Estimation of maximum heart rate from cardiopulmonary exercise testing
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Background: When prescribing exercise training, percentage of heart rate maximum (HRmax) is often used to guide exercise intensity. To be able to use heart rate (HR) as a measure of exercise intensity, it is important to know what an individual’s HRmax is. Although several equations have been established to calculate an individual’s HR, there is a large inter-individual variation in HRmax, making such estimations less valid. In exercise studies, a maximum effort cardiopulmonary exercise test (CPX) is often undertaken at baseline to establish the maximum work load or maximum oxygen uptake of the subjects. It is a common practice to add some beats (usually 5-6) to the highest HR obtained during a CPX to estimate the HRmax . There is, however, a lack of data providing evidence for such an addition. Our aim was therefore to investigate how well a maximum HR obtained during a CPX would predict the maximum HR obtained during a test designed to reach HRmax. Methods: We included 68 participants (31 women/37 men, age 43±19, VO2peak. 50,6 ±6,9). All subjects underwent two different tests, on separate days; a CPX using a individualized ramp protocol and a maximum effort interval test designed to reach HRmax. HRmax prediction models based on maximum HR reached at the CPX test were derived from multiple linear regression analysis. We also included other independent variables that can affect the HRmax; age, gender, fitness level, height and weight. Results: The maximum HR reached at the CPX test (HrVO2) explained 90,2% of the HRmax at the interval test. The regression equation obtained in this study, HRmax = HrVO2 x 0,954 + 11,391, includes only HrVO2 as a variable. The other independent variables gave only minimal changes in R² and were thus excluded from the equation. Conclusion: The maximum HR obtained in a CPX test to exhaustion provides a fairly accurate estimate of the HRmax.