Exercise duration and intensity are important parameters in exercise prescription and play a major role in improving insulin sensitivity (including transient and persistent improvement effects following cessation of training) in patients with type 2 diabetes mellitus (T2DM). However, whether duration or intensity of exercise is the more important factor has yet to be established. Therefore, we aimed to determine whether exercise prescriptions differing in duration and intensity differ in their ability to aid T2DM patients to retain insulin sensitivity following the conclusion of a period of training. Sedentary T2DM patients (age 51.2 ± 1.3 years) were assigned to either a low-intensity (50% VO(2peak), n = 27) or a high-intensity exercise group (75% VO(2peak), n = 28), and followed a 12-week exercise program of 5 sessions/week and 240 kcal/session. Insulin sensitivity (oral glucose tolerance test, ISI) was measured when subjects were sedentary and at 16-24 h and 15 days after the final training bout. The low-intensity group spent more training time to training per exercise session than the high-intensity group (56.1 ± 3.0 min/session vs. 34.3 ± 2.4 min/session) (P < 0.01), but the total amount of energy expended was the same. ISI was increased in both groups 16-24 h after the final training session, but only the low-intensity group still had elevated ISI 15 days after the cessation of training. These findings suggest that in T2DM patients, the persistent training-induced improvements in insulin sensitivity may be more dependent on exercise duration than exercise intensity in regimens with the same level of energy expenditure.