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 (VO₂) 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 VO₂ when comparing HRDP_2SEG, HRDP_Dmax, and RCP. Strong correlations were found between HRDP_2SEG, HRDP_Dmax, and RCP when using HR and VO₂. 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, VO₂ at HRDP and RCP yielded stronger relationships to 5K_time than HR. Therefore, VO₂ at HRDP may be a better predictor of running performance than HR.