Cold and heat exposure: Evidence-Based Supplement Guide

Cold water triggers a strong hormonal response. In young men immersed for an hour in water at 14 degrees C, noradrenaline rose by 530 percent, dopamine by 250 percent and metabolic rate by 350 percent (PMID 10751106). Mild cold also activates brown fat. Brown fat activity was seen in 23 of 24 healthy men during mild cold exposure, and it was lower in men with more body fat (PMID 19357405). Timing matters if you lift. In 21 active men who strength trained twice a week for 12 weeks, ten minutes of cold water immersion after each session was compared with an active cool-down. Strength and muscle mass increased more with the active cool-down (PMID 26174323). Repeated exercise in the heat leads to heat acclimation. A review lists improved sweating and skin blood flow, lower body temperature, better fluid balance and better aerobic performance in hot conditions among the adaptations (PMID 25943654).

1. **Keep cold water immersion away from strength sessions if muscle gain is your priority** (PMID 26174323). 2. **Start cold exposure gradually**, because the hormonal and metabolic response to cold water is large (PMID 10751106). 3. **Acclimatise to heat through repeated exercise in warm conditions** before training or competing in the heat (PMID 25943654).

The cold water training study ran for 12 weeks (PMID 26174323). The hormonal response was measured during a single hour of immersion (PMID 10751106). The size of heat adaptations depends on the intensity, duration, frequency and number of heat exposures (PMID 25943654).

- **These are small studies in men**: 21 active men in the cold water training study and 24 men in the brown fat study (PMID 26174323, 19357405). - **The hormone study measured a single immersion** in young men (PMID 10751106). - **The heat acclimation review is about exercise in the heat**, not passive sauna use (PMID 25943654). - **No sauna-specific finding from the source article is included here.** - **This guide has not been reviewed by a clinician.** `reviewStatus` above says so.

- **Cold water raises heart rate and blood pressure.** Both rose during immersion at 14 degrees C (PMID 10751106), so talk to a clinician first if you have a heart or blood pressure condition. - **Never immerse in very cold water alone.** - **Build heat exposure up gradually, and stop if you feel unwell.**

No ingredient is linked from this guide. It covers cold water and heat exposure, and it does not point to a product.

| PMID | Title | | --- | --- | | 10751106 | "Human physiological responses to immersion into water of different temperatures" | | 19357405 | "Cold-activated brown adipose tissue in healthy men" | | 26174323 | "Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training" | | 25943654 | "Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports" |