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Wan HY, Bunsawat K, Amann M. Autonomic cardiovascular control during exercise. Am J Physiol Heart Circ Physiol 2023; 325:H675-H686. [PMID: 37505474 PMCID: PMC10659323 DOI: 10.1152/ajpheart.00303.2023] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 07/11/2023] [Accepted: 07/23/2023] [Indexed: 07/29/2023]
Abstract
The cardiovascular response to exercise is largely determined by neurocirculatory control mechanisms that help to raise blood pressure and modulate vascular resistance which, in concert with regional vasodilatory mechanisms, promote blood flow to active muscle and organs. These neurocirculatory control mechanisms include a feedforward mechanism, known as central command, and three feedback mechanisms, namely, 1) the baroreflex, 2) the exercise pressor reflex, and 3) the arterial chemoreflex. The hemodynamic consequences of these control mechanisms result from their influence on the autonomic nervous system and subsequent alterations in cardiac output and vascular resistance. Although stimulation of the baroreflex inhibits sympathetic outflow and facilitates parasympathetic activity, central command, the exercise pressor reflex, and the arterial chemoreflex facilitate sympathetic activation and inhibit parasympathetic drive. Despite considerable understanding of the cardiovascular consequences of each of these mechanisms in isolation, the circulatory impact of their interaction, which occurs when various control systems are simultaneously activated (e.g., during exercise at altitude), has only recently been recognized. Although aging and cardiovascular disease (e.g., heart failure, hypertension) have both been recognized to alter the hemodynamic consequences of these regulatory systems, this review is limited to provide a brief overview on the action and interaction of neurocirculatory control mechanisms in health.
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Affiliation(s)
- Hsuan-Yu Wan
- Department of Anesthesiology, University of Utah, Salt Lake City, Utah, United States
| | - Kanokwan Bunsawat
- Geriatric Research, Education, and Clinical Center, George E. Wahlen Department of Veterans Affairs Medical Center, Salt Lake City, Utah, United States
- Division of Geriatrics, Department of Internal Medicine, University of Utah, Salt Lake City, Utah, United States
| | - Markus Amann
- Department of Anesthesiology, University of Utah, Salt Lake City, Utah, United States
- Geriatric Research, Education, and Clinical Center, George E. Wahlen Department of Veterans Affairs Medical Center, Salt Lake City, Utah, United States
- Division of Geriatrics, Department of Internal Medicine, University of Utah, Salt Lake City, Utah, United States
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Laginestra FG, Favaretto T, Giuriato G, Martignon C, Barbi C, Pedrinolla A, Cavicchia A, Venturelli M. Concurrent metaboreflex activation increases chronotropic and ventilatory responses to passive leg movement without sex-related differences. Eur J Appl Physiol 2023; 123:1751-1762. [PMID: 37014452 PMCID: PMC10363078 DOI: 10.1007/s00421-023-05186-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Accepted: 03/17/2023] [Indexed: 04/05/2023]
Abstract
Previous studies in animal models showed that exercise-induced metabolites accumulation may sensitize the mechanoreflex-induced response. The aim of this study was to assess whether the magnitude of the central hemodynamic and ventilatory adjustments evoked by isolated stimulation of the mechanoreceptors in humans are influenced by the prior accumulation of metabolic byproducts in the muscle. 10 males and 10 females performed two exercise bouts consisting of 5-min of intermittent isometric knee-extensions performed 10% above the previously determined critical force. Post-exercise, the subjects recovered for 5 min either with a suprasystolic circulatory occlusion applied to the exercised quadriceps (PECO) or under freely-perfused conditions (CON). Afterwards, 1-min of continuous passive leg movement was performed. Central hemodynamics, pulmonary data, and electromyography from exercising/passively-moved leg were recorded throughout the trial. Root mean square of successive differences (RMSSD, index of vagal tone) was also calculated. Δpeak responses of heart rate (ΔHR) and ventilation ([Formula: see text]) to passive leg movement were higher in PECO compared to CON (ΔHR: 6 ± 5 vs 2 ± 4 bpm, p = 0.01; 3.9 ± 3.4 vs 1.9 ± 1.7 L min-1, p = 0.02). Δpeak of mean arterial pressure (ΔMAP) was significantly different between conditions (5 ± 3 vs - 3 ± 3 mmHg, p < 0.01). Changes in RMSSD with passive leg movement were different between PECO and CON (p < 0.01), with a decrease only in the former (39 ± 18 to 32 ± 15 ms, p = 0.04). No difference was found in all the other measured variables between conditions (p > 0.05). These findings suggest that mechanoreflex-mediated increases in HR and [Formula: see text] are sensitized by metabolites accumulation. These responses were not influenced by biological sex.
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Affiliation(s)
- Fabio Giuseppe Laginestra
- Department of Neurosciences, Biomedicine, and Movement, University of Verona, Verona, Italy.
- Department of Internal Medicine, University of Utah, 500 Foothill Drive, Salt Lake City, UT, 84148, USA.
