Nowadays, whole-body cryotherapy is a medical physical treatment widely used in sports medicine. Recovery from injuries (e.g., trauma, overuse) and after-season recovery are the main purposes for application. However, the most recent studies confirmed the anti-inflammatory, anti-analgesic, and anti-oxidant effects of this therapy by highlighting the underlying physiological responses. In addition to its therapeutic effects, whole-body cryotherapy has been demonstrated to be a preventive strategy against the deleterious effects of exercise-induced inflammation and soreness. Novel findings have stressed the importance of fat mass on cooling effectiveness and of the starting fitness level on the final result. Exposure to the cryotherapy somehow mimics exercise, since it affects myokines expression in an exercise-like fashion, thus opening another possible window on the therapeutic strategies for metabolic diseases such as obesity and type 2 diabetes. From a biochemical point of view, whole-body cryotherapy not always induces appreciable modifications, but the final clinical output (in terms of pain, soreness, stress, and post-exercise recovery) is very often improved compared to either the starting condition or the untreated matched group. Also, the number and the frequency of sessions that should be applied in order to obtain the best therapeutic results have been deeply investigated in the last years. In this article, we reviewed the most recent literature, from 2010 until present, in order to give the most updated insight into this therapeutic strategy, whose rapidly increasing use is not always based on scientific assumptions and safety standards.
Local and systemic cold therapies (cryotherapies) are widely used to relieve symptoms of various diseases including inflammation, pain, muscle spasms, and swelling, especially chronic inflammatory ones, injuries, and overuse symptoms (Bettoni et al., 2013; Jastrzabek et al., 2013). The beneficial effects of cold as a therapeutic agent have been known for a long time, with ancient population aware about the reinvigorating effects of cold water either taken orally or used for baths. The use of cold, mainly locally, still remains in our daily common activities. A still up-to-date survey of a sample of Irish emergency physicians highlighted the fact that 73% of consultants frequently “prescribe” cold, 7% never suggest to use cryotherapy, and 30% is unsure about the benefits of using cold. Experience (47%) and common sense (27%) were the most frequently declared reasons for using ice, while only 17% referred to scientific reasoning (Collins, 2008).
Forty years ago, following personal observations of Prof. Toshiro Yamauchi (who recognized that the combination of cold and physical exercise was beneficial for clinical outcomes of treatments received by his patients’, affected by rheumatoid arthritis, coming back from mountain localities after winter holidays), whole-body cryotherapy was introduced into clinical practice (Yamauchi et al., 1981a,b).
At present, the use of very cold air in special, controlled chambers may be proposed for treating symptoms of various diseases (Bouzigon et al., 2016). Beside its clinical applications, a brief full body exposure to dry air at cryogenic temperatures lower than −110°C has become widely popular in sports medicine, often used to enhance recovery after injuries and to counteract inflammatory symptoms resulting from overuse or pathology (Furmanek et al., 2014). The number of studies about the use of whole-body cryotherapy (WBC) in sports medicine is growing, however, it is still lower than the topic’s potential if the wide range of application of this methodology is considered. Studies published on athletes had mainly focused on post-training or competitive season recovery. Only a limited number of papers had investigated the effects of WBC used in preparation phase for competitive season to enhance form and performance, or during periods of high intensity of training to limit overuse and overreaching. Studies should be acknowledged to define safety, effectiveness, and efficacy of the treatment in athletes and to discover underlying molecular mechanisms supporting the claimed beneficial effects.
This review article collects the most recent literature (since 2010, Banfi et al., 2010b) on whole-body cryotherapy with the purpose of delivering a complete and updated overview of the newest findings and the directions taken in research in this field. In particular, given the high number of new scientific findings mostly associated with great technological developments of this therapeutic method, this review discusses both technical aspects (i.e., therapeutic protocols, contraindications, thermoregulatory responses) and effects on a wide range of physiological (i.e., hematological, metabolic, energetic, endocrinological, skeletal, muscular, inflammatory) and functional parameters (post-exercise and post-traumatic recovery, pain, performance). We are aware of the limitations of this literature review. Almost all published research included in this review discuss results of using whole-body cryotherapy without providing any insight into molecular mechanisms involved in observed responses to the treatment. Also, although the review takes a non-systematic approach, an alternative meta-analysis would only offer a limited article coverage due to the type and, sometimes, the quality of available papers. Furthermore, we only reviewed reports on the WBC procedures performed in cryochambers (regardless of the cooling system, but considering the operating temperature); we do not consider treatments performed in cryosauna (also named cryocabins). Exposure to cold in a cryosauna cannot be deemed whole-body since during the treatment the head remains outside of the cabin. The two settings were concluded to, activate different molecular pathways and, possibly, exert different outcomes. Indeed, in a cryosauna, cooling is delivered through direct insufflation of liquid nitrogen vapors into the box. Free vapors are heavy and tend to remain within the cabin, below the chin; contrarily, in a nitrogen-cooled cryochamber liquid nitrogen fluxes through pipes inside the chamber’s wall, and thus, there is no free nitrogen within the chamber. These differences also account for different safety standards of these treatments: free nitrogen vapor in a cryosauna could be potentially hazardous due to the risk of asphyxia.
