Background: Peripheral muscle weakness can be caused by both peripheral muscle and neural alterations. Although peripheral alterations cannot totally explain peripheral muscle weakness in COPD, the existence of an activation deficit remains controversial. The heterogeneity of muscle weakness (between 32 and 57% of COPD patients) is generally not controlled in studies and could explain this discrepancy. This study aimed to specifically compare voluntary and stimulated activation levels in COPD patients with and without muscle weakness. Methods: Twenty-two patients with quadriceps weakness (COPD MW), 18 patients with preserved quadriceps strength (COPD NoMW) and 20 controls were recruited. Voluntary activation was measured through peripheral nerve (VA peripheral) and transcranial magnetic (VA cortical) stimulation. Corticospinal and spinal excitability (MEP/Mmax and Hmax/Mmax) and corticospinal inhibition (silent period duration) were assessed during maximal voluntary quadriceps contractions. Results: COPD MW exhibited lower VA cortical and lower MEP/Mmax compared with COPD NoMW (p < 0.05). Hmax/Mmax was not significantly different between groups (p = 0.25). Silent period duration was longer in the two groups of COPD patients compared with controls (p < 0.01). Interestingly, there were no significant differences between all COPD patients taken together and controls regarding VA cortical and MEP/Mmax. Conclusions: COPD patients with muscle weakness have reduced voluntary activation without altered spinal excitability. Corticospinal inhibition is higher in COPD regardless of muscle weakness. Therefore, reduced cortical excitability and a voluntary activation deficit from the motor cortex are the most likely cortical mechanisms implicated in COPD muscle weakness. The mechanisms responsible for cortical impairment and possible therapeutic interventions need to be addressed.

The study was registered at www.clinicaltrials.gov as NCT01679782.

When two tasks are performed simultaneously, they compete for attentional resources, resulting in a performance decrement in one or both tasks. Patients with attention disorders have a reduced ability to perform several tasks simultaneously (e.g., talking while walking), which increases the fall risk and frailty. This study assessed the cognitive and motor performances of patients with COPD and healthy controls within a dual-task walking paradigm. A subobjective was to assess the impact of a pulmonary rehabilitation program on the dual-task performances in COPD. Twenty-five patients with COPD and 20 controls performed a cognitive task (subtraction) and a 15-m walking test separately (single-task; ST) and jointly (dual-task; DT). In addition, a subsample of 10 patients performed the same evaluations 5 weeks later after a pulmonary rehabilitation program following current recommendations. Cognitive and gait performances in ST showed no differences between patients with COPD and controls (all p > 0.05). However, COPD patients exhibited a greater increase in gait variability than controls in DT (4.07 ± 1.46% vs. 2.17 ± 0.7%, p < 0.001). The pulmonary rehabilitation program had no effect on the dual-task impairment for the subsample of patients (p = 0.87). This study provides evidence of insufficient attentional resources to successfully deal with DT in patients with COPD, and this was expressed through an exaggerated increase in gait variability in DT walking. Given the high risk of falls and disability associated with altered gait variability, dual-task training interventions should be considered in pulmonary rehabilitation programs.

No abstract

No abstract

To determine and/or adjust exercise training intensity for patients when the cardiopulmonary exercise test is not accessible, the determination of dyspnoea threshold (defined as the onset of self-perceived breathing discomfort) during the 6-min walk test (6MWT) could be a good alternative. The aim of this study was to evaluate the feasibility and reproducibility of self-perceived dyspnoea threshold and to determine whether a useful equation to estimate ventilatory threshold from self-perceived dyspnoea threshold could be derived. A total of 82 patients were included and performed two 6MWTs, during which they raised a hand to signal self-perceived dyspnoea threshold. The reproducibility in terms of heart rate (HR) was analysed. On a subsample of patients (n=27), a stepwise regression analysis was carried out to obtain a predictive equation of HR at ventilatory threshold measured during a cardiopulmonary exercise test estimated from HR at self-perceived dyspnoea threshold, age and forced expiratory volume in 1 s. Overall, 80% of patients could identify self-perceived dyspnoea threshold during the 6MWT. Self-perceived dyspnoea threshold was reproducibly expressed in HR (coefficient of variation=2.8%). A stepwise regression analysis enabled estimation of HR at ventilatory threshold from HR at self-perceived dyspnoea threshold, age and forced expiratory volume in 1 s (adjusted r=0.79, r=0.63, and relative standard deviation=9.8 bpm). This study shows that a majority of patients with chronic obstructive pulmonary disease can identify a self-perceived dyspnoea threshold during the 6MWT. This HR at the dyspnoea threshold is highly reproducible and enable estimation of the HR at the ventilatory threshold.

No abstract

No abstract