Specifically, we examined whether higher fitness levels would be associated with greater concentrations of N-acetylaspartate (NAA). NAA is a nervous system specific metabolite (Nadler and Cooper 1972) found predominantly

in cell bodies of neurons (Moffett et al. 1991). We reasoned that if aerobic fitness was predominantly influencing cerebral vasculature, NAA levels should not vary as a function of aerobic fitness. However, if aerobic fitness influences the number or viability of neurons, in addition to possibly influencing vasculature, then higher aerobic fitness levels Inhibitors,research,lifescience,medical should be associated with greater concentrations of NAA or offset any age-related reduction in NAA. Such a finding would support the argument that aerobic fitness influences neuronal viability in aged humans and provides additional insight about the mechanisms by which fitness enhances cognition. Methods Participants

One hundred Inhibitors,research,lifescience,medical thirty-seven community-dwelling participants (90 females; 47 males) between the ages of 58 and 80 years (mean age = 66.08; SD = 5.50 see Table 1) were recruited from Champaign-Urbana and east-central Illinois to participate in a randomized exercise intervention trial spanning one year. The results described in this study are limited to the baseline assessment of cardiorespiratory fitness and NAA. All participants were screened for cognitive impairment Inhibitors,research,lifescience,medical using the modified Mini-Mental Status Examination (Stern et al. 1987) and were excluded if the minimum score of 51 was not obtained (maximum score of 57). Additional inclusion criteria consisted of having normal or corrected to

normal vision, absence of clinical RG7204 Depression as measured by the five-item Inhibitors,research,lifescience,medical Geriatric Depression Scale (>3; Sheikh and Yesavage 1986), and not very physically active as defined by participation in physical activity on two or fewer days of the week in the Inhibitors,research,lifescience,medical past six months. All participants met or surpassed safety criteria for participating in an MR study, including no history of head trauma, head or neck surgery, diabetes, neuropsychiatric or neurological conditions including brain tumors, or having any ferrous metallic implants that could cause injury due to the magnetic field. Individuals reporting the use of psychiatric or neurological medications were excluded from participation in the study. Finally, all participants provided physician’s 3-mercaptopyruvate sulfurtransferase consent to engage in fitness testing and signed an informed consent approved by the University of Illinois. Table 1 Participant characteristics. Aerobic fitness assessment Aerobic fitness (VO2 peak) was assessed by graded maximal exercise testing on a motor-driven treadmill. The participant walked at a speed slightly faster than their normal walking pace (1.5–4.3 miles per hour), with increasing grade increments of 2% every other minute.