Chronic Fatigue Syndrome Research Today is a free monthly online journal that collates and summarizes the latest research about Chronic Fatigue Syndrome, including details on myalgic encephalomyelitis (me), diagnosis, gradual and sudden onset.

Assessment of muscle fatigue during exercise in chronic obstructive pulmonary disease.

Saey D, Côté CH, Mador MJ, Laviolette L, LeBlanc P, Jobin J, Maltais F

Centre de Recherche, Hôpital Laval, Institut Universitaire de Cardiologie et de Pneumologie de l'Université Laval, 2725 Chemin Ste-Foy, Québec G1V 4G5, Canada.

Contractile fatigue is associated with exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). Contractile fatigue may be assessed by quantifying the decline in strength after a fatiguing protocol but this may pose practical problems. The purpose of this study was to investigate the relationship between the decline in quadriceps strength, quadriceps electrical activity, perception of leg fatigue, and arterial lactate level in patients with COPD during constant work-rate cycling exercise. The decline in quadriceps strength was significantly associated with the decrease in electromyographic median frequency (r = 0.606), leg fatigue perception (r = 0.453), and arterial lactate level (r = 0.384). Using the receiver-operating-characteristic curve, it was found that a 4% decline in electromyographic median frequency had a 94% sensitivity and a 75% specificity to predict contractile fatigue. We conclude that contractile fatigue commonly occurs during cycling exercise in COPD. The electromyographic median frequency appears to be a valuable indirect marker to predict contractile leg fatigue.

Published 14 June 2006 in Muscle Nerve, 34(1): 62-71.
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