Prescription of aerobic exercise for Type 2 diabetes mellitus (Type 2 DM) in clinical practice is frequently based on exercise intensity at maximum heart rate (60<HR(max)<79%), heart rate reserve (50<HR(reserve)<74%), and rating of perceived exertion (12<RPE<13). We examined these parameters in Japanese males with Type 2 DM at ventilatory threshold (VT) to investigate the exercise capacity of Type 2 DM patients and re-evaluate the exercise prescription. Fifty-six Japanese Type 2 DM males without autonomic neuropathy [age, 53.5+/-7.7 years; body mass index (BMI), 23.7+/-3.6 kg/m(2)] were enrolled and compared with 56 age- and BMI-matched healthy Japanese males. VT was determined breath by breath during exercise test using a ramp protocol and rates of oxygen consumption (VO(2)), work rate (WR), HR, DeltaHR, %HR(max), %HR(reserve), and RPE were measured at VT. Type 2 DM patients had significantly lower VO(2) (3.6+/-0.4 metabolic equivalents (METs)) and WR (62+/-14 W) than controls (VO(2), 3.9+/-0.6 METs; WR, 74+/-13 W). %HR(reserve), (32.6+/-7.7%) was also significantly lower compared with controls (37.6+/-8.3%), while %HR(max), was not different. RPE was also similar in diabetics (12.4+/-1.5) and controls (12.9+/-1.2), however, it was significantly lower in diabetic patients aged 60-69 years (11.8+/-2.0) and those with distal symmetric sensory neuropathy (12.2+/-1.0). Our results indicate reduced exercise capacity in Japanese Type 2 DM males and the exercise intensity of 60%HR(max), 30%HR(reserve), and RPE 12 is recommended in elderly diabetics and those with diabetic sensory neuropathy.