Muscle-Specific Atrophy After 6 Weeks of Overtraining with Eccentric Muscle Actions in Rats

Details

• Personal Author:
  Stauber WT ; Willems MET
• Description:
  To examine adaptations for slow- and fast-twitch muscles after overtraining with eccentric muscle actions. Using subcutaneous electrical stimulation (70 Hz, 0.2 ms pulse duration, 20-40 V), plantar flexor muscles (i.e., slow-twitch soleus and fast-twitch plantaris and gastrocnemius muscles) of female Sprague Dawley rats (4-5 mo) were trained (5 d/wk for 6 wks) with eccentric muscle actions (5x10). Eccentric muscle actions occurred between ankle positions of 140 degrees to 40 degrees (velocity approximately 400 degrees ·s-1) and were followed by unresisted concentric muscle actions. Rats limited to cage activity served as control. Weights of adrenal glands and plantar flexor muscles were taken. Fiber size distributions and mean fiber areas were determined using serial cross-sections (thickness 8 um) and image analysis. Fiber type shifts were documented for the soleus muscle using immunohistochemistry. Adrenal glands were enlarged by 17% (overtraining: 72 +/- 3 mg (mean +/- SE), control: 62 +/- 1 mg (n = 16 in each group), p < 0.05). Mass of the soleus muscle was decreased by 19% (overtraining: 116 +/- 3 mg (n = 16), control: 130 +/- 3 mg (n = 10), p < 0.05). After overtraining, smaller fiber sizes were present in the gastrocnemius medialis and soleus muscles resulting in a decrease of the mean fiber areas by 26% and 13%, respectively (p < 0.05). An atrophic response was not observed for the plantaris muscle. In the soleus muscle, the number of fast fibers increased from 17.4 +/- 0.9% (control) to 22.0 +/- 1.5% (overtraining) - an increase by 26% (p < 0.05). Overtraining with eccentric muscle actions resulted in atrophy in the soleus and gastrocnemius muscles but not in the plantaris muscle. Adaptation to overtraining with eccentric muscle actions appears to be muscle-specific and was largest for slow-twitch muscles. [Description provided by NIOSH]
• Subjects:
  Case Reports Demography Dust Environmental Monitoring Lung Lung Diseases Manufacturing And Industrial Facilities Mining Mortality Neoplasms Occupational Health Respiratory System Respiratory Tract Diseases Risk Assessment Safety Smokers Vehicle Emissions

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• Keywords:
  Animals Animal Studies Diseases Injuries Injury Prevention Laboratory Animals Muscles Muscle Tissue Musculoskeletal System Musculoskeletal System Disorders Skeletal System

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• ISSN:
  0195-9131
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Abstract or Summary
• 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:
  35
• Issue:
  5
• NIOSHTIC Number:
  nn:20029555
• Citation:
  Med Sci Sports Exerc 2003 May; 35(5)(Suppl 1):S238
• Email:
  mwillems@hsc.wvu.edu
• Federal Fiscal Year:
  2003
• NORA Priority Area:
  Disease and Injury: Musculoskeletal Disorders of the Upper Extremities
• Performing Organization:
  West Virginia University, Morgantown, West Virginia
• Peer Reviewed:
  False
• Start Date:
  19920101
• Source Full Name:
  Medicine and Science in Sports and Exercise
• Supplement:
  1
• End Date:
  20050531
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:cddda911f6310a3cee0a28289ae8f883e848a01bc2163e8c2e5aa9a2dcaae9b4676c3c2bea404f208da8a8dba447fbe4a8358fc11aff9ee8a9a8f458724f0670
• Download URL:
  https://stacks.cdc.gov/view/cdc/190510/cdc_190510_DS1.pdf
• File Type:
  [PDF - 38.57 KB ]