The aim of this study is to describe the percentages loads of heart rate and oxygen consumption achieved by athletes in duathlon sprint competitions (5km run, 20km bike and 2.5km run = C1-BK-C2) For the study, the physiological data were collected from five duathlon sprint competitions very similar in altitude and terrain. Ten male athletes, chosen from high national level duathletes, participated in the study. Continuous recordings of heart rate were obtained during competitions and subsequently in the laboratory where they were tested by two maximal graded exercise tests, one on a treadmill and another on a cycle ergometer, to obtain physiological reference values for each athlete. The results show that athletes had a very similar percentage of heart rate in the three competition sectors, with C1: 94.63%±3%; BK: 94.50%±2.94% and C2: 92.71%±3.54%.

The oxygen consumption levels were estimated as a dependent variable by linear regression, from heart rate and oxygen consumption values of the effort test, showing a similar values in three segments (C1: 89.70%±6.11%; BK: 85.73%±6.89%, C2: 87.30%±8.67%). The lowest VO2% of BK with respect to C1 and C2 (p<.01) could be justified by lower use of total muscle mass and therefore a lower energy expenditure. The study showed that in sprint duathlon competitions the per cent load of the heart rate range between 92% and 95% of maximal heart rate and oxygen consumption between 85% and 89% of VO2max, confirming high levels of maximal aerobic power and heart rate. These data being considered as a reference for the use of sports training loads in continuous, variable continuous, and long interval extended types of sport.