“…For instance, studies have shown that physical activity and fitness are separable at the level of individual differences (Jacobs et al, 1993; Laye et al, 2015; Williams, 2001), either because it is feasible that the same individual can achieve daily moderate-to-vigorous exercise while being sedentary the rest of the day (Craft et al, 2012; Pate et al, 2008), or because there are determinants of cardiorespiratory fitness that account for variance beyond habitual physical activity such as genetics, which may account for about half of the variance in individual differences in fitness (Bouchard et al, 1999; Bouchard et al, 2011). In addition, more nuanced approaches for objectively measuring physical activity are now available (Chen et al, 2012; Rowlands et al, 2015), and these provide an opportunity to more objectively test what features of daily physical activity (Copeland and Esliger, 2009; Tudor-Locke et al, 2013) are associated with brain health in aging populations (Makizako et al, 2014; Varma et al, 2014).…”