title: Fatigue-induced adjustment in antagonist coactivation by old adults during a steadiness task.
abstract: The purpose of this study was to determine the adjustments in the level of coactivation during a steadiness task performed by young and old adults after the torque-generating capacity of the antagonist muscles was reduced by a fatiguing contraction. Torque steadiness (coefficient of variation) and electromyographic activity of the extensor and flexor carpi radialis muscles were measured as participants matched a wrist extensor target torque (10% maximum) before and after sustaining an isometric contraction (30% maximum) with wrist flexors to task failure. Time to failure was similar (P = 0.631) for young (417 ± 121 s) and old (452 ± 174 s) adults. The reduction in maximal voluntary contraction torque (%initial) for the wrist flexors after the fatiguing contraction was greater (P = 0.006) for young (32.5 ± 13.7%) than old (21.8 ± 6.6%) adults. Moreover, maximal voluntary contraction torque for the wrist extensors declined for old (-13.7 ± 12.7%; P = 0.030), but not young (-5.4 ± 13.8%; P = 0.167), adults. Torque steadiness during the matching task with the wrist extensors was similar before and after the fatiguing contraction for both groups, but the level of coactivation increased after the fatiguing contraction for old (P = 0.049) but not young (P = 0.137) adults and was twice the amplitude for old adults (P = 0.002). These data reveal that old adults are able to adjust the amount of antagonist muscle activity independent of the agonist muscle during steady submaximal contractions.
authors: Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island; Department of Integrative Physiology, University of Colorado, Boulder, Colorado christopher_arellano@brown.edu.
authors: Christopher J
authors: CJ
authors: Arellano
authors: Department of Integrative Physiology, University of Colorado, Boulder, Colorado.
authors: David
authors: D
authors: Caha
authors: Department of Integrative Physiology, University of Colorado, Boulder, Colorado.
authors: Joseph E
authors: JE
authors: Hennessey
authors: Department of Physical Education and Sport Sciences, Aristotle University of Thessaloniki, Serres, Greece; and.
authors: Ioannis G
authors: IG
authors: Amiridis
authors: Laboratory of Applied Biology, Neurosciences Institute, Université Libre de Bruxelles, Brussels, Belgium;
authors: Stéphane
authors: S
authors: Baudry
authors: Department of Integrative Physiology, University of Colorado, Boulder, Colorado.
authors: Roger M
authors: RM
authors: Enoka
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology*; D004550:Elbow / Q000502:physiology; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D019415:Torque; D014953:Wrist / Q000502:physiology
keywords: aging; electromyogram; fatigue; steadiness; wrist torque