Overview
Geoff is a lecturer in Sport and Exercise Science and a member of the Institute for Applied Human Physiology. He recently joined Bangor University in 2024 after completing postgraduate training in environmental physiology and two postdoctoral fellowships studying the regulation of cerebral blood flow and neuroimaging. Geoff has had the opportunity to practice these areas of expertise around the world (e.g., Peru, Croatia) working with unique populations in various extreme environments (indigenous high altitude populations, free divers). Overall, these experiences have broadened Geoff’s scientific approach where he employs a diverse array of physiological research techniques (transcranial Doppler ultrasound, MRI, thermometry, etc.).
The successful coordination between cardiovascular, respiratory, autonomic, and thermoregulatory systems is essential to physiological homeostasis, particularly in environmentally or physiologically compromised scenarios. Natural (aging) and human-made (climate change) processes can increase the risk of serious health conditions such as heat stroke or cognitive impairment. Geoff’s research program examines the integrative cardiorespiratory aspects of human health and performance. His specific research interests include human health throughout the lifespan and how the environment influences that process – specifically, the human health impacts of climate change as well as the benefits of physical activity on cardiovascular health during the aging process.
Please email me if you are interested in postgraduate or postdoctoral opportunities.
Qualifications
- Postdoctoral Fellowship
McMaster University, 2022–2024 - Postdoctoral Fellowship
Western University, Ontario, 2020–2022 - PhD
University of British Columbia, Okanagan, 2016–2020 - MSc
University of Ottawa, 2013–2016 - BSc
University of Ottawa, 2009–2013
Research Interests
Areas of research: 1) cardiovascular and thermoregulatory responses to extreme environments (heat, cold, diving), and 2) cerebrovascular regulation in health and aging. Both themes require an integrative approach assessing multiple organ systems that function to support to regulate thermal and cardiorespiratory homeostasis during combined environmental stressors (e.g., exercise, heat, and pollution), or to maintain cerebral oxygen delivery and therefore neural processes.
Postgraduate Project Opportunities
Publications
2024
- E-pub ahead of printAcute isometric and dynamic exercise do not alter cerebral sympathetic nerve activity in healthy humans
Tymko, M. M., Drapeau, A., Vieira-Coelho, M. A., Labrecque, L., Imhoff, S., Coombs, G. B., Langevin, S., Fortin, M., Châteauvert, N., Ainslie, P. N. & Brassard, P., 13 Apr 2024, (E-pub ahead of print) In: Journal of Cerebral Blood Flow and Metabolism. 12 p.
Research output: Contribution to journal › Article › peer-review - PublishedStanding middle cerebral artery velocity predicts cognitive function and gait speed in older adults with cognitive impairment, and is impacted by sex differences
Fitzgibbon-Collins, L. K., Coombs, G. B., Noguchi, M., Parihar, S., Hughson, R. L., Borrie, M., Peters, S., Shoemaker, J. K. & Bhangu, J., Jan 2024, In: Cerebral circulation - cognition and behavior. 6, p. 100198
Research output: Contribution to journal › Article › peer-review
2023
- PublishedAge- and sex-related differences in sympathetic vascular transduction and neurohemodynamic balance in humans
D'Souza, A. W., Hissen, S. L., Manabe, K., Takeda, R., Washio, T., Coombs, G. B., Sanchez, B., Fu, Q. & Shoemaker, J. K., 1 Oct 2023, In: American Journal of Physiology - Heart and Circulatory Physiology. 325, 4, p. H917-H932
Research output: Contribution to journal › Article › peer-review - PublishedCerebral O2 and CO2 transport in isovolumic haemodilution: Compensation of cerebral delivery of O2 and maintenance of cerebrovascular reactivity to CO2
Carr, J. M., Ainslie, P. N., MacLeod, D. B., Tremblay, J. C., Nowak-Flück, D., Howe, C. A., Stembridge, M., Patrician, A., Coombs, G. B., Stacey, B. S., Bailey, D. M., Green, D. J. & Hoiland, R. L., Jan 2023, In: Journal of Cerebral Blood Flow and Metabolism. 43, 1, p. 99-114 16 p.
