The correlation between quadriceps muscle strength and endurance and exercise performance in patients with COPD.

To determine the association between quadriceps muscle strength (QMS) and endurance (QME) and exercise capacity in patients with COPD after stratification for sex and resting lung function (LF). Data were collected from 3,246 patients with COPD (60% men, 64 ± 9 yr), including measures of exercise capacity [peak aerobic capacity (peakV̇o2), 6-min walk distance (6MWD)] and isokinetic QMS and QME. Patients were stratified for sex, forced expiratory volume in 1 s (>50/≤50% predicted), single breath carbon monoxide diffusing capacity (>50/≤50% predicted), and residual volume (>140/≤140% predicted). After stratification for resting LF, QMS and QME were significantly associated with peakV̇o2 (r range: 0.47-0.61 and 0.49-0.65 for men and 0.53-0.66 and 0.48-0.67 for women, respectively) and 6MWD (r range: 0.29-0.42 and 0.44-0.55 for men and 0.25-0.54 and 0.34-0.55 for women, respectively) (P < 0.001). Regression models demonstrated that QMS and QME were significant determinants of peakV̇o2 (explained variance R2 range: 35.6%-48.8% for men and 36.8%-49.0% for women) and 6MWD (R2 range: 24.3%-43.3% for men and 28.4%-40.3% for women), independent of age and fat-free mass. Quadriceps muscle function was significantly associated with peakV̇o2 and 6MWD in male and female patients with COPD after stratification for resting LF, in which QME appear to be a more important determinant than QMS. This underlines the importance of systematically evaluating both quadriceps muscle strength and endurance in in all patients with COPD.NEW & NOTEWORTHY Our findings identified quadriceps muscle function as an important determinant of exercise capacity across a wide spectrum of lung function. Quadriceps muscle endurance appears to be a more important determinant than quadriceps muscle strength, underlining the importance of including both the measurement of quadriceps muscle strength and endurance in routine assessment for all patient with COPD.

Impact of pulmonary rehabilitation on activities of daily living in patients with chronic obstructive pulmonary disease.

A high proportion of patients with chronic obstructive pulmonary disease (COPD) experience problems during the performance of activities of daily living (ADLs). We aimed to determine the effects of a comprehensive 8-wk pulmonary rehabilitation program on the physiologic response to and performance of ADLs in patients with COPD. Before and after pulmonary rehabilitation, 31 patients with COPD [71% men; mean age: 64.2 (SD 8.4) years; mean forced expiratory volume in the first second: 54.6 (SD 19.9) % predicted] performed physical function tests, the Canadian Occupational Performance Measure (COPM), and an ADL test consisting of the following: putting on socks, shoes, and vest; stair climbing; washing up four dishes, cups, and saucers; doing groceries and putting away groceries in a cupboard; folding eight towels; and vacuum cleaning for 4 min. Metabolic load, ventilation, and dynamic hyperinflation were assessed using an Oxycon mobile device. In addition, symptoms of dyspnea and fatigue and time to complete ADLs were recorded. After rehabilitation, patients with COPD used a significantly lower proportion of their peak aerobic capacity and ventilation to perform ADLs, accompanied by lower Borg scores for dyspnea and fatigue. Furthermore, patients needed significantly less time to complete ADLs. Dynamic hyperinflation occurred during the performance of ADLs, which did not change following pulmonary rehabilitation. Changes in physical function, including six-min walk distance, constant work rate test, quadriceps muscle strength, and COPM were significantly correlated with change in average total oxygen uptake during the performance of the ADL test. A comprehensive pulmonary rehabilitation program can improve the physiologic response to and actual performance of ADLs in patients with COPD. NEW & NOTEWORTHY A high proportion of patients with chronic obstructive pulmonary disease (COPD) experience problems during the performance of activities of daily living (ADLs). This study clearly demonstrated that a comprehensive pulmonary rehabilitation program can improve the performance of ADLs in patients with COPD, indicated by a significantly shorter time to perform ADLs and a lower metabolic load and dyspnea sensation.