Thermoregulation and thermal sensation during whole-body water immersion at different water temperatures in healthy individuals: A scoping review

Effects of cold-water immersion on energy expenditure, ad-libitum energy intake and appetite in healthy adults

INTRODUCTION

Cold-water immersion is a popular method typically used to reduce exercise induced muscle damage and improve health and wellbeing. Despite these benefits, there is emerging evidence to suggest the temperature of the water exposure can influence energy intake in the subsequent hours. The study aim was to investigate the influence of water temperature on energy expenditure and post-water immersion ad-libitum energy intake in resting adults. Participants with a range of body masses, but otherwise healthy and physically active males (n = 10) and females (n = 5), participated in three randomised trials in a repeated measures crossover design, with a minimum of 7-days apart. Participants were immersed to sternum level for 30-minutes in either cold-water (16 °C), thermoneutral-water (35 °C) or a no-water thermoneutral ambient air control (26 °C). Participants completed appetite related visual analogue scales throughout and were presented with an ad-libitum homogenous pasta meal and asked to eat until 'comfortably full'.

RESULTS

Repeated measures ANOVA showed participants consumed more energy after immersion in cold-water (2783 ± 909 kJ) versus both thermoneutral-water (1817 ± 862 kJ) and thermoneutral ambient air (1894 ± 233 kJ). There were no differences in any of the appetite VAS. Core temperature remained stable throughout the 30 min immersion period across trials, however an after-drop in core temperature was observed for 15 mins following cold-water immersion when compared to both thermoneutral water (P < 0.001), and thermoneutral air (P = 0.004). Although the exact mechanisms are yet to be elucidated, further research is required to identify if the after-drop in core temperature is a potential mechanism responsible for compensatory food intake post cold-water immersion.

CONCLUSION

When presented with an ad-libitum meal directly after cold-water immersion, participants consumed more in comparison to both thermoneutral water immersion and thermoneutral ambient air. With cold water immersion becoming popular, these findings have practical and clinical relevance for individuals' conscious about body mass management.

Optimal duration of whole-body cryostimulation exposure to achieve target skin temperature: influence of body mass index-a randomized cross-over controlled trial

BACKGROUND

The efficacy of whole-body cryostimulation (WBC) may be influenced by individual characteristics. The aim of this study is to determine the optimal exposure time required to reach the analgesic threshold of 13.6 °C, which has been proposed to be a target temperature to be reached at skin level. Our objective is also to follow the skin temperature changes during and after WBC considering the participants body mass index (BMI).

METHODS

Thirty healthy men were assigned into 2 groups based on their BMI [normal weight (n = 15; BMI = 21.53 ± 1.63 kg·m-2) and overweight (n = 15; BMI = 27.98 ± 1.16 kg·m-2)]. In a random order, each participant experienced a 4-min WBC exposure, as well as a control session with no cold exposure. Skin temperature was measured using a thermal imaging camera during and after cold exposure.

RESULTS

Normal weight participants reached the threshold in 4 min, whereas overweight participants reached it in 3 min 30 s. Following WBC, a rapid mean skin temperature (MsT°) increase was observed for both groups, immediately after exposure. However, after 30 min, MsT° remained significantly lower than at baseline.

CONCLUSION

Our findings suggest that appropriate WBC dosage may differ according to BMI. Understanding the impact of such variable on cold exposure outcomes can help to optimize WBC treatments and maximize potential benefits.

The effect of underwater massage during hot water immersion on acute cardiovascular and mood responses

PURPOSE

There is emerging evidence that demonstrates the health benefits of hot water immersion including improvements to cardiovascular health and reductions in stress and anxiety. Many commercially available hot tubs offer underwater massage systems which purport to enhance many benefits of hot water immersion, however, these claims have yet to be studied.

METHODS

Twenty participants (4 females) completed three, 30-min sessions of hot-water immersion (beginning at 39 °C) in a crossover randomized design: with air massage (Air Jet), water massage (Hydro Jet) or no massage (Control). Cardiovascular responses comprising; heart rate, blood pressure and superficial femoral artery blood flow and shear rate were measured. State trait anxiety, basic affect, and salivary cortisol were recorded before and after each trial. Data were analysed using a mixed effects model.

