A New Fitness Dependent Maximal Protocol for Determination of Heart Rate Deflection Point

Heart Rate Deflection Point (HRDP) is a downward or upward change from the linear HR-work relationship evidenced during progressive incremental exercise testing which is reported to be coincident with the anaerobic threshold (AT). The aim of this study was to design and introduce a new fitness- dependent maximal treadmill test protocol according to the subjects’ status for determining HRDP.Sixteen active young males (Vo2max mean ± SD = 48.31± 8.12 ml·kg·min−1) completed a fitness-dependent HRDP maximal treadmill test protocol to volitional exhaustion (GXT) with continuous respiratory gas measurements. Polar Vantage Sport Tester XL was used to monitor heart rate performance curve (HRPC) throughout the protocol. Mod-Dmax method in light of parallel straight-line slope (PSLS) mathematical model used for determining HRDP. The Bland and Altman plots and intraclass correlation coefficient (ICC) were used to assess the agreement between the HRDP and gas measurements. The results showed that fitness- dependent test protocol results in HRDP in all of the subjects. High agreement revealed between HRDP and end-tidal carbon dioxide (PETCo2) (±1.96; 95% CI = -3.0 to +3.5 b/min; ICC=0.88). According to this study results, designed treadmill time fixed fitness dependent protocol via Mod-Dmax method is an accurate approach for determining HRDP.