Heart rate deflection related to lactate performance curve and plasma catecholamine response during incremental cycle ergometer exercise

The correlation between the behaviour of the heart rate/work performance (f_cW) curve and blood lactate ([la]_b) and plasma adrenaline/noradrenaline concentrations ([A]/[NA]) during incremental cycle ergometer exercise was investigated. A group of 21 male sports students was divided into two groups: group I, with a clear deflection of thef_cW curve; group II, without or with an inverse deflection of thef_cW curve. The aerobic threshold (Th_aer) and the lactate turn point (LTP) were defined. Between Th_aer and maximal work performance (f_cW_max) the behaviour of thef_cW curve as well as the behaviour of [la^–]_b and [A]. [NA] were described mathematically. Thef_c, systolic blood pressure (BP_S),W, [la^–]_b, [A] and [NA] at rest, Th_aer, LTP,f_cW_max, after 3 and 6 min of recovery (Re₃/Re₆) were calculated. A significant difference between the two groups could only be detected forf_c at LTP, Re₃ and Re₆ (P < 0.05). No significant, correlation could be found between individualf_cW-behaviour and individual time course of [la^–]_b, [A] and [NA]. However, a significant correlation was visible between [la^–/W-behaviour and individual catecholamine response. These results and the fact that the different flattening at the top of thef_cW curve was related to diminished stress-dependent myocardial function led us to the conclusion that it is possible that sympathetic drive is not directly involved in mechanisms of regulation between load dependentf_c and myocardial function. In addition, individualf_cW behaviour was independent of BP_S andW_max, or individual conditions of energy supply.