Three-Phase Time Course of Physiological Variables During Incremental Cycling In Young Male and Female Subjects

Abstract

There is still some debate on the time course of selected physiological variables during incremental exercise that may be used for the determination of objective sub maximal markers of performance. PURPOSE: The aim of our study was to re-examine the lactate turn-point concept introduced schematically in 1980 compared to selected markers of exercise performance. METHODS: Fifty young, healthy male (25) and female (25) sport students served as subjects in this investigation. The first (LTP1) and the second (LTP2) lactate turn-point as well as first and second turn-points (TP) for heart rate (HR) and the ventilatory variables of pulmonary ventilation (VE), fractional expired oxygen (FEO2) and carbon dioxide (FECO2), tidal volume (VT), breathing frequency (fB), oxygen uptake (VO2), and carbon dioxide production (VCO2) were determined by means of computer aided linear regression break point analysis. RESULTS: All measured variables showed an observable three-phase behavior and two turn-points could be determined in most cases. LTP1 and LTP2 could be detected in all subjects. Most of the first and all of the second turn-points were significantly related in both female and male subjects, respectively. No significant difference could be found between all first turn-points with the exception of HRTP1 in male and female subjects, respectively. No significant difference could be found between all second turn-points for power output (P), heart rate (HR), blood lactate concentration (La) and oxygen uptake (VO2) in both male and female subjects. All variables except lactate (LA) and breathing frequency (fB) were significantly different between female and male subjects at comparable sub-maximal percentages of maximal power output. CONCLUSION: We suggest that the turn-point concept may be applied to almost all physiological variables obtained in a standard incremental cycle ergometer exercise test. The significant relationship of all second TPs suggests a general change in the whole body regulation at this defined submaximal exercise performance.