Enhancing memory through physical activity: beneficial effect on internal memory strategy use in older adults

The aim was to evaluate the use of an internal strategy (i.e., subjective organization) in relation to physical activity (PA) level in older adults. We expected (1) an effect of age on memory performance and subjective organization, in favor of younger adults, and (2) an association between PA and memory performance and between PA and organization index, particularly in older adults. Forty-five younger (M = 27.58 yo) and 45 older adults (M = 71.49 yo) learned a list of 19 semantically unrelated concrete nouns and took three consecutive recalls. An index was calculated from the order in which the words were recalled (pairwise frequency index, PFI). Participants reported their PA over the past year. Three General Linear Models were conducted to examine: (1) the effect of age and PFI on memory, (2) the effect of age and PA on memory, and (3) the effect of age and PA on PFI. Mediation analyses tested whether subjective organization (PFI) mediated the relationship between PA and memory recall. Younger adults recalled more words and used more subjective organization than older adults. In both age groups, those with better memory performance also used more subjective organization. Positive correlations were found between PA and memory performance in both younger and older adults, and between PA and subjective organization only in older adults. The mediation analysis revealed that PA's effect on memory was partially mediated by subjective organization, explaining 39% of the effect. The present study revealed that higher PA level in older adults was associated with increased recall and use of subjective organization strategy, addressing a gap in understanding the benefits of PA on memory during aging. The results are discussed in terms of the possible implication of executive functions, particularly for their role in implementing effective memory strategies during encoding.