Research output: Contribution to journal › Article › peer-review - PublishedDifferential Expression of Vascular-Related MicroRNA in Circulating Endothelial Microvesicles in Adults With Spinal Cord Injury: A Pilot Study
Park, A. J., Fandl, H. K., Garcia, V. P., Coombs, G. B., DeSouza, N. M., Greiner, J. J., Barak, O. F., Mijacika, T., Dujic, Z., Ainslie, P. N. & DeSouza, C. A., 3 Apr 2023, In: Topics in spinal cord injury rehabilitation. 29, 2, p. 34-42 9 p.
Research output: Contribution to journal › Article › peer-review - PublishedHemoglobin and cerebral hypoxic vasodilation in humans: Evidence for nitric oxide-dependent and S-nitrosothiol mediated signal transduction
Hoiland, R. L., MacLeod, D. B., Stacey, B. S., Caldwell, H. G., Howe, C. A., Nowak-Flück, D., Carr, J. M., Tymko, M. M., Coombs, G. B., Patrician, A., Tremblay, J. C., Van Mierlo, M., Gasho, C., Stembridge, M., Sekhon, M. S., Bailey, D. M. & Ainslie, P. N., Sept 2023, In: Journal of Cerebral Blood Flow and Metabolism. 43, 9, p. 1519-1531 13 p.
Research output: Contribution to journal › Article › peer-review - PublishedImpact of ischemic heart disease and cardiac rehabilitation on cerebrovascular compliance
Coombs, G. B., Al-Khazraji, B. K., Suskin, N. & Shoemaker, J. K., 1 Oct 2023, In: Journal of applied physiology (Bethesda, Md. : 1985). 135, 4, p. 753-762 10 p.
Research output: Contribution to journal › Article › peer-review - PublishedThe interactive effects of age and sex on the neuro-cardiovascular responses during fatiguing rhythmic handgrip exercise
D'Souza, A. W., Takeda, R., Manabe, K., Hissen, S. L., Washio, T., Coombs, G. B., Sanchez, B., Fu, Q. & Shoemaker, J. K., 15 Jul 2023, In: Journal of Physiology. 601, 14, p. 2877-2898 22 p.
Research output: Contribution to journal › Article › peer-review
2022
- PublishedCommon carotid artery responses to the cold-pressor test are impaired in individuals with cervical spinal cord injury
Sarafis, Z. K., Squair, J. W., Barak, O. F., Coombs, G. B., Soriano, J. E., Larkin-Kaiser, K. A., Lee, A. H. X., Hansen, A., Vodopic, M., Romac, R., Grant, C., Charbonneau, R., Mijacika, T., Krassioukov, A. V., Ainslie, P. N., Dujic, Z. & Phillips, A. A., 1 Dec 2022, In: American Journal of Physiology - Heart and Circulatory Physiology. 323, 6, p. H1311-H1322
Research output: Contribution to journal › Article › peer-review - PublishedGlobal Research Expedition on Altitude-related Chronic Health 2018 Iron Infusion at High Altitude Reduces Hypoxic Pulmonary Vasoconstriction Equally in Both Lowlanders and Healthy Andean Highlanders
Patrician, A., Dawkins, T., Coombs, G. B., Stacey, B., Gasho, C., Gibbons, T., Howe, C. A., Tremblay, J. C., Stone, R., Tymko, K., Tymko, C., Akins, J. D., Hoiland, R. L., Vizcardo-Galindo, G. A., Figueroa-Mujíca, R., Villafuerte, F. C., Bailey, D. M., Stembridge, M., Anholm, J. D., Tymko, M. M. & Ainslie, P. N., Apr 2022, In: Chest. 161, 4, p. 1022-1035 14 p.
Research output: Contribution to journal › Article › peer-review - PublishedPassive leg cycling increases activity of the cardiorespiratory system in people with tetraplegia
Soriano, J. E., Romac, R., Squair, J. W., Barak, O. F., Sarafis, Z. K., Lee, A. H. X., Coombs, G. B., Vaseghi, B., Grant, C., Charbonneau, R., Mijacika, T., Krassioukov, A. V., Ainslie, P. N., Larkin-Kaiser, K. A., Phillips, A. A. & Dujic, Z., 3 Mar 2022, In: Applied Physiology, Nutrition, and Metabolism. 47, 3, p. 269-277 9 p.
Research output: Contribution to journal › Article › peer-review
2021
- PublishedDistinct contributions of skin and core temperatures to flow-mediated dilation of the brachial artery following passive heating
Coombs, G. B., Tremblay, J. C., Shkredova, D. A., Carr, J. M. J. R., Wakeham, D. J., Patrician, A. & Ainslie, P. N., 1 Jan 2021, In: Journal of applied physiology (Bethesda, Md. : 1985). 130, 1, p. 149-159 11 p.
Research output: Contribution to journal › Article › peer-review - PublishedGlobal Reach 2018: Nitric oxide-mediated cutaneous vasodilation is reduced in chronic, but not acute, hypoxia independently of enzymatic superoxide formation
Coombs, G. B., Akins, J. D., Patik, J. C., Vizcardo-Galindo, G. A., Figueroa-Mujica, R., Tymko, M. M., Stacey, B. S., Iannetelli, A., Bailey, D. M., Villafuerte, F. C., Ainslie, P. N. & Brothers, R. M., 20 Aug 2021, In: Free radical biology & medicine. 172, p. 451-458 8 p.
Research output: Contribution to journal › Article › peer-review - PublishedHourly staircase sprinting exercise "snacks" improve femoral artery shear patterns but not flow-mediated dilation or cerebrovascular regulation: a pilot study
Caldwell, H. G., Coombs, G. B., Rafiei, H., Ainslie, P. N. & Little, J. P., May 2021, In: Applied Physiology, Nutrition, and Metabolism. 46, 5, p. 521-529 9 p.
Research output: Contribution to journal › Article › peer-review - PublishedNormobaric hypoxia does not alter the critical environmental limits for thermal balance during exercise-heat stress
Coombs, G. B., Cramer, M. N., Ravanelli, N., Imbeault, P. & Jay, O., Jan 2021, In: Experimental Physiology. 106, 1, p. 359-369 11 p.
Research output: Contribution to journal › Article › peer-review - PublishedTemporal changes in pulmonary gas exchange efficiency when breath-hold diving below residual volume
Patrician, A., Spajić, B., Gasho, C., Caldwell, H. G., Dawkins, T., Stembridge, M., Lovering, A. T., Coombs, G. B., Howe, C. A., Barak, O., Drviš, I., Dujić, Ž. & Ainslie, P. N., Apr 2021, In: Experimental Physiology. 106, 4, p. 1120-1133 14 p.
Research output: Contribution to journal › Article › peer-review - PublishedThe 2018 Global Research Expedition on Altitude-related Chronic Health (REACH) to Cerro de Pasco, Peru: An Experimental Overview
Tymko, M. M., Hoiland, R. L., Tremblay, J. C., Stembridge, M., Dawkins, T. G., Coombs, G. B., Patrician, A., Howe, C. A., Gibbons, T. D., Moore, J. P., Simpson, L. L., Steinback, C. D., Meah, V. L., Stacey, B. S., Bailey, D. M., MacLeod, D. B., Gasho, C., Anholm, J. D., Bain, A. R., Lawley, J. S., Villafuerte, F. C., Vizcardo-Galindo, G. & Ainslie, P. N., Jan 2021, In: Experimental Physiology. 106, 1, p. 86-103 18 p.
Research output: Contribution to journal › Article › peer-review
2020
- PublishedAcute reductions in haematocrit increase flow-mediated dilatation independent of resting nitric oxide bioavailability in humans
Hoiland, R. L., Tremblay, J. C., Stacey, B. S., Coombs, G. B., Nowak-Flück, D., Tymko, M. M., Patrician, A., Stembridge, M., Howe, C. A., Bailey, D. M., Green, D. J., MacLeod, D. B. & Ainslie, P. N., Oct 2020, In: Journal of Physiology. 598, 19, p. 4225-4236 12 p.
Research output: Contribution to journal › Article › peer-review - PublishedEffects of circulating extracellular microvesicles from spinal cord-injured adults on endothelial cell function
Brewster, L. M., Coombs, G. B., Garcia, V. P., Hijmans, J. G., DeSouza, N. M., Stockelman, K. A., Barak, O. F., Mijacika, T., Dujic, Z., Greiner, J. J., Phillips, A. A., Ainslie, P. N. & DeSouza, C. A., 17 Apr 2020, In: Clinical science (London, England : 1979). 134, 7, p. 777-789 13 p.
Research output: Contribution to journal › Article › peer-review - PublishedEvidence for temperature-mediated regional increases in cerebral blood flow during exercise
Caldwell, H. G., Coombs, G. B., Howe, C. A., Hoiland, R. L., Patrician, A., Lucas, S. J. E. & Ainslie, P. N., Apr 2020, In: Journal of Physiology. 598, 8, p. 1459-1473 15 p.
Research output: Contribution to journal › Article › peer-review - PublishedGlobal REACH 2018: The Effect of an Expiratory Resistance Mask with Dead Space on Sleep and Acute Mountain Sickness During Acute Exposure to Hypobaric Hypoxia
Carr, J., Stone, R., Tymko, C., Tymko, K., Coombs, G. B., Hoiland, R. L., Howe, C. A., Tymko, M. M., Ainslie, P. N. & Patrician, A., Sept 2020, In: High Altitude Medicine and Biology. 21, 3, p. 297-302 6 p.
Research output: Contribution to journal › Article › peer-review - PublishedGlobal REACH 2018: The influence of acute and chronic hypoxia on cerebral haemodynamics and related functional outcomes during cold and heat stress
Gibbons, T. D., Tymko, M. M., Thomas, K. N., Wilson, L. C., Stembridge, M., Caldwell, H. G., Howe, C. A., Hoiland, R. L., Akerman, A. P., Dawkins, T. G., Patrician, A., Coombs, G. B., Gasho, C., Stacey, B. S., Ainslie, P. N. & Cotter, J. D., Jan 2020, In: Journal of Physiology. 598, 2, p. 265-284 20 p.
Research output: Contribution to journal › Article › peer-review - PublishedInternal carotid and brachial artery shear-dependent vasodilator function in young healthy humans
Carr, J. M. J. R., Hoiland, R. L., Caldwell, H. G., Coombs, G. B., Howe, C. A., Tremblay, J. C., Green, D. J. & Ainslie, P. N., Dec 2020, In: Journal of Physiology. 598, 23, p. 5333-5350 18 p.
Research output: Contribution to journal › Article › peer-review - PublishedVascular dysfunction following breath-hold diving
Barak, O. F., Janjic, N., Drvis, I., Mijacika, T., Mudnic, I., Coombs, G. B., Thom, S. R., Madic, D. & Dujic, Z., Feb 2020, In: Canadian journal of physiology and pharmacology. 98, 2, p. 124-130 7 p.
Research output: Contribution to journal › Article › peer-review
2019
- PublishedAcute effect of Finnish sauna bathing on brachial artery flow-mediated dilation and reactive hyperemia in healthy middle-aged and older adults
Gravel, H., Coombs, G. B., Behzadi, P., Marcoux-Clément, V., Barry, H., Juneau, M., Nigam, A. & Gagnon, D., Jul 2019, In: Physiological Reports. 7, 13, p. e14166
Research output: Contribution to journal › Article › peer-review - PublishedAcute heat stress reduces biomarkers of endothelial activation but not macro- or microvascular dysfunction in cervical spinal cord injury
Coombs, G. B., Barak, O. F., Phillips, A. A., Mijacika, T., Sarafis, Z. K., Lee, A. H. X., Squair, J. W., Bammert, T. D., DeSouza, N. M., Gagnon, D., Krassioukov, A. V., Dujic, Z., DeSouza, C. A. & Ainslie, P. N., 1 Mar 2019, In: American Journal of Physiology - Heart and Circulatory Physiology. 316, 3, p. H722-H733
Research output: Contribution to journal › Article › peer-review - PublishedCerebrovascular function is preserved during mild hyperthermia in cervical spinal cord injury
Coombs, G. B., Vucina, D., Caldwell, H. G., Barak, O. F., Mijacika, T., Lee, A. H. X., Sarafis, Z. K., Squair, J. W., Krassioukov, A. V., Phillips, A. A., Dujic, Z. & Ainslie, P. N., Nov 2019, In: Spinal cord. 57, 11, p. 979-984 6 p.
Research output: Contribution to journal › Article › peer-review - PublishedGlobal REACH 2018: High Blood Viscosity and Hemoglobin Concentration Contribute to Reduced Flow-Mediated Dilation in High-Altitude Excessive Erythrocytosis
Tremblay, J. C., Hoiland, R. L., Howe, C. A., Coombs, G. B., Vizcardo-Galindo, G. A., Figueroa-Mujíca, R. J., Bermudez, D., Gibbons, T. D., Stacey, B. S., Bailey, D. M., Tymko, M. M., MacLeod, D. B., Gasho, C., Villafuerte, F. C., Pyke, K. E. & Ainslie, P. N., Jun 2019, In: Hypertension (Dallas, Tex. : 1979). 73, 6, p. 1327-1335 9 p.
Research output: Contribution to journal › Article › peer-review - PublishedGlobal Reach 2018: reduced flow-mediated dilation stimulated by sustained increases in shear stress in high-altitude excessive erythrocytosis
Tremblay, J. C., Coombs, G. B., Howe, C. A., Vizcardo-Galindo, G. A., Figueroa-Mujíca, R. J., Bermudez, D., Tymko, M. M., Villafuerte, F. C., Ainslie, P. N. & Pyke, K. E., 1 Nov 2019, In: American Journal of Physiology - Heart and Circulatory Physiology. 317, 5, p. H991-H1001
Research output: Contribution to journal › Article › peer-review - PublishedPassive heat therapy for cerebral protection: new ideas of age-old concepts
Coombs, G. B. & Tremblay, J. C., Jan 2019, In: Journal of Physiology. 597, 2, p. 371-372 2 p.
Research output: Contribution to journal › Article › peer-review - PublishedSleep-disordered breathing is associated with brain vascular reactivity in spinal cord injury
Squair, J. W., Lee, A. H. X., Sarafis, Z. K., Coombs, G., Barak, O., Cragg, J. J., Mijacika, T., Pecotic, R., Krassioukov, A. V., Dogas, Z., Dujic, Z. & Phillips, A. A., 10 Dec 2019, In: Neurology. 93, 24, p. e2181-e2191
Research output: Contribution to journal › Article › peer-review - PublishedSpinal Cord Disruption Is Associated with a Loss of Cushing-Like Blood Pressure Interactions
Saleem, S., Sarafis, Z. K., Lee, A. H. X., Squair, J. W., Barak, O. F., Sober-Williams, E., Suraj, R., Coombs, G. B., Mijacika, T., West, C. R., Krassioukov, A. V., Ainslie, P. N., Dujic, Z., Tzeng, Y.-C. & Phillips, A. A., 1 May 2019, In: Journal of Neurotrauma. 36, 9, p. 1487-1490 4 p.
Research output: Contribution to journal › Article › peer-review - PublishedThe Effect of an Expiratory Resistance Mask with Dead Space on Sleep, Acute Mountain Sickness, Cognition, and Ventilatory Acclimatization in Normobaric Hypoxia
Patrician, A., Tymko, M. M., Caldwell, H. G., Howe, C. A., Coombs, G. B., Stone, R., Hamilton, A., Hoiland, R. L. & Ainslie, P. N., Mar 2019, In: High Altitude Medicine and Biology. 20, 1, p. 61-70 10 p.
Research output: Contribution to journal › Article › peer-review - PublishedThermoregulatory adaptations with progressive heat acclimation are predominantly evident in uncompensable, but not compensable, conditions
Ravanelli, N., Coombs, G., Imbeault, P. & Jay, O., 1 Oct 2019, In: Journal of applied physiology (Bethesda, Md. : 1985). 127, 4, p. 1095-1106 12 p.
