The effect of arm support on supraspinatus muscle load during simulated assembly work and welding.
The effect of arm support, by a suspension device, on muscle load in the supraspinatus muscle was evaluated with simultaneous intramuscular pressure measurement and electromyography (EMG) in nine healthy subjects. Two work situations, a low load assembly type of work, and welding with a higher shoulder muscle load, were simulated in the laboratory. Each subject performed three work-cycles of each type, with and without arm support. Arm suspension reduced supraspinatus muscle load in both work situations with reduction in pressure of 34% and 22% respectively, and reduction in normalized EMG of 20% and 17% respectively. The reduction of muscle load was significant, but in the welding situation with arm-suspension 10-15 N, average muscle pressure was still high enough to reduce muscle blood flow. The interpretation of the importance of this load reduction for the development of work-related shoulder pain is problematic.
Järvholm
U
U
Department of Orthopaedics, University of Göteborg, East Hospital, Sweden.
Palmerud
G
G
Kadefors
R
R
Herberts
P
P
D000328:Adult; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008875:Middle Aged; D009132:Muscles / Q000502:physiology*; D009989:Orthotic Devices; D012016:Reference Values; D012782:Shoulder / Q000502:physiology*; D014896:Welding; D014937:Work