%HRmax target heart rate is dependent on heart rate performance curve deflection

The percent of maximal heart rate (%HRmax) model is widely used to determin e training intensities in healthy subjects and patients when prescribing tr aining intensities in these groups of subjects. Purpose: The aim of the stu dy was to investigate the influence of the time course of the heart rate pe rformance curve (HRPC) on the accuracy of target training heart rate. Metho ds: Sixty-two young healthy male subjects performed an incremental cycle er gometer exercise test until voluntary exhaustion. Subjects were then divide d into four groups according to the time course of the HR-PC. Groups were c lassified in regular HR response (k(HR2) > 0.2), indifferent HR response (0 < k(HR2) < 0.2), linear HR response (k(HR2) = 0), and inverted HR response (k(HR2) < 0). The first and the second lactate turn point (LTP1, LTP2) as well as the heart rate turn point (HRTP) were determined as submaximal mark ers of performance. Linear regression lines were calculated for HR in the t hree regions of energy supply defined by LTP1, and LTP2. Results: HR at LTP 1 and HRmax was not significantly different between all four groups. HR at LTP2 was dependent on the time course of the HRPC and was significantly low er (P < 0.05) as k(HR2) decreased. Power output and blood lactate concentra tion at LTP1, LTP2 and maximal workload (P-max) were not significantly diff erent between the groups. Conclusion: From our data, we conclude that targe t training HR detected by means of the %HRmax method may be overestimated i n cases where the HR response is not regular, as it was found in many of ou r subjects.