title: The effects of chronic exercise training status on motor unit activation and deactivation control strategies.
abstract: This study examined the mechanomyographic (MMGRMS) amplitude-force relationships for 5 (age = 19.20 ± 0.45 years) aerobically trained (AT), 5 (age = 25 ± 4.53 years) resistance-trained (RT) and 5 (age = 21.20 ± 2.17 years) sedentary (SED) 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. MMG and skinfold thickness were recorded from the vastus lateralis. b and a terms were calculated from the natural log-transformed MMGRMS-force relationships (linearly increasing and decreasing segments) for each participant. An average of MMGRMS was calculated for the entire steady force segment. The b terms for the RT (0.727 ± 0.334) and SED (0.622 ± 0.281) were significantly greater (P < 0.05) than the AT (0.159 ± 0.223) and were greater during the linearly increasing (0.622 ± 0.426) than decreasing (0.383 ± 0.269) segments when collapsed across segments and training status, respectively. MMGRMS during the steady force segment and skinfold thicknesses were not different among training statuses (P = 0.106, P = 0.142). Motor unit (MU) activation strategies were influenced as a function of exercise training status and muscle action. Future research is needed to fully understand the implications of these changes in MU control strategies as a result of chronic exercise training on exercise and athletic performance.
authors.affiliation: a Neuromechanics Laboratory, Department of Health, Sport, and Exercise Sciences , University of Kansas , Lawrence , KS , USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Trevino
authors.affiliation: a Neuromechanics Laboratory, Department of Health, Sport, and Exercise Sciences , University of Kansas , Lawrence , KS , USA.
authors.forename: Trent J
authors.initials: TJ
authors.lastname: Herda
mesh_terms: D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D006801:Humans; D052097:Quadriceps Muscle / Q000502:physiology*; D055070:Resistance Training; D057185:Sedentary Behavior; D012885:Skinfold Thickness; D055815:Young Adult
keywords: exercise training; isometric trapezoidal muscle action; log-transform model; mechanomyography; motor unit control strategies