Background:It has been reported that high intensity long term training in elite athletes may increase risk of immune function.Objectives:This study is to examine training effects on immunoglobulin and changes of physiological stress and physical fitness level induced by increased cold stress during 12-week winter off-season training in elite Judoists.Patients and Methods:Twenty-nine male participants (20 ± 1 years) were assigned to only Judo training (CG, n = 9), resistance training combined with Judo training (RJ, n = 10), and interval training combined with Judo training (IJ, n = 10). Blood samples collected at rest, immediately after all-out exercise, and 30-minute recovery period were analyzed for testing IgA, IgG, and IgM, albumin and catecholamine levels.Results:VO2max and anaerobic mean power in IJ (P < 0.05) and anaerobic power in RJ (P < 0.05) were significantly increased after 12-week training compared to CG. There was no significant interaction effect (group × period) in albumin after 12-week training; however, there was a significant interaction effect (group × period) in epinephrine after 12-week training (F (4, 52) = 3.216, P = 0.002) and immediately after all-out exercise and at 30-minute recovery (F (2, 26) = 14.564, P = 0.008). There was significantly higher changes in epinephrine of RJ compared to IJ at 30-minute recovery (P = 0.045). There was a significant interaction effect (group × period) in norepinephrine after 12-week training (F (4, 52) = 8.141, P < 0.0001), at rest and immediately after all-out exercise (F (2, 26) = 9.570, P = 0.001), and immediately after all-out exercise and at 30-minute recovery (F (2, 26) = 8.862, P = 0.001).Conclusions:Winter off-season training of IJ increased physical fitness level as well as physical stress induced by overtraining. Along with increased physical stress, all groups showed reduced trend of IgA; however, there was no group difference based on different training methods.