Effets physiologiques de l’immersion dans l’eau

Aidez votre corps à mieux dormir en faisant l’expérience d’un refroidissement de la température corporelle avant de se coucher. J’ai besoin de faire plus de recherches, mais récemment (réf.: Peter ATTIA podcast), j’ai entendu parler de recherches convaincantes confirmant les bienfaits pour la santé de l’utilisation fréquente des saunas.

RESEARCH REVIEW 2018 : Physiological Effects From Water Immersion

STUDY : Water temperature affects heart rate and core body temperature during whole body immersion

Background

Whole body immersion (WI) is one of the oldest therapeutic concepts of medicine and still constitutes a significant role in the area of CAM as well as in rehabilitation facilities. Medical baths have strong effects on the cardiovascular regulation and the autonomic nervous system, mainly mediated by buoyancy, hydrostatic pressure and water temperature. However, scientific literature with respect to this medical practice is limited. In particular, little is known about the effects of different water temperatures on heart rate, heart rate variability (HRV) and body core temperature. Hence, we investigated the effects of WI with water temperatures of 33 and 36 °C (indifferent temperature) and 39 °C on heart rate, HRV and core body temperature before, during and after bathing.

Methods

In total 21 healthy subjects (average age: 24.3±2.3 years, 11 female, 10 male) underwent WI with water temperatures of 33 °C (WI33), 36 °C (WI36), 39 °C (WI39). “Dry-bath”(DB; bathtub without water to assure same body position as during WI) was used as a control. The procedure consisted of three successive intervals: 30 min resting in a supine position, 20 min WI and 30 min rest in the supine position. The recording of an electrocardiogram was started after 20 min of rest before WI. It was continued throughout the rest of the procedure. In addition, core body temperature was recorded using a rectal sensor. Here, we report on the effects with respect to the last 60 s at the end of each interval.

Results

During WI33, WI36 and DB the average heart rate was not affected (70.2, 74.2, and 67.2 beats/min) compared to baseline before WI. Correspondingly, the standard deviation of normal-to-normal heartbeats (SDNN) did not change (68, 63, 62 ms). Furthermore, the core body temperature was not affected (36.9, 37.0, 37.0 °C). However, during WI39 the heart rate increased to 97 beats/min and SDNN decreased to 24 ms. At the same time the core body temperature increased to 37.5 °C. During rest after WI39 the core body temperature stayed at 37.5 °C, but the heart rate decreased to 73.9 beats/min and SDNN increased to 60 ms.

Conclusion

WI with a water temperature of 39 °C increased heart rate and core body temperature and decreased HRV. Hence, WI at this temperature induces moderate cardiovascular stress and moderate hyperthermia. Spectral components of HRV and more specific analysis of temperature regulation may reveal more subtle changes during WI at different water temperatures.

STUDY : Effects of bath water and bathroom temperatures on human thermoregulatory function and thermal perception during half-body bathing in winter

We clarified the effects of hot water and bathroom temperatures on human thermoregulatory function and thermal perception during half-body bathing in the winter season. Subjects were eight healthy male volunteers aged 27.4±6.0 yr. Subjects were requested to stand quietly for 1 min in either a 14 or 25°C bathroom, and then to bathe for 20 min in a bathtub filled up to the epigastrium with water at either 39 or 42°C. The following physiological parameters were measured continuously: tympanic temperature as core temperature, skin temperature at the chest, skin blood flow at the forearm and sweat rate on the back of the hand. At the same time we measured thermal sensation and comfort votes as physiological responses before, whilst, and after bathing several times. At the same bathroom temperature, bathing in the 42°C water elevated tympanic and skin temperatures, skin blood flow and sweat rate more than bathing at 39°C. Similarly, under the same water temperature, bathing in the 25°C bathroom increased those parameters more than in the 14°C bathroom. Subjects felt warm and comfortable during bathing in the 39°C water in the 25°C bathroom because of the reduced cold stress because of the bathroom temperature. They felt warm with a neutral sensation during bathing in the 42°C water in the 14°C bathroom because of the reduction in heat stress from the not water temperature. We suggest that during half-body bathing at a low water temperature but high bathroom temperature is better physiologically and psychologically, and that during half-body bathing at a hot water temperature, a low bathroom temperature is better psychologically.

STUDY : Core Body Temperature and Sleep of Older Female Insomniacs Before and After Passive Body Heating

Abstract: The purpose of this study was to investigate the relationship between core body temperature and sleep in older female insomniacs and changes in that relationship as a result of passive body heating (PBH). An increase in body temperature early in the evening by way of PBH in older female insomniacs increased SWS in the early part of the sleep period and improved sleep continuity. Fourteen older female insomniacs (60–73 years old) participated in at least two consecutive nights of PBH involving hot (40–40.5°C) baths 1.5 – 2 hours before bedtime. Hot baths resulted in a significant delay in the phase of the core body tempera- ture rhythm compared to baseline nights. This delay in temperature phase paralleled the improvements in sleep quality.


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