title: The effects of training status and muscle action on muscle activation of the vastus lateralis.
abstract: This study examined the electromyographic amplitude-force relationships for 5 (age = 19.20 ± 0.45 yrs) aerobically-trained, 5 (age = 25 ± 4.53 yrs) resistance-trained, and 5 (age = 21.20 ± 2.17 yrs) sedentary individuals. Participants performed an isometric trapezoidal muscle action at 60% maximal voluntary contraction of the leg extensors that included linearly increasing, steady force, and linearly decreasing muscle actions. Electromyography was recorded from the vastus lateralis. The b (slopes) and a (y-intercepts) terms were calculated from the natural log-transformed electromyographic amplitude-force relationships (linearly increasing and decreasing segments) for each participant. An average of the electromyographic amplitude was calculated for the entire steady force segment. The b terms for the resistance-trained (1.384 ± 0.261) were greater than the aerobically-trained (0.886 ± 0.130, P = 0.003) and sedentary (0.955 ± 0.105, P = 0.008) participants during the linearly increasing segment, whereas, there were no differences in b terms among training statuses for the linearly decreasing segment. The b terms for the resistance-trained were greater (P = 0.019) during the linearly increasing segment than decreasing segment (1.186 ± 0.181), however, the b terms for the aerobically-trained were lower (P = 0.017) during the linearly increasing than decreasing segment (1.054 ± 0.176). The a terms from the log-transformed electromyographic amplitude- force relationships and electromyographic amplitude during the steady force segment were not different among training statuses (P = 0.187, P = 0.910). The linearity of the electromyographic amplitude patterns of response (b terms) recording during increasing and decreasing muscle actions may provide insight on motor unit control strategy differences as a result of exercise training status and muscle action, however, the a terms of these patterns and electromyographic amplitude during a steady force contraction did not distinguish among training statuses.
authors.affiliation: Neuromechanics Laboratory, Department of Health, Sport, and Exercise Sciences, University of Kansas, Lawrence, United States.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Trevino
authors.affiliation: Neuromechanics Laboratory, Department of Health, Sport, and Exercise Sciences, University of Kansas, Lawrence, United States.
authors.forename: Trent J
authors.initials: TJ
authors.lastname: Herda
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography / Q000706:statistics & numerical data; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D064797:Physical Conditioning, Human / Q000502:physiology; D052097:Quadriceps Muscle / Q000502:physiology*; D055070:Resistance Training; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult