No abstract

Eccentric ergometer training (EET) is increasingly being proposed as a therapeutic strategy to improve skeletal muscle strength in various cardiorespiratory diseases, due to the principle that lengthening muscle actions lead to high force-generating capacity at low cardiopulmonary load. One clinical population that may particularly benefit from this strategy is chronic obstructive pulmonary disease (COPD), as ventilatory constraints and locomotor muscle dysfunction often limit efficacy of conventional exercise rehabilitation in patients with severe disease. While the feasibility of EET for COPD has been established, the nature and extent of adaptation within COPD muscle is unknown. The aim of this study was therefore to characterize the locomotor muscle adaptations to EET in patients with severe COPD, and compare them with adaptations gained through conventional concentric ergometer training (CET). Male patients were randomized to either EET (n = 8) or CET (n = 7) for 10 weeks and matched for heart rate intensity. EET patients trained on average at a workload that was three times that of CET, at a lower perception of leg fatigue and dyspnea. EET led to increases in isometric peak strength and relative thigh mass (p < 0.01) whereas CET had no such effect. However, EET did not result in fiber hypertrophy, as morphometric analysis of muscle biopsies showed no increase in mean fiber cross-sectional area (p = 0.82), with variability in the direction and magnitude of fiber-type responses (20% increase in Type 1, p = 0.18; 4% decrease in Type 2a, p = 0.37) compared to CET (26% increase in Type 1, p = 0.04; 15% increase in Type 2a, p = 0.09). EET had no impact on mitochondrial adaptation, as revealed by lack of change in markers of mitochondrial biogenesis, content and respiration, which contrasted to improvements (p < 0.05) within CET muscle. While future study is needed to more definitively determine the effects of EET on fiber hypertrophy and associated underlying molecular signaling pathways in COPD locomotor muscle, our findings promote the implementation of this strategy to improve muscle strength. Furthermore, contrasting mitochondrial adaptations suggest evaluation of a sequential paradigm of eccentric followed by concentric cycling as a means of augmenting the training response and attenuating skeletal muscle dysfunction in patients with advanced COPD.

No abstract

Little attention has been given to the impact of chronic obstructive pulmonary disease (COPD) on work productivity loss. Individuals with COPD are at risk of reduced working hours, absenteeism, presenteeism and early retirement [1]. Studies have been focused mostly on patients attending outpatient clinics [2], which exclude individuals with undiagnosed COPD, thus limiting the external validity of the findings. There are very few population-based cohort studies [3-6], few reports on presenteeism [5], and a lack of objective measures to define COPD [6]. There would be value in knowing the extent of work productivity loss in individuals with mild COPD, or those who are yet undiagnosed. This could further translate into the allocation of health management programmes in the workplace. We evaluated work productivity loss (measured as absenteeism and/or presenteeism) between individuals with mild to moderate COPD and those without COPD. We hypothesised that working individuals with COPD, having mild and moderate airflow obstruction with a high symptom burden would have greater work productivity loss than those with a low symptom burden. Our study was embedded in the Canadian Cohort Obstructive Pulmonary Disease (CanCOLD) study, an ongoing multicentre study involving subjects with COPD, sampled from the general population (see BOURBEAU et al. [7], for full details). For the purpose of the current study, inclusion criteria for employed COPD and non-COPD control subjects were as follows: ⩾40 years old, having paid employment at the time of study enrolment and a post-bronchodilator forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) <0.70 for COPD versus FEV1/FVC ⩾0.70 for non-COPD. All participants provided written informed consent and the study was approved by the respective institutional ethical review boards. Subjects with spirometrically defined COPD, who reported prior physician-diagnosed COPD, chronic bronchitis, or emphysema upon entering the CanCOLD study were identified as "diagnosed" subjects, and subjects with spirometrically defined COPD, who had not received a COPD diagnosis prior to enrolment in the study, were identified as having "undiagnosed" COPD. The overall work productivity loss, i.e. absenteeism and/or presenteeism, was measured by the health and labour questionnaire (HLQ) [8], a generic and validated instrument. Absenteeism refers to health-related absence from work, whereas presenteeism refers to the act of attending work while sick, e.g. decreased work quality or quantity. Symptom burden was measured using the COPD Assessment Test (CAT) [9]. Subjects with CAT scores <10 were classified as low symptom burden and those with CAT scores ⩾10 as high symptom burden [10]. Comparisons between groups for descriptive summaries were performed using ANOVA or the Kruskal-Wallis test for continuous variables, and the Chi-squared test for dichotomous variables. The level of significance was set at p<0.05. All analyses were carried out using the SAS version 9.1.3 software (SAS Institute Inc., Cary, NC...