Decreased Chronotiropic Drive as an Adaptation to Chronic Exercise; Possible Mechanisms

Cardiovascular function was determined at rest and during exercise in twenty-eight healthy, elite distance runners. Maximum heart rate was 184±6 b·min -1, which was more than one SD lower than the age predicted value (p < 0.001), and an inverse correlation was observed between maximum heart rate and VO 2 max (r = - 0.82, p < 0.001). The most aerobically trained athlete, a 27 year old male, presented with a maximum heart rate of 139b·min -1 . Echo-cardiac ultrasound revealed unremarkable intra-cardiac dimensions and flow characteristics relative to other endurance-trained athletes. A decreased chronotropic drive may represent a favourable physiological adaptation to endurance exercise which increases cardiovascular efficiency.