The aims of the present study were 1) to re-assess two existent methods and to increase consistency of kef-estimates, defined as the half maximal constant of the relative rate of carbohydrate oxidation (relCHOox) approximated as a function of blood lactate concentration (BLC) (relCHOox = 100/(l+kelIBLC2), 2) to identificate the fitting models, which adequately described oxygen uptake (V02), carbon dioxide (VC02) and BLC during incremental exercise tests, which allowed 3) to examine the relationship between kef and given indicators of maximal and sub-maximal performance, and 4) to analyse the effect of gender on kel. To address aims 1 to 3, 104 subjects performed an incremental power test with V02, VC02 and BLC measurements. 59 tests provided four or more power increments before the respiratory exchange ratio (RER) reached 1.0. Main findings: 1) kef-approximations excluding stages with RER higher than 1.0 and/or evidence of hyperventilation provided highest kel-estimates (p < 0.01).2) BLC during progressive exercise was more appropriately described as a continuous mono-exponential function whereas V02 and VC02 provided a better fit when a multiple linear threshold responses model was applied. 3) kel was independent of peak performance or intensity at lactate threshold at 2 and 4 mmol•rl or at maximum rate of fat oxidation. However, kel was interrelated (p < 0.01) with cross-over point (equal energy derived from carbohydrate and fat oxidation). To address aim 4, 14 males and 11 females were tested with incremental power tests providing increasing relCHOox at four or more subsequently increasing power stages with an RER< 1.0, kel was independent of gender. Highest kel-approximates after exclusion of stages with RER > 1.0 and/or evidence of hyperventilation suggests underestimation of kef in previous studies. Interrelation between kel and cross-over point intensity supports kel as an indicator of CHO management during exercise, which is independent of peak performance, lactate threshold concepts, maximum fat oxidation and gender.