Whole body cryotherapy was initially intended for use in a clinical setting to treat patients with conditions such as multiple sclerosis and rheumatoid arthritis . WBC is provided in over 50 European hospitals and medical clinics and it has now been used in many spas, and athletic training facilities as well.   Elite athletes have reported using the treatment to alleviate delayed onset muscle soreness (DOMS) after exercise   and recreational athletes have started to emulate elite athletes in using these treatments after exercise. Reductions in muscle and skin tissue temperature after WBC exposure may stimulate cutaneous receptors and excite the sympathetic adrenergic fibres, causing constriction of local arterioles and venules .    There has been a study that suggests that WBC stimulates the autonomic nervous system (ANS), with a predominance of parasympathetic tone activation, after exposure but it does not appear to have been duplicated. 
But I'm not more aggressive—a behavior change often tied to testosterone. That's not surprising to Robert Sapolsky, ., a neuroendocrinologist at Stanford University and a leading researcher on stress and behavior. "It's really not the case that testosterone 'causes' aggressive behavior," he says. "Instead, it makes the brain more sensitive to social cues that trigger aggression. And in support of that, a guy's testosterone level isn't a very good predictor of how likely he is to be aggressive."