Whole-body cryotherapy (WBC) involves brief exposure to sub-zero temperatures, typically ranging from -166°F to -240°F, inside a specialized chamber. A typical session lasts two to four minutes, exposing the skin to hyper-cooled air. This immediate temperature drop prompts the body to react defensively, requiring an expenditure of energy. This article investigates the physiological mechanisms and estimated caloric expenditure associated with cryotherapy.
How the Body Reacts to Extreme Cold
Exposure to the severe cold initiates a rapid, protective physiological response aimed at maintaining core temperature. The skin’s temperature drops quickly, triggering the nervous system to signal the body to generate heat. This initial response involves vasoconstriction, where blood vessels near the skin’s surface narrow, redirecting blood flow toward the internal organs.
The primary mechanism for energy expenditure is thermogenesis, the process of heat production. This heat generation is largely accomplished through non-shivering thermogenesis, a metabolic process that does not involve muscle contractions. This process is significantly influenced by the activation of Brown Adipose Tissue (BAT), often called brown fat.
Unlike white fat, which stores energy, brown fat burns calories (fatty acids and glucose) to create heat. Cold exposure stimulates the sympathetic nervous system, leading to the activation of BAT. This activation increases the body’s metabolic rate as it attempts to restore thermal balance. The body’s subsequent work to return to a normal internal temperature is where most of the energy is consumed.
Quantifying Calorie Burn Estimates
The actual calories burned during the brief two- to four-minute cryotherapy session are relatively minimal. Energy expenditure during the exposure is estimated to be low, perhaps only 30 to 50 calories, as the body’s core temperature remains stable. The significant metabolic effect comes from the sustained increase in energy expenditure that occurs in the hours following the treatment, often called the “afterburn” effect.
Studies suggest that the total caloric expenditure, including the afterburn, can range widely from 200 to 800 calories following a single session. This energy is used as the body works to restore homeostasis and reheat the tissues. The increased energy expenditure is a result of the body’s need to fuel the thermogenic processes triggered by the cold shock. For some individuals, the resting metabolic rate may rise substantially during this post-session period.
Why the Calorie Burn Varies
A precise, fixed number for cryotherapy calorie expenditure is impossible due to significant individual variability. A major factor is the individual’s body composition, particularly the amount of metabolically active brown adipose tissue (BAT). People with a higher percentage of BAT tend to exhibit a greater thermogenic response and a higher calorie burn when exposed to cold.
The specific parameters of the session also modulate the energy demand. A longer duration or colder temperature requires more energy from the body. The amount of clothing worn during the session influences the skin temperature drop, which affects the intensity of the body’s defensive reaction. A person’s baseline metabolic rate and overall level of adaptation to cold exposure also play a role. Frequent users may experience a different response over time as the body adapts to repeated cold stress.