Research output: Contribution to journal › Article › peer-review
2018
- PublishedHighs and lows of hyperoxia: physiological, performance, and clinical aspects
Brugniaux, J. V., Coombs, G. B., Barak, O. F., Dujic, Z., Sekhon, M. S. & Ainslie, P. N., 1 Jul 2018, In: American Journal of Physiology - Regulatory Integrative and Comparative Physiology. 315, 1, p. R1-R27
Research output: Contribution to journal › Review article › peer-review - PublishedMaximum Skin Wettedness after Aerobic Training with and without Heat Acclimation
Ravanelli, N., Coombs, G. B., Imbeault, P. & Jay, O., Feb 2018, In: Medicine and Science in Sports and Exercise. 50, 2, p. 299-307 9 p.
Research output: Contribution to journal › Article › peer-review - PublishedSeverity-dependent influence of isocapnic hypoxia on reaction time is independent of neurovascular coupling
Caldwell, H. G., Coombs, G. B., Tymko, M. M., Nowak-Flück, D. & Ainslie, P. N., 1 May 2018, In: Physiology and Behavior. 188, p. 262-269 8 p.
Research output: Contribution to journal › Article › peer-review - PublishedVentilatory and cerebrovascular regulation and integration at high-altitude
Hoiland, R. L., Howe, C. A., Coombs, G. B. & Ainslie, P. N., Aug 2018, In: Clinical Autonomic Research . 28, 4, p. 423-435 13 p.
Research output: Contribution to journal › Review article › peer-review - PublishedWavelet decomposition analysis is a clinically relevant strategy to evaluate cerebrovascular buffering of blood pressure after spinal cord injury
Saleem, S., Vucina, D., Sarafis, Z., Lee, A. H. X., Squair, J. W., Barak, O. F., Coombs, G. B., Mijacika, T., Krassioukov, A. V., Ainslie, P. N., Dujic, Z., Tzeng, Y.-C. & Phillips, A. A., 1 May 2018, In: American Journal of Physiology - Heart and Circulatory Physiology. 314, 5, p. H1108-H1114
Research output: Contribution to journal › Article › peer-review
2017
- PublishedAlarming blood pressure changes during routine bladder emptying in a woman with cervical spinal cord injury
Lee, A. H. X., Phillips, A. A., Squair, J. W., Barak, O. F., Coombs, G. B., Ainslie, P. N., Sarafis, Z. K., Mijacika, T., Vucina, D., Dujic, Z. & Krassioukov, A. V., 28 Dec 2017, In: Spinal cord series and cases. 3, 17101.
Research output: Contribution to journal › Article › peer-review - PublishedThermoregulatory responses to exercise at a fixed rate of heat production are not altered by acute hypoxia
Coombs, G. B., Cramer, M. N., Ravanelli, N., Imbeault, P. & Jay, O., 1 May 2017, In: Journal of applied physiology (Bethesda, Md. : 1985). 122, 5, p. 1198-1207 10 p.
Research output: Contribution to journal › Article › peer-review
2016
- PublishedA comparison of thermoregulatory responses to exercise between mass-matched groups with large differences in body fat
Dervis, S., Coombs, G. B., Chaseling, G. K., Filingeri, D., Smoljanic, J. & Jay, O., 15 Mar 2016, In: Journal of applied physiology (Bethesda, Md. : 1985). 120, 6, p. 615-23 9 p.
Research output: Contribution to journal › Article › peer-review - PublishedIce Slurry Ingestion Leads to a Lower Net Heat Loss during Exercise in the Heat
Morris, N. B., Coombs, G. & Jay, O., Jan 2016, In: Medicine and Science in Sports and Exercise. 48, 1, p. 114-22 9 p.
Research output: Contribution to journal › Article › peer-review
2015
- PublishedAcute acetaminophen ingestion does not alter core temperature or sweating during exercise in hot-humid conditions
Coombs, G. B., Cramer, M. N., Ravanelli, N. M., Morris, N. B. & Jay, O., Jun 2015, In: Scandinavian Journal of Medicine and Science in Sports. 25 Suppl 1, p. 96-103 8 p.
Research output: Contribution to journal › Article › peer-review - PublishedIsolating the independent influence of body fat on thermoregulatory responses to exercise
Coombs, G. B., Stamatakis, E. & Jay, O., Jul 2015, In: European Journal of Applied Physiology. 115, 7, p. 1601-2 2 p.
Research output: Contribution to journal › Article