1860 The aim of the study was to test protocol variations on the heart rate performance curve (HRPC) and the heart rate turn point (HRTP) according to Conconi et al. (Int J. Sports Med. 1996, 17: 509-519). Respiratory gas exchange variables were used to define the 3 phases of energy supply(I,II,III). 18 healthy young male subjects performed 4 tests (T1-T4). T1: uniform speed (S) increments every 60 s. Subjects were than randomized for the next tests. T2: uniform S increments every 20 s; T3: like T2, in the second half of phase III greater acceleration in S. T4: like T2, at the begin of phase III greater acceleration in S. No differences were found in the degree of the deflection of the HRPC expressed as factor kHR between T1(0.228±0.225) and T2 (0.248±0.231) but an increase was found in T3 (0.533±0.248) and T4 (0.770±0.258). 11 subjects showed a deflection in the HRPC in all tests, and no significant difference could be found for S, HR and VO2 at the HRTP. HRTP was not found in 7 subjects in T1 and T2, due to linearity of the HRPC. In T3 and T4 subjects showed a deflection of HRPC resulting from the protocol. A HRTP was found to be dependent on the start of the acceleration in S. In cases with a linear time course in the HRPC in T1 and T2, in T3 a HRTP was found at 15.6 km/h and in T4 at 13.6 km/h, respectively. The Conconi test protocol with an accelerated increase in S in the final phase of the test has a major influence on the occurrence of the HRTP in cases of near linear HRPC.