title: Variations in the relationship between the frequency content of EMG signals and the rate of torque development in voluntary and elicited contractions.
abstract: Our purpose was to characterize the relationship between EMG mean power frequency (MPF) or median frequency (MF) and rate of torque development in voluntary ballistic and electrically elicited isometric contractions. Twenty-three healthy adults participated in two sets of experiments performed on elbow flexor muscles. For Experiment 1, subjects were asked to generate voluntary ballistic contractions by reaching four different target torque levels (20, 40, 60 and 100% of the maximal voluntary contraction (MVC)) as fast as they could. For Experiment 2, electrical (M-waves) and mechanical (twitches) responses to electrical stimulation of the nerves supplying the biceps brachii and brachioradialis muscles were recorded with the subjects at rest and with a background isometric contraction of 15% MVC. MPF, MF and rate of torque development (% MVC/s) were calculated for both voluntary and elicited contractions. Significant positive correlations were observed between MPF and rate of torque development for the voluntary contractions, whereas significant negative correlations were observed between the two variables for elicited contractions. This suggests that factors other than muscle fiber composition influence the frequency content of EMG signals and/or the rate of torque development, and that the effect of these factors will vary between voluntary and elicited contractions.
authors.affiliation: Graduate Program in Physical Therapy and Rehabilitation Science, University of Iowa, 2600 Steindler Building, Iowa City, IA 52242, USA. martin-bilodeau@uiowa.edu
authors.forename: Martin
authors.initials: M
authors.lastname: Bilodeau
authors.forename: Jeff
authors.initials: J
authors.lastname: Houck
authors.forename: Tyler
authors.initials: T
authors.lastname: Cuddeford
authors.forename: Shreela
authors.initials: S
authors.lastname: Sharma
authors.forename: Nora
authors.initials: N
authors.lastname: Riley
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology*; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D005542:Forearm / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D016014:Linear Models; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D019415:Torque