Exercise and climatic heat both induce heat stress. Their synergistic effect, when excessive, may impair physical and cognitive performance, cause hyperthermia, and be detrimental to a child's well-being and health. In contrast, when the body is exposed to a cold environment, exercise-induced thermogenesis will help to prevent excessive body cooling. Therefore, hypothermia (core body temperature of 35o C or less) is more likely to occur during rest than during exercise.