New research highlights how the time of day affects hormonal and lipid responses to ice baths, with significant differences observed between morning and evening sessions.
Conducted by researchers from the Technical University of Munich, the study aimed to explore the effects of time-of-day on the physiological responses following cold exposure.
Utilizing twelve healthy participants (six men and six women), the study involved administering ice baths at temperatures between 8-12 °C for five minutes, both in the morning and evening. Participants maintained controlled conditions prior to each session, avoiding intense exercise and standardized their meals prior to the tests to mitigate confounding dietary effects.
The analysis focused on measuring key hormones—noradrenaline, adrenaline, and cortisol—alongside various lipid levels through plasma analysis pre-bath and at five minutes and thirty minutes post-bath.
Significantly, the findings revealed variations in the participants' plasma fatty acid concentrations. Ice baths performed in the morning resulted in increased plasma fatty acids, showing initial levels of 5.1% which increased to 6.0% after five minutes (P = 0.029) and to 6.3% after thirty minutes (P = 0.008). Conversely, the evening baths did not elicit such increases.
Noradrenaline levels increased markedly following both morning and evening sessions—127% and 144%, respectively—indicating the role of cold exposure as a significant activator for this hormone. The study noted no time-of-day differences for noradrenaline, adrenaline or the hormone cortisol, which was higher overall during morning sessions (179 ± 108 pg/ml morning; 91 ± 59 pg/ml evening, P = 0.013).
The combination of findings suggests the potential influence of circadian rhythms on responses to cold exposures, with specific metabolic processes being modulated by the timing of the event.
Despite the limited sample size, the study concluded the need for comprehensive investigations on how hormonal fluctuations related to time-of-day affect lipid metabolism and muscular responses to cold exposure.
This exploratory human study could pave the way for future research, emphasizing potential applications for athletes and individuals utilizing ice baths for recovery protocols.