Neuromuscular fatigue after maximal exercise in patients with cystic fibrosis

• Published in: Journal of electromyography and kinesiology Vol. 21; no. 2; pp. 242 - 248
• Main Authors: Vallier, J.M, Gruet, M, Mely, L, Pensini, M, Brisswalter, J
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2011
• Subjects: Adult; Chronic respiratory disease; Cystic fibrosis; Cystic Fibrosis - physiopathology; Electromyogram; Exercise limitation; Female; Humans; Male; Muscle Contraction; Muscle Fatigue; Muscle, Skeletal - physiopathology; Neuromuscular Junction; Physical Endurance; Physical Exertion; Physical Medicine and Rehabilitation; Quadriceps fatigue; Synaptic Transmission; vastus medialis; RMS M; BF; biceps femoris; root mean square; MVV; VCO 2; cystic fibrosis; EMG; BRI max; CF; P max; VO 2; maximal power; Quadriceps fatigue; Chronic respiratory disease; oxygen uptake; Electromyogram; root mean square of the M-wave; forced expiratory volume in one second; minute ventilation; maximum voluntary ventilation; breathing reserve index at maximum exercise; FEV 1; electromyography; carbon dioxide production; VM; maximal voluntary contraction; RMS; V E; MVC; COPD; chronic obstructive pulmonary disease; Exercise limitation
• ISSN: 1050-6411; 1873-5711
• DOI: 10.1016/j.jelekin.2010.10.010

Abstract The aim of this study was to determine whether patients with cystic fibrosis (CF), despite their ventilatory limitation, would develop neuromuscular fatigue of quadriceps muscles following a maximal cycling exercise. Eleven adults with CF (age = 26.8 ± 6.9 years; forced expiratory volume in 1 s = 54.1 ± 12.8% predicted) and 11 age-matched healthy subjects performed a maximal incremental cycle test with respiratory gas exchange measurements. Maximal voluntary contraction (MVC) and electromyographic (EMG) activity of the vastus medialis muscle were recorded before and after exercise. Neural and contractile properties of the quadriceps were also investigated using femoral nerve electrical stimulation. Patients had lower exercise capacity, peak oxygen uptake and MVC than controls. MVC fell significantly postexercise in both groups (CF: −20 ± 10%, controls: −19 ± 6%; p < 0.01). EMG root mean square values, M-wave amplitude and duration were unchanged in both groups. Peak twitch (−46.9 ± 13.8%), maximal rate of twitch torque development (−50.3 ± 13.8%) and relaxation (−35.2 ± 19.5%) were all reduced after exercise in CF patients. The control group followed the same pattern (−38.4 ± 14.4%, −42.1 ± 14.7% and −15 ± 20.4%) but the statistical significance was not reached for the maximal rate of twitch torque relaxation. In conclusion, CF patients demonstrated lower limb fatigue following symptom-limited cycle exercise, which was comparable to that exhibited by healthy controls. This fatigue may be due to contractile impairments and not to transmission failure. Further studies should be conducted in a larger sample to confirm these preliminary results.