| | - Thomas Favaretto
- Department of Neurosciences, Biomedicine, and Movement, University of Verona, Verona, Italy
| | - Gaia Giuriato
- Department of Neurosciences, Biomedicine, and Movement, University of Verona, Verona, Italy
| | - Camilla Martignon
- Department of Neurosciences, Biomedicine, and Movement, University of Verona, Verona, Italy
| | - Chiara Barbi
- Department of Neurosciences, Biomedicine, and Movement, University of Verona, Verona, Italy
| | - Anna Pedrinolla
- Department of Neurosciences, Biomedicine, and Movement, University of Verona, Verona, Italy
| | - Alessandro Cavicchia
- Department of Neurosciences, Biomedicine, and Movement, University of Verona, Verona, Italy
- Respiratory Rehabilitation of the Institute of Lumezzane, Istituti Clinici Scientifici Maugeri IRCCS, Lumezzane, Italy
| | - Massimo Venturelli
- Department of Neurosciences, Biomedicine, and Movement, University of Verona, Verona, Italy
- Department of Internal Medicine, University of Utah, 500 Foothill Drive, Salt Lake City, UT, 84148, USA
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Aranda LC, Ribeiro IC, Freitas TO, Degani-Costa LH, Dias DS, DE Angelis K, Paixão AO, Brum PC, Oliveira ASB, Vianna LC, Nery LE, Silva BM. Enhanced Respiratory Frequency Response to Lower Limb Mechanoreceptors Activation in Patients with Chronic Obstructive Pulmonary Disease. Med Sci Sports Exerc 2023; 55:418-429. [PMID: 36730960 DOI: 10.1249/mss.0000000000003065] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
PURPOSE To investigate the mechanoreflex control of respiration and circulation in patients with chronic obstructive pulmonary disease (COPD). METHODS Twenty-eight patients with moderate-to-severe COPD (mean ± SD: 67.0 ± 7.9 yr, 10 women) and 14 age- and sex-matched controls (67.9 ± 2.6 yr, 7 women) participated in the study. Their dominant knee was passively moved to stimulate mechanoreceptors, whereas vastus lateralis surface electrical activity checked active contractions. A differential pressure flowmeter, an electrocardiogram, and a servo-controlled finger photoplethysmograph acquired cardiorespiratory data. To gain insight into the mechanoreflex arc, we further analyzed reduced/oxidized glutathione ratio and mechanoreceptor-related gene expression in a vastus lateralis biopsy of additional nine patients (63.9 ± 8.1 yr, 33% women) and eight controls (62.9 ± 9.1 yr, 38% women). RESULTS Patients with COPD had a greater peak respiratory frequency response (COPD: Δ = 3.2 ± 2.3 vs Controls: 1.8 ± 1.2 cycles per minute, P = 0.036) and a smaller peak tidal volume response to passive knee movement than controls. Ventilation, heart rate, stroke volume, and cardiac output peak responses, and total peripheral resistance nadir response, were unaltered by COPD. In addition, patients had a diminished glutathione ratio (COPD: 13.3 ± 3.8 vs controls: 20.0 ± 5.5 a.u., P = 0.015) and an augmented brain-derived neurotrophic factor expression (COPD: 2.0 ± 0.7 vs controls: 1.1 ± 0.4 a.u., P = 0.002) than controls. Prostaglandin E receptor 4, cyclooxygenase 2, and Piezo1 expression were similar between groups. CONCLUSIONS Respiratory frequency response to mechanoreceptors activation is increased in patients with COPD. This abnormality is possibly linked to glutathione redox imbalance and augmented brain-derived neurotrophic factor expression within locomotor muscles, which could increase mechanically sensitive afferents' stimulation and sensitivity.
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Affiliation(s)
| | | | | | - Luiza H Degani-Costa
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Division of Respiratory Medicine, Department of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, SP, BRAZIL
| | | | | | - Ailma O Paixão
- School of Physical Education and Sport, University of São Paulo, São Paulo, SP, BRAZIL
| | - Patricia C Brum
- School of Physical Education and Sport, University of São Paulo, São Paulo, SP, BRAZIL
| | - Acary S B Oliveira
- Department of Neurology and Neurosurgery, UNIFESP, São Paulo, SP, BRAZIL
| | - Lauro C Vianna
- NeuroV̇ASQ˙-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasilia, Brasilia, Federal District, BRAZIL
| | - Luiz E Nery
- Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Division of Respiratory Medicine, Department of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, SP, BRAZIL
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Wan HY, Weavil JC, Thurston TS, Georgescu VP, Morrissey CK, Amann M. On the hemodynamic consequence of the chemoreflex and muscle mechanoreflex interaction in women and men: two tales, one story. J Physiol 2022; 600:3671-3688. [PMID: 35710103 PMCID: PMC9378608 DOI: 10.1113/jp283051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 06/14/2022] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The cardiovascular response resulting from the activation of the muscle mechanoreflex (MMR), or the chemoreflex (CR), was previously shown to be different between women and men; this study focused on the hemodynamic consequence of the interaction of these two sympathoexcitatory reflexes. MMR and CR were activated by passive leg movement and exposure to hypoxia (O2 -CR), or hypercapnia (CO2 -CR), respectively. Individual and interactive reflex effects on central and peripheral hemodynamics were quantified in healthy young women and men. In men, the MMR:O2 -CR and MMR:CO2 -CR interactions restricted peripheral hemodynamics, likely by potentiating sympathetic vasoconstriction. In women, the MMR:O2 -CR interaction facilitated central and peripheral hemodynamics, likely by potentiating sympathetic vasodilation; however, the MMR:CO2 -CR interaction was simply additive for the central and peripheral hemodynamics. The interaction between the MMR and the CR exerts a profound influence on the autonomic control of cardiovascular function in humans, with the hemodynamic consequences differing between women and men. ABSTRACT The cardiovascular response resulting from the individual activation of the muscle mechanoreflex (MMR), or the chemoreflex (CR), is different between men and women. Whether the hemodynamic consequence resulting from the interaction of these sympathoexcitatory reflexes is also sex-dependent remains unknown. MMR and CR were activated by passive leg movement (LM) and exposure to hypoxia (O2 -CR), or hypercapnia (CO2 -CR), respectively. Twelve young men and 12 young women completed two experimental protocols: 1) resting in normoxia (PET O2 : ∼83mmHg, PET CO2 : ∼34mmHg), normocapnic hypoxia (PET O2 : ∼48mmHg, PET CO2 : ∼34mmHg), and hyperoxic hypercapnia (PET O2 : ∼524mmHg, PET CO2 : ∼44mmHg); 2) LM under the same gas conditions. During the MMR:O2 -CR coactivation, in men, the observed blood pressure (MAP) and cardiac output (CO) were not different (additive effect), while the observed leg blood flow (LBF) and vascular conductance (LVC) were significantly lower (hypo-additive), compared with the sum of the responses elicited by each reflex alone. In women, the observed MAP was not different (additive) while the observed CO, LBF, and LVC were significantly greater (hyper-additive), compared with the summated responses. During the MMR:CO2 -CR coactivation, in men, the observed MAP, CO, and LBF were not different (additive), while the observed LVC was significantly lower (hypo-additive), compared with the summated responses. In women, the observed MAP was significantly higher (hyper-additive), while the observed CO, LBF, and LVC were not different (additive), compared with the summated responses. The interaction of the MMR and CR has a pronounced influence on the autonomic cardiovascular control, with the hemodynamic consequences differing between men and women. Abstract figure legend The chemoreflex and the muscle mechanoreflex are sympathoexcitatory mechanisms which, via neural feedback to the cardiovascular centre in the medulla, mediate neurocirculatory responses during physical activity. The interaction of the peripheral chemoreflex and muscle mechanoreflex potentiates vasoconstriction in men, but potentiates vasodilatation in women (left panel). The interaction of the central chemoreflex and muscle mechanoreflex also potentiates vasoconstriction in men, whereas the reflex interaction is simply additive for the vasomotor tone in women (right panel). This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Hsuan-Yu Wan
- Department of Anesthesiology, University of Utah, Salt Lake City, UT
| | - Joshua C Weavil
- Geriatric Research, Education, and Clinical Center, VAMC, Salt Lake City, UT
| | - Taylor S Thurston
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT
| | - Vincent P Georgescu
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT
| | | | - Markus Amann
- Department of Anesthesiology, University of Utah, Salt Lake City, UT.,Geriatric Research, Education, and Clinical Center, VAMC, Salt Lake City, UT.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT
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Chen C, Kolbe J, Wilsher ML, De Boer S, Paton JFR, Fisher JP. Cardiorespiratory responses to muscle metaboreflex activation in fibrosing interstitial lung disease. Exp Physiol 2022; 107:527-540. [PMID: 35298060 PMCID: PMC9314965 DOI: 10.1113/ep090252] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 03/10/2022] [Indexed: 11/21/2022]
Abstract
New Findings What is the central question of this study? We determined whether sensory feedback from metabolically sensitive skeletal muscle afferents (metaboreflex) causes a greater ventilatory response and higher dyspnoea ratings in fibrosing interstitial lung disease (FILD). What is the main finding and its importance? Ventilatory responses and dyspnoea ratings during handgrip exercise and metaboreflex isolation were not different in FILD and control groups. Blood pressure and heart rate responses to handgrip were attenuated in FILD but not different to controls during metaboreflex isolation. These findings suggest that the muscle metaboreflex contribution to the respiratory response to exercise is not altered in FILD.
