Michael J Macartney1, Sean R Notley2, Christophe L Herry3, Andrew J E Seely3,4,5, Ronald J Sigal2,6,7, Glen P Kenny8,9. 1. School of Health Sciences, College of Health and Medicine, University of Tasmania, Hobart, Australia. 2. Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, 125 University, Room 367, Montpetit Hall, Ottawa, ON, K1N 6N5, Canada. 3. Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Canada. 4. Thoracic Surgery and Critical Care Medicine, The Ottawa Hospital, Ottawa, Canada. 5. Department of Medicine, University of Ottawa, Ottawa, Canada. 6. Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Canada. 7. Departments of Medicine, Cardiac Sciences and Community Health Sciences, Cumming School of Medicine, Faculties of Medicine and Kinesiology, University of Calgary, Calgary, Canada. 8. Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, 125 University, Room 367, Montpetit Hall, Ottawa, ON, K1N 6N5, Canada. gkenny@uottawa.ca. 9. Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Canada. gkenny@uottawa.ca.
Abstract
AIMS: Cardiac autonomic modulation, as assessed by heart rate variability (HRV), is independently attenuated by both type 1 diabetes (T1D) and exercise-heat stress, although their combined effects remain unclear. We therefore assessed HRV during exercise-heat stress in young individuals (18-37 years) with (n = 14) and without type 1 diabetes (n = 14). METHODS: Participants completed 30-min seated rest and three, 30-min bouts of semi-recumbent cycling at light, moderate, and vigorous metabolic heat productions (200, 250, 300 W/m2, respectively), each followed by 30-min recovery. Body core temperature (Tcore) and electrocardiogram were recorded throughout and analyzed during the final 5-min of rest and each exercise period. RESULTS: Relative to baseline, Tcore was increased in both groups, albeit to a greater extent in type 1 diabetes during vigorous exercise (T1D, 1.1 ± 0.3 °C; control, 0.8 ± 0.3 °C; P < 0.05). Overall HRV (as reflected by entropy) was attenuated throughout exercise relative to baseline in both groups, with the magnitude of the reduction greater in type 1 diabetes during vigorous exercise (T1D, - 108%; control, - 70%; P < 0.05). CONCLUSIONS: Given the negative correlations between decreased HRV and cardiac risk, our novel observations indicate that vigorous exercise in hot environments may pose a health concern for individuals with type 1 diabetes.
AIMS: Cardiac autonomic modulation, as assessed by heart rate variability (HRV), is independently attenuated by both type 1 diabetes (T1D) and exercise-heat stress, although their combined effects remain unclear. We therefore assessed HRV during exercise-heat stress in young individuals (18-37 years) with (n = 14) and without type 1 diabetes (n = 14). METHODS:Participants completed 30-min seated rest and three, 30-min bouts of semi-recumbent cycling at light, moderate, and vigorous metabolic heat productions (200, 250, 300 W/m2, respectively), each followed by 30-min recovery. Body core temperature (Tcore) and electrocardiogram were recorded throughout and analyzed during the final 5-min of rest and each exercise period. RESULTS: Relative to baseline, Tcore was increased in both groups, albeit to a greater extent in type 1 diabetes during vigorous exercise (T1D, 1.1 ± 0.3 °C; control, 0.8 ± 0.3 °C; P < 0.05). Overall HRV (as reflected by entropy) was attenuated throughout exercise relative to baseline in both groups, with the magnitude of the reduction greater in type 1 diabetes during vigorous exercise (T1D, - 108%; control, - 70%; P < 0.05). CONCLUSIONS: Given the negative correlations between decreased HRV and cardiac risk, our novel observations indicate that vigorous exercise in hot environments may pose a health concern for individuals with type 1 diabetes.
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