Muscular load characterization during isometric shoulder abductions with varying force

Details

• Personal Author:
  Iridiastadi H ; Nussbaum MA ; van Dieën JH
• Description:
  This study sought to characterize muscle loading and fatigue during static shoulder abductions with varying force. In a supine posture, participants maintained fixed shoulder abductions against a time-varying external resistance, generated by a dynamometer-spring mechanism. Patterns (cumulative distribution) of the external resistance were varied by selecting different 10th and 90th percentiles of the distribution. Dynamometer angular velocities were also varied, to reflect different rates of cyclic muscle contraction. The degree of local fatigue development was assessed by common measures, including endurance time, strength reduction, and perceived discomfort. Myoelectric (EMG) signals were continuously obtained from the middle deltoid muscle throughout experimental exercise (60min max). Changes in EMG root-mean-square (RMS) and spectral measures (derived from 1-s windows at peaks in the cyclic contractions) were used as manifestations of muscle fatigue. For each minute, the RMS signal was further reduced using two methods, the cumulative probability distribution of EMG (CPDE) and exposure variation analysis (EVA). The former resulted in three percentile values (10th, 50th, and 90th), whereas the latter method resulted in 10 different measures (grouped by EMG activity level and duration). A main finding of the study was the applicability of several common fatigue indicators for these cyclic, repetitive exertions. Overall, the use of CPDE and EVA to characterize task differences and predict muscle fatigue was found to have limited value. [Description provided by NIOSH]
• Subjects:
  Fatigue Men Musculoskeletal Diseases Musculoskeletal System Occupational Health Safety Women
• Keywords:
  Author Keywords: Localized Muscle Fatigue Contraction-joints CPDE Electromyography EVA Exposure Assessment Force Humans Muscle-function Muscles Musculoskeletal-system Musculoskeletal-system-disorders Physical-fitness Physical-reactions Physiological-effects Physiological-function Physiology Posture

  More +
• ISSN:
  1050-6411
• Document Type:
  Text
• Funding:
  Cooperative Agreement
• Genre:
  Journal Article
• Place as Subject:
  OSHA Region 3 ; Virginia
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  18
• Issue:
  4
• NIOSHTIC Number:
  nn:20043294
• Citation:
  J Electromyogr Kinesiol 2008 Aug; 18(4):695-703
• Email:
  nussbaum@vt.edu
• Federal Fiscal Year:
  2008
• Performing Organization:
  Virginia Polytechnic Institute and State University
• Peer Reviewed:
  True
• Start Date:
  20040915
• Source Full Name:
  Journal of Electromyography and Kinesiology
• End Date:
  20100630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:690770b016564c0e2206bba905584fb03d2ea342d1dea9349e2a17057ec178d375fa05657336aa66c28ad2035a2cf94685a7b8efd63af4aa4a3f7c0b4a1f0ed5
• Download URL:
  https://stacks.cdc.gov/view/cdc/195222/cdc_195222_DS1.pdf
• File Type:
  [PDF - 6.04 MB ]