Master of Science (MS)
Recent work suggests repeated cold exposure raises energy expenditure, partly due to sympathetic nervous system stimulation, which indicates repeated cold exposure as a possible strategy to combat obesity without significant behavioral changes. PURPOSE: (1) To examine the acute resting metabolic rate (RMR) response to mild cold exposure of 16° C and the acute autonomic nervous system (ANS) response to two cold exposures of 16° C and 4° C through heart rate variability (HRV) indices; and (2) to examine whether 4 weeks of daily cold exposure would result in adaptations in the metabolic and autonomic responses to acute cold exposure. METHODS: RMR and HRV measurements were used to measure acute cold exposure response at 22° C and prolonged cold exposure response after 90 minutes at 16° C. HRV measurements were also used for acute exposure at 22° C and continuously during 20 minutes of cold exposure at 4° C. RMR and ANS responses to 16° C following 20 sessions (400 minutes) of repeated cold exposure were measured. RMR was measured using a metabolic cart and ANS activity was examined through the measurement of HRV. RESULTS: A significant increase in RMR of 11% (p=0.03) and an increase in Total Power that approached significance (p=0.07) was measured after 90 minutes of exposure to 16° C. Upon exposure to 4° C, significant (p<0.05) increases in Total Power, High Frequency, and RMSSD indices of HRV were measured with Low Frequency approaching significance (p=0.07). No significant findings were measured after repeated cold exposure in comparison to baseline measurements. CONCLUSION: Acute cold exposure of 16° C resulted in a significant increase in RMR of 11% with increased activation of the autonomic nervous system measured at both 16° C and 4° C. Twenty sessions of repeated cold exposure of 4° C did not significantly alter acute responses to cold exposure. There was no evidence of a change in autonomic balance toward a hyper-adrenergic state due to cold exposure. These findings suggest repeated cold exposure may be an effective tool for significantly increasing metabolic rate without changing autonomic balance toward a hyper-adrenergic state.
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Simmons, Jonathan A., "Autonomic Nervous System Response to Repeated Cold Exposure" (2012). LSU Master's Theses. 2819.