1
|
Gorini Pereira F, McBryde M, Reynolds M, Sackett JR, Chapman CL, Gideon EA, Schlader ZJ, Johnson BD. Activation of cardiac parasympathetic and sympathetic activity occurs at different skin temperatures during face cooling. Am J Physiol Regul Integr Comp Physiol 2024; 326:R357-R369. [PMID: 38436059 DOI: 10.1152/ajpregu.00196.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 02/21/2024] [Accepted: 02/23/2024] [Indexed: 03/05/2024]
Abstract
Sufficiently cold-water temperatures (<7°C) are needed to elicit the sympathetic response to the cold pressor test using the hand. However, it is not known if stimulating the trigeminal nerve via face cooling, which increases both sympathetic and cardiac parasympathetic activity, also has a threshold temperature. We tested the hypothesis that peak autonomic activation during a progressive face cooling challenge would be achieved when the stimulus temperature is ≤7°C. Twelve healthy participants (age: 25 ± 3 yr, four women) completed our study. Six pliable bags, each containing water or an ice slurry (34°C, 28°C, 21°C, 14°C, 7°C, and 0°C) were applied sequentially to participants' forehead, eyes, and cheeks for 5 min each. Mean arterial pressure (photoplethysmography; index of sympathetic activity) and heart rhythm (3-lead ECG) were averaged in 1-min increments at the end of baseline and throughout each temperature condition. Heart rate variability in the time [(root mean square of successive differences (RMSSD)] and frequency [high-frequency (HF) power] domains was used to estimate cardiac parasympathetic activity. Data are presented as the increase from baseline ± SD. Mean arterial pressure only increased from baseline in the 7°C (13.1 ± 10.3 mmHg; P = 0.018) and 0°C (25.2 ± 7.8 mmHg; P < 0.001) conditions. Only the 0°C condition increased RMSSD (160.6 ± 208.9 ms; P = 0.009) and HF power (11,450 ± 14,555 ms2; P = 0.014) from baseline. Our data indicate that peak increases in sympathetic activity during face cooling are initiated at a higher forehead skin temperature than peak increases in cardiac parasympathetic activity.
Collapse
Affiliation(s)
- Felipe Gorini Pereira
- Department of Kinesiology, School of Public Health, Indiana University, Bloomington, Indiana, United States
| | - Muhamed McBryde
- Center for Research and Education in Special Environments, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York, United States
| | - Morgan Reynolds
- Center for Research and Education in Special Environments, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York, United States
| | - James R Sackett
- Center for Research and Education in Special Environments, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York, United States
| | - Christopher L Chapman
- Center for Research and Education in Special Environments, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York, United States
| | - Elizabeth A Gideon
- Center for Research and Education in Special Environments, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York, United States
| | - Zachary J Schlader
- Department of Kinesiology, School of Public Health, Indiana University, Bloomington, Indiana, United States
- Center for Research and Education in Special Environments, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York, United States
| | - Blair D Johnson
- Department of Kinesiology, School of Public Health, Indiana University, Bloomington, Indiana, United States
- Center for Research and Education in Special Environments, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York, United States
| |
Collapse
|
2
|
Tourula E, Lenzini M, Rhodes A, Hetz SE, Pearson J. Facial fanning reduces heart rate but not tolerance to a simulated hemorrhagic challenge following exercise heat stress in young healthy humans. Am J Physiol Regul Integr Comp Physiol 2024; 326:R210-R219. [PMID: 38105763 DOI: 10.1152/ajpregu.00180.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 11/02/2023] [Accepted: 12/12/2023] [Indexed: 12/19/2023]
Abstract
We investigated whether reducing face skin temperature alters arterial blood pressure control and lower body negative pressure (LBNP) tolerance after exercise heat stress. Eight subjects (1 female; age, 27 ± 9 yr) exercised at ∼63% V̇o2max until core temperature had increased ∼1.5°C before undergoing LBNP to presyncope either with fanning to return face skin temperature to baseline (Δ-5°C, Fan trial) or without (No Fan trial). LBNP tolerance was quantified as cumulative stress index (CSI; mmHg·min). Before LBNP, whole body and face skin temperatures were elevated from baseline in both trials (38.0 ± 0.5°C and 36.3 ± 0.5°C, respectively, both P < 0.001). During LBNP, face skin temperature decreased in the Fan trial (30.9 ± 1.0°C) but was unchanged in the No Fan trial (36.1 ± 0.6°C, between trials P < 0.001). Mean arterial pressure was not different between trials (P = 0.237) and was similarly reduced at presyncope in both trials (from 82 ± 7 to 67 ± 8 mmHg, P < 0.001). During LBNP, heart rate was attenuated in the Fan trial at Mid LBNP (146 ± 16 vs. 158 ± 12 beats/min, P = 0.036) and at peak heart rate (158 ± 15 vs. 170 ± 15 beats/min; P < 0.001). LBNP tolerance was not different between trials (321 ± 248 vs. 328 ± 115 mmHg·min, P = 0.851). In exercise heat-stressed individuals, lowering face skin temperature to normothermic values suppressed heart rate thereby altering cardiovascular control during a simulated hemorrhagic challenge without reducing tolerance.
