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FORCE AND FATIGUE IN HUMAN TYPE I MUSCLE FIBRES: A SURFACE EMG STUDY IN PATIENTS WITH CONGENITAL MYOPATHY AND TYPE I FIBRE PREDOMINANCE
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1991
Year
Fibre PredominanceMore Emg VoltageMuscle FunctionEmg AmplitudeOrthopaedic SurgeryMuscle FibresKinesiologyMuscle InjurySkeletal MuscleExerciseApplied PhysiologyHealth SciencesRehabilitationHuman Musculoskeletal SystemNeuromuscular PathologyPhysiologyExercise PhysiologyElectromyographyExercise TestMedicineNeuromusculoskeletal Disorder
An isometric ischaemic intermittent m.biceps brachii exercise test is performed by 4 patients suffering from congenital myopathies which are characterized by a 100% type I fibre predominance, and by 26 healthy volunteers. Thirty contractions per minute are made at an 80% of maximal voluntary contraction level. It is found that type I muscle fibres have a fourfold lower force-generating capacity than type II muscle fibres. The EMG amplitude shows that more EMG voltage is needed per unit force in the patients with 100% type I fibres compared with controls. Under standardized fatiguing circumstances the power density frequency spectrum shows a weaker shift to lower frequencies in patients with 100% type I muscle fibres compared with controls. The muscle fibre conduction velocity (MFCV) of type I muscle fibres shows no decline during ischaemic exercise indicating an unimpaired muscle membrane excitability.