Received January 7, 2005
Revised February 18, 2005
Accepted after revision February 28, 2005
Emphysema-induced reductions in locomotory skeletal muscle contractile function
John Mattson 1*
James Martin 2
1 Gustavus Adolphus College
2 University of Utah
* To whom correspondence should be addressed. E-mail: jmattson{at}gac.edu.
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Abstract |
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Patients with COPD suffer from locomotory skeletal muscle contractile dysfunction. This may be due to the disease per se or as a result of some confounding factor. Therefore, the purpose of this investigation was to determine if emphysema: 1) reduces force production; 2) increases fatigability; and 3) impairs the speed of recovery in locomotory skeletal muscle in an accepted animal model in which many confounding variables can be controlled. To explore this issue, in-situ mechanical properties of gastrocnemius were measured in Syrian Golden hamsters 8 mo after intratracheal instillation of either saline (control, n=5) or elastase (emphysema, n=7). Emphysema increased excised lung volume [80% (P<0.01)], increased fatigability [control = 25% and emphysema = 55% reduction in maximal strength after 4 minutes of repeated contractions (P<0.05)] and decreased the recovery rate [half-times of recovery; control = 7±7 s and emphysema = 92±92 s (P<0.05)] of gastrocnemius muscle. In contrast, emphysema had no effect on maximal force, whether related to body mass or muscle mass, nor force-velocity characteristics of gastrocnemius muscle. These data demonstrate that emphysema, independent of physical activity levels, pharmacological intervention, and/or nutritional status, can increase fatigability and impair the speed of recovery of locomotory skeletal muscle contractile function which may contribute to exercise intolerance of COPD patients.
Key Words:
Muscle fatigue, Respiration, Skeletal muscle
