# Cold-Water Immersion Promotes Antioxidant Enzyme Activation in Elite Taekwondo Athletes
## 4 Discussion
### Variation of Antioxidant Enzyme Concentration According to CWI for Elite Takekwondo Athletes  
Taekwondo is a sport in which a player must be nimble enough to exploit the opponent's weak points with explosive kicks; thus, active muscles are utilized alternately at a high intensity. Furthermore, players must compete in at least 5-7 matches in a single day [50; 51], during which there is the accumulation of hydrogen ions, phosphorus, ammonia, and lactate. This accumulation has an impact on muscle metabolism, local muscle fatigue, and neuromuscular activities [52; 53]. Moreover, high-intensity training, excessive training, and strenuous training without appropriate rest periods also induce fatigue, undermine athletic performance, and can cause sport-related injuries [54]. In addition, they cause muscle contraction and structural damages to cell membranes and muscles, thereby disturbing muscle fiber homeostasis and leading to oxidative stress. However, lowering ROS levels after exercise can also have the opposite effect [55]. This is attributable to the fact that ROS is needed for appropriate muscle contraction during rest and physical activity [42]. In 1996, [PERSON] et al. suggested that CWI is a classic method of alleviating muscle injury. Furthermore, they reported that CWI treats muscle injuries by lowering local vascular permeability and edema by inducing vasoconstriction while increasing the pain threshold [56]. Another study reported that CWI can regulate the physiological effects of exercise and can be used for treating exercise-induced injuries [57]. Regarding prior research on cold treatment, one study reported that a single session using ice increased antioxidant enzyme activity in untrained volunteers [19]. However, our findings showed that a single CWI session partially increased antioxidant enzyme activity. That is, there were no significant differences in SOD levels between groups, but there was an interaction effect. Moreover, CWI treatment increased GPX concentration, and there were interactions between groups. Thus, a single CWI session can be applied in different ways according to the study methodology. In another similar study, low-temperature stimulation once per day increased SOD activity [58], showing that the outcomes varied, even with the same cold treatment. However, ice-cold water treatment did not increase antioxidant enzyme activation [43], which is in line with our findings, but inconsistent with the findings of other studies [44; 58]. Elevated antioxidant enzyme activity attests to increased ROS concentration. However, such ROS production could be beneficial, as it may cause stimulating changes, and does not damage the body [18, 59]. Therefore, as an oxidant, ice-water immersion stimulates and enhances antioxidant capacity [43]. In another study utilizing cold treatment, a whole-body cryotherapy (WBC) session used as a pre-training stimulation in a multiday training camp had adverse effects on elite athletes by diminishing both lipid peroxide level and antioxidant enzyme activities [60, 61]. Nevertheless, WBC and CWI are increasingly used in professional sports to facilitate rehabilitation following an injury, as they lower oxidative stress, inflammatory reactions, and pain from vigorous exercise [19, 57, 60, 61]. In particular, CWI continues to be researched using various study designs, which help support the claim that it is an effective method to delay or prevent physical fatigue, muscle fatigue, and diminished athletic performance suffered by athletes who undergo high-intensity training or compete in multiple games. Therefore, the inconsistent effects of CWI on the oxidant/antioxidant balance in the human body would probably be helpful in maintaining an ROS concentration that is the most appropriate for both rest and exercise [43]. Inconsistent results pertaining to the effects of CWI on lipid peroxide and antioxidant enzymes were shown in previous studies [43, 44, 60, 61].