title: Heavy-resistance exercise-induced increases in jump performance are not explained by changes in neuromuscular function.
abstract: Post-activation potentiation (PAP) is the increased involuntary muscle twitch response to stimulation following strong contraction. The enhancement to whole-body explosive muscular performance (PE) after heavy-resistance exercise is often attributed to modulations in neuromuscular function that are proposed to reflect PAP, but the evidence to support this is equivocal. We assessed the neuromuscular basis of PE using transcranial magnetic stimulation (TMS) of the primary motor cortex, and electrical stimulation of the femoral nerve. Eleven male athletes performed heavy-resistance exercise with measures of countermovement jump (CMJ) pre- and 8 min post-exercise. Pre-exercise and after the final CMJ, single- and paired-pulse TMS were delivered during submaximal isometric knee-extensor contractions to measure corticospinal excitability, short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF), with motor evoked potentials recorded from rectus femoris. Twitch responses to motor nerve stimulation during and post maximum-knee-extensor contractions were studied to quantify voluntary activation (VA) and potentiated twitch (Qtw,pot). The experimental protocol successfully induced PE (+4 ± 1% change in CMJ, P = 0.01), but no changes were observed for maximum voluntary force, VA, corticospinal excitability, SICI or ICF (all P > 0.05), and Qtw,potdeclined (P < 0.001). An enhancement of muscular performance after heavy-resistance exercise was not accompanied by PAP, or changes in measures of neuromuscular function.
authors.affiliation: Faculty of Health and Life Sciences, Northumbria University, Newcastle-upon-Tyne, UK.
authors.forename: K
authors.initials: K
authors.lastname: Thomas
authors.affiliation: Faculty of Health and Life Sciences, Northumbria University, Newcastle-upon-Tyne, UK.
authors.forename: A
authors.initials: A
authors.lastname: Toward
authors.affiliation: Faculty of Health and Life Sciences, Northumbria University, Newcastle-upon-Tyne, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: West
authors.affiliation: Faculty of Health and Life Sciences, Northumbria University, Newcastle-upon-Tyne, UK.|Water Research Group, School of Environmental Sciences and Development, Northwest University, Potchefstroom, South Africa.
authors.forename: G
authors.identifier: http://orcid.org/0000-0001-8494-2043
authors.initials: G
authors.lastname: Howatson
authors.affiliation: Faculty of Health and Life Sciences, Northumbria University, Newcastle-upon-Tyne, UK.
authors.forename: S
authors.initials: S
authors.lastname: Goodall
mesh_terms: D000200:Action Potentials; D000328:Adult; D056352:Athletes; D054874:Athletic Performance / Q000502:physiology*; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D015444:Exercise / Q000502:physiology; D005267:Femoral Nerve / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology; D011712:Pyramidal Tracts / Q000502:physiology; D052097:Quadriceps Muscle / Q000502:physiology*; D055070:Resistance Training; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: Athletic performance; intracortical facili-tation; neuromuscular physiology; post-activation potentiation; short-interval intracortical inhibition; transcranial magnetic stimulation; voluntary activa-tion