In the present paper we refer to “whole-body cryotherapy,” which is the most commonly used term to define the methodology, but also to “whole-body cryostimulation,” which better describes effects of WBC in improving the metabolic and inflammatory responses as well as in enhancing recovery from exercise and injuries. In contrast, the term “cryotherapy” refers to a real therapy aimed at treating painful symptoms of inflammatory or traumatic conditions.
Standardized protocol for WBC
WBC is performed in special chambers, with the temperature and humidity strictly controlled. A subject, minimally dressed (for e.g., bathing suit, socks, clogs, headband, and surgical mask to avoid direct exhalation of humid air), enters a vestibule chamber at −60°C, where he stays for about 30 s of body adaptation and then passes to a cryochamber at −110° to −140°C, depending on the cooling system (electrical or nitrogen), where he remains for no more than 3 min. It is mandatory to remove any sweat before entry to avoid the risk of skin burning and necrosis. Access to the chamber is allowed only in the presence of a skilled personnel, controlling the procedures. A patients is free to leave the chamber at any time.
Being a medical therapy, WBC should follow strict guidelines and indications. Currently accepted contraindications for WBC include: cryoglobulinaemia, cold intolerance, Raynaud disease, hypothyroidism, acute respiratory system disorders, cardio-vascular system diseases (unstable angina pectoris, cardiac failure in III and IV stage according to NYHA), purulent-gangrenous cutaneous lesions, sympathetic nervous system neuropathies, local blood flow disorders, cachexia, and hypothermia, as well as claustrophobia and mental disorders hindering cooperation with patients during the treatment. When performed in the appropriate and controlled conditions, WBC is a safe procedure, which was demonstrated to be deleterious neither for lung (Smolander et al., 2006) nor heart function (Banfi et al., 2009a); however, recorded observation of a very slight, clinically irrelevant increase in the systolic blood pressure (Lubkowska and Szygula, 2010) justifies precautions indicated for patients affected by cardiovascular conditions.
Studying body temperature modifications following WBC, in comparison to changes observed in response to other cooling techniques, represents a hot topic. This is thought to be important since cooling effectiveness is the function of temperature decrease within a certain range.
Shifts in skin temperature (Tsk) of chosen body regions monitored by thermography and contact thermometry, before and immediately after a single WBC session (30 s at −60°C, 3 min at −120°C) showed, for the first time, the influence of body mass index (BMI) on the range of alternations. The highest magnitude of temperature changes was observed within lower extremities (tibias: −8.7°C; feet: −5.2°C), the mean total body temperature decreased by 5.8°C, while the internal body temperature dropped only by 0.8°C. The mean changes of temperatures at different sites correlated with BMI (r = −0.46); for example, explicative images show that temperature decreased down to 8.1° and 7.9°C in a thin volunteer (BMI <25 kg/m2) and down to 4.8° and 5.5°C in an obese participant (BMI > 30 kg/m2), in the chest and back regions, respectively (Cholewka et al., 2012). Even more precisely than BMI, the fat-free mass index (FFMI: fat-free mass/height2) and body fat percentage in males were both found to correlate with changes in skin temperature following WBC, (Hammond et al., 2014). Body composition was, thus, observed to be one of the main determinants of potential temperature changes and, possibly, of therapy’s effectiveness. Cooling efficacy, indeed, differs between males and females as demonstrated by Hammond et al.; however, despite females having higher levels of adiposity than males, they experience greater mean temperature changes compared to males (12.07 ± 1.55°C vs. 10.12 ± 1.86°C). Compared to males, females have 20% smaller body mass, 14% more fat, 33% smaller lean body mass, and 18% smaller surface area, a higher subcutaneous to visceral fat ratio and a smaller ratio of fat mass index (FMI) to FFMI. Furthermore, females’ BSA-to-mass ratio is higher than males, and the heat loss increases proportionally to this ratio. Under cold stress, females have a more extensively vasoconstricted periphery, with greater surface heat losses and show a significantly reduced sensitivity of the shivering response. Taken together these evidences could explain the discrepancy in cooling efficiency between sexes (Hammond et al., 2014).
