title: Modelling suppressed muscle activation by means of an exponential sigmoid function: validation and bounds.
abstract: The aim of this study was to establish how well a three-parameter sigmoid exponential function, DIFACT, follows experimentally obtained voluntary neural activation-angular velocity profiles and how robust it is to perturbed levels of maximal activation. Six male volunteers (age 26.3±2.73 years) were tested before and after an 8-session, 3-week training protocol. Torque-angular velocity (T-ω) and experimental voluntary neural drive-angular velocity (%VA-ω) datasets, obtained via the interpolated twitch technique, were determined from pre- and post-training testing sessions. Non-linear regression fits of the product of DIFACT and a Hill type tetanic torque function and of the DIFACT function only were performed on the pre- and post-training T-ω and %VA-ω datasets for three different values of the DIFACT upper bound, αmax, 100%, 95% & 90%. The determination coefficients, R(2), and the RMS of the fits were compared using a two way mixed ANOVA and results showed that there was no significant difference (p<0.05) due to changing αmax values indicating the DIFACT remains robust to changes in maximal activation. Mean R(2) values of 0.95 and 0.96 for pre- and post-training sessions show that the maximal voluntary torque function successfully reproduces the T-ω raw dataset.
authors: School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK.
authors: Dimitrios
authors: D
authors: Voukelatos
authors: School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK. Electronic address: m.t.g.pain@lboro.ac.uk.
authors: Matthew Tg
authors: MT
authors: Pain
mesh_terms: D000328:Adult; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D008433:Mathematics; D008954:Models, Biological; D008962:Models, Theoretical; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D012044:Regression Analysis; D015203:Reproducibility of Results; D019415:Torque
keywords: Force; Interpolate twitch; Quadriceps; Velocity