Relationship between Cardiovascular Fitness and Arterial Stiffness, Heart Rate Variability, Quality of Sleep in Middle-aged Male Firefighters. KINESIOLOGY, 2017, 19(2): 23-31. [PURPOSE] The aim of this study was the relationship between cardiovascular fitness and arterial stiffness, heart rate varia-bility, and quality of sleep in middle-aged male firefighters. [METHODS] The subjects were 180 firefighters who were exam-ined for cardiovascular fitness, arterial stiffness, heart rate variability, and sleep quality at the National Fitness Center in 2016. The maximal oxygen uptake was measured by exercise test. The marker of arterial stiffness was the brachial-ankle pulse wave velocity. The heart rate variability index used time domain analysis and frequency domain. The quality of sleep was assessed by the quality index of the Korean version of Pittsburgh. [RESULTS] There was a correlation between cardiorespiratory fitness and arterial stiffness(r=-0.292, p<.05). LF/HF in cardiovascular fitness and heart rate variability(r=-0.318, p<.05). However, there was no correlation between cardiorespiratory fitness and sleep quality. [CONCLUSIONS] These results can be used as a basis for judging the importance of cardiorespiratory fitness enhancement to prevent the risk of cardiovascular disease in firefighters.