HISTOCHEMICAL AND MORPHOLOGICAL-CHARACTERISTICS OF THE VASTUS LATERALIS MUSCLE IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

Purpose and Methods: In this study, we examined the fiber-type proport ions, cross-sectional areas (CSA), and capillarization from needle bio psies of the vastus lateralis muscle in 20 patients with chronic obstr uctive pulmonary disease (COPD) (FEV1 = 37 +/- 11% predicted, peak (V) over dot O-2 = 13 +/- 4 mL.min(-1).kg(-1)) and nine age-matched norma l subjects (peak (V) over dot O-2 = 33 +/- 7 mL.min(-)1.kg(-1)). The e ffects of endurance training on these parameters were also evaluated i n 11 of the 20 patients with COPD. Results: The proportion of Type I f iber was smaller in COPD than normals (34 +/- 14% vs 58 +/- 16 in norm als, P < 0.0005) with a corresponding increase in Type IIb fiber (P = 0.015). The CSA of Type I, IIa, and IIab fibers was also smaller in CO PD. The capillary to fiber ratio tended to be reduced in patients, but this difference did not reach statistical significance (P = 0.15). Th e number of capillary contact for Type I, IIa, and IIab fibers was sig nificantly reduced in COPD compared with normal subjects (P < 0.05). W hen corrected for the CSA, this parameter was similar for both groups. After training, peak (V) over dot O-2 increased by 11% (P < 0.05), th e fiber-type proportion remained unchanged, and the CSA of Type I and IIa fibers increased by 31 and 21%, respectively (P < 0.05). Although the number of capillary contact for each fiber types increased with tr aining, the capillary to fiber ratio and the number of capillary conta ct for the different fiber types relative to their CSA remain unchange d. Conclusions: We conclude that in COPD, 1) the vastus lateralis musc le is characterized by a marked decrease in Type I fiber proportion, a n increase in Type IIb, fiber proportion, a decrease in Type I, IIa, a nd Ilab fiber CSA and by a relatively preserved capillarization; and 2 ) a 12-wk training program induces a significant increase in Type I an d IIa CSA.