RELATIONSHIP BETWEEN BLOOD pH, POTASSIUM AND THE HEART RATE PERFORMANCE CURVE

Abstract

628 An explanation of the heart rate performance curve (HRPC) deflection (Conconi test) is still missing. A significant relationship between the HR response and the myocardial function was found earlier (Int. J. Sports Med. 15, 1994: 232-237). The influence of metabolic acidosis on the HRPC is questioned. Aim of this study was to investigate the relationship between blood pH and potassium (K+) on the direction and the degree of the deflection of the HRPC during incremental cycle ergometer exercise. 29 male subjects (age 21±2 yrs) performed an incremental exercise test (20 W.min−1). The degree and the direction of the deflection of the HRPC (kHR) was assessed by means of second degree polynomial fitting between the first lactate tum point (LTP1) and maximal power (Pmax). kHR was neither related to absolute values of pH and lactate (La) nor to the changes of these variables between the second lactate turn point (LTP2) and Pmax. kHR was related (not significantly) to the change in K+ between LTP2 and Pmax (R=−0.328; P=0.051) but not to K+max. Heart rate (HR) at LTP2 was significantly related to kHR (R=0.651; P<0.001). A heart rate turn point (HRTP) was obtained in 17 cases and power (P) at HRTP (232 ± 32 W) was not significantly different from P at LTP2 (235 ± 30 W). From our data we may conclude that the individual heart rate response during incremental cycle ergometer exercise is not influenced by the lactate but possibly by potassium. This study was supported by AVL-List Graz