The effect of exercise on peripheral muscle in emphysema: a preliminary investigation

Emphysema has been associated with loss of aerobic muscle fibers and decreased blood supply. However, when these changes begin and whether exercise can prevent these changes is unknown. The purpose of this study was to examine peripheral muscle at different time points during the development of emphysema and to determine the additional effects of muscle activity. In a series of 3 experiments, emphysema was induced in hamsters. Exercise was simulated through surgical overload (OV) of the plantaris muscle of one leg. Animals were sacrificed at 1, 3, and 5 months following emphysema induction. Fiber type composition and capillary-to-fiber ratio (CFR) were determined. There were no significant changes in fiber type composition in the 1-month group. A significant increase in type IIA fiber composition (mean 72.0 vs. 54.5%) and decrease in type IIB fiber (mean 13.3 vs. 28.1%) was seen in the non-overloaded muscles following 3 months. In the 5-month group, there was a significant decrease in percentage of type I fibers (mean 14.7 vs. 28.0%). There were no significant differences in fiber type composition in the OV limb, regardless of duration. The CFR was significantly lower in the OV limb after 5-months of emphysema (mean 0.92 vs. 1.55 cap/fiber). Muscle overload prevented emphysema-associated changes in fiber type composition, but not in CFR. Peripheral muscle is affected early in the course of emphysema and chronic overload may play an important role in preserving normal muscle composition.