RELATIONSHIP BETWEEN PERCENTAGES OF HEART RATE RESERVE AND OXYGEN UPTAKE RESERVE DURING CYCLING AND RUNNING: A VALIDATION STUDY

This study investigated the relationship between percentages of heart rate reserve (%HRR) and oxygen uptake reserve (%(V) over dotO(2)R) during a cardiopulmonary exercise test (CPET) and discrete bouts of isocaloric cycling and treadmill running. Thirty men visited the laboratory 3 times for anthropometrical and resting (V) over dot(2) assessments, and perform cycling and running CPETs. Ten men visited the laboratory twice more to investigate the validity of the %HRR-%(V)over dotO(2)R relationships during isocaloric bouts of cycling and running at 75%(V) over dotO(2)R with energy expenditures of 400 kcals. The %HRR was significantly higher than the %(V) over dotO(2)R during both CPETs at all exercise intensities (p < 0.001). During isocaloric exercise bouts, mean %HRR-%(V) over dotO(2)R differences of 6.5%and 7.0% were observed for cycling and running, respectively (p = 0.007-p < 0.001). The %HRR and %(V) over dotO(2)R increased over time (p< 0.001), the rate of which was influenced by exercise modality (p < 0.001). On average, heart rate was 5 (p = 0.007) and 8 (p < 0.001) b.min(-1) higher than predicted from the second energy expenditure quartile for cycling and running, respectively; however, observed (V)over dotO(2) was lower than predicted during all quartiles for cycling, and the first quartile for running. Consequently, time to achieve the target energy expenditure was greater than predicted (p < 0.01). In conclusion, the %HRR-%(V) over dot(2)R relationship observed during CPET data did not accurately transpose to prolonged isocaloric bouts of cycling and running. In addition, power outputs and speeds defined by the American College of Sports Medicine equations for cycling and running, respectively, overestimated (V) over dotO(2) and energy expenditure.