Cold & Heat
Deliberate temperature exposure is one of the oldest biohacking interventions, and one of the most misunderstood. The social media version of cold plunges and saunas rarely matches the research. A 2018 study in Mayo Clinic Proceedings associated regular sauna use with reduced cardiovascular mortality, but the protocols that produced those results look nothing like most people's sauna routines.
These articles break down the actual science of hormetic stress, the biological principle that controlled exposure to mild stressors triggers adaptive responses that improve resilience. We cover cold exposure and its effects on norepinephrine, brown fat activation, and inflammation markers. We examine sauna use and its documented effects on heat shock proteins, cardiovascular function, and all-cause mortality risk.
Practical protocols are specific: temperature ranges, exposure durations, frequency, timing relative to exercise, and which combinations of cold and heat produce synergistic effects versus interference. We also cover contraindications: who should avoid extreme temperature exposure and why.
Every protocol references published research from journals like the European Journal of Applied Physiology, JAMA Internal Medicine, and the Journal of Science and Medicine in Sport.
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Frequently asked questions
How cold does the water need to be for cold exposure benefits?
Most research showing benefits uses water temperatures between 10-15°C (50-59°F). The norepinephrine response (which drives many of the alertness and mood benefits) appears to plateau around 14°C. Going colder does not necessarily produce proportionally greater benefits but does increase the risk of hypothermia and cold shock response.
Does cold exposure after exercise hurt muscle gains?
Yes, there is evidence that cold water immersion immediately after resistance training can blunt the inflammatory signaling needed for muscle adaptation. A 2015 study in the Journal of Physiology found reduced muscle protein synthesis when cold exposure followed strength training. If muscle growth is a priority, separate your cold exposure from resistance training by at least 4-6 hours.
How often should I use a sauna for health benefits?
The Finnish sauna studies that showed the strongest cardiovascular mortality reduction used frequencies of 4-7 sessions per week at 80-100°C for 15-20 minutes. A 2015 study in JAMA Internal Medicine found that men who used a sauna 4-7 times per week had a 40% lower risk of all-cause mortality compared to once-weekly users. However, the optimal frequency for any individual depends on their cardiovascular health and tolerance.