Costello analyzed reduction in skin, muscle (vastus lateralis, at 1, 2, and 3 cm) and rectal temperatures following a single exposure to either WBC (−110°C) or cold-water immersion (CWI, at 8°C). Immediately after these procedures, the maximum drop in Tsk was observed with WBC (−12.1 ± 1.0°C), marking a bigger drop compared to CWI (−8.8 ± 2.0°C). On the contrary, core (−0.3° to −0.4°C) and muscle (−1.2° to −2.0°C) temperatures shifted slightly with no differences between the two treatments and the maximum decrease occurring after 60 min (Costello et al., 2012b). Similar results were obtained on changes in Tsk at the patellar region; a greater drop was observed with WBC immediately after the procedure, while 10–60 min after the treatment a lower temperature was reached with CWI (Costello et al., 2014). Interestingly, the authors had set the question whether or not either WBC or CWI were capable of achieving the Tsk (<13°C) believed to be required for analgesic purposes (Bleakley and Hopkins, 2010), yet they concluded that this temperature was reached by neither of the two procedures (Costello et al., 2014). Zalewski et al. confirmed that the maximum drop in core temperature occurred 50–60 min post-WBC (Zalewski et al., 2014).
In a systematic review, comparing 10 controlled trials, considering either a 10 min-long ice pack application, 5 min CWI, or 2.5–3 min WBC (−110° to −195°C), the authors illustrated that the largest reduction in Tsk was obtained by the ice pack application due to the higher heat transfer constant (k = 2.18) compared to water (k = 0.58) and air (k = 0.024). The obtained results confirmed negligible intramuscular temperature variation regardless of the cooling modality as well as importance of adiposity in determining cooling efficiency (k = 0.23 vs. k = 0.46 of muscles; Bleakley et al., 2014).
In summary, the following reports have been made about the WBC treatment:
– WBC is a medical practice that must be performed in specialized facilities under supervision of a well-trained personnel.
– WBC has contraindications that must be considered before prescription.
– Cooling efficiency and, possibly, treatment effectiveness can be influenced by body composition.
– Due to differences in body composition, cooling efficiency is potentially greater in females than in males.
– WBC effectiveness in lowering Tsk exceeds that of CWI; muscle and core temperatures seem to decrease in a similar way in response to both treatments.
– The maximum decrease in core temperature has been noted 50–60 min post-WBC.
The study of hematological response to WBC allows to define a wide range of effects covering modification of oxygen supply potential, inflammatory response, and coagulation function.
Erythrocytes and hemoglobin
We studied hematological parameters, including iron metabolism ones, in 27 athletes belonging to National Italian Rugby Team, during a summer camp (Lombardi et al., 2013a). Two daily sessions of WBC (3 min, −140°C) were performed for seven consecutive days, one in the morning before the first training session, the second in the evening after the second training session. Athletes were strictly controlled for diet, especially the correct iron uptake. A typical plasma volume shift due to a prolonged training session of aerobic exercises was taken into account when interpreting the results. Among hematological parameters, erythrocytes (RBC), hematocrit (Ht), and hemoglobin (Hb) decreased noticeably; particularly, Hb decreased from 15.06 ± 0.84 to 14.70 ± 0.62 g/dL. Red cell distribution width (RDW) increased, indicating a rise of anisocytosis of RBC, although reticulocytes were stable, but the immature fraction of reticulocytes (IRF) was significantly decreased (Lombardi et al., 2013a). A decrease of hemoglobinization could be a specific feature of the WBC treatment. Indeed, a similar decrease of Hb (about 0.3 g/dL) and IRF had been previously reported in rugby players, however, in that case, RBC and Ht had not been affected (Banfi et al., 2008). This difference could be attributable to a milder WBC protocol, with only five WBC (one per day, at −110°C). The decrease in the levels of Hb as well as RBC and Ht, is transitory and it recovered during continuative treatments as demonstrated by Szygula and colleagues in a study performed on students of the Polish National Military Academy, who can be considered physically active subjects, continuously performing exercises and controlled for variables as diet and lifestyle (Szygula et al., 2014). Recruited