Gripp, F, Lacerda, ACR, Gonçalves, R, and Szmuchrowski, L. Sustained, prolonged exercise at stable heart rate defined by the deflection point identification method. J Strength Cond Res 23(2): 632-637, 2009-The objectives of this study were to identify the heart rate deflection point (HRDP) assessed according to the Conconi test method, to evaluate the ability of trained cyclists to pedal for 90 minutes while remaining within a stable heart rate (HR) range determined by identifying the HRDP, and to discuss the motor and physiological parameters recorded during this long-duration exercise. Ten trained men cyclists (V̇O2max: 64.1 ± 8.86 ml·kg−1·min−1) had their HRDPs determined. One week later, they performed continuous exercise for 90 minutes on a cycle ergometer at a stable HR sustained within a range comprising the HRDP ± 5 bpm. Subjects' HR and power output values were registered at each minute. Blood lactate, blood glucose, and body temperature were measured at rest and during exercise. All exercise was performed inside an environmental chamber (temperature of 22° C, relative humidity of 60%). In the first 5 minutes, the participants increased power output to reach the HRDP, and adjustments were required in their physiological parameters to meet this exercise demand. Between the 5th and the 30th minutes, HRDP had already been reached by all participants; nevertheless, all the other physiological and motor parameters were adjusting to this exercise demand. After 30 minutes of exercise, the physiological and motor variables had already adjusted to the new demand and remained stable until the end of exercise (blood lactate was not significantly different from 4 mmol·L−1). These results suggest the efficacy of the HRDP as an auxiliary method for prescribing and controlling sport training: after the defined HRDP has been reached, the technique confirms maintenance of power output, as well as the other physiological parameters, at threshold levels until the end of exercise.