There are many studies quantifying the anaerobic contribution in high intensity exercises with or without intervals. However, the anaerobic contribution during lower intensities have not been investigated sufficiently. The aim of this study was to quantify the anaerobic contribution in the low to moderate intensity range when including intensity fluctuations, and to investigate the effects of fluctuations with different amplitudes during stationary bicycle pedaling exercise. Fifteen participants ranging from sedentary to well-trained performed three tests. Thie first was a maximal test and was performed to obtain the maximal aerobic power (MAP) of the participants, with 5-minute incremental stages of 25 W until fatigue. The second and third tests were the main tests for quantification of the anaerobic contribution and included four modalities of low to moderate intensity fluctuations around 50% or 60% MAP with the amplitude of ±5% or ±10%MAP, where each modality was composed of 10 bouts of 2 minutes. Participants performed two of the four modalities on each of the main test days in a randomized cross-over order. When instances of negative values for anaerobic metabolic rate were converted to zero (pos.AnaMR), the relative anaerobic contribution was around 4% and 7.5% for amplitudes of ±5% MAP and ±10% MAP respectively, no matter if the baseline intensity was at 50% or 60% MAP. There was statistically significant effect of amplitude on AnaMR (p<0.001) but not for effect of intensity (p=0.226) and the interaction effect (p=0.429). The relative anaerobic contribution when those negative instances of AnaMR were taken into consideration (net AnaMR) was around 1.5% for all the four modalities with no statistically significant effect of intensity (p=0.236), amplitude (p=0.719) or interaction effect (p=0.784) on AnaMR.When taking the pos.AnaMR into account, there is a substantial increase in the relative AnaMR at each intensity from amplitude of ±5% MAP to ±10 MAP. This denotes that the effect of amplitude on the relative AnaMR is much bigger than that of intensity of low to moderate range, considering that the changes in intensity did not have significant effect on AnaMR by itself.