cadets were divided into two groups of 15 subjects; one group was treated with WBC, the other did not receive the treatment. Hematological parameters were measured after 10, 20, and 30 sessions, which were performed daily in a cryochamber at −130°C, for 3 min. After 10 sessions, Hb decreased from a mean of 15.1 ± 0.74–14.4 ± 0.94 g/dL and remained at this concentration after 20 sessions (14.5 ± 0.71 g/dL). It then rose to 15.1 ± 1.1 g/dL after 30 sessions. Similar changes were observed for Ht and RBC. The decrease of Hb, RBC and Ht lasted through 20 sessions of the WBC treatment; then the bone marrow reacted by releasing new RBCs (Szygula et al., 2014). A decrease in Hb and RBC was already described in elite Polish field hockey players after 18 sessions of WBC (Straburzyńska-Lupa et al., 2007). Hb also showed a decreasing though not statistically significant trend, dropping from 15.0 ± 1.0 to 14.4 ± 0.8 g/dL, in nine collegiate physically active subjects, who had completed 30 min step up/down exercise, aimed at inducing delayed-onset muscle soreness (DOMS), and had been treated with two daily WBC sessions for 5 consecutive days. In opposite, the control group, which had undergone the same DOMS-inducing training without the WBC or any other recovery treatment, experienced stable levels of Hb (Ziemann et al., 2014). Nevertheless, some data revealed that Hb and RBC were stable in 12 professional tennis players, following 10 sessions of WBC applied twice a day, at –120°C for 3 min, over 5 days, during a controlled training camp (Ziemann et al., 2012) as well as in 16 kayakers treated twice a day for the first 10 days of a 19 day physical training cycle (Sutkowy et al., 2014). It is thus, possible that shifts in Hb and RBC induced by WBC are dependent on the discipline and baseline hematological profile. This issue, however, still has not been investigated. Mean curpuscular volume (MCV) grew following the WBC treatment applied in rugby players and in field hockey players (Straburzyńska-Lupa et al., 2007; Lombardi et al., 2013a); in the latter group values of MCV, mean curpuscular hemoglobin (MCH), and of mean curpuscular hemoglobin concentration (MCHC) remained elevated up to a week after the end of the treatment (Straburzyńska-Lupa et al., 2007).
A slight dehemoglobinazion has two direct consequences. Firstly, since the OFF-score, a parameter used to calculate the probability of blood doping in athletes, depends on Hb concentration and Ret count (Sottas et al., 2010; Robinson et al., 2011; which remained stable), WBC may reduce the result of this score and, thus, cannot be considered a performance enhancing practice. On the other hand, the use of WBC to mask illicit practices is unjustified because the potential decrease in Hb is too small and the change itself is short-lasting and/or temporary (Lombardi et al., 2013a). Secondly, the decrease in Hb and RBC should be considered when the timeline of recovery strategies, within a competitive season, is drawn.
Martial status was not modified after the treatment in 27 rugby players submitted to two daily WBC sessions for 7 consecutive days (Lombardi et al., 2013a). Only soluble transferring receptor (sTfR) increased significantly, but not pathologically, possibly demonstrating initial high functional iron demand (Lombardi et al., 2013b). Similar results were obtained in a more recent paper by Dulian and colleagues. Regardless of the fitness level, in a cohort of obese subjects (BMI > 30 kg/m2), serum iron and ferritin remained unchanged after the 1st and 10th WBC session. Only hepcidin, a hepatocyte-derive peptide hormone mediating iron depletion in inflammation (Lombardi et al., 2013b), decreased moderately (Dulian et al., 2015).
WBC enhances hemolysis, which could explain the Hb decrease during initial phase of the treatment. A decrease of haptoglobin, scavenger protein for free Hb released from broken RBC was described in the above-mentioned paper by Szygula and co-workers, after 10 and 20 WBC sessions, but a recovery appeared after 30 sessions, following the changes in Hb and RBC. Contemporarily, bilirubin increased, reflecting Hb catabolism. Hemolysis stimulated release of erythropoietin (EPO), which increased by 4.5% compared to baseline after 10 sessions, and further by 10.8 and 10.1% after 20 and 30 sessions, respectively, possibly supporting the recovery of RBC number after the initial decrease. Even in the case of EPO, the shifts in concentrations remained within physiological ranges (Szygula et al., 2014).
