Saunas, cold plunges, and contrast showers have been around for centuries, but newer fans, especially those who want to improve their recovery and resilience, call it by a different name: thermo-hacking.
For a former rugby player and fitness enthusiast, Teddy Teece, his work exploring how the body adapts to controlled stress demonstrates the appeal of these tools. They’re simple, low-cost, and grounded in physiology rather than marketing, but they shouldn’t be treated as shortcuts. The more useful view is to treat them as training.
This article explains what happens in the body during heat and cold exposure, what the research does and doesn’t support, and how someone new to the practice can begin without taking unnecessary risks.
What Thermo-Hacking Actually Means
Thermo-hacking is an informal term, but it represents the intentional use of temperature extremes to trigger a response from the body. This could mean sauna sessions, hot baths, cold showers, ice baths, open-water swimming, and the practice of alternating between hot and cold, often called contrast therapy.
The process that underlies all of these things is hormesis, which is a term for a small, controlled dose of stress. Hormesis prompts the body to adapt and become more capable of handling stress in the future.
Exercise and fasting both work this way, but heat and cold can also promote this process. The stressor itself is uncomfortable in the moment, but the body responds by mobilizing resources. With repetition, the response becomes more efficient.
Repetition is what matters, because users’ expectations have to be managed. Thermo-hacking is not a magic cure or a replacement for your body’s needs, but it’s a lever that can support recovery, mood, and energy when it sits alongside sleep, nutrition, movement, and social connection.
This is the same logic behind what Teddy Teece calls holistic fitness, which is an approach that integrates physical health, mental wellbeing, purpose, and community as a way of building resilience rather than chasing any single metric.
How Heat Exposure Works in the Body
Sitting in a sauna or hot bath raises core body temperature and in response, the heart rate climbs, blood vessels near the skin widen, and blood flow to the extremities increases. This is because the body works to shed heat. For the cardiovascular system, a sauna session has some features in common with moderate exercise.
At the cellular level, heat prompts the production of heat shock proteins, helping other proteins fold correctly and repair damage. This is one reason researchers are interested in heat exposure for muscle recovery and long-term health.
Regular sauna use has been associated with better cardiovascular outcomes in observational studies, particularly from Finland. Of course, association is not proof of cause. The people who sauna most often may differ in other ways, but the pattern has held up across several large cohorts.
Heat also has a mental effect. Many people find a sauna session forces a pause, which can be practical for high-stress individuals. There is nothing to do except sit, breathe, and tolerate discomfort. For a professional whose days are dominated by screens and decisions, that enforced stillness can be as valuable as anything happening in the muscles.
How Cold Exposure Works in the Body
Cold does the opposite. As blood vessels constrict, blood is pulled toward the core, and the nervous system fires a sharp stress response. Norepinephrine, a neurotransmitter tied to alertness and focus, rises. It can stay elevated for a period after leaving the water, which is why a cold shower produces such a pronounced feeling of being awake.
Cold exposure also activates brown adipose tissue, a type of fat that generates heat by burning energy. Repeated exposure appears to increase brown fat activity, which is why many people claim cold exposure benefits the metabolism, although the real-world effect on body composition is modest for most people.
Cold’s clearest evidence shows in its reduction of perceived soreness after hard training. You’ll often see athletes using ice baths for a reason.
There’s a trade-off, however. Cold water immersion after strength training may blunt some of the signaling that drives muscle growth. This means that someone with the primary goal of building muscle might want to separate cold sessions from lifting sessions by several hours, while someone prioritizing next-day readiness for competition may accept the trade.
Teddy Teece on Thermo-Hacking as Part of a Larger System
Teddy Teece came to these questions through his experience in athletic competition. His interest in performance science and sport psychology have outlasted and as a member of the Olympic Club and Tahoe local he enjoys proximity to heat and cold exposure – namely through e-foiling and other adventure activities that get him into the lake.
That background shows in how he frames recovery tools. He describes them as parts of a system, not isolated tricks.
In his framework, thermo-hacking sits alongside natural movement, mental health, and community as one component of a broader foundation. The point here isn’t that individuals should optimize a single variable. Instead, they should aim to build a base stable enough to support the demands of work, leadership, and service.
That system’s view runs through his approach to resilience and recovery, and it explains a natural caution toward any practice presented as a standalone solution.
He’s also an advocate of grounding personal opinions in research, an approach he describes as something a good scholar should do. Applied to hot and cold exposure, that means separating what is well supported, like reduced soreness and short-term alertness, from what is still speculative, like long-term disease prevention.
A Sensible Way to Start
If you’re new to the practice, the guiding principle is gradual progression. Your body adapts to what it’s exposed to. There is no advantage in jumping into the extreme end.
With heat, a first sauna session can be short. You should aim to be in the range of ten to fifteen minutes at a moderate temperature and follow it up with time to cool down and rehydrate. Duration can extend as tolerance builds. Signs of dizziness, nausea, or a racing heart are reasons to leave, not to push through.
With cold, a cold shower or a brief dip in cool rather than icy water is a reasonable entry point. A minute or two is plenty at first. The goal here is to keep yourself calm and control your breathing instead of enduring as long as possible. Over time, water temperature can drop and duration can increase, though there are diminishing returns beyond a few minutes.
Contrast therapy, alternating heat and cold, is popular in spa settings and can feel especially restorative. Most of the time, protocols will involve several minutes of heat followed by a short cold exposure, repeated a few times and typically ending on cold.
Consistency matters more than intensity here. Contrast work rewards treating recovery as a practice rather than a one-time intervention.
Safety Considerations Worth Taking Seriously
Because these practices act on the cardiovascular system, they’re not appropriate for everyone. People with heart conditions, uncontrolled blood pressure, or a history of fainting should talk to a physician before starting. The same applies to anyone who is pregnant or taking medication that affects heart rate or circulation.
Everyone should keep a few rules in mind. Never combine heat or cold exposure with alcohol. Never do cold water immersion alone, especially in open water, where the cold shock response can cause involuntary gasping and loss of muscle control within seconds. Hydrate before and after sauna use. And always pay attention to how your body responds over days and weeks, not just in the moment. Chronic overexposure to any stressor eventually undermines the adaptation it was meant to produce.
Handled with that kind of respect, heat and cold are among the most accessible recovery tools available, requiring little equipment, fitting into most schedules, and asking mainly for patience and attention. That may be the most honest way to describe thermo-hacking: less a hack than a habit.
About Teddy Teece
Teddy Teece is the Managing Partner of Kea Capital Partners, an investment firm focused on New Zealand’s light industrial sector. A Wharton MBA candidate, he has built companies across finance, technology, executive coaching, and real estate. He has also developed a forty-acre retreat property near Boulder, Colorado, dedicated to connection, wellness, and community, and his work increasingly focuses on helping people build healthier foundations through holistic fitness, his term for comprehensive wellness.