Collapse
Affiliation(s)
- Erica Tourula
- William J. Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado Colorado Springs, Colorado, United States
- Department of Kinesiology, H. H. Morris Human Performance Laboratories, School of Public Health, Indiana University, Bloomington, Indiana, United States
| | - Miramani Lenzini
- William J. Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado Colorado Springs, Colorado, United States
| | - Addison Rhodes
- William J. Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado Colorado Springs, Colorado, United States
| | - Sarah E Hetz
- William J. Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado Colorado Springs, Colorado, United States
| | - James Pearson
- William J. Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado Colorado Springs, Colorado, United States
| |
Collapse
|
3
|
Nordine M, Schwarz A, Bruckstein R, Gunga HC, Opatz O. The Human Dive Reflex During Consecutive Apnoeas in Dry and Immersive Environments: Magnitude and Synchronicity. Front Physiol 2022; 12:725361. [PMID: 35058791 PMCID: PMC8764278 DOI: 10.3389/fphys.2021.725361] [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: 06/15/2021] [Accepted: 11/23/2021] [Indexed: 11/13/2022] Open
Abstract
Introduction: The human dive reflex (HDR), an O2 conserving reflex, is characterised by an interplay of central parasympathetic and peripheral sympathetic reactions, which are presumed to operate independently of each other. The HDR is fully activated during apnoea with facial immersion in water and complete immersion in water is thought to increase the magnitude of HDR during consecutive apnoeas. A comparison of HDR activity between consecutive apnoeas in full-body immersion with consecutive apnoeas in dry conditions has not been fully explored. Also, the interplay between parasympathetic and sympathetic reactions involved in the HDR has not been thoroughly analysed. Methods: 11 human volunteers performed 3 consecutive 60 s apnoeas with facial immersion in dry conditions (FIDC) and 3 consecutive apnoeas with facial immersion in full immersion (FIFI). Heart rate (HR), R-R interval (RRI), finger pulse amplitude (FPA), splenic width (SW) and SpO2 were all measured before, during and after apnoeas. A one-way ANOVA using Dunn's post hoc test was performed to assess HDR activity, and a Pearson's correlation test was performed to assess HDR synchronisation between physiological parameters during both conditions. Results: Although HDR activity was not significantly different between both conditions, HR and RRI showed progressively greater changes during FIFI compared with FIDC, while SW and FPA changes were relatively equivalent. During FIDC, significant correlations were found between SW & SpO2 and FPA & SpO2. During FIFI, significant correlations were found between RRI & FPA, SW & FPA, HR & SpO2 and FPA & SpO2. Discussion: While there was no significant difference found between HDR activity during FIDC and FIFI, consecutive apnoeas during FIFI triggered a greater magnitude of cardiac activity. Furthermore, significant correlations between RRI and SW with FPA indicate a crosstalk between parasympathetic tone with splenic contraction and increased peripheral sympathetic outflow during FIFI compared to FIDC. In conclusion, HDR activity during consecutive apnoeas does not differ between FIDC and FIFI. There appears to be however a greater level of synchronicity during apnoeas in FIFI compared to FIDC and that this is most likely due to the physiological effects of immersion, which could induce neural recruitment and increased cross talk of HDR pathways.
Collapse
Affiliation(s)
- Michael Nordine
- Charité Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Clinic for Anesthesiology, Campus Benjamin Franklin Berlin, Berlin, Germany
| | - Anton Schwarz
- Monash School of Medicine, Monash University, Clayton, VIC, Australia
| | - Renana Bruckstein
- Charité Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Clinic for Anesthesiology, Campus Benjamin Franklin Berlin, Berlin, Germany
| | - Hanns-Christian Gunga
- Charité Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Clinic for Anesthesiology, Campus Benjamin Franklin Berlin, Berlin, Germany
| | - Oliver Opatz
- Charité Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Clinic for Anesthesiology, Campus Benjamin Franklin Berlin, Berlin, Germany
| |
Collapse
|
4
|
Seeley AD, Giersch GEW, Charkoudian N. Post-exercise Body Cooling: Skin Blood Flow, Venous Pooling, and Orthostatic Intolerance. Front Sports Act Living 2021; 3:658410. [PMID: 34079934 PMCID: PMC8165173 DOI: 10.3389/fspor.2021.658410] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 04/16/2021] [Indexed: 12/28/2022] Open
Abstract
Athletes and certain occupations (e.g., military, firefighters) must navigate unique heat challenges as they perform physical tasks during prolonged heat stress, at times while wearing protective clothing that hinders heat dissipation. Such environments and activities elicit physiological adjustments that prioritize thermoregulatory skin perfusion at the expense of arterial blood pressure and may result in decreases in cerebral blood flow. High levels of skin blood flow combined with an upright body position augment venous pooling and transcapillary fluid shifts in the lower extremities. Combined with sweat-driven reductions in plasma volume, these cardiovascular alterations result in levels of cardiac output that do not meet requirements for brain blood flow, which can lead to orthostatic intolerance and occasionally syncope. Skin surface cooling countermeasures appear to be a promising means of improving orthostatic tolerance via autonomic mechanisms. Increases in transduction of sympathetic activity into vascular resistance, and an increased baroreflex set-point have been shown to be induced by surface cooling implemented after passive heating and other arterial pressure challenges. Considering the further contribution of exercise thermogenesis to orthostatic intolerance risk, our goal in this review is to provide an overview of post-exercise cooling strategies as they are capable of improving autonomic control of the circulation to optimize orthostatic tolerance. We aim to synthesize both basic and applied physiology knowledge available regarding real-world application of cooling strategies to reduce the likelihood of experiencing symptomatic orthostatic intolerance after exercise in the heat.
Collapse
Affiliation(s)
- Afton D Seeley
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, MA, United States.,Oak Ridge Institute of Science and Education, Belcamp, MD, United States
| | - Gabrielle E W Giersch
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, MA, United States.,Oak Ridge Institute of Science and Education, Belcamp, MD, United States
| | - Nisha Charkoudian
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, MA, United States
| |
Collapse
|
5
|
Johnson BD, O'Leary MC, McBryde M, Sackett JR, Schlader ZJ, Leddy JJ. Face cooling exposes cardiac parasympathetic and sympathetic dysfunction in recently concussed college athletes. Physiol Rep 2019; 6:e13694. [PMID: 29741235 PMCID: PMC5941219 DOI: 10.14814/phy2.13694] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 04/06/2018] [Indexed: 12/24/2022] Open
Abstract
We tested the hypothesis that concussed college athletes (CA) have attenuated parasympathetic and sympathetic responses to face cooling (FC). Eleven symptomatic CA (age: 20 ± 2 years, 5 women) who were within 10 days of concussion diagnosis and 10 healthy controls (HC; age: 24 ± 4 years, 5 women) participated. During FC, a plastic bag filled with ice water (~0°C) was placed on the forehead, eyes, and cheeks for 3 min. Heart rate (ECG) and blood pressure (photoplethysmography) were averaged at baseline and every 60 sec during FC. High‐frequency (HF) power was obtained from spectral analysis of the R‐R interval. Data are presented as a change from baseline. Baseline heart rate (HC: 61 ± 12, CA: 57 ± 12 bpm; P = 0.69), mean arterial pressure (MAP) (HC: 94 ± 10, CA: 96 ± 13 mmHg; P = 0.74), and HF (HC: 2294 ± 2314, CA: 2459 ± 2058 msec2; P = 0.86) were not different between groups. Heart rate in HC decreased at 2 min (−7 ± 11 bpm; P = 0.02) but did not change in CA (P > 0.43). MAP increased at 1 min (HC: 12 ± 6, CA: 6 ± 6 mmHg), 2 min (HC: 21 ± 7, CA: 11 ± 7 mmHg), and 3 min (HC: 20 ± 6, CA: 13 ± 7 mmHg) in both groups (P < 0.01 for all) but the increase was greater at each interval in HC (P < 0.02). HF increased at 1 min (12354 ± 11489 msec2; P < 0.01) and 2 min (5832 ± 8002 msec2; P = 0.02) in HC but did not change in CA (P > 0.58). The increase in HF at 1 min was greater in HC versus CA (P < 0.01). These data indicate that symptomatic concussed patients have impaired cardiac parasympathetic and sympathetic activation.
Collapse
Affiliation(s)
- Blair D Johnson
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Morgan C O'Leary
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Muhamed McBryde
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - James R Sackett
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Zachary J Schlader
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - John J Leddy
- UBMD, Department of Orthopaedics and Sports Medicine, University at Buffalo, Buffalo, New York
| |
Collapse
|
6
|
Hu J, Shen H, Teng CG, Han D, Chu GP, Zhou YK, Wang Q, Wang B, Wu JZ, Xiao Q, Liu F, Yang HB. The short-term effects of outdoor temperature on blood pressure among children and adolescents: finding from a large sample cross-sectional study in Suzhou, China. INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2019; 63:381-391. [PMID: 30694394 DOI: 10.1007/s00484-019-01671-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 12/12/2018] [Accepted: 01/10/2019] [Indexed: 06/09/2023]
Abstract
Although several studies have demonstrated a short-term association between outdoor temperature and blood pressure (BP) among various adult groups, evidence among children and adolescents is lacking. One hundred ninety-four thousand one hundred four participants from 2016 Health Promotion Program for Children and Adolescents (HPPCA) were analyzed through generalized linear mixed-effects models to estimate the short-term effects of two outdoor temperature variables (average and minimum temperature) on participants' BP. Decreasing outdoor temperature was associated with significant increases in systolic BP (SBP), diastolic BP (DBP), and prevalence of hypertension during lag 0 through lag 6. Additionally, daily minimum temperature showed a more apparent association with participants' BP. The estimated increases (95% confidence interval) in SBP and DBP at lag 0 were 0.82 (0.72, 0.92) mmHg and 2.28 (2.20, 2.35) mmHg for a 1 °C decrease in daily minimum temperature, while those values were 0.11 (0.10, 0.12) mmHg and 0.25 (0.24, 0.26) mmHg for a 1 °C decrease in daily average temperature, respectively. The effects of temperature on BP were stronger among female, as well as those with young age and low body mass index. It demonstrated that short-term decreases in outdoor temperature were significantly associated with rises in BP among children and adolescents. This founding has some implications for clinical management and research of BP. Meanwhile, public health intervention should be designed to reduce the exposure to cold temperature for protecting children and adolescents' BP.
Collapse
Affiliation(s)
- Jia Hu
- Suzhou Center for Disease Prevention and Control, 72 Sanxiang Road, Suzhou, 215004, Jiangsu, China.
| | - Hui Shen
- Suzhou Center for Disease Prevention and Control, 72 Sanxiang Road, Suzhou, 215004, Jiangsu, China
| | - Chen-Gang Teng
- Suzhou Center for Disease Prevention and Control, 72 Sanxiang Road, Suzhou, 215004, Jiangsu, China
| | - Di Han
- Suzhou Center for Disease Prevention and Control, 72 Sanxiang Road, Suzhou, 215004, Jiangsu, China
| | - Guang-Ping Chu
- Health Center for Women and Children of Gusu District, Suzhou, Jiangsu, China
| | - Yi-Kai Zhou
- MOE Key Lab of Environment and Health, Institute of Environmental Medicine, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, Hubei, China
| | - Qi Wang
- Department of Epidemiology & Biostatistics, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, China
| | - Bo Wang
- Suzhou Center for Disease Prevention and Control, 72 Sanxiang Road, Suzhou, 215004, Jiangsu, China
| | - Jing-Zhi Wu
- Suzhou Center for Disease Prevention and Control, 72 Sanxiang Road, Suzhou, 215004, Jiangsu, China
| | - Qi Xiao
- Suzhou Center for Disease Prevention and Control, 72 Sanxiang Road, Suzhou, 215004, Jiangsu, China
| | - Fang Liu
- Suzhou Center for Disease Prevention and Control, 72 Sanxiang Road, Suzhou, 215004, Jiangsu, China
| | - Hai-Bing Yang
- Suzhou Center for Disease Prevention and Control, 72 Sanxiang Road, Suzhou, 215004, Jiangsu, China.
| |
Collapse
|
7
|
Schlader ZJ, Chapman CL, Benati JM, Gideon EA, Vargas NT, Lema PC, Johnson BD. Renal Hemodynamics During Sympathetic Activation Following Aerobic and Anaerobic Exercise. Front Physiol 2019; 9:1928. [PMID: 30687130 PMCID: PMC6335335 DOI: 10.3389/fphys.2018.01928] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Accepted: 12/21/2018] [Indexed: 12/30/2022] Open
Abstract
We tested the hypotheses that prior aerobic (Study 1) or anaerobic (Study 2) exercise attenuates the increase in renal vascular resistance (RVR) during sympathetic stimulation. Ten healthy young adults (5 females) participated in both Study 1 (aerobic exercise) and Study 2 (anaerobic exercise). In Study 1, subjects completed three minutes of face cooling pre- and post- 30 min of moderate intensity aerobic exercise (68 ± 1% estimate maximal heart rate). In Study 2, subjects completed two minutes of the cold pressor test pre- and post- the completion of a 30 s maximal effort cycling test (Wingate Anaerobic Test). Both face cooling and the cold pressor test stimulate the sympathetic nervous system and elevate RVR. The primary dependent variable in both Studies was renal blood velocity, which was measured at baseline and every minute during sympathetic stimulation. Renal blood velocity was measured via the coronal approach at the distal segment of the right renal artery with pulsed wave Doppler ultrasound. RVR was calculated from the quotient of mean arterial pressure and renal blood velocity. In Study 1, renal blood velocity and RVR did not differ between pre- and post- aerobic exercise (P ≥ 0.24). Face cooling decreased renal blood velocity (P < 0.01) and the magnitude of this decrease did not differ between pre- and post- aerobic exercise (P = 0.52). RVR increased with face cooling (P < 0.01) and the extent of these increases did not differ between pre- and post- aerobic exercise (P = 0.74). In Study 2, renal blood velocity was 2 ± 2 cm/s lower post- anaerobic exercise (P = 0.02), but RVR did not differ (P = 0.08). The cold pressor test decreased renal blood velocity (P < 0.01) and the magnitude of this decrease did not differ between pre- and post- anaerobic exercise (P = 0.26). RVR increased with the cold pressor test (P < 0.01) and the extent of these increases did not differ between pre- and post- anaerobic exercise (P = 0.12). These data indicate that 30 min of moderate intensity aerobic exercise or 30 s of maximal effort anaerobic exercise does not affect the capacity to increase RVR during sympathetic stimulation following exercise.
Collapse
Affiliation(s)
- Zachary J. Schlader
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, United States
| | - Christopher L. Chapman
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, United States
| | - Julia M. Benati
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, United States
| | - Elizabeth A. Gideon
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, United States
| | - Nicole T. Vargas
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, United States
| | - Penelope C. Lema
- Department of Emergency Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
| | - Blair D. Johnson
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, United States
| |
Collapse
|
8
|
Trotter CE, Pizzey FK, Batterson PM, Jacobs RA, Pearson J. Small reductions in skin temperature after onset of a simulated hemorrhagic challenge improve tolerance in exercise heat-stressed individuals. Am J Physiol Regul Integr Comp Physiol 2018; 315:R539-R546. [DOI: 10.1152/ajpregu.00182.2018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated whether small reductions in skin temperature 60 s after the onset of a simulated hemorrhagic challenge would improve tolerance to lower body negative pressure (LBNP) after exercise heat stress. Eleven healthy subjects completed two trials (High and Reduced). Subjects cycled at ~55% maximal oxygen uptake wearing a warm water-perfused suit until core temperatures increased by ~1.2°C before lying supine and undergoing LBNP to presyncope. LBNP tolerance was quantified as cumulative stress index (CSI; product of each LBNP level multiplied by time; mmHg·min). Skin temperature was similarly elevated from baseline before LBNP and remained elevated 60 s after the onset of LBNP in both High (37.72 ± 0.52°C) and Reduced (37.95 ± 0.54°C) trials (both P < 0.0001). At 60%CSI skin temperature remained elevated in the High trial (37.51 ± 0.56°C) but was reduced to 34.97 ± 0.72°C by the water-perfused suit in the Reduced trial ( P < 0.0001 between trials). Cutaneous vascular conductance was not different between trials [High: 1.57 ± 0.43 vs. Reduced: 1.39 ± 0.38 arbitrary units (AU)/mmHg; P = 0.367] before LBNP but decreased to 0.67 ± 0.19 AU/mmHg at 60%CSI in the Reduced trial while remaining unchanged in the High trial ( P = 0.002 between trials). CSI was higher in the Reduced (695 ± 386 mmHg·min) relative to the High (441 ± 290 mmHg·min; P = 0.023) trial. Mean arterial pressure was not different between trials at presyncope (High: 62 ± 10 vs. Reduced: 62 ± 9 mmHg; P = 0.958). Small reductions in skin temperature after the onset of a simulated hemorrhagic challenge improve LBNP tolerance after exercise heat stress. This may have important implications regarding treatment of an exercise heat-stressed individual (e.g., soldier) who has experienced a hemorrhagic injury.
Collapse
Affiliation(s)
- Claire E. Trotter
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
| | - Faith K. Pizzey
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
| | - Philip M. Batterson
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
| | - Robert A. Jacobs
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
| | - James Pearson
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
| |
Collapse
|
9
|
Hodges GJ, Kiviniemi AM, Mallette MM, Klentrou P, Falk B, Cheung SS. Effect of passive heat exposure on cardiac autonomic function in healthy children. Eur J Appl Physiol 2018; 118:2233-2240. [PMID: 30069604 DOI: 10.1007/s00421-018-3957-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 07/27/2018] [Indexed: 12/19/2022]
Abstract
PURPOSE The aim of this study was to examine the effect of passive heat stress on heart rate variability parameters in healthy children. METHOD Fifteen children (9.3 ± 1.6 years) of both sexes (eight male) participated in two randomized experimental conditions separated by 5-12 days. Children were seated for 2 h in an environmental chamber for two sessions: neutral (22.4 ± 0.1 °C, 40.4 ± 6.5% RH) and hot (34.9 ± 0.3 °C, 36.6 ± 6.2% RH) conditions. Electrocardiogram, mean skin temperature, tympanic temperature, and blood pressure were recorded. Five min epochs were averaged for analysis of cardiac autonomic function over the 2-h protocol. RESULT Mean skin and tympanic temperatures and heart rate increased during the hot condition (all p < 0.01) while mean arterial pressure decreased (p < 0.01). During the hot condition, root-mean-square difference of successive normal RR intervals (45 ± 9 to 38 ± 7 ms), and low- (LF, 1536 ± 464 vs. 935 ± 154 ms2) and high-frequency power (HF, 1544 ± 693 vs. 866 ± 355 ms2) decreased, whereas LF/HF ratio increased (1.64 ± 0.24 vs. 2.40 ± 0.23 au); all indices were different from neutral (all p < 0.05). These were all unchanged throughout the neutral condition (all p > 0.05), except for LF/HF ratio which decreased during the neutral condition (p < 0.05). CONCLUSION Mild hyperthermia elicited marked changes in cardiac autonomic control in young children. These data suggest that, in healthy children, vagal withdrawal is responsible for the cardiac autonomic response to hyperthermia.
Collapse
Affiliation(s)
- Gary J Hodges
- Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada
| | - Antti M Kiviniemi
- Research Unit of Internal Medicine, Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland
| | - Matthew M Mallette
- Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada
| | - Panagiota Klentrou
- Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada
- Centre for Bone and Muscle Health, Faculty of Applied Health Sciences, Brock University, St. Catharines, ON, L2S 3A1, Canada
| | - Bareket Falk
- Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada
- Centre for Bone and Muscle Health, Faculty of Applied Health Sciences, Brock University, St. Catharines, ON, L2S 3A1, Canada
| | - Stephen S Cheung
- Department of Kinesiology, Faculty of Applied Health Sciences, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada.
| |
Collapse
|
10
|
Schlader ZJ, O'Leary MC, Sackett JR, Johnson BD. Face cooling reveals a relative inability to increase cardiac parasympathetic activation during passive heat stress. Exp Physiol 2018; 103:701-713. [PMID: 29450933 DOI: 10.1113/ep086865] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 02/12/2018] [Indexed: 01/31/2023]
Abstract
NEW FINDINGS What is the central question of this study? Does passive heat stress attenuate the increase in cardiac parasympathetic stimulation, vascular resistance and blood pressure evoked by face cooling? What is the main finding and its importance? Passive heat stress attenuates the capacity to increase cardiac parasympathetic activation and impairs the ability to increase vascular resistance during sympathoexcitation, which ultimately results in a relative inability to increase blood pressure. These findings cast doubt on the efficacy of face cooling at augmenting blood pressure during orthostasis while heat stressed. ABSTRACT We tested the hypothesis that passive heat stress attenuates the increase in cardiac parasympathetic stimulation, vascular resistance and blood pressure evoked by face cooling. During normothermia and when intestinal temperature was elevated by 1.0 ± 0.2°C, 10 healthy young adults underwent 3 min of face cooling. Face cooling was accomplished by placing a 2.5 litre bag of ice water (0 ± 0°C) over the cheeks, eyes and forehead. Primary variables included forehead skin temperature, mean arterial pressure and systemic, forearm and cutaneous vascular resistances. Indices of heart rate variability in the time domain provided an index of cardiac parasympathetic activity. The magnitude of reduction in forehead skin temperature during face cooling was slightly greater during normothermia (-17.6 ± 1.9 versus -16.3 ± 3.0°C, P = 0.03). Increases in heart rate variability evoked by face cooling were attenuated during heat stress. Changes in systemic, forearm and cutaneous vascular resistances during face cooling were virtually abolished during heat stress (P < 0.01). However, when forearm and vascular data were reported as conductance, differences between normothermia and heat stress were not apparent (P ≥ 0.62). Nevertheless, the increase in mean arterial pressure was attenuated during heat stress with face cooling (at 3 min: 2 ± 7 mmHg) compared with normothermia (at 3 min: 19 ± 7 mmHg, P < 0.01). These data indicate that passive heat stress attenuates face cooling-evoked increases in cardiac parasympathetic activation, vascular resistance and blood pressure. However, they also indicate that changes in indices of vascular resistance do not always reflect equivalent changes in conductance.
Collapse
Affiliation(s)
- Zachary J Schlader
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - Morgan C O'Leary
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - James R Sackett
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| | - Blair D Johnson
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
| |
Collapse
|