Abstract Exercise limitation and dyspnoea are hallmarks of fibrosing interstitial lung disease (FILD); however, the physiological mechanisms are poorly understood. In other respiratory diseases, there is evidence that an augmented muscle metaboreflex may be implicated. We hypothesized that metaboreflex activation in FILD would result in elevated ventilation and dyspnoea ratings compared to healthy controls, due to augmented muscle metaboreflex. Sixteen FILD patients (three women, 69±14 years; mean±SD) and 16 age‐matched controls (four women, 67±7 years) were recruited. In a randomized cross‐over design, participants completed two min of rhythmic handgrip followed by either (i) two min of post‐exercise circulatory occlusion (PECO trial) to isolate muscle metaboreflex activation, or (ii) rested for four min (Control trial). Minute ventilation (V˙E; pneumotachometer), dyspnoea ratings (0–10 Borg scale), mean arterial pressure (MAP; finger photoplethysmography) and heart rate (HR; electrocardiogram) were measured. V˙E was higher in the FILD group at baseline and exercise increased V˙E similarly in both groups. V˙E remained elevated during PECO, but there was no between‐group difference in the magnitude of this response (ΔV˙E FILD 4.2 ± 2.5 L·min–1 vs. controls 3.6 ± 2.4 L·min–1, P = 0.596). At the end of PECO, dyspnoea ratings in FILD were similar to controls (1.0 ± 1.3 units vs. 0.5 ± 1.1 units). Exercise increased MAP and HR (P < 0.05) in both groups; however, responses were lower in FILD. Collectively, these findings suggest that there is not an augmented effect of the muscle metaboreflex on breathing and dyspnoea in FILD, but haemodynamic responses to handgrip are reduced relative to controls.
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Affiliation(s)
- Charlotte Chen
- Manaaki Manawa - The Centre for Heart Research, Department of Physiology, Faculty of Medical & Health Sciences, University of Auckland, New Zealand
| | - John Kolbe
- Manaaki Manawa - The Centre for Heart Research, Department of Physiology, Faculty of Medical & Health Sciences, University of Auckland, New Zealand.,Department of Medicine, Faculty of Medical & Health Sciences, University of Auckland, New Zealand.,Respiratory Services, Auckland District Health Board, Auckland, New Zealand
| | - Margaret L Wilsher
- Department of Medicine, Faculty of Medical & Health Sciences, University of Auckland, New Zealand.,Respiratory Services, Auckland District Health Board, Auckland, New Zealand
| | - Sally De Boer
- Respiratory Services, Auckland District Health Board, Auckland, New Zealand
| | - Julian F R Paton
- Manaaki Manawa - The Centre for Heart Research, Department of Physiology, Faculty of Medical & Health Sciences, University of Auckland, New Zealand
| | - James P Fisher
- Manaaki Manawa - The Centre for Heart Research, Department of Physiology, Faculty of Medical & Health Sciences, University of Auckland, New Zealand
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Fullerton MM, Passfield L, MacInnis MJ, Iannetta D, Murias JM. Prior exercise impairs subsequent performance in an intensity- and duration-dependent manner. Appl Physiol Nutr Metab 2021; 46:976-985. [PMID: 33641346 DOI: 10.1139/apnm-2020-0689] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Prior constant-load exercise performed for 30-min at or above maximal lactate steady state (MLSSp) significantly impairs subsequent time-to-task failure (TTF) compared with TTF performed without prior exercise. We tested the hypothesis that TTF would decrease in relation to the intensity and the duration of prior exercise compared with a baseline TTF trial. Eleven individuals (6 males, 5 females, aged 28 ± 8 yrs) completed the following tests on a cycle ergometer (randomly assigned after MLSSp was determined): (i) a ramp-incremental test; (ii) a baseline TTF trial performed at 80% of peak power (TTFb); (iii) five 30-min constant-PO rides at 5% below lactate threshold (LT-5%), halfway between LT and MLSSp (Delta50), 5% below MLSSp (MLSS-5%), MLSSp, and 5% above MLSSp (MLSS+5%); and (iv) 15- and 45-min rides at MLSSp (MLSS15 and MLSS45, respectively). Each condition was immediately followed by a TTF trial at 80% of peak power. Compared with TTFb (330 ± 52 s), there was 8.0 ± 24.1, 23.6 ± 20.2, 41.0 ± 14.8, 52.2 ± 18.9, and 75.4 ± 7.4% reduction in TTF following LT-5%, Delta50, MLSS-5%, MLSSp, and MLSS+5%, respectively. Following MLSS15 and MLSS45 there were 29.0 ± 20.1 and 69.4 ± 19.6% reductions in TTF, respectively (P < 0.05). It is concluded that TTF is reduced following prior exercise of varying duration at MLSSp and at submaximal intensities below MLSS. Novelty: Prior constant-PO exercise, performed at intensities below MLSSp, reduces subsequent TTF performance. Subsequent TTF performance is reduced in a linear fashion following an increase in the duration of constant-PO exercise at MLSSp.
