Biomaterial Database

Relation between electromyogram and force in fatigue. 1985

H Kranz, and J F Cassell, and G F Inbar

The relationship between the surface electromyogram (SEMG) and force was examined during maximal voluntary contraction (MVC). Isometric MVC of elbow flexors were studied in 18 subjects who performed 27 trials, each consisting of six MVCs lasting 45 s at intervals of 30 s. There was a decrease in the median frequency (Fm) of the SEMG and of the compound action potentials (CAP) during MVC. The CAPs demonstrated that the fall in Fm was associated with a proportional increase in signal power, whereas CAP amplitude did not decrease, indicating intact neuromuscular transmission. The SEMG root-mean-square amplitude remained fairly constant, progressively deviating from force with time of contraction (r = 0.40). When SEMG amplitude was corrected for the Fm change, it tracked force more closely (r = 0.68), indicating a fall in motoneuron drive during MVC. The corrected SEMG was used to calculate the change in the generalized firing rate of motoneurons. The firing rate decreased 60% in the first and sixth contractions, tracked force closely, and corresponded to the firing rate fall seen in late adaptation of motoneurons (r = 0.90, P less than 0.001).

UI	MeSH Term	Description	Entries
D009046	Motor Neurons	Neurons which activate MUSCLE CELLS.	Neurons, Motor,Alpha Motorneurons,Motoneurons,Motor Neurons, Alpha,Neurons, Alpha Motor,Alpha Motor Neuron,Alpha Motor Neurons,Alpha Motorneuron,Motoneuron,Motor Neuron,Motor Neuron, Alpha,Motorneuron, Alpha,Motorneurons, Alpha,Neuron, Alpha Motor,Neuron, Motor
D009119	Muscle Contraction	A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.	Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D004576	Electromyography	Recording of the changes in electric potential of muscle by means of surface or needle electrodes.	Electromyogram,Surface Electromyography,Electromyograms,Electromyographies,Electromyographies, Surface,Electromyography, Surface,Surface Electromyographies
D005221	Fatigue	The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli.	Lassitude
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000200	Action Potentials	Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.	Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential