Analysis of the heart rate deflection point as a tool for exercise prescription in subjects with COPD - a cross-sectional study.

Background : Prescription of exercise training in subjects with chronic obstructive pulmonary disease (COPD) remains a challenge in clinical practice. The heart rate deflection point (HRDP) is an option to reduce costs, reflects the anaerobic threshold and it is noninvasive; however its applicability in COPD is still unknown. Aim : To compare HRDP with gas exchange threshold values (GET) in subjects with COPD. Methods : Thirty-one subjects were evaluated in this cross-sectional study, diagnosed with COPD. The subjects performed an incremental exercise test on a treadmill to determine the GET, peak oxygen consumption (VO _2PEAK ), speed corresponding to VO _2PEAK (sVO _2PEAK ), and peak values of heart rate (HR _PEAK ). To determine HRDP the heart rate values observed were plotted as a function of intensity. Results : The HRDP was visible in 96.77% of subjects. There was no difference between HRDP and GET (p = 0.07) and a moderate intraclass correlation coefficient (ICC): 0.74 [0.52-0.87] and high limits of agreements were presented (±1.1 km·h ^-1 ). Conclusion : The HRDP cannot be used to determine the limits between the physiological domains of these subjects. Thus, although significant correlation was found between HRDP and GET, their application for training prescription and monitoring in subjects with COPD proved to be limited.