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Affiliation(s)
| | - Louis Passfield
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.,School of Sport and Exercise Sciences, University of Kent, Canterbury, United Kingdom
| | | | - Danilo Iannetta
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
| | - Juan M Murias
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
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Amann M, Wan HY, Thurston TS, Georgescu VP, Weavil JC. On the Influence of Group III/IV Muscle Afferent Feedback on Endurance Exercise Performance. Exerc Sport Sci Rev 2020; 48:209-216. [PMID: 32658041 DOI: 10.1249/jes.0000000000000233] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This review discusses evidence suggesting that group III/IV muscle afferents affect locomotor performance by influencing neuromuscular fatigue. These neurons regulate the hemodynamic and ventilatory response to exercise and, thus, assure appropriate locomotor muscle O2 delivery, which optimizes peripheral fatigue development and facilitates endurance performance. In terms of central fatigue, group III/IV muscle afferents inhibit motoneuronal output and thereby limit exercise performance.
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Affiliation(s)
| | - Hsuan-Yu Wan
- Department of Anesthesiology, University of Utah
| | - Taylor S Thurston
- Geriatric Research, Education, and Clinical Center, Salt Lake City VAMC, Salt Lake City, UT
| | - Vincent P Georgescu
- Geriatric Research, Education, and Clinical Center, Salt Lake City VAMC, Salt Lake City, UT
| | - Joshua C Weavil
- Geriatric Research, Education, and Clinical Center, Salt Lake City VAMC, Salt Lake City, UT
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White M, Bruce R. The role of muscle mechano and metaboreflexes in the control of ventilation: breathless with (over) excitement? Exp Physiol 2020; 105:2250-2253. [DOI: 10.1113/ep088460] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 08/27/2020] [Accepted: 09/02/2020] [Indexed: 11/08/2022]
Affiliation(s)
- Michael White
- School of Sport Exercise and Rehabilitation Sciences University of Birmingham Birmingham UK
| | - Richard Bruce
- Centre for Human and Applied Physiological Sciences School of Basic and Medical Sciences King's College London London UK
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Wan HY, Weavil JC, Thurston TS, Georgescu VP, Bledsoe AD, Jessop JE, Buys MJ, Richardson RS, Amann M. The muscle reflex and chemoreflex interaction: ventilatory implications for the exercising human. J Appl Physiol (1985) 2020; 129:691-700. [PMID: 32816637 DOI: 10.1152/japplphysiol.00449.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We examined the interactive influence of the muscle reflex (MR) and the chemoreflex (CR) on the ventilatory response to exercise. Eleven healthy subjects (5 women/6 men) completed three bouts of constant-load single-leg knee-extension exercise in a control trial and an identical trial conducted with lumbar intrathecal fentanyl to attenuate neural feedback from lower-limb group III/IV muscle afferents. The exercise during the two trials was performed while breathing ambient air ([Formula: see text] ~97%, [Formula: see text]~84 mmHg, [Formula: see text] ~32 mmHg, pH ~7.39), or under normocapnic hypoxia ([Formula: see text] ~79%, [Formula: see text] ~43 mmHg, [Formula: see text] ~33 mmHg, pH ~7.39) or normoxic hypercapnia ([Formula: see text] ~98%, [Formula: see text] ~105 mmHg, [Formula: see text] ~50 mmHg, pH ~7.26). During coactivation of the MR and the hypoxia-induced CR (O2-CR), minute ventilation (V̇e) and tidal volume (VT) were significantly greater compared with the sum of the responses to the activation of each reflex alone; there was no difference between the observed and summated responses in terms of breathing frequency (fB; P = 0.4). During coactivation of the MR and the hypercapnia-induced CR (CO2-CR), the observed ventilatory responses were similar to the summated responses of the reflexes (P ≥ 0.1). Therefore, the interaction between the MR and the O2-CR exerts a hyperadditive effect on V̇e and VT and an additive effect on fB, whereas the interaction between the MR and the CO2-CR is simply additive for all ventilatory parameters. These findings reveal that the MR:CR interaction further augments the ventilatory response to exercise in hypoxia.NEW & NOTEWORTHY Although the muscle reflex and the chemoreflex are recognized as independent feedback mechanisms regulating breathing during exercise, the ventilatory implications resulting from their interaction remain unclear. We quantified the individual and interactive effects of these reflexes during exercise and revealed differential modes of interaction. Importantly, the reflex interaction further amplifies the ventilatory response to exercise under hypoxemic conditions, highlighting a potential mechanism for optimizing arterial oxygenation in physically active humans at high altitude.
