Commentary on Current Literature
Are Patients with COPD More Active after Pulmonary Habitual Physical Activity in Daily Life Correlates
Rehabilitation? Pitta F, Troosters T, Probst VLanger D, Positively with Markers for Mitochondrial Capac-
Decramer M, Gosselink R. Reprinted with permission from ity. Reprinted with permission from Journal of Applied
Chest. 2008;134:273-280. © 2008 American College of Physiology. 2008;105:561-568. © 2008 American Physi-
Chest Physicians. ologic Society.
Background: Despite a variety of benefits brought by Physical exercise training is a powerful tool to maintain
pulmonary rehabilitation to patients with COPD, it is or improve mitochondrial density and function (mito-
unclear whether these patients are more active during daily chondrial capacity). This study aims to determine whether
life after the program. Methods: Physical activities in daily mitochondrial capacity is also associated with habitual
life (activity monitoring), pulmonary function (spirometry), physical activity in daily life (PADL). The capacity of clas-
exercise capacity (incremental cycle-ergometer testing sic markers for mitochondrial density, ie, the capacity of
and 6-min walk distance testing), muscle force (quadri- citrate synthase (CS) and succinate dehydrogenase (SDH),
ceps and handgrip force, and inspiratory and expiratory as well the capacity of cytochrome c oxidase (COX) and
maximal pressures), quality of life (chronic respiratory beta-hydroxyacyl-CoA dehydrogenase (HAD), was deter-
disease questionnaire), and functional status (pulmonary mined in homogenized muscle biopsy samples obtained
functional status and dyspnea questionnaire-modified ver- from the vastus lateralis muscle of nonexercising healthy
sion) were assessed at baseline, after 3 months of a mul- young (age 20 ± 2 yr) subjects (31 women, 7 men). PADL
tidisciplinary rehabilitation program, and at the end of a was measured during two periods of 14 days using a tri-
6-month multidisciplinary rehabilitation program in 29 axial accelerometer for movement registration. CS, SDH,
patients (mean [± SD] age, 67 ± 8 years; FEV1, 46 ± 16% and COX were positively associated with PADL [P < 0.05,
predicted). Results: Exercise capacity, muscle force, quality R = 0.36, 95% confidence interval (CI): 1.3.10-4 to 2.2.10-
of life, and functional status improved significantly after 3
; P < 0.05, R=0.39, 95% CI: 1.1.10-5 to 9.9.10-5; and P <
3 months of pulmonary rehabilitation (all p < 0.05), with 0.05, R = 0.33, 95% CI: 7.5.10-6 to 3.6.10-4, respectively],
further improvements in muscle force, functional status, and HAD tended to correlate positively with PADL (P =
and quality of life at 6 months. Movement intensity during 0.06, R = 0.31, 95% CI: -2.2.10-5 to 1.1.10-3). The popula-
walking improved significantly after 3 months (p = 0.046) tion was subsequently stratified bas