Levels of leukocytes did not show any changes after 14 sessions of WBC (twice a day, over 7 days) in the group of 27 rugby players, belonging to National Italian Rugby Team, studied during a summer camp (Lombardi et al., 2013a). The same was found for the group of 16 kayakers treated twice a day for the first 10 days of a 19 day physical training cycle (Sutkowy et al., 2014).
At the same time, leukocytes increased in the students of the Polish Military Academy after 10 and 20 sessions, but returned to baseline values after 30 sessions. The increase trend covered both granulocytes and lymphocytes (Szygula et al., 2014). Similar increase was also reported in tennis players, but not for subcategories of granulocytes and lymphocytes (Ziemann et al., 2012). Despite the increase, leukocytes always remained within the physiological range. Mobilization of leukocytes from the bone marrow and organs of residence has been hypothesized as a possible cause of these increases although an explanation of this phenomenon is still lacking.
In endurance trained runners, a simulated 45 min trail run, designed specifically to trigger exercise-induced muscle damage (EIMD), followed by four sessions of WBC applied once a day, resulted in an increase in neutrophil count of 114% compared to baseline, with the maximum peak recorded 1 h after the exercise. The correspondent increase in neutrophils, following passive recovery, accounted for 101% shift against baseline. The authors hypothesized that the increase of circulating neutrophils stimulated angiogenesis (via vascular endothelial growth factor—VEGF expression) and the consequent improved perfusion was associated with a reduced delayed onset of muscle soreness (DOMS) and, hence, an improved recovery (Pournot et al., 2011).
Platelets did not shift in response to WBC sessions applied in groups of rugby and tennis players (Lombardi et al., 2013a; Ziemann et al., 2014) nor students of the Polish Military Academy (Szygula et al., 2014).
In summary, the following reports have been made about the WBC treatment:
– WBC causes a decrease in Hb, Ht, and RBC after 5, 10, and 20 sessions. A recovery of hemoglobinization is reached after 30 sessions. Ret counts remains unaffected by WBC.
– The effect of WBC on RBC and Hb can be influenced by the type and intensity of physical training since in some groups of athletes these changes did not occur.
– Hemolysis may be the cause behind the drop in RBC, Hb, and Ht following the WBC treatment of 10–20 sessions.
– EPO is induced in the course of WBC with the aim to recover to baseline levels of RBC and Hb.
– WBC should not have a boosting effect on bone marrow and is not influencing athletes’ hematological parameters usually controlled to test for illicit bone marrow stimulation.
– The level of leukocytes either does not change or only slightly increases in response to WBC. Cryotherapy possibly mobilizes leukocytes, especially neutrophils, with a positive effect on DOMS.
– Platelets are not affected by WBC.
Performance recovery using different cooling methods, especially CWI and contrast water immersion, has been extensively studied so far. Their average effect on recovery of trained athletes is rather limited, as reported in a recent review, but under appropriate conditions (whole-body cooling, recovery from sprint exercise) post-exercise cooling has positive effects even for elite athletes (Poppendieck et al., 2013).
Positive effects induced by WBC after 96 h were reported in 18 physically active subjects, who performed a single maximal eccentric contractions of the left knee extensors, through two WBC sessions (−110°C) 24 and 48 h after exercise. The effects were negative at 24 and 48 h post-exercise (Costello et al., 2012a). Positive effects were also reported 24 and 48 h after the treatment in nine runners completing a simulated 48-min trail run, submitted to three WBC sessions, immediately after the exercise as well as 1 and 2 days after (Hausswirth et al., 2011).
Eleven endurance athletes were tested twice in a randomized crossover design with 5 × 5 min of high intensity running followed by 1 h of passive recovery, including either WBC (−110°C, 3 min) or a 3 min walk. Time-to-exhaustion difference between a ramp-test protocol before running and 1 h post-recovery was lower in WBC-treated subjects. WBC improves acute recovery during high-intensity intermittent exercise in thermoneutral conditions. This could be induced by enhanced oxygenation of the working muscles as well as by reduction of cardiovascular strain and increased work economy at submaximal intensities (Krüger et al., 2015). In addition to beneficial effects on inflammation and muscle damage, WBC induces peripheral vasoconstriction, which improves muscle oxygenation (Hornery et al., 2005), lowers submaximal heart rate and increases stroke volume (Zalewski et al., 2014), stimulates autonomic nervous parasympathetic activity and increases norepinephrine (Hausswirth et al., 2013). These effects favor post-exercise recovery and induce analgesia (Krüger et al., 2015).
