Cryotherapy works by dropping your skin temperature low enough to trigger a cascade of protective responses: blood vessels constrict, nerve signaling slows, and your body ramps up heat production to defend its core temperature. The magic number appears to be a skin surface temperature of about 13.6°C (roughly 57°F), the threshold where measurable physiological changes kick in. What happens after that point is a coordinated stress response involving your circulatory, nervous, and hormonal systems.
What Happens to Your Blood Vessels
The moment cold hits your skin, blood vessels near the surface clamp down. This vasoconstriction is the body’s first move to prevent heat loss, redirecting blood away from the skin and toward your organs. The reduction is dramatic: blood flow to cooled skin drops by more than 75% from its baseline level.
What makes this interesting is what happens after the cold stops. You might expect blood flow to bounce back immediately, but it doesn’t. Research from the Journal of Biomechanical Engineering found that blood flow actually continues to drop for about 10 minutes after cooling ends, even as skin temperature starts climbing back up. The recovery is slow and gradual, meaning the circulatory effects of a cryotherapy session outlast the session itself by a significant margin. This lingering constriction is part of why cryotherapy can reduce swelling and inflammation well after you step out of the cold.
Eventually, blood vessels do reopen, and the resulting “rebound” surge of blood flow is thought to help flush metabolic waste from tissues. This alternating pattern of constriction followed by dilation is central to how cold therapy promotes recovery.
How Cold Dulls Pain Signals
Cold slows down the speed at which nerves transmit signals. A study published in the British Journal of Sports Medicine measured this directly at the ankle: as skin temperature dropped to 10°C, nerve conduction velocity decreased by a cumulative 32.8%. Slower nerve signals mean pain messages take longer to reach the brain and arrive weaker when they do. Both pain threshold (the point where you start feeling pain) and pain tolerance (how much pain you can handle) increased in the cooled area.
This is why cryotherapy provides near-immediate pain relief. The target skin temperature of 13.6°C corresponds to roughly a 10% reduction in nerve conduction velocity, which researchers consider the minimum needed for meaningful clinical pain relief. In whole-body cryotherapy chambers, people with a normal body weight typically reach this threshold in about 4 minutes of exposure. People with higher body mass reach it slightly faster, around 3 minutes and 30 seconds, likely because differences in tissue composition affect how quickly skin cools.
The Hormonal Surge
Extreme cold triggers a spike in norepinephrine, a hormone and neurotransmitter that sharpens alertness, constricts blood vessels, and plays a role in mood regulation and pain suppression. After a first session in a chamber set to minus 110°C, plasma norepinephrine roughly doubled, jumping from an average of 173 to 352 nanograms per liter. This is the same chemical your body releases during intense focus or a fight-or-flight response, which explains the energized, clear-headed feeling many people report after a session.
There’s an adaptation effect, though. By the fifth session at the same temperature, the norepinephrine increase was smaller and no longer statistically significant. Your body learns to handle the cold stimulus more efficiently, which may mean the acute hormonal “rush” becomes less pronounced with repeated use.
Effects on Inflammation
Cryotherapy shifts the balance between pro-inflammatory and anti-inflammatory signaling molecules in the blood. A meta-analysis of 11 randomized controlled trials, published in Scientific Reports, found two consistent changes after whole-body cryotherapy: levels of IL-1β (a protein that drives inflammation and tissue damage) decreased, while levels of IL-10 (a protein that calms inflammation) increased. Notably, levels of IL-6, another commonly measured inflammatory marker, did not change significantly.
The practical takeaway is that cryotherapy doesn’t broadly suppress all inflammation. It appears to selectively dial down certain aggressive inflammatory pathways while boosting the body’s own anti-inflammatory signals. Athletes showed the strongest reductions in IL-1β, while people with obesity saw the greatest increases in the anti-inflammatory IL-10. This selectivity may explain why cryotherapy helps with exercise-related soreness without completely shutting down the inflammatory processes that are actually necessary for tissue repair.
Muscle Soreness and Recovery
For post-exercise soreness, cryotherapy performs well compared to doing nothing, and it may have a slight edge over other cold therapies. A network meta-analysis published in BMC Musculoskeletal Disorders compared multiple recovery methods head-to-head and ranked whole-body cryotherapy as the most effective intervention for reducing delayed-onset muscle soreness (DOMS), with an 88.3% probability of being the top option. Cold water immersion and contrast water therapy (alternating hot and cold) also outperformed passive recovery, but cryotherapy came out on top.
The mechanisms overlap but differ in important ways from an ice bath. Water conducts heat about 25 times more efficiently than air, so cold water immersion actually cools deeper muscle tissue more effectively. Cryotherapy chambers, despite using air temperatures as low as minus 110°C to minus 140°C, only penetrate about 2 millimeters into the skin. The extreme surface cooling triggers a powerful nervous system and hormonal response, but the soreness reduction likely comes more from systemic effects (the norepinephrine spike, the inflammatory shift) than from directly cooling sore muscles.
The Metabolic and Calorie Question
Your body burns calories to maintain its core temperature during and after cold exposure. This is thermogenesis, and it does happen during cryotherapy, though the scale is debated. One study estimated that a single localized cryotherapy session extracted roughly 1,330 calories worth of heat from the body. Across three sessions, participants lost an average of 0.54 kilograms, which closely matched the 0.52 kilograms predicted by calculating how much fat the body would need to burn to replace that lost heat.
These numbers come with caveats. Core body temperature only rose by 0.3°C during the sessions, a change that wasn’t statistically significant. The calorie estimates also depend heavily on the specific equipment and protocol used. Cryotherapy can nudge your metabolism upward temporarily, but it’s not a substitute for sustained caloric deficit if weight loss is your goal.
Who Should Avoid Cryotherapy
The list of conditions that make cryotherapy unsafe is longer than most people expect. An international expert panel identified permanent contraindications that span nearly every organ system. The cardiovascular concerns alone include uncontrolled high blood pressure, Raynaud’s syndrome, peripheral artery disease, recent blood clots, and pulmonary embolism within the past six months.
Other conditions on the exclusion list include cold-related immune disorders (like cryoglobulinemia, where proteins in the blood clump together in cold temperatures), type 1 diabetes, severe asthma, COPD in advanced stages, epilepsy, glaucoma, and any active or untreated cancer. Cold allergy, which causes hives or more severe reactions upon cold exposure, is also a firm contraindication. Even claustrophobia makes the list, since whole-body chambers are enclosed spaces where panic could delay a safe exit.
The extreme temperatures involved place real stress on the cardiovascular and respiratory systems. The sudden vasoconstriction that makes cryotherapy effective for recovery can be dangerous if your blood vessels or heart are already compromised.