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Affiliation(s)
- Hsuan-Yu Wan
- Department of Anesthesiology, University of Utah, Salt Lake City, Utah
| | - Joshua C Weavil
- Geriatric Research, Education, and Clinical Center, Salt Lake City Veterans Affairs Medical Center, Utah
| | - Taylor S Thurston
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah
| | - Vincent P Georgescu
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah
| | - Amber D Bledsoe
- Department of Anesthesiology, University of Utah, Salt Lake City, Utah
| | - Jacob E Jessop
- Department of Anesthesiology, University of Utah, Salt Lake City, Utah
| | - Michael J Buys
- Department of Anesthesiology, University of Utah, Salt Lake City, Utah
| | - Russell S Richardson
- Geriatric Research, Education, and Clinical Center, Salt Lake City Veterans Affairs Medical Center, Utah.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah.,Department of Internal Medicine, University of Utah, Salt Lake City, Utah
| | - Markus Amann
- Department of Anesthesiology, University of Utah, Salt Lake City, Utah.,Geriatric Research, Education, and Clinical Center, Salt Lake City Veterans Affairs Medical Center, Utah.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah.,Department of Internal Medicine, University of Utah, Salt Lake City, Utah
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Nicolai EN, Settell ML, Knudsen BE, McConico AL, Gosink BA, Trevathan JK, Baumgart IW, Ross EK, Pelot NA, Grill WM, Gustafson KJ, Shoffstall AJ, Williams JC, Ludwig KA. Sources of off-target effects of vagus nerve stimulation using the helical clinical lead in domestic pigs. J Neural Eng 2020; 17:046017. [PMID: 32554888 PMCID: PMC7717671 DOI: 10.1088/1741-2552/ab9db8] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Objective Clinical data suggest that efficacious vagus nerve stimulation (VNS) is limited by side effects such as cough and dyspnea that have stimulation thresholds lower than those for therapeutic outcomes. VNS side effects are putatively caused by activation of nearby muscles within the neck, via direct muscle activation or activation of nerve fibers innervating those muscles. Our goal was to determine the thresholds at which various VNS-evoked effects occur in the domestic pig—an animal model with vagus anatomy similar to human—using the bipolar helical lead deployed clinically. Approach Intrafascicular electrodes were placed within the vagus nerve to record electroneurographic (ENG) responses, and needle electrodes were placed in the vagal-innervated neck muscles to record electromyographic (EMG) responses. Main results Contraction of the cricoarytenoid muscle occurred at low amplitudes (~0.3 mA) and resulted from activation of motor nerve fibers in the cervical vagus trunk within the electrode cuff which bifurcate into the recurrent laryngeal branch of the vagus. At higher amplitudes (~1.4 mA), contraction of the cricoarytenoid and cricothyroid muscles was generated by current leakage outside the cuff to activate motor nerve fibers running within the nearby superior laryngeal branch of the vagus. Activation of these muscles generated artifacts in the ENG recordings that may be mistaken for compound action potentials representing slowly conducting Aδ-, B-, and C-fibers. Significance Our data resolve conflicting reports of the stimulation amplitudes required for C-fiber activation in large animal studies (>10 mA) and human studies (<250 μA). After removing muscle-generated artifacts, ENG signals with post-stimulus latencies consistent with Aδ- and B-fibers occurred in only a small subset of animals, and these signals had similar thresholds to those that caused bradycardia. By identifying specific neuroanatomical pathways that cause off-target effects and characterizing the stimulation dose-response curves for on- and off-target effects, we hope to guide interpretation and optimization of clinical VNS.
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Affiliation(s)
- Evan N Nicolai
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Mayo Clinic, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN, United States of America
- Wisconsin Institute of Neuroengineering (WITNe), University of Wisconsin-Madison, WI, United States of America
| | - Megan L Settell
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Mayo Clinic, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN, United States of America
- Wisconsin Institute of Neuroengineering (WITNe), University of Wisconsin-Madison, WI, United States of America
| | - Bruce E Knudsen
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Department of Neurosurgery, Mayo Clinic, Rochester, MN, United States of America
- Wisconsin Institute of Neuroengineering (WITNe), University of Wisconsin-Madison, WI, United States of America
| | - Andrea L McConico
- Department of Neurosurgery, Mayo Clinic, Rochester, MN, United States of America
| | - Brian A Gosink
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Department of Neurosurgery, University of Wisconsin-Madison, Madison, WI, United States of America
| | - James K Trevathan
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute of Neuroengineering (WITNe), University of Wisconsin-Madison, WI, United States of America
| | - Ian W Baumgart
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Erika K Ross
- Abbott Neuromodulation, Plano, TX, United States of America
| | - Nicole A Pelot
- Department of Biomedical Engineering, Duke University, Durham, NC, United States of America
| | - Warren M Grill
- Department of Biomedical Engineering, Duke University, Durham, NC, United States of America
| | - Kenneth J Gustafson
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States of America
- Louis Stokes Cleveland VA Medical Center, Cleveland, OH, United States of America
| | - Andrew J Shoffstall
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States of America
- Louis Stokes Cleveland VA Medical Center, Cleveland, OH, United States of America
| | - Justin C Williams
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Department of Neurosurgery, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute of Neuroengineering (WITNe), University of Wisconsin-Madison, WI, United States of America
| | - Kip A Ludwig
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Department of Neurosurgery, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute of Neuroengineering (WITNe), University of Wisconsin-Madison, WI, United States of America
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Wan HY, Weavil JC, Thurston TS, Georgescu VP, Hureau TJ, Bledsoe AD, Buys MJ, Jessop JE, Richardson RS, Amann M. The exercise pressor reflex and chemoreflex interaction: cardiovascular implications for the exercising human. J Physiol 2020; 598:2311-2321. [PMID: 32170732 DOI: 10.1113/jp279456] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 03/10/2020] [Indexed: 01/11/2023] Open
Abstract
KEY POINTS Although the exercise pressor reflex (EPR) and the chemoreflex (CR) are recognized for their sympathoexcitatory effect, the cardiovascular implication of their interaction remains elusive. We quantified the individual and interactive cardiovascular consequences of these reflexes during exercise and revealed various modes of interaction. The EPR and hypoxia-induced CR interaction is hyper-additive for blood pressure and heart rate (responses during co-activation of the two reflexes are greater than the summation of the responses evoked by each reflex) and hypo-additive for peripheral haemodynamics (responses during co-activation of the reflexes are smaller than the summated responses). The EPR and hypercapnia-induced CR interaction results in a simple addition of the individual responses to each reflex (i.e. additive interaction). Collectively, EPR:CR co-activation results in significant cardiovascular interactions with restriction in peripheral haemodynamics, resulting from the EPR:CR interaction in hypoxia, likely having the most crucial impact on the functional capacity of an exercising human. ABSTRACT We investigated the interactive effect of the exercise pressor reflex (EPR) and the chemoreflex (CR) on the cardiovascular response to exercise. Eleven healthy participants (5 females) completed a total of six bouts of single-leg knee-extension exercise (60% peak work rate, 4 min each) either with or without lumbar intrathecal fentanyl to attenuate group III/IV afferent feedback from lower limbs to modify the EPR, while breathing either ambient air, normocapnic hypoxia (Sa O2 ∼79%, Pa O2 ∼43 mmHg, Pa CO2 ∼33 mmHg, pH ∼7.39), or normoxic hypercapnia (Sa O2 ∼98%, Pa O2 ∼105 mmHg, Pa CO2 ∼50 mmHg, pH ∼7.26) to modify the CR. During co-activation of the EPR and the hypoxia-induced CR (O2 -CR), mean arterial pressure and heart rate were significantly greater, whereas leg blood flow and leg vascular conductance were significantly lower than the summation of the responses evoked by each reflex alone. During co-activation of the EPR and the hypercapnia-induced CR (CO2 -CR), the haemodynamic responses were not different from the summated responses to each reflex response alone (P ≥ 0.1). Therefore, while the interaction resulting from the EPR:O2 -CR co-activation is hyper-additive for blood pressure and heart rate, and hypo-additive for peripheral haemodynamics, the interaction resulting from the EPR:CO2 -CR co-activation is simply additive for all cardiovascular parameters. Thus, EPR:CR co-activation results in significant interactions between cardiovascular reflexes, with the impact differing when the CR activation is achieved by hypoxia or hypercapnia. Since the EPR:CR co-activation with hypoxia potentiates the pressor response and restricts blood flow to contracting muscles, this interaction entails the most functional impact on an exercising human.