Although these evidences, a recent meta-analysis by Bleakley et al., based on a small number of randomized studies, highlighted that WBC sustains improvements in subjective recovery and muscle soreness following metabolic or mechanical overload, but little benefit toward functional recovery (Bleakley et al., 2014). The authors concluded that, until further researches will be available, less expensive cooling modality (local ice-pack, cold water immersion) would be used in order to gain the same physiological and clinical effects to WBC.
Three-minute WBC exposure significantly differ from a 1–2-min exposure. Blood volume decreased within vastus lateralis and gastrocnemius occurred 0–5 min after WBC in 14 professional rugby players. Oxyhemoglobin and deoxyhemoglobin increased in 15 min post-WBC, reaching baseline values indicative of venous pooling. Extreme cold induces vasodilation after constriction in very short time. Gastrocnemius is more susceptible to pooling at all exposure times than vastus lateralis. Two-minute WBC exposure causes changes in core and Tsk, tissue oxygenation in vastus lateralis, and gastrocnemius and thermal sensation. The optimum exposure time is 30 s at −60°C followed by 2 min WBC at −135°C (Selfe et al., 2014).
It is also crucial to keep a constant temperature between two consecutive treatments. Door opening and subject permanence within a chamber increase temperature and reduce therapeutic effectiveness, particularly for electrical cryochambers, but also for liquid nitrogen-cooled chambers. A 2 min wait between two consecutive treatments would allow temperature recovery to therapeutic levels.
The number of sessions is crucial for WBC effectiveness, as previously discussed. A recent Cochrane review, reporting on the absence of beneficial effects of WBC on prevention and treatment of muscle soreness in athletes, involves on only four papers. One out of these four papers talked about six treatments in cryocabin, the other two investigated the effects of a single treatment in a cryochamber and the final one reported the effects of only three treatments in a cryochamber (Costello et al., 2015). A single session is probably not sufficient to exert any significant effect. Twenty consecutive sessions should be a minimum for effectiveness evaluation; 30 sessions should be the optimum, because a complete hematological and immunological recovery after the initial response is possible (Szygula et al., 2014). Studies evaluating long-term WBC treatment are not easily performable in professional athletes during competitive seasons, but they could be proposed during training and summer camps. Although offseason injuries are rarer than contusions incurred during competitions, it is important to note that standardization of exercise and training offseason is more easily achievable.
Furthermore, randomization is very difficult, if not impossible, to be proposed to elite athletes, and professional teams: the treatment is proposed to improve recovery or to prevent injuries, thus, it should not be limited to a subgroup of athletes. On the other hand, when WBC is used for accelerating recovery from trauma/injury, only injured athletes are treated. Crossover studies could be more easily performed during training camps (but not during competitive season), but they would be only devoted to physiological modifications and not to recovery.
Different, and sometime discrepant results presented in current literature could be attributable to different levels of subjects ranging from “physically active” to “elite” to “national/international selection.” A stratification of WBC effects should be evoked for different subjects, because of different adaptation to effort, recovery capacity/velocity, and energy metabolism.
Based on the findings here collected, the majority of evidence supports effectiveness of WBC in relieving symptomatology of the whole set of inflammatory conditions that could affect an athlete. A small number of studies that did not report any positive effects should, however, not be neglected. The same applies to improvement of post-exercise recovery, and noteworthy, to limiting or even preventing EIMD. The perception of WBC is changing from a conventionally intended symptomatic therapy to a stimulating treatment able to enhance the anti-inflammatory and -oxidant barriers and to counteract harmful stimuli. Importantly, cooling effectiveness depends on the percentage of fat mass of a subject and the starting fitness level. These results, combined with evidence that WBC somehow mimics exercise, at least in its ability to induce a pulsatile expression of myokines (IL-6, irisin), open another window of possible therapeutic strategies for obesity and type 2 diabetes.
As above highlighted, some of the applied WBC protocols have been ineffective in inducing appreciable modifications of certain biochemical parameters. However, in these cases, the final clinical output (in a subjective assessment: in terms of pain, soreness, stress, and recovery) was significantly improved even when compared to other recovery strategies.
WBC, used either as a therapy or stimulation, is a medical treatment and as such it has contraindications and standard safety procedures. The undeniable risks for the users can be rendered negligible if all the procedures are conducted following precise rules under supervision of highly-skilled personnel. If these procedures are carefully followed, WBC is absolutely safe.
Originally published in Frontiers in Physiology by Giovanni Lombardi, Ewa Ziemann and Giuseppe Banfi1
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