Whole Body Cryotherapy

Whole-body cryotherapy (WBC) is a health promoting treatment that involves short exposures to air temperatures below −100°C ^[1]. WBC treatments last approximately 2-5 minutes and the frequency of treatments can vary based on the purpose of use. The patient is placed in a small cabin that emits a dry cold mist that is suctioned from a neighbouring liquid nitrogen tank. This results in a dramatic yet brief reduction in body temperatures. The cold only penetrates a very small amount distance into the dermis and despite sounding extremely cold and unbearable, it is generally not a uncomfortable procedure. This is because the cold is so dry, as opposed to cold we would normally experience on a cold winter day, which has some humidity to it. The treatments also becomes more tolerable and comfortable with each session. During exposure, individuals wear minimal clothing to cover more sensitive body areas.

Cryotherapy has traditionally been applied with ice packs or cold-water immersions. WBC is becoming more accessible and many athletes are using it routinely. WBC is purported to work by causing intense stimulation of the immune system and promoting accelerated healing of muscles, tendons, and joints while alleviating pain as a result of endorphin release. As a result, it is marketed to help improve endurance and strength, improve sleep patterns, and lower levels of stress and anxiety. It is also marketed as an anti-aging treatment that can improve skin tone by rejuvenating the body's cells. When looking at the evidence behind some of these claims, a review found that WBC modifies many health parameters. These include a decrease in proinflammatory cytokines, adaptive changes in antioxidant status, and positive effects on muscular enzymes associated with muscle damage (creatine kinase and lactate dehydrogenase) ^[2]. However, this result was not found in a number of other studies looking at muscle damage. The review also concluded that exposure to WBC is safe and does not deleteriously effect cardiac or immunological function. The purported mechanism of action of WBC includes direct tissue-temperature reductions, a decrease in inflammatory biomarkers, a decrease of oxidative stress, and increases in norepinephrine concentrations. This article will review selections of the clinical evidence available for WBC.

Temperature Reduction

WBC is purported to be more effective at lowering tissue temperature (and thus have more health promoting effects). In analyzing the difference between ice packs, cold water immersions, and WBC, the largest skin-temperature reductions are associated with ice packs ^[1]. Subcutaneous tissue temperature reductions are consistently small regardless of the cooling medium used as were core-temperature reductions. However, skin temperature can get lower with WBC if done for a slightly longer duration or if the temperature used is lower. Typically treatments increase steadily in intensity as individuals are better able to tolerate them. Overall, the temperature reductions found with WBC in the literature appear less intense and thus may not be effective for pain relief. The thermal properties of biological tissue make it difficult to cool below the skin surface ^[1]. Subcutaneous tissue has an insulating effect on the body. It is also important to note that the intensity of temperature reduction varies by body part, with bony regions experiencing larger reductions. The composition of individual patients will also play an important role in determining whether or not WBC will be the most effective modality.

Inflammation

In one recent study, the authors investigated the effect of passive recovery versus WBC ^[3]. They utilized endurance trained males who completed two experimental trials separated by 1 month in a randomized crossover design. When using WBC in this study, they applied it once daily for 96 hours post-exercise. The authors measured IL-1, IL-6, IL-10, TNF-α, CRP at numerous time points. They found that a significant reductions in IL-1 and CRP at specific time points following exercise compared to passive recovery, but TNF-α, IL-10, and IL-6 remained unchanged. Overall they conclude that WBC was effective in reducing inflammatory processes ^[3]. They believe the mechanism of action can be explained via vasoconstriction at the muscular level and by the decrease in pro-inflammatory cytokine activity.

A separate study examined professional tennis players after the tournament season ^[4]. In this study, they applied WBC twice a day for 5 days and found that it resulted in a decrease in TNF-α and IL-6, and an increase in cortisol. Overall, this meant that WBC was more effective for the recovery process than training. The authors also found that WBC did not affect resting metabolic rate. Although WBC is purported to help decrease muscle damage, the available evidence suggests that it does not affect markers of muscle damage after exercise ^[1]. A number of studies find that it does not effect creatine kinase, lactate dehydrogenase, or aspartate aminotransferase, all of which are markers of muscle damage.

With regards to functional recovery, one study found that utilizing WBC immediately and at 24 and 48 hours after intense trail running resulted in improvements in strength, pain, and fatigue compared to controls ^[5]. In this study, they also tested other modalities (far infrared and passive modalities), but found that WBC was the most effective (recovery occurring within 1 hour post-treatment). One study that examined the effects of WBC as a treatment for adhesive capsulitis found that there were significant improvements by adding WBC to the treatment interventions ^[6]. In this study, WBC with physical therapy modalities and joint mobilization was compared to joint mobilization alone. 30 patients in a hospital underwent treatments and were assigned to one of the two groups. The results showed that patients in the WBC group had the greatest improvements in their visual analog scale, active range of motion, and in their shoulder assessment forms.

Oxidative Stress and Parasympathetic Activity

WBC is purported to help decrease oxidative stress in the body and thus could potentially be used as an anti-aging therapy. One study that examined the effect of WBC on oxidative stress utilized 3-minute treatments once per day at temperatures of -130 °C ^[7]. They measured total antioxidant status, SOD levels, non-enzymatic antioxidant-uric acid (UA), and lipid peroxidation. After completing a total of ten WBC therapy sessions, the authors found that total antioxidant status and UA levels were significantly increased in comparison to non-WBC. Thus, the authors conclude that WBC improves the antioxidant capabilities of the body. One study that examined parasympathetic activity and blood catelcholamine responses following a single session of WBC found that WBC induced large stimulations of the autonomic nervous system ^[8]. In this study, changes in thermal, physiological and subjective variables were recorded before and during the 20-min after each cryostimulation. They found that WBC caused an increase in blood pressure, a decrease in heart rate, and a substantial increase in plasma norepinephrine. The authors concluded that WBC effectively stimulated the autonomic nervous system, with a predominance of parasympathetic tone activation. One study examined salivary steroid hormone response to WBC in elite rugby players ^[9]. 25 professional rugby players belonging to the Italian National Team underwent a 7-day cryotherapy protocol consisting of 2 daily sessions. Saliva samples were taken in the morning before WBC and the evening after the second WBC. The samples were analyzed for a number of hormones. The results showed that cortisol and DHEA showed reductions after the 2 WBC sessions the first day. After 14 sessions, cortisol, DHEA, and estradiol decreased, while testosterone increased as did the testosterone to cortisol ratio. The authors conclude that WBC modifies salivary steroid hormone profiles, even as early as after 2 treatments.

Conclusion

Based on the evidence available to date, WBC is extremely safe, with no adverse effects being described in the literature. WBC certainly causes some degree of temperature decrease, but the magnitude varies per body part, based on duration, and based on the temperatures used. The evidence suggests that it can decrease a number of inflammatory mediators and there is conflicting evidence on whether it can decrease markers of muscle damage. From a functional perspective, it appears to help with strength, pain, and fatigue after exercise. Studies we described also show improvements in antioxidant status, as well as hormone levels. Overall, the evidence is still quite preliminary so no extreme conclusions should be drawn. Please see your Naturopathic Doctor for further evaluation.