RESULTS

Post immersion, heart rate increased (Δ31bpm, P < 0.001, d = 1.38), mean arterial blood pressure decreased (Δ16 mmHg, P < 0.001, d = -0.66), with no difference between conditions. Blood flow and mean shear rate increased following immersion (P < 0.001, Δ362 ml/min, d = 1.20 and Δ108 s-1, d = 1.00), but these increases were blunted in the Air Jet condition (P < 0.001,Δ171 ml/min, d = 0.43 and Δ52 s-1, d = 0.52). Anxiety and salivary cortisol were reduced (P = 0.003, d = -0.20, P = 0.014, d = -0.11), but did not vary between conditions. Enjoyment did not vary between conditions.

CONCLUSION

These data demonstrate positive acute responses to hot water immersion on markers of cardiovascular function, anxiety, and stress. There was no additional benefit of water-based massage, while air-based massage blunted some positive vascular responses due to lower heat conservation of the water.

Arm cooling selectively impacts sensorimotor control

The benefits of cold have long been recognized in sport and medicine. However, it also brings costs, which have more rarely been investigated, notably in terms of sensorimotor control. We hypothesized that, in addition to peripheral effects, cold slows down the processing of proprioceptive cues, which has an impact on both feedback and feedforward control. We therefore compared the performances of participants whose right arm had been immersed in either cold water (arm temperature: 14°C) or lukewarm water (arm temperature: 34°C). In experiment 1, we administered a Fitts's pointing task and performed a kinematic analysis to determine whether sensorimotor control processes were affected by the cold. Results revealed 1) modifications in late kinematic parameters, suggesting changes in the use of proprioceptive feedback, and 2) modifications in early kinematic parameters, suggesting changes in action representations and/or feedforward processes. To explore our hypothesis further, we ran a second experiment in which no physical movement was involved, and thus no peripheral effects. Participants were administrated a hand laterality task, known to involve implicit motor imagery and assess the internal representation of the hand. They were shown left- and right-hand images randomly displayed in different orientations in the picture plane and had to identify as quickly and as accurately as possible whether each image was of the left hand or the right hand. Results revealed slower responses and more errors when participants had to mentally rotate the cooled hand in the extreme orientation of 160°, further suggesting the impact of cold on action representations.NEW & NOTEWORTHY We investigated how arm cooling modulates sensorimotor representations and sensorimotor control. Arm cooling induced changes in early kinematic parameters of pointing, suggesting an impact on feedforward processes or hand representation. Arm cooling induced changes in late kinematic parameters of pointing, suggesting an impact on feedback processes. Arm cooling also affected performance on a hand laterality task, suggesting that action representations were modified.

Termination of Cardiopulmonary Resuscitation in Mountain Rescue: A Scoping Review and ICAR MedCom 2023 Recommendations

Lugnet, Viktor, Miles McDonough, Les Gordon, Mercedes Galindez, Nicolas Mena Reyes, Alison Sheets, Ken Zafren, and Peter Paal. Termination of cardiopulmonary resuscitation in mountain rescue: a scoping review and ICAR MedCom 2023 recommendations. High Alt Med Biol. 24:274-286, 2023. Background: In 2012, the International Commission for Mountain Emergency Medicine (ICAR MedCom) published recommendations for termination of cardiopulmonary resuscitation (CPR) in mountain rescue. New developments have necessitated an update. This is the 2023 update for termination of CPR in mountain rescue. Methods: For this scoping review, we searched the PubMed and Cochrane libraries, updated the recommendations, and obtained consensus approval within the writing group and the ICAR MedCom. Results: We screened a total of 9,102 articles, of which 120 articles met the inclusion criteria. We developed 17 recommendations graded according to the strength of recommendation and level of evidence. Conclusions: Most of the recommendations from 2012 are still valid. We made minor changes regarding the safety of rescuers and responses to primary or traumatic cardiac arrest. The criteria for termination of CPR remain unchanged. The principal changes include updated recommendations for mechanical chest compression, point of care ultrasound (POCUS), extracorporeal life support (ECLS) for hypothermia, the effects of water temperature in drowning, and the use of burial times in avalanche rescue.