What Is Contrast Therapy?

By Dr. Susanna Søberg, PhD · Søberg Institute · soeberginstitute.com

Contrast therapy has become one of the most discussed practices in the global wellness industry. Athletes use it for recovery. Spas offer it as a premium service. Biohackers incorporate it into daily routines. And an expanding body of peer-reviewed research is confirming what practitioners have long observed — that the deliberate alternation of cold and heat produces measurable physiological benefits.

But what is contrast therapy, exactly? How does it work? What does the science say? And how do you do it correctly?

This article answers those questions — with the science behind each one.

The Definition — What Is Contrast Therapy?

Contrast therapy is the deliberate and structured alternation between cold exposure and heat exposure — typically cold water immersion or cold showers combined with sauna, hot water immersion, or steam — for specific physiological effect.

The practice is sometimes called hot-cold therapy, thermal contrast therapy, or contrast bathing. At its core, it involves exposing the body to significant temperature changes in a controlled, intentional sequence — not simply going from a cold shower to a warm room, but following a structured protocol designed to produce specific outcomes.

The key word is structured. Contrast therapy is not simply getting cold and then warm. It is the application of thermal stress in a specific sequence, at specific intensities, for specific durations — with the order and structure of that sequence directly influencing the physiological outcome.

This is the central insight of the Søberg Principle, published in Cell Reports Medicine in 2021 by Dr. Susanna Søberg, PhD — that in contrast therapy, how you structure the session determines what your body does in response to it.

The History of Contrast Therapy

The use of cold and heat for health is ancient. Roman bathhouses alternated between hot and cold pools. Scandinavian sauna culture has included cold lake plunging for centuries. Traditional Finnish sauna practice almost always concludes with cold exposure. Nordic and Eastern European traditions have long recognised the physiological power of thermal contrast.

What is new is the science. Over the past two decades — and accelerating significantly in the past decade — researchers have begun to quantify exactly what contrast therapy does to the human body at a cellular and systemic level.

Dr. Søberg's 2021 publication in Cell Reports Medicine was a landmark contribution to this growing body of evidence — the first peer-reviewed study to examine not just whether contrast therapy produces metabolic benefits, but precisely how the structure of the protocol influences those benefits.

How Contrast Therapy Works — The Physiology

When you expose your body to cold, a cascade of physiological responses is triggered. Your blood vessels constrict. Your sympathetic nervous system activates. Norepinephrine surges — in some studies, cold water immersion produces a 200-300% increase in norepinephrine levels. Your body begins to generate heat to protect core temperature.

When you move to heat, the opposite occurs. Blood vessels dilate. Blood flow to the periphery increases. The parasympathetic nervous system begins to activate. Heat shock proteins are produced, contributing to cellular repair and recovery.

The deliberate alternation between these two states — done in a structured sequence — creates a kind of training stimulus for the cardiovascular system, the nervous system, and the metabolic system simultaneously.

The body adapts to what it is consistently asked to do. Regular, structured contrast therapy trains the body's ability to regulate temperature, manage stress, and recover efficiently — producing adaptations that extend well beyond the session itself.

The Science-Backed Benefits of Contrast Therapy

Metabolic activation and brown fat

Cold exposure activates brown adipose tissue — metabolically active fat that burns calories to generate heat. Dr. Søberg's research confirmed that structured contrast therapy, when structured correctly according to the Søberg Principle, produces significant brown fat activation with measurable metabolic outcomes including improved insulin sensitivity and increased caloric expenditure.

Nervous system regulation

The alternation between cold-induced sympathetic activation and heat-induced parasympathetic recovery creates a powerful training stimulus for the autonomic nervous system. Regular practice is associated with improved stress resilience, lower baseline cortisol, and better nervous system regulation — the ability to move between activated and recovered states more efficiently.

Recovery and inflammation

Contrast therapy is widely used in elite sport for recovery. The combination of cold-induced vasoconstriction and heat-induced vasodilation creates a pumping effect on the circulatory system, accelerating the clearance of metabolic waste and the delivery of oxygen and nutrients to recovering tissue. Research suggests contrast therapy reduces markers of inflammation and accelerates muscle recovery compared to passive rest.

Cardiovascular health

Regular contrast therapy trains the cardiovascular system's ability to respond to thermal stress — improving vascular tone, blood pressure regulation, and overall cardiovascular resilience. The repeated vascular response to cold and heat is sometimes described as a passive form of cardiovascular exercise.

Mental health and mood

The norepinephrine release triggered by cold exposure has significant implications for mood and mental health. Multiple studies have associated cold water immersion with improvements in depression symptoms, anxiety, and overall mood. The physiological mechanism is well understood — norepinephrine is a key neurotransmitter in mood regulation, and cold exposure produces one of the most significant norepinephrine responses of any non-pharmacological intervention.

