title: Muscle sympathetic nerve activity (MSNA) during high-intensity, isometric leg exercise in humans.
abstract: Muscle sympathetic nerve activity (MSNA) is activated during mild-intensity isometric handgrip exercise, but not during isometric leg exercise at a similarly relative intensity. It is unclear whether MSNA is increased by leg exercise at heavy intensity in humans. We aimed to examine how MSNA responds to high-intensity, isometric leg exercise in humans. Eight young healthy male volunteers performed isometric plantar flexions of high intensity (70% of MVC) for 2 min, followed by 2 min of post-exercise muscle ischemia (PEMI; isolated muscle metaboreflex stimulation), with monitoring of muscle sympathetic nerve activity (MSNA), heart rate and arterial blood pressure. MSNA was increased at the onset of exercise (p<0.05), and further increased to 512 +/- 111% of baseline at the second min of exercise (p<0.05). Furthermore, MSNA remained elevated above baseline during PEMI (259 +/- 41 % of baseline, p<0.05). Heart rate also rose at the onset of the test (P<0.05) and gradually increased all through the test (p<0.05), but decreased to baseline level during PEMI. Mean blood pressure was progressively increased from the onset to the end of test (p<0.05), and remained elevated above baseline during PEMI (p<0.05). In summary, MSNA was increased progressively throughout high-intensity, isometric plantar flexion in humans, primarily due to muscle metaboreflex.
authors.affiliation: Department of Autonomic Neuroscience, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Kamiya
authors.forename: D
authors.initials: D
authors.lastname: Michikami
authors.forename: Q
authors.initials: Q
authors.lastname: Fu
authors.forename: Y
authors.initials: Y
authors.lastname: Niimi
authors.forename: S
authors.initials: S
authors.lastname: Iwase
mesh_terms: D000328:Adult; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007866:Leg / Q000294:innervation / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D013979:Tibial Nerve / Q000502:physiology