Mathematical Modeling and Expression of Heart Rate Deflection Point using Heart Rate and Oxygen Consumption

Heart rate deflection point (HRDP) can be determined through different mathematical-modeling procedures, such as bi-segmental linear regression (2SEG) or maximal distance model (Dmax). The purpose was to compare heart rate (HR) and oxygen consumption (VO(2)) at HRDP when using 2SEG and Dmax, and to examine their relationships with respiratory compensation point (RCP) and running performance. Nineteen participants completed a graded exercise test (GXT), to determine HRDP and RCP, and a 5km treadmill time trial (5K(time)). No differences were found in HR or VO(2) when comparing HRDP(2SEG), HRDP(Dmax), and RCP. Strong correlations were found between HRDP(2SEG), HRDP(Dmax), and RCP when using HR and VO(2). No relationships were found between 5K(time) and HR at HRDP or RCP; however, strong relationships were found with VO2. While 2SEG and Dmax may be interchangeable in determining HRDP, VO(2) at HRDP and RCP yielded stronger relationships to 5K(time) than HR. Therefore, VO(2) at HRDP may be a better predictor of running performance than HR.