title: Muscle metaboreceptors modulate postexercise sweating, but not cutaneous blood flow, independent of baroreceptor loading status.
abstract: We examined whether sustained changes in baroreceptor loading status during prolonged postexercise recovery can alter the metaboreceptors' influence on heat loss. Thirteen young males performed a 1-min isometric handgrip exercise (IHG) at 60% maximal voluntary contraction followed by 2 min of forearm ischemia (to activate metaboreceptors) before and 15, 30, 45, and 60 min after a 15-min intense treadmill running exercise (>90% maximal heart rate) in the heat (35°C). This was repeated on three separate days with continuous lower body positive (LBPP, +40 mmHg), negative (LBNP, -20 mmHg), or no pressure (Control) from 13- to 65-min postexercise. Sweat rate (ventilated capsule; forearm, chest, upper back) and cutaneous vascular conductance (CVC; forearm, upper back) were measured. Relative to pre-IHG levels, sweating at all sites increased during IHG and remained elevated during ischemia at baseline and similarly at 30, 45, and 60 min postexercise (site average sweat rate increase during ischemia: Control, 0.13 ± 0.02; LBPP, 0.12 ± 0.02; LBNP, 0.15 ± 0.02 mg·min(-1)·cm(-2); all P < 0.01), but not at 15 min (all P > 0.10). LBPP and LBNP did not modulate the pattern of sweating to IHG and ischemia (all P > 0.05). At 15-min postexercise, forearm CVC was reduced from pre-IHG levels during both IHG and ischemia under LBNP only (ischemia: 3.9 ± 0.8% CVCmax; P < 0.02). Therefore, we show metaboreceptors increase postexercise sweating in the middle to late stages of recovery (30-60 min), independent of baroreceptor loading status and similarly between skin sites. In contrast, metaboreflex modulation of forearm but not upper back CVC occurs only in the early stages of recovery (15 min) and is dependent upon baroreceptor unloading.
authors.affiliation: Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Canada;
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Paull
authors.affiliation: Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Canada;
authors.forename: Sheila
authors.initials: S
authors.lastname: Dervis
authors.affiliation: Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Canada;
authors.forename: Ryan
authors.initials: R
authors.lastname: McGinn
authors.affiliation: Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Canada;
authors.forename: Baies
authors.initials: B
authors.lastname: Haqani
authors.affiliation: Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Canada; FAME Laboratory, Department of Exercise Science, University of Thessaly, Trikala, Greece; and.
authors.forename: Andreas D
authors.initials: AD
authors.lastname: Flouris
authors.affiliation: Laboratory for Applied Human Physiology, Graduate School of Human Development and Environment, Kobe University, Kobe, Japan.
authors.forename: Narihiko
authors.initials: N
authors.lastname: Kondo
authors.affiliation: Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Canada; gkenny@uottawa.ca.
authors.forename: Glen P
authors.initials: GP
authors.lastname: Kenny
mesh_terms: D000293:Adolescent; D017704:Baroreflex; D001794:Blood Pressure; D002628:Chemoreceptor Cells / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D005542:Forearm / Q000098:blood supply*; D006339:Heart Rate; D006801:Humans; D007511:Ischemia; D008150:Lower Body Negative Pressure; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000294:innervation* / Q000378:metabolism; D011311:Pressoreceptors / Q000378:metabolism*; D011897:Random Allocation; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply*; D013546:Sweating; D013997:Time Factors; D055815:Young Adult
keywords: baroreflex; heat loss responses; metaboreflex; postexercise; thermoregulation