Abstract
Abstract Introduction: COPD presents decrease in oxidative metabolism with possible losses of cardiovascular adjustments, suggesting slow kinetics microvascular oxygen during intense exercise. Objective: To test the hypothesis that chronic obstructive pulmonary disease (COPD) patients have lower muscle performance in physical exercise not dependent on central factors, but also greater muscle oxygen extraction, regardless of muscle mass. Methods: Cross-sectional study with 11 COPD patients and nine healthy subjects, male, paired for age. Spirometry and body composition by DEXA were evaluated. Muscular performance was assessed by maximal voluntary isometric contraction (MVIC) in isokinetic dynamometer and muscle oxygen extraction by the NIRS technique. Student t-test and Pearson correlation were applied. A significance level of p<0.05 was adopted. Results: Patients had moderate to severe COPD (FEV1 = 44.5 ± 9.6% predicted; SpO2 = 94.6 ± 1.6%). Lean leg mass was 8.3 ± 0.9 vs. 8.9 ± 1.0 kg (p =0.033), when comparing COPD and control patients, respectively. The decreased muscle oxygen saturation corrected by muscle mass was 53.2% higher (p=0.044) in the COPD group in MVIC-1 and 149.6% higher (p=0.006) in the MVIC-2. Microvascular extraction rate of oxygen corrected by muscle mass and total work was found to be 114.5% higher (p=0.043) in the COPD group in MVIC-1 and 210.5% higher (p=0.015) in the MVIC-2. Conclusion: COPD patients have low muscle performance and high oxygen extraction per muscle mass unit and per unit of work. The high oxygen extraction suggests that quantitative and qualitative mechanisms can be determinants of muscle performance in patients with COPD.
Highlights
chronic obstructive pulmonary disease (COPD) presents decrease in oxidative metabolism with possible losses of cardiovascular adjustments, suggesting slow kinetics microvascular oxygen during intense exercise
Several studies have demonstrated that maximum strength is associated with the level of daily physical activity [4], it is a better predictor of mortality (compared to age, body mass index (BMI) and FEV1 - forced expiratory volume in the irst second) [5] and correlates with peak oxygen consumption and the oxygen uptake ef iciency slope (OUES) [6] in COPD
The COPD group was determined according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) and classi ied as stage II-III; showing forced expiratory volume (FEV1) less than 80% of predicted value and FEV1/forced vital capacity (FVC) less than 0.70
Summary
COPD presents decrease in oxidative metabolism with possible losses of cardiovascular adjustments, suggesting slow kinetics microvascular oxygen during intense exercise. Objective: To test the hypothesis that chronic obstructive pulmonary disease (COPD) patients have lower muscle performance in physical exercise not dependent on central factors, and greater muscle oxygen extraction, regardless of muscle mass. Instead of aerobic, is a better predictor of the ability to perform lower limb physical activity among patients with COPD [3]. Several studies have demonstrated that maximum strength is associated with the level of daily physical activity [4], it is a better predictor of mortality (compared to age, body mass index (BMI) and FEV1 - forced expiratory volume in the irst second) [5] and correlates with peak oxygen consumption (peak VO2) and the oxygen uptake ef iciency slope (OUES) [6] in COPD. Maximum isometric strength is better associated with numerous types of functional testing rather than the VO2peak and Wattspeak obtained from cardiopulmonary testing [7]
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