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Affiliation(s)
- Hsuan-Yu Wan
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA
| | - Joshua C Weavil
- Geriatric Research, Education, and Clinical Center, Salt Lake City, UT, VAMC, USA
| | - Taylor S Thurston
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT, USA
| | - Vincent P Georgescu
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT, USA
| | - Thomas J Hureau
- Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
| | - Amber D Bledsoe
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA
| | - Michael J Buys
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA
| | - Jacob E Jessop
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA
| | - Russell S Richardson
- Geriatric Research, Education, and Clinical Center, Salt Lake City, UT, VAMC, USA.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT, USA.,Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
| | - Markus Amann
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA.,Geriatric Research, Education, and Clinical Center, Salt Lake City, UT, VAMC, USA.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT, USA.,Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
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12
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Bruce RM, Jolley C, White MJ. Control of exercise hyperpnoea: Contributions from thin-fibre skeletal muscle afferents. Exp Physiol 2019; 104:1605-1621. [PMID: 31429500 DOI: 10.1113/ep087649] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 08/16/2019] [Indexed: 12/16/2022]
Abstract
NEW FINDINGS What is the topic of this review? In this review, we examine the evidence for control mechanisms underlying exercise hyperpnoea, giving attention to the feedback from thin-fibre skeletal muscle afferents, and highlight the frequently conflicting findings and difficulties encountered by researchers using a variety of experimental models. What advances does it highlight? There has been a recent resurgence of interest in the role of skeletal muscle afferent involvement, not only as a mechanism of healthy exercise hyperpnoea but also in the manifestation of breathlessness and exercise intolerance in chronic disease. ABSTRACT The ventilatory response to dynamic submaximal exercise is immediate and proportional to metabolic rate, which maintains isocapnia. How these respiratory responses are controlled remains poorly understood, given that the most tightly controlled variable (arterial partial pressure of CO2 /H+ ) provides no error signal for arterial chemoreceptors to trigger reflex increases in ventilation. This review discusses evidence for different postulated control mechanisms, with a focus on the feedback from group III/IV skeletal muscle mechanosensitive and metabosensitive afferents. This concept is attractive, because the stimulation of muscle mechanoreceptors might account for the immediate increase in ventilation at the onset of exercise, and signals from metaboreceptors might be proportional to metabolic rate. A variety of experimental models have been used to establish the contribution of thin-fibre muscle afferents in ventilatory control during exercise, with equivocal results. The inhibition of afferent feedback via the application of lumbar intrathecal fentanyl during exercise suppresses ventilation, which provides the most compelling supportive evidence to date. However, stimulation of afferent feedback at rest has no consistent effect on respiratory output. However, evidence is emerging for synergistic interactions between muscle afferent feedback and other stimulatory inputs to the central respiratory neuronal pool. These seemingly hyperadditive effects might explain the conflicting findings encountered when using different experimental models. We also discuss the increasing evidence that patients with certain chronic diseases exhibit exaggerated muscle afferent activation during exercise, resulting in enhanced cardiorespiratory responses. This might provide a neural link between the well-established limb muscle dysfunction and the associated exercise intolerance and exertional dyspnoea, which might offer therapeutic targets for these patients.
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Affiliation(s)
- Richard M Bruce
- Centre for Human and Applied Physiological Sciences, School of Basic and Medical Sciences, King's College London, London, UK
| | - Caroline Jolley
- Centre for Human and Applied Physiological Sciences, School of Basic and Medical Sciences, King's College London, London, UK
| | - Michael J White
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
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Lam E, Greenhough E, Nazari P, White MJ, Bruce RM. Muscle metaboreflex activation increases ventilation and heart rate during dynamic exercise in humans. Exp Physiol 2019; 104:1472-1481. [DOI: 10.1113/ep087726] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 06/11/2019] [Indexed: 11/08/2022]
Affiliation(s)
- Elliot Lam
- Centre for Human and Applied Physiological SciencesSchool of Basic and Medical Sciences, King's College London London UK
| | - Evelyn Greenhough
- Centre for Human and Applied Physiological SciencesSchool of Basic and Medical Sciences, King's College London London UK
| | - Parsa Nazari
- Centre for Human and Applied Physiological SciencesSchool of Basic and Medical Sciences, King's College London London UK
| | - Michael J. White
- School of Sport, Exercise and Rehabilitation SciencesUniversity of Birmingham Birmingham UK
| | - Richard M. Bruce
- Centre for Human and Applied Physiological SciencesSchool of Basic and Medical Sciences, King's College London London UK
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Joshi H, Edgell H. Sex differences in the ventilatory and cardiovascular response to supine and tilted metaboreflex activation. Physiol Rep 2019; 7:e14041. [PMID: 30916469 PMCID: PMC6436143 DOI: 10.14814/phy2.14041] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 03/08/2019] [Indexed: 12/26/2022] Open
Abstract
Women have attenuated exercise pressor responses compared to men; however, their cerebrovascular and ventilatory responses have not been previously measured. Furthermore, recent evidence has shown that posture change can influence the response of the metaboreflex but this has only been tested in men. Young and healthy men (n = 14; age: 21 ± 2) and women (n = 11; age: 19 ± 1) underwent 40% MVC static handgrip exercise (HG) for 2 min followed by 3 min of post-exercise circulatory occlusion (PECO) in the supine and 70° tilted postures. In supine position during HG and PECO only men had an increase in ventilation (Men: Baseline: 12.5 ± 1.7 L/min, HG: 18.6 ± 5.3 L/min, PECO: 17.7 ± 10.3 L/min; Women: Baseline: 12.0 ± 1.5 L/min, HG: 12.4 ± 1.2 L/min, PECO: 11.5 ± 1.3 L/min; Sex × Time interaction P = 0.037). In supine position during HG and PECO men and women had similar reductions in cerebrovascular conductance (Men: Baseline: 0.79 ± 0.13 cm/sec/mmHg, HG: 0.68 ± 0.18 cm/sec/mmHg, PECO: 0.61 ± 0.19 cm/s/mmHg; Women: Baseline: 0.87 ± 0.13 cm/sec/mmHg, HG: 0.83 ± 0.14 cm/sec/mmHg, PECO: 0.75 ± 0.17 cm/sec/mmHg; P < 0.015 HG/PECO vs. baseline). When comparing the response to PECO in the supine versus upright postures there was a significant attenuation in the increase in mean arterial pressure in both men and women (Supine posture: Men: +23.3 ± 14.5 mmHg, Women: +12.0 ± 7.3 mmHg; Upright posture: Men: +15.7 ± 14.1 mmHg, Women: +7.7 ± 6.7 mmHg; Main effect of sex P = 0.042, Main effect of posture P < 0.001). Our results indicate sexually dimorphic ventilatory responses to HG and PECO which could be due to different interactions of the metaboreflex and chemoreflex. We have also shown evidence of attenuated metaboreflex function in the upright posture in both men and women.
