One likely factor which may influence physical activity adherence is perceived exercise effort. The study investigators reported, based on a small study, that perceived exercise effort is worse in people with T2D than in healthy obese controls, as measured by the Borg Rating of Perceived Exertion (RPE), even during low intensity exercise. Thus, one strategy to increase physical activity in T2D is to first identify the mediators of RPE in the proposed study and then to address them in future studies. The preliminary data suggest that likely mediators of RPE are both objective and subjective in nature. A key objective mediator of RPE is serum lactate level during exercise, which is a physiological marker of effort, and is disproportionately elevated in people with T2D vs. healthy controls. A key subjective mediator of RPE is self-efficacy, which influences the perception of exercise effort, and is disproportionately worse in people with T2D vs. healthy controls. To develop optimal physical activity interventions for people with T2D, the study investigators must understand whether RPE differences vary across the spectrum of exercise intensities (Aim 1), and the investigators must also determine the mediators of RPE across exercise intensities (Aim 2). Mediators of RPE in low-to-moderate intensity exercise are particularly important, because walking is a preferred physical activity for people with T2D.