The purpose of this study was to identify the limiting factors for VO2max and quantitatively estimate the contribution of those factors by the Regression model for trained runners and untrained students. Ten untrained male college students and ten male collegiate distance runners participated in this study. VO2max, Qmax, and HRmax were measured during a graded exercise test on treadmill. No differences existed in HRmax and a-vO2 diffmax between the two groups. The runners had the greater values of VO2max, Qmax, and SVmax (r < 0.01), but the smaller value for body mass (r < 0.05). VO2max was not correlated to Qmax, a-vO2 diffmax, HRmax, SVmax, and body mass for the students. Whereas, VO2max was positively correlated to Qmax and a-vO2 diffmax (r < 0.01), negatively correlated to HRmax (r < 0.05) and body mass (r < 0.01), but not correlated to SVmax for the runners. Further analysis using the Stepwise Regression yielded a model for the runners, VO2max=1.245 a-vO2 diffmax + 0.769 Qmax – 0.603 Wt. – 0.0004 (r < 0.01). To compare the runners with the students, O2 transport capacity was responsible for the change in VO2max with training, which were consistent with the cross-sectional studies. However, both O2 transport and utilization capacities were critical in determining VO2max for the runners if the Regression procedure was used as the experimental model. According to the model, the a-vO2 diffmax had the greatest contribution in determining runner’s VO2max. Therefore, whether oxidative capacity in skeletal muscle is a limiting factor for VO2max depends on the experimental model. Since no limiting factors were correlated to VO2max and no regression model was yielded for the students, it seems that endurance training changes the relationship between VO2max and its limiting factors. The relationship between VO2max and its limiting factors seems specific to populations varied with conditioning. The primary limiting factors for VO2max may be changeable according to the length of training.