, 13.8 to 17.2 for the forearm flexors, and 9.9 to 12.4 for the forearm extensors. Pairwise comparisons between milking units did not reveal statistically significant differences in muscle activity levels across milking unit designs. However, a general pattern of higher muscle activity was observed with specific milking units. Milking unit weight, milk tube spread, and teat cup shape may explain differences in muscle activity levels.
  
  
  CONCLUSIONS
  Milking unit design may influence muscle activity levels among parlor workers. Small reductions in muscle activity associated with milking unit design have the potential to delay the onset of fatigue or development of musculoskeletal health outcomes among parlor workers.
authors.affiliation: The University of Texas Health Science Center at Houston, School of Public Health, San Antonio Regional Campus, TX, USA. Electronic address: david.i.douphrate@uth.tmc.edu.
authors.forename: David I
authors.initials: DI
authors.lastname: Douphrate
authors.affiliation: The University of Texas Health Science Center at Houston, School of Public Health, San Antonio Regional Campus, TX, USA.
authors.forename: David
authors.initials: D
authors.lastname: Gimeno Ruiz de Porras
authors.affiliation: University of Iowa, College of Public Health, Iowa City, IA, USA.
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Nonnenmann
authors.affiliation: New Mexico State University, Dairy Extension, Clovis, NM, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Hagevoort
authors.affiliation: Colorado State University, Environmental and Radiological Health Sciences, Ft. Collins, CO, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Reynolds
authors.affiliation: The University of Texas Health Science Center at Houston, School of Public Health, San Antonio Regional Campus, TX, USA.
authors.forename: Anabel
authors.initials: A
authors.lastname: Rodriguez
authors.affiliation: University of Iowa, College of Public Health, Iowa City, IA, USA.
authors.forename: Nathan B
authors.initials: NB
authors.lastname: Fethke
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003612:Dairying / Q000295:instrumentation*; D057645:Deltoid Muscle / Q000502:physiology*; D004576:Electromyography; D004867:Equipment Design; D006804:Ergonomics; D005542:Forearm / Q000502:physiology; D006801:Humans; D008297:Male; D064171:Superficial Back Muscles / Q000502:physiology*; D013647:Task Performance and Analysis; D014481:United States; D055815:Young Adult
keywords: Dairy; Electromyography; Equipment; Milking unit