title: Investigations of the time series structure of the EMG during sustained isometric contractions of back muscles.
abstract: The experiment aimed at elucidating electromyographic signs of fatigue of lumbar muscles. On two days, 4 subjects had to hold 4 different target forces to fatigue. Bipolar surface EMG's were derived at the L3 level. The time series structure of the EMG's was characterized by means of autoregressive models. The r.m.s.- value did not reveal uniform time-dependent changes, except for an increase during the highest force level. The variance explained by a linear stochastic process systematically increased during the sustained contractions. The mean power frequencies exhibited similar changes.
mesh_terms: D000328:Adult; D001415:Back; D004576:Electromyography; D005221:Fatigue / Q000503:physiopathology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology*