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Research interests

• Human integrative physiology.
• Interactions between the autonomic nervous and cardiovascular systems.
• Impact of age and biological sex.
• Influence of aerobic fitness, habitual physical and sedentary activity patterns.

Member – Canadian Society for Exercise Physiology
Member – American College of Sports Medicine
Member – American Physiological Society

Peer-Reviewed Work Over Past 5 Years (* indicates trainees under supervision):

• *Liu, H., *M.E. Shivgulam, *B.D. Schwartz, D.S. Kimmerly, and M.W. O’Brien. A systematic review of reviews on the impact of exercise training on pulse wave velocity in adults. American Journal of Physiology: Heart and Circulatory Physiology, 2023. Online ahead of print. doi: 10.1152/ajpheart.00249.2023.
• Ìý*Courish, M., *M.E. Shivgulam, J. MacLeod, D.S. Kimmerly, and M.W. O’Brien. Case studies in physiology: Impact of unilateral dual-brachial arteries on endothelial-dependent and independent vasodilation. Applied Physiology, Nutrition and Metabolism, 2023. Online ahead of print. doi: 10.1139/apnm-2023-0170.
• *M.W. O’Brien, *Schwartz, B.D., *M.E. Shivgulam, S. Daley, R.J. Frayne, and D.S. Kimmerly. Higher habitual lying time is inversely associated with vagal-related heart rate variability outcomes in younger adults. Applied Physiology, Nutrition and Metabolism, 2023. Online ahead of print. doi: 10.1139/apnm-2023-0167.
• *O’Brien, M.W., *M.E. Shivgulam, *B.D. Schwartz, *Y. Wu, S. Daley, D.S. Kimmerly, and R.J. Frayne. Validity of ActivPAL CREA software detection of sitting and lying during free-living conditions. Physiological Measurements, 44(7), 2023. doi: 10.1088/1361-6579/ace14e.
• *O’Brien, M.W., M. Nardone, M. Foster, Y. Coovadia, C.W. Usselman, C.E. Taylor, P.J. Millar, and D.S. Kimmerly. Higher sympathetic transduction is independently associated with greater very short-term diastolic blood pressure variability in young healthy males and females. Clinical Autonomic Research, 2023. Online ahead of print. doi: 10.1007/s10286-023-00949-7.
• *Schwartz, B.D., *M.E. Shivgulam, *J.L. Petterson, *Y. Wu, R.J. Frayne, *M.W. O’Brien, and D.S. Kimmerly. More moderate-intensity physical activity and less prolonged sedentary time are associated with better very short-term systolic blood pressure variability in healthy adults. Journal of Human Hypertension, 2023. Online ahead of print. doi: 10.1038/s41371-023-00832-y.
• *Shivgulam, M.E., *H. Liu, *B.D. Schwartz, J.E. Langley, N.W. Bray, D.S. Kimmerly and *M.W. O’Brien. Impact of exercise training interventions on flow-mediated dilation in adults: An Umbrella Review. Sports Medicine, 53(6): 1161-1174, 2023. doi: 10.1007/s40279-023-01837-w.
• *Pellerine, L.P., *J.L. Petterson, *M.E. Shivgulam, P.J. Johansson, P. Hettiarachchi, D.S. Kimmerly, R.J. Frayne, and M.W. O’Brien. Step length, but not stepping cadence, strongly predicts physical activity intensity during jogging and running. Measurement of Physical Education and Exercise Science, 1-10, 2023. https://doi.org/10.1080/1091367X.2023.2188118.
• *Liu, H., M.W. *O’Brien, *S. Rayner, and D.S. Kimmerly. Are supine assessments an ecologically valid method to characterize sitting-induced declines in lower-limb vascular health? Letter to the Editor. American Journal of Physiology: Heart and Circulatory Physiology, 325(1): H142-H144, 2023.Ìý doi: 10.1152/ajpheart.00121.2023.
• *Liu, H., *M.W., O’Brien, *Y. Wu, *C.M. Bustamante, and D.S. Kimmerly. An acute bout of prolonged sitting blunts popliteal endothelium-independent dilation in young, healthy adults. Journal of Applied Physiology, 134(3): 521-528, 2023. doi: 10.1152/japplphysiol.00712.2022.
• *O’Brien, M.W., *J.L. Petterson, L.P. Pellerine, *M.E. Shivgulam, D.S. Kimmerly, R.J. Frayne, P. Hettiarachchi, and P.J. Johansson. Moving beyond the characterization of activity intensity bouts as square-wave signals. Journal for the Measurement of Physical Behaviour, 6(2): 162-167, 2023. https://doi.org/10.1123/jmpb.2022-0041.
• *O’Brien, M.W., D.S. Kimmerly, and O. Theou. Sex-specific frailty and chronological age normative carotid artery intima-media thickness values using the Canadian Longitudinal Study of Aging. Vascular, 2023. Online ahead of print. doi: 10.1177/17085381231157125.
• *O’Brien, M.W., D.S. Kimmerly, and O. Theou. Impact of age and sex on the relationship between carotid artery intima-media thickness and frailty level in the Canadian Longitudinal Study of Aging. Journal of Cardiology, 82(2): 140-145, 2023. doi: 10.1016/j.jjcc.2023.01.004.
• *O’Brien, M.W., W.S. Daley, *B.D. Schwartz, *M.E. Shivgulam, *Y. Wu, D.S. Kimmerly, and R.J. Frayne. Characterization of detailed sedentary postures using a tri-monitor ActivPAL configuration in free-living conditions. Sensors 4;23(2): 587, 2023. doi: 10.3390/s23020587.
• Ìý*O’Brien, M.W., L.P. Pellerine, *M.E. Shivgulam, and D.S. Kimmerly. Disagreements in physical activity monitor validation study guidelines create challenges in conducting validity studies. Frontiers In Digital Health, 10;4:1063324, 2023. doi: 10.3389/fdgth.2022.1063324.
• *Badrov, M.B., D.A. Keir, G. Tomlinson, C.F. Notarius, P.J. Millar, D.S. Kimmerly, J.K. Shoemaker, E. Keys, and J.S. Floras. Normal and excessive muscle sympathetic nerve activity in heart failure: implications for future trials of therapeutic autonomic modulation. European Journal of Heart Failure, 25(2): 201-210, 2022. doi:10.1002/ejhf.2749
• *Mekari, S., R.J.L. Murphy, A.R.A. MacKinnon, Q. Hollohan, S.C. MacDougall, *M.K. Courish, D.S. Kimmerly, and H.F. Neyedli. Head-down tilt bed rest improves executive function amongst younger adults: A pilot project. Scientific Reports, 12(1): 20888, 2022. doi: 10.1038/s41598-022-25123-3.
• *Shivgulam, M.E., *J.L. Petterson, *L. Pellerine, D.S. Kimmerly and M.W. O’Brien.The Stryd foot pod is a valid measure of stepping cadence during treadmill walking and running. Journal for the Measurement of Physical Behaviour, 6(1): 73-78, 2023. https://doi.org/10.1123/jmpb.2022-0031.
• *O’Brien, M.W., *M.E. Shivgulam, *J.L. Petterson, *Y. Wu, R.J Frayne, S. Mekari, and D.S. Kimmerly. Habitual sedentary time and stationary time are inversely related to aerobic fitness. Sports Medicine and Health Science, 4(4): 260-266, 2022. doi: 10.1016/j.smhs.2022.10.002.
• *Badrov, M.B., D.A. Keir, C.F. Notarius, P.J. Millar, D.S. Kimmerly, J.K. Shoemaker, and J.S. Floras. Influence of sex and age on the relationship between cardiorespiratory fitness and muscle sympathetic nerve activity in healthy adults. American Journal of Physiology: Heart and Circulatory Physiology: 323(5): H934-H940, 2022. doi: 10.1152/ajpheart.00450.2022.
• *Wu, Y., *J.L. Petterson, N.W. Bray, D.S. Kimmerly, and *W.M. O’Brien. Validity of the activPAL monitor to measure physical activity: A systematic review. Gait and Posture, 97: 165-173, 2022. doi: 10.1016/j.gaitpost.2022.08.002.
• *O’Brien, M.W., *B.D. Schwartz, *J.L. Petterson, and D.S. Kimmerly. Comparison of signal-averaging and regression approaches to analyzing sympathetic transduction. Clinical Autonomic Research, 32(4): 299-302, 2022. doi: 10.1007/s10286-022-00874-1.
• *O’Brien, M.W., S. Mekary and D.S. Kimmerly. Aging, cardiorespiratory fitness and sympathetic transduction. Aging, 14(10): 4189-4190, 2022. doi: 10.18632/aging.204091.
• *O’Brien, M.W., *M.E. Shivgulam, *J.L. Petterson, *Y. Wu, *J.A. Johns, R.J Frayne, and D.S. Kimmerly. Substituting stationary time with moderate-intensity activity may improve flow-mediated dilation. Journal of Cardiopulmonary Rehabilitation and Prevention: 42(6): E105-E107, 2022. doi: 10.1097/HCR.0000000000000716.
• *Pellerine, L., D.S. Kimmerly, J. Fowles and *M.W. O’Brien. Calibrating the Physical Activity Vital Sign to estimate habitual moderate-to-vigorous physical activity more accurately: A cautionary tale. Journal for the Measurement of Physical Behaviour, 5(2): 103-110, 2022. https://doi.org/10.1123/jmpb.2021-0055.ÌýÌý
• *O’Brien, M.W., *Y. Wu, *J.L. Petterson, N.W. Bray, and D.S. Kimmerly. Validity of the activPAL monitor to distinguish postures: A systematic review. Gait and Posture, 94: 107-113, 2022. doi: 10.1016/j.gaitpost.2022.03.002.
• *Shivgulam, M.E., *M.W. O’Brien, *J.A. Johns, *J.L. Petterson, *Y. Wu, R.J. Frayne, and D.S. Kimmerly. Impact of habitual sedentary patterns on popliteal artery endothelial-dependent vasodilation in healthy adults. Vascular Medicine, 27(2):120-126, 2022. doi: 10.1177/1358863X211065494.
• *O’Brien, M.W., *H. Liu, * M.E. Shivgulam, J.E. Langley, N.W. Bray, and D.S. Kimmerly. The impact of exercise training interventions on flow-mediated dilation: An umbrella review protocol. Healthy Populations Journal, 2(1), 2022. https://doi.org/10.15273/hpj.v2i1.11249.
• *O’Brien, M.W., *J.L. Petterson, and D.S. Kimmerly. Impact of sampling duration on spontaneous neurohemodynamic transduction. Letter to the Editor, Clinical Autonomic Research, 32(2):155-158, 2022. doi: 10.1007/s10286-022-00861-6.
• *O’Brien, M.W., *J.L. Petterson, *J.A. Johns, S. Mekary and D.S. Kimmerly. The impact of different step rate threshold methods on physical activity intensity in older adults. Gait and Posture, 94: 51-57, 2022. doi: 10.1016/j.gaitpost.2022.02.030.
• *O’Brien, M.W., *Y. Wu, *J.L. Petterson, R. Frayne and D.S. Kimmerly. Ecological validity of prolonged sitting studies – How well do they represent real life sedentary patterns? Translational Journal for the American College of Sports Medicine, 7(1):e000182, Winter 2022. doi: 10.1249/TJX.0000000000000182.
• *O’Brien, M.W., and D.S. Kimmerly. Is ‘not different’ enough to conclude similar cardiovascular responses across sexes? (Perspective). American Journal of Physiology: Heart and Circulatory Physiology, 322(3): H355-H358, 2022. doi: 10.1152/ajpheart.00687.2021.
• *Petterson, J.L., *M.W. O’Brien, *D.J. Ramsay, *W. Johnston, C.D. O’Neill, S. Dogra, S. Mekari, J.S. Floras, and D.S. Kimmerly. Sympathetic neurohemodynamic transduction is attenuated in older males independent of age-related declines in aerobic fitness. Clinical Autonomic Research, 32(1): 73-76, 2022. doi: 10.1007/s10286-021-00845-y.
• *O’Brien, M.W., *J.L. Petterson, *Y. Wu, N.W. Bray, and D.S. Kimmerly. What is the impact of physical behaviours on low-flow-mediated vasoconstriction? A systematic review of observational and intervention studies. Vascular Medicine, 27(2):193-202, 2022. doi: 10.1177/1358863X211073480.
• *O’Brien, M.W., *J.A. Johns, R.J. Frayne, and D.S. Kimmerly. Comparison of habitual stepping cadence analysis methods: Relationship with step counts. Gait and Posture, 92: 328-332, 2021. doi: 10.1016/j.gaitpost.2021.12.006
• *O’Brien, M.W., *J.L. Petterson, *J.A. Johns, S. Mekary and D.S. Kimmerly. A larger low-flow mediated constrictor response is associated with augmented flow-mediated dilation in the popliteal artery. Clinical Physiology and Functional Imaging, 41(6): 497-504, 2021. doi: 10.1111/cpf.12725.
• *Liu, H*., *M.W. O’Brien, *J.A. Johns, and D.S. Kimmerly. Does aerobic fitness impact prolonged sitting-induced popliteal artery dysfunction? European Journal of Applied Physiology, 121(11): 3233–3241, 2021. doi: 10.1007/s00421-021-04796-0.
• *O’Brien, M.W., *Y. Wu, *J.A. Johns, *J. Poitras and D.S. Kimmerly. Development and validation of an activPAL accelerometry count-based model of physical activity intensity in adults. Medical Engineering and Physics, 95: 45-50, 2021. doi: 10.1016/j.medengphy.2021.07.014.
• *O’Brien, M.W., *A. Al-Hinnawi, *J.A. Johns and D.S. Kimmerly. Spontaneous cardiovagal baroreflex sensitivity is unaffected by an acute bout of prolonged sitting: No impact of sex, menstrual or oral contraceptive pill phases. Clinical Autonomic Research, 31(6): 783-786, 2021. doi: 10.1007/s10286-021-00820-7.
• *O’Brien, M.W., D.S. Kimmerly and S. Mekary. Greater habitual moderate-to-vigorous physical activity is associated with better executive function and higher prefrontal oxygenation in older adults. GeroScience, 43(6): 2707-2718, 2021. doi: 10.1007/s11357-021-00391-5
• *O’Brien, M.W., *A. Al-Hinnawi, *Y. Wu, *J.L. Petterson, *M.E. Shivgulam, *J.A. Johns, R. Frayne and D.S. Kimmerly. The influence of habitual breaks in sedentary time on cardiovagal baroreflex sensitivity. Applied Physiology Nutrition and Metabolism, 46(9): 1143-1146, 2021. doi: 10.1139/apnm-2021-0246.
• *O’Brien, M.W., *D. Ramsay, C.D. O’Neill, *J.L. Petterson, S. Dogra, S. Mekary, and D.S. Kimmerly. Aerobic fitness is inversely associated with neurohemodynamic transduction and blood pressure variability in older adults. GeroScience, 43(6): 2737-2748, 2021. doi: 10.1007/s11357-021-00389-z.
• *Taylor, K.S., D.A. Keir, N. Haruki, D.S. Kimmerly, P.J. Millar, H. Murai, and J.S. Floras. Comparison of cortical autonomic network-linked sympathetic excitation by Mueller manoeuvres and breath holds in subjects with and without obstructive sleep apnea. Front Physiol, 12:678630, 2021. https://doi.org/10.3389/fphys.2021.678630.ÌýÌý
• *O’Brien, M.W., *D. Ramsay, *W. Johnston and D.S. Kimmerly. The association between habitual posture and intensity-related physical activity with sympathetic neurohemodynamic transduction in young males. Clinical Autonomic Research, 31(2): 339-341, 2021. doi: 10.1007/s10286-021-00802-9.
• *O’Brien, M.W., *J.L. Petterson, and D.S. Kimmerly. An open-source program to analyze spontaneous sympathetic neurohemodynamic transduction. Journal of Neurophysiology, 125(3): 972-976, 2021. doi: 10.1152/jn.00002.2021.
• *O’Brien, M.W., *J.A. Johns, *J.L. Petterson, S. Mekary and D.S. Kimmerly. The impact of age and sex on brachial and popliteal artery endothelial-dependent vasodilator and vasoconstrictor function. Experimental Gerontology, 145 111221. https://doi.org/10.1016/j.exger.2020.111221.
• *O’Brien, M.W., *D. Ramsay, *W. Johnston and D.S. Kimmerly. Aerobic fitness and sympathetic responses to spontaneous muscle sympathetic nerve activity in young males. Clinical Autonomic Research, 31(2): 253–261, 2021. doi: 10.1007/s10286-020-00734-w.
• *Petterson, J.L., *M.W. O’Brien, *J.A. Johns, *J. Chiasson and D.S. Kimmerly. Influence of prostaglandins and endothelial-derived hyperpolarizing factors on brachial and popliteal endothelial-dependent function in young adults. Journal of Applied Physiology, 130: 17-25, 2021. doi: 10.1152/japplphysiol.00698.2020.
• *Wu, Y., J.A. Johns, *J. Poitras, D.S. Kimmerly and *M.W. O’Brien. Improving the criterion validity of the activPAL in determining physical activity intensity during laboratory and free-living conditions. Journal of Sport Sciences, 39(7):826-834, 2021. doi: 10.1080/02640414.2020.1847503.
• *Mekari, S., H.F. Neyedli, S. Fraser, *M.W. O’Brien, R. Martins, K. Evans, R. Aucoin, J. Chiekwe, Q. Hollohan, D.S. Kimmerly and O. Dupuy. High-intensity interval training improves cognitive inhibition and flexibility in older adults. Brain Sciences, 10(11):796, 2020. doi: 10.3390/brainsci10110796.
• *O’Brien, M.W., *J.A. Johns, *A. Al-Hinnawi, and D.S. Kimmerly. Popliteal flow-mediated dilatory responses to a bout of prolonged sitting between earlier and later phases of natural menstrual and contraceptive pill cycles. Journal of Applied Physiology, 129(4): 637-645, 2020. doi: 10.1152/japplphysiol.00424.2020.
