Performance of Plantar Flexor Muscles with Eccentric and Isometric Contractions in Intact Rats

Details

• Personal Author:
  Stauber WT ; Willems MET
• Description:
  To examine the changes in performance of active plantar flexor muscles of rats by controlled dorsiflexion (i.e., stretching of muscles) at two angular velocities. Repeated stretches (30) at two velocities of ankle rotation [slow stretch (0.87 rads x s(-1) (i.e., 50 degrees x (s-1))), fast stretch (10.47 rad x s(-1) (i.e., 600 degrees x s-1))] were superimposed on maximally active muscles from an ankle position of 1.57 rad to 0.70 rad (i.e., from 90 degrees to 40 degrees). Repeated isometric contractions (30) of the same duration (1,900 ms) and rest interval (3 min) were performed at 1.13 rad (i.e., 65 degrees). Performance was assessed by measuring the isometric torque at ankle positions of 1.57 and 0.70 rad, work during concentric contractions [range of motion 1.22 rad (i.e., 70 degrees)], and the time to produce 50% of the maximal isometric torque. Thirty isometric contractions resulted in a linear reduction in torque (total deficit of 13.8% at 1.57 rad), whereas for slow and fast stretches, half of the total, nonlinear deficit at 1.57 rad (about 30%) was completed after six stretches. Increases in half contraction times were larger for stretches than for isometric contractions. Reductions in isometric torque were greater at an ankle position of 1.57 rad than at 0.70 rad. One hour of rest after the repeated stretches and isometric contractions did not restore muscle performance. Isometric contractions of skeletal muscle can create a torque deficit which is much less than that after stretches. Repeated fast and slow stretches resulted in similar torque deficits which did not recover after a rest period of 1 h. [Description provided by NIOSH]
• Subjects:
  Engineering Environmental Exposure Environmental Health Environmental Pollution Mining Occupational Exposure Occupational Health Safety
• Keywords:
  Animals Animal Studies Ankle Author Keywords: Skeletal Muscle Dynamometer Injuries Laboratory Animals Muscle Force Muscle Injury Muscle Stress Muscle Tension Musculoskeletal System Disorders Skeletal Disorders Skeletal Stress Velocity

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• ISSN:
  0195-9131
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  OSHA Region 3 ; West Virginia
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  32
• Issue:
  7
• NIOSHTIC Number:
  nn:20024468
• Citation:
  Med Sci Sports Exerc 2000 Jul; 32(7):1293-1299
• Email:
  mwillems@hsc.wvu.edu
• Federal Fiscal Year:
  2000
• NORA Priority Area:
  Disease and Injury: Musculoskeletal Disorders of the Upper Extremities
• Performing Organization:
  West Virginia University, Morgantown, West Virginia
• Peer Reviewed:
  True
• Start Date:
  19920101
• Source Full Name:
  Medicine and Science in Sports and Exercise
• End Date:
  20050531
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:d4ea82d04175a8f333fe09b02aa690a27194fbd97469b0814d9db864581d0c2ed4f781e2bc2b4d8935579b610aef5f19c6f4dd7675c29c578e32ee8fedcb6c64
• Download URL:
  https://stacks.cdc.gov/view/cdc/196258/cdc_196258_DS1.pdf
• File Type:
  [PDF - 99.41 KB ]