Longevity and cellular health

Heat stress — particularly sauna exposure — activates heat shock proteins, which play a role in cellular repair, protein folding, and protection against cellular damage. Long-term sauna use has been associated in epidemiological studies with reduced all-cause mortality and lower rates of cardiovascular disease. Contrast therapy combines these heat-induced benefits with the cold-induced metabolic and nervous system effects.

The Søberg Principle — Why Structure Matters

The most significant advance in the scientific understanding of contrast therapy in recent years has been the recognition that the structure of the protocol — and specifically the order in which cold and heat are applied — directly influences the physiological outcome.

This is the insight at the core of the Søberg Principle, published by Dr. Susanna Søberg in Cell Reports Medicine in 2021.

The Søberg Principle established that ending a contrast therapy session with cold produces a stronger and more sustained metabolic response than ending with heat. The cold-first-at-end protocol produces greater brown fat activation, a stronger norepinephrine response, and more significant metabolic outcomes than heat-first-at-end protocols.

This finding transformed the way contrast therapy is understood and practiced. It shifted the conversation from "does contrast therapy work" to "how do you structure it to work most effectively" — a fundamentally more useful and more scientific question.

The Søberg Principle is now one of the most referenced findings in the global contrast therapy space, discussed on Huberman Lab, The Joe Rogan Experience, and in major international health media including The New York Times, The Times, and The Guardian.

Contrast Therapy in Practice — What It Looks Like

Contrast therapy can be practiced in many settings — from home cold showers and portable saunas to dedicated contrast therapy facilities and luxury spa environments.

The most common formats include:

•        Cold water immersion (ice bath or cold plunge) combined with sauna — the most studied and most effective format

•        Cold shower combined with hot shower — accessible for home practice

•        Cold water immersion combined with steam room or hot tub — common in spa and hotel wellness settings

•        Open water swimming combined with sauna — the traditional Nordic format

The specific temperatures, durations, and number of rounds vary based on the individual, their experience level, their health status, and their goals. What does not vary — according to the Søberg Principle — is the importance of ending with cold for maximum metabolic benefit.

Who Should Not Do Contrast Therapy

Contrast therapy is not appropriate for everyone. Individuals with certain cardiovascular conditions, Raynaud's syndrome, certain autoimmune conditions, or who are pregnant should consult a physician before beginning a contrast therapy practice. Cold water immersion carries real physiological risks — particularly cold shock response, hyperventilation, and hypothermia — that require proper education and gradual progression to manage safely.

Dr. Søberg's Cold Water Immersion Course at the Søberg Institute covers the full safety science — including cold shock, hyperventilation, hypothermia, heart health considerations, and Raynaud's syndrome — in evidence-based detail. Starting with proper education significantly reduces risk and significantly improves outcomes.

The Thermalist® Method — Contrast Therapy as a System

The Thermalist® Method is Dr. Søberg's structured contrast therapy system — the world's leading science-based operating system for cold and heat exposure, built on the Søberg Principle and over 15 years of research.

For individuals, the Thermalist® Method is available through four online courses at the Søberg Institute:

•        Thermalist® Method at Home — a 3.5-hour self-paced introduction to the full method

•        Cold Water Immersion Course — the full science of cold, including comprehensive safety guidance

•        The 3 Week Thermalist Cure® — a structured 3-week programme combining cold, heat, and breathwork

•        The Søberg® 12-Week Reset — a guided 12-week metabolic protocol

For wellness operators, the Thermalist® Recovery System is available for licensing to premium wellness facilities, spa hotels, and hospitality operators at thermalist.com. The system includes structured contrast therapy programmes, staff certification, guided sound experiences, and a member-facing app ecosystem — all built on the peer-reviewed science of the Søberg Principle.

Summary — What Is Contrast Therapy?

Contrast therapy is the deliberate, structured alternation between cold and heat exposure for specific physiological benefit. It activates brown fat, trains the nervous system, supports recovery and inflammation management, improves cardiovascular health, and produces measurable metabolic outcomes — when practiced correctly and consistently.

The most important advance in understanding contrast therapy in recent years is the Søberg Principle — the peer-reviewed finding published in Cell Reports Medicine in 2021 by Dr. Susanna Søberg, PhD, establishing that the structure of a contrast therapy session directly determines its physiological outcome.

Contrast therapy is not a trend. It is ancient practice validated by modern science. And the Søberg Principle is the scientific foundation that makes it possible to practice it not just enthusiastically, but intelligently.

For wellness operators seeking to bring structured, science-based contrast therapy programming to their facility — visit thermalist.com.