• *Johns, J.A., *M.W. O’Brien, A. Bungay, and D.S. Kimmerly. Sex and light physical activity impact popliteal, but not brachial artery flow-mediated dilation in physically active young adults. Applied Physiology, Nutrition and Metabolism, 45(12): 1387-1395, 2020. doi: 10.1139/apnm-2020-0308.
• *Keir, D., M. Badrov, G. Tomlinson, C. Notarius, D.S. Kimmerly, P. Millar, J.K. Shoemaker and J. S. Floras. Influence of sex and age on muscle sympathetic nerve activity of healthy normotensive adults. Hypertension, 76(3): 997-1005, 2020. doi: 10.1161/HYPERTENSIONAHA.120.15208
• *Johns, J.A., R.J Frayne, *J.A. Goreham, D.S. Kimmerly and *M.W. O’Brien. ­­­­­­The bout cadence method improves the quantification of stepping cadence in free-living conditions. Gait and Posture, 79: 96-101, 2020. doi: 10.1016/j.gaitpost.2020.04.014.
• *O’Brien, M.W., *J.A. Johns, J.R. Fowles and D.S. Kimmerly. Validity of the activPAL and height-adjusted curvilinear cadence-METs equations in healthy adults. Measurement in Physical Education and Exercise Science, 24(2): 147-156, 2020. https://doi.org/10.1080/1091367X.2020.1724112
• *O’Brien, M.W., *J.A. Johns, *S.A. Robinson, *A. Bungay, S. Mekary and D.S. Kimmerly. Impact of high-intensity interval training, moderate-intensity continuous training and resistance training on endothelial function in older adults. Medicine and Science in Sports and Exercise, 52(5): 1057-1067, 2020. doi: 10.1249/MSS.0000000000002226.
• *O’Brien, M.W., *J.A. Johns, *T.W. Dorey, R.J. Frayne, J.R. Fowles, S. Mekary and D.S. Kimmerly. Meeting international aerobic physical activity guidelines is associated with enhanced cardiovagal baroreflex sensitivity in older adults. Clinical Autonomic Research, 30(2): 139-148, 2020 doi: 10.1007/s10286-019-00641-9.
• *Mekari, S., O. *Dupuy, *R. Martins, *K. Evans, D.S. Kimmerly, *S. Fraser and H.F. Neyedli. The effects of cardiorespiratory fitness on executive function and prefrontal oxygenation in older adults. GeroScience, 41(5): 681-690, 2019. doi: 10.1007/s11357-019-00128-5.
• *O’Brien, M.W., *J.A. Johns, *T.D. Williams and D.S. Kimmerly. Sex does not influence impairments in popliteal endothelial-dependent vasodilation or vasoconstrictor responses following prolonged sitting. Journal of Applied Physiology, 127(3): 679-687, 2019. doi: 10.1152/japplphysiol.00887.2018.
• *O’Brien, M.W., *J.A. Johns, *S.A. Robinson, S. Mekary and D.S. Kimmerly. Relationship between brachial and popliteal artery low-flow mediated constriction in older adults: Impact of aerobic fitness on vascular endothelial function. Journal of Applied Physiology, 127(1): 134-142, 2019. doi: 10.1152/japplphysiol.00092.2019.
• *Robinson, S.A., *M. W. O’Brien, S.A. Grandy, *S. Heinze-Milne and D.S. Kimmerly. Short-term supplement of virgin coconut oil improves endothelial-dependent dilation but not exercise-mediated hyperemia in young adults. Nutrition Research, 67:17-26, 2019. doi: 10.1016/j.nutres.2019.03.016.
• *Dorey, T.W., *M. W. O’Brien and D.S. Kimmerly. The influence of aerobic fitness on electrocardiogram and heart rate variability parameters in young and older adults. Autonomic Neuroscience: Basic and Clinical, 217:66-70, 2019. doi: 10.1016/j.autneu.2019.01.004.
• *MacDonald, M., *H. Khan, *S. Kraeutner, *F. Usai, *E. Rogers, D.S. Kimmerly, G. Dechman and S. Boe. Intensity of acute exercise but not aerobic fitness impacts on corticospinal excitability. Applied Physiology, Nutrition and Metabolism, 44(8):869-78, 2019. doi: 10.1139/apnm-2018-0643.
• *O’Brien, M.W., S. Mekary, *S.A. Robinson, *J.A. Johns and D.S. Kimmerly. The relationship between aerobic fitness and low-flow-mediated constriction in older adults. European Journal of Applied Physiology, 119(2): 351-359, 2019. doi: 10.1007/s00421-018-4044-3.ÌýÌýÌýÌýÌý

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