The data will be analyzed using mixed-factor ANOVA with time (pre- and post-) as a within-subjects factor and condition (exercise or control) as a between-subjects factor on learning and memory, hippocampal, and cardiorespiratory fitness outcomes (see Specific Aims/Hypotheses 1 and 2 in the Primary Study Objectives and Study Hypothesis sections). Effect sizes will be expressed as partial eta-squared (ηp2) and Cohen's d [Cohen, 1988]. Spearman's rho rank-order correlations (ρ) will be performed for the associations among changes in cardiorespiratory fitness, hippocampal structure/function, and learning and memory for those who underwent the treadmill walking exercise training condition (See Specific Aims/Hypotheses 3 and 4 in the Secondary Study Objectives and Study Hypothesis sections). The effect sizes from the interaction terms from the ANOVAs and correlations will serve as effect sizes for the subsequent power analyses required for a subsequent Phase II RCT.