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Affiliation(s)
- Hitesh Joshi
- School of Kinesiology and Health SciencesYork UniversityTorontoOntarioCanada
| | - Heather Edgell
- School of Kinesiology and Health SciencesYork UniversityTorontoOntarioCanada
- Muscle Health Research CentreYork UniversityTorontoOntarioCanada
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15
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Alghaith JM, Balanos GM, Eves FF, White MJ. Sensitivity of the human ventilatory response to muscle metaboreflex activation during concurrent mild hypercapnia. Exp Physiol 2018; 104:359-367. [PMID: 30588681 DOI: 10.1113/ep087224] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 12/14/2018] [Indexed: 01/08/2023]
Abstract
NEW FINDINGS What is the central question of this study? What is the relationship between the level of systemic hypercapnia and the magnitude of the additional hyperpnoea produced in response to a standardized level of muscle metaboreflex activation? What is the main finding and its importance? When a standardized activation of the muscle metaboreflex was combined with exposure to increasing levels of hypercapnia, the hyperpnoea this caused increased linearly. The concept of a synergistic interaction between the muscle metaboreflex and the central chemoreflex in humans is supported by this finding. ABSTRACT Ventilation increases during muscle metaboreflex activation when postexercise circulatory occlusion (PECO) traps metabolites in resting human muscle, but only in conditions of concurrent systemic hypercapnia. We hypothesize that a linear relationship exists between the level of hypercapnia and the magnitude of the additional hyperpnoea produced in response to a standardized level of muscle metaboreflex activation. Fifteen male subjects performed four trials, in which the end-tidal partial pressure of carbon dioxide ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>P</mml:mi> <mml:mrow> <mml:mrow><mml:mi>ET</mml:mi> <mml:mo>,</mml:mo> <mml:mi>C</mml:mi></mml:mrow> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> </mml:math> ) was elevated by 1, 3, 7 or 10 mmHg above resting values using a dynamic end-tidal forcing system. In each trial, subjects were seated in an isometric dynamometer designed to measure ankle plantar flexor force. Rest for 2 min in room air was followed by 15 min of exposure to one of the four levels of hypercapnia, at which 5 min further rest was followed by 2 min of sustained isometric calf muscle contraction at 50% of predetermined maximal voluntary strength. Immediately before cessation of exercise, a cuff around the upper leg was inflated to a suprasystolic pressure to cause PECO for 3 min, before its deflation and a further 5 min of rest, concluding exposure to hypercapnia. The PECO consistently elevated mean arterial blood pressure by ∼10 mmHg in all trials, indicating similar levels of metaboreflex activation. Increased ventilation during PECO was related to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>P</mml:mi> <mml:mrow> <mml:mrow><mml:mi>ET</mml:mi> <mml:mo>,</mml:mo> <mml:mi>C</mml:mi></mml:mrow> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> </mml:math> as described by the following linear regression equation: Change in minute ventilation (l min-1 ) = 0.85 × <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>P</mml:mi> <mml:mrow> <mml:mrow><mml:mi>ET</mml:mi> <mml:mo>,</mml:mo> <mml:mi>C</mml:mi></mml:mrow> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> </mml:math> (mmHg) + 0.80 (l min-1 ). This finding supports our hypothesis and furthers the idea of a synergistic interaction between muscle metaboreflex activation and central chemoreflex stimulation.
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Affiliation(s)
- Jassim M Alghaith
- School of Sport, Exercise and Rehabilitation Sciences , University of Birmingham, Birmingham, UK
| | - George M Balanos
- School of Sport, Exercise and Rehabilitation Sciences , University of Birmingham, Birmingham, UK
| | - Francis F Eves
- School of Sport, Exercise and Rehabilitation Sciences , University of Birmingham, Birmingham, UK
| | - Michael J White
- School of Sport, Exercise and Rehabilitation Sciences , University of Birmingham, Birmingham, UK
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Bruce RM. The control of ventilation during exercise: a lesson in critical thinking. ADVANCES IN PHYSIOLOGY EDUCATION 2017; 41:539-547. [PMID: 29066604 DOI: 10.1152/advan.00086.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 09/11/2017] [Accepted: 09/15/2017] [Indexed: 06/07/2023]
Abstract
Learning the basic competencies of critical thinking are very important in the education of any young scientist, and teachers must be prepared to help students develop a valuable set of analytic tools. In my experience, this is best achieved by encouraging students to study areas with little scientific consensus, such as the control mechanisms of the exercise ventilatory response, as it can allow greater objectivity when evaluating evidence, while also giving students the freedom to think independently and problem solve. In this article, I discuss teaching strategies by which physiology, biomedical science, and sport science students can simultaneously develop their understanding of respiratory control mechanisms and learn to critically analyze evidence thoroughly. This can be best achieved by utilizing both teacher-led and student-led learning environments, the latter of which encourages the development of learner autonomy and independent problem solving. In this article, I also aim to demonstrate a systematic approach of critical assessment that students can be taught, adapt, and apply independently. Among other things, this strategy involves: 1) defining the precise phenomenon in question; 2) understanding what investigations must demonstrate to explain the phenomenon and its underlying mechanisms; 3) evaluating the explanations/mechanisms of the phenomenon and the evidence for them; and 4) forming strategies to produce strong evidence, if none exists.
