RT Journal Article
SR Electronic
T1 Effects of a low-intensity single-leg exercise on fatigue and muscle oxygenation in patients with chronic obstructive pulmonary disease (COPD)
JF European Respiratory Journal
JO Eur Respir J
FD European Respiratory Society
SP P3570
VO 42
IS Suppl 57
A1 Fernanda Ribeiro
A1 Valérie Coats
A1 Didier Saey
A1 François Maltais
YR 2013
UL http://erj.ersjournals.com/content/42/Suppl_57/P3570.abstract
AB In COPD, single-leg exercises allow to study muscle dysfunction mechanisms in isolation from exagerated ventilatory demand and dyspnea. Therefore, we studied the effect of a knee-extension exercise on quadriceps fatigue and its possible association with cardiorespiratory demand and oxygen extraction at the muscle level.Methods: Eight patients with moderate-to-severe COPD (FEV1 = 45 ± 13% of predicted) performed an isokinetic knee-extension exercise at 40% of their maximal peak torque. Quadriceps isometric maximal voluntary contraction (MVC) and magnetic-stimulated twitch (Twpot) were measured before and after exercise to characterize muscle fatigue. Cardiorespiratory demand and muscle oxygenation (deoxyhemoglobin/myoglobin concentration, [HHb], by near-infrared spectroscopy) were assessed during exercise.Results: Patients performed a total of 7.4 ± 1.0 kJ of muscle work, which resulted in a reduction of both MVC and Twpot of -11 ± 8 % and -22 ± 25 %, respectively. Five patients presented muscle fatigue (> 15 % reduction in Twpot). At the end of exercise, dyspnea and leg-fatigue Borg scores were 2.0 ± 1.0 and 0.7 ± 0.8, respectively. No significant changes in muscle oxygenation (Δ[HHb] = 13 ± 12%, p = 0.08) were seen. Changes in muscle oxygenation were not associated with muscle strength loss. Peak minute ventilation and oxygen uptake represented, on average, 50% and 41% of peak value achieved during a symptom-limited maximal exercise test.Conclusion: Despite low cardiorespiratory demand and exercise load, a single-leg exercise induced muscle fatigue in the absence of muscle deoxygenation in some patients with moderate-to-severe COPD.