RELATION BETWEEN STEADY STATE LACTATE CONCENTRATION AND RESPIRATORY QUOTIENT DURING PROLONGED EXERCISE OF HIGH INTENSITY

Abstract

1395 The purpose of the present study was to evaluate whether deviations of the respiratory quotient (RQ) measured by spirometry (RQs) exceeding 1,0 can be ascribed solely to changes in body CO2 content. 9 male middle and long distance runners (age 22.9 ± 3.9 years, LBM 61.3 ± 5.1 kg. 4 mmol-threshold 4.47 ± 0.31 m/s) underwent two exercise tests of a constant load (4.59 ± 0.19 m/s, 15 to 30 minutes duration) with and without a 3-minute preload of supramaximal intensity (5,48 ± 0.25 m/s) on a treadmill. VCO2, VO2 (by open spirometry), arterialized capillary blood lactate concentration, PaCO2 and pH were measured to correct RQs. We used the formula given by CLODE et al. 1969 and a self developed algorithm for calculating the metabolic RQ (RQm). Our findings show that under conditions of constant load near the maximal lactate steady state blood lactate concentration (SSCLa) is associated with values of RQs clearly exceeding 1,0. Even after using the correction formulas the RQm still remains elevated. Correction by the self developed algorithm (RQGM) diminishes the steady state RQ more effectively than by the formula of CLODE et al.(RQCC). TableTableOur self developed algorithm contains correction formulas for different influences, including ventilatory, acid-base-equilibrium and those dependent on further metabolic pathways. Neglecting the latter influence RQs still clearly exceeds 1,0 even during steady state conditions (no preload: 0.9843 ± 0.025, preload: 1.036 ± 0.047). It can be concluded that the deviation of the RQs during exercise of high intensity can not be assigned solely to changes of CO2 content. Further research is needed to elucidate the kind of metabolic pathways which influence the RQs to higher values.