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Affiliation(s)
- Richard M Bruce
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
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17
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Parkes MJ. Reappraisal of systemic venous chemoreceptors: might they explain the matching of breathing to metabolic rate in humans? Exp Physiol 2017; 102:1567-1583. [DOI: 10.1113/ep086561] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 09/07/2017] [Indexed: 12/20/2022]
Affiliation(s)
- M. J. Parkes
- School of Sport, Exercise and Rehabilitation Sciences; University of Birmingham; Edgbaston Birmingham B15 2TT UK
- National Institute for Health Research/Wellcome Trust Birmingham Clinical Research Facility; University Hospitals Birmingham National Health Service Foundation Trust; Birmingham B15 2TH UK
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Bruce RM, Turner A, White MJ. Ventilatory responses to muscle metaboreflex activation in chronic obstructive pulmonary disease. J Physiol 2016; 594:6025-6035. [PMID: 27170272 DOI: 10.1113/jp272329] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 05/05/2016] [Indexed: 12/31/2022] Open
Abstract
KEY POINTS Recent evidence indicates a role for group III/IV muscle afferents in reflex control of the human ventilatory response to exercise. Dyspnoea in chronic obstructive pulmonary disease (COPD) may be linked to this reflex response. This study shows that activation of the muscle metaboreflex causes a ventilatory response in COPD patients but not in healthy controls. This indicates abnormal involvement of muscle afferents in the control of ventilation in COPD which may be a contributing factor to exercise dyspnoea. ABSTRACT Blockade of thin fibre muscle afferent feedback during dynamic exercise reduces exercise hyperpnoea in health and chronic obstructive pulmonary disease (COPD). Therefore, we hypothesised that activation of the muscle metaboreflex at rest would cause hyperpnoea. We evaluated the effect of muscle metaboreflex activation on ventilation, in resting COPD patients and healthy participants. Following a bout of rhythmic hand grip exercise, post exercise circulatory occlusion (PECO) was applied to the resting forearm to sustain activation of the muscle metaboreflex, in 18 COPD patients (FEV1 /FVC ratio < 70%), 9 also classified as chronically hypercapnic, and 9 age- and gender-matched controls. The cardiovascular response to exercise and the sustained blood pressure elevation during PECO was similar in patients and controls. During exercise ventilation increased by 6.64 ± 0.84 in controls and significantly (P < 0.05) more, 8.38 ± 0.81 l min-1 , in patients. During PECO it fell to baseline levels in controls but remained significantly (P < 0.05) elevated by 2.78 ± 0.51 l min-1 in patients until release of circulatory occlusion, with no significant difference in responses between patient groups. Muscle metaboreflex activation causes increased ventilation in COPD patients but not in healthy participants. Chronic hypercapnia in COPD patients does not exaggerate this response. The muscle metaboreflex appears to be abnormally involved in the control of ventilation in COPD and may be a contributing factor to exercise dyspnoea.
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Affiliation(s)
- Richard M Bruce
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, UK
| | - Alice Turner
- School of Clinical and Experimental Medicine, University of Birmingham, UK
| | - Michael J White
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, UK.
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Bruce RM, White MJ. The ventilatory response to muscle afferent activation during concurrent hypercapnia in humans: central and peripheral mechanisms. Exp Physiol 2015; 100:896-904. [DOI: 10.1113/ep085024] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 05/14/2015] [Indexed: 01/25/2023]
Affiliation(s)
- Richard M. Bruce
- School of Sport, Exercise and Rehabilitation Sciences; University of Birmingham; UK
| | - Michael J. White
- School of Sport, Exercise and Rehabilitation Sciences; University of Birmingham; UK
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Abstract
NEW FINDINGS What is the topic of this review? This brief review describes the work of Professor John Coote and colleagues at the University of Birmingham, which has contributed to understanding of the role of muscle afferent involvement in cardiorespiratory control in exercise. What advances does it highlight? The seminal findings of John Coote's early work are highlighted, as well as more recent developments in the field, especially the role of muscle afferents in the control of human ventilation during exercise. Through the work of John Coote, research into the role of muscle afferent involvement in cardiorespiratory control has had strong links with Birmingham since the late 1960s. This brief review gives an historical background to John's early work and how his research and mentorship of colleagues continues to have a profound influence on the field today.
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Affiliation(s)
- Michael J White
- * School of Sport, Exercise & Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
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Porszasz J, Rambod M, van der Vaart H, Rossiter HB, Ma S, Kiledjian R, Casaburi R. Sinusoidal high-intensity exercise does not elicit ventilatory limitation in chronic obstructive pulmonary disease. Exp Physiol 2013; 98:1102-14. [PMID: 23335005 DOI: 10.1113/expphysiol.2012.070375] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
During exercise at critical power (CP) in chronic obstructive pulmonary disease (COPD) patients, ventilation approaches its maximum. As a result of the slow ventilatory dynamics in COPD, ventilatory limitation during supramaximal exercise might be escaped using rapid sinusoidal forcing. Nine COPD patients [age, 60.2 ± 6.9 years; forced expiratory volume in the first second (FEV(1)), 42 ± 17% of predicted; and FEV(1)/FVC, 39 ± 12%] underwent an incremental cycle ergometer test and then four constant work rate cycle ergometer tests; tolerable duration (t(lim)) was recorded. Critical power was determined from constant work rate testing by linear regression of work rate versus 1/t(lim). Patients then completed fast (FS; 60 s period) and slow (SS; 360 s period) sinusoidally fluctuating exercise tests with mean work rate at CP and peak at 120% of peak incremental test work rate, and one additional test at CP; each for a 20 min target. The value of t(lim) did not differ between CP (19.8 ± 0.6 min) and FS (19.0 ± 2.5 min), but was shorter in SS (13.2 ± 4.2 min; P < 0.05). The sinusoidal ventilatory amplitude was minimal (37.4 ± 34.9 ml min(-1) W(-1)) during FS but much larger during SS (189.6 ± 120.4 ml min(-1) W(-1)). The total ventilatory response in SS reached 110 ± 8.0% of the incremental test peak, suggesting ventilatory limitation. Slow components in ventilation during constant work rate and FS exercises were detected in most subjects and contributed appreciably to the total response asymptote. The SS exercise was associated with higher mid-exercise lactate concentrations (5.2 ± 1.7, 7.6 ± 1.7 and 4.5 ± 1.3 mmol l(-1) in FS, SS and CP). Large-amplitude, rapid sinusoidal fluctuation in work rate yields little fluctuation in ventilation despite reaching 120% of the incremental test peak work rate. This high-intensity exercise strategy might be suitable for programmes of rehabilitative exercise training in COPD.
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Affiliation(s)
- Janos Porszasz
- Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, 1124 West Carson Street, Torrance, CA 90502, USA
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