The purpose of the present investigation was to examine the effects of an exercise-based intervention on the daily physical activity (PA) above the lactate threshold under free-living conditions. A total of 81 middle-aged to older males (51 +/- 7 years) were randomly assigned into one of 2 groups. The subjects' body weight, visceral fat area, lactate threshold (LT), and PA levels were measured before and after the 8-week lifestyle intervention. The PA levels were assessed using a pedometer with a uni-axial accelerometer (Lifecorder, Kenz, Nagoya). During the intervention, 300 min/week of exercise at LT was targeted in the exercise group. The LT was determined by the log-log transformation method. The subjects in the control group were instructed to maintain their usual lifestyles. In the exercise group, the body weight, visceral fat area and LT significantly improved after the intervention. In contrast, the duration of PA at an intensity of LT, >3 METs and >6 METs did not differ significantly. The present investigation did not find significant changes in the PA at LT under free-living conditions as a result of an 8-week exercise-based intervention, although the participants successfully improved their aerobic capacity and body composition.