The Experimental Effects Of Acute Exercise Duration On Episodic Memory

PURPOSE: The catecholamine hypothesis posits that elevated levels of noradrenaline, from high-intensity acute exercise, should enhance episodic memory performance. In support of this theory, past work demonstrates that high-intensity acute exercise improves episodic memory (e.g., Winter et al., 2007; Loprinzi et al., 2023). This theory also predicts that longer duration (i.e., > 30 minutes) moderate-intensity acute exercise will elevate noradrenaline and, consequently, improve episodic memory. The present experiment aimed to test this prediction by evaluating if, compared to a non-exercise control and shorter duration (20-min) moderate-intensity exercise, longer duration (40-min) moderate-intensity acute exercise would be optimal in improving episodic memory. METHODS: Twenty-three participants (Mage = 19.7 years) at the University of Mississippi completed a fully-crossed, counterbalanced, within-subject study design. Participants completed four primary conditions, including two non-exercise control conditions (20- and 40-min of rest) and two exercise conditions (20- and 40-min of moderate-intensity acute exercise). For all four conditions, and after rest/exercise, participants learned a list of 15 unique words. Memory (free recall) was assessed 20-minutes and 24-hours later. Linear mixed model analyses were computed separately for both memory outcomes, with Participant serving as a random effect variable and Condition (Control v Exercise) and Duration (20 or 40 min) as fixed effects variables. RESULTS: With the number of correctly recalled words at the 20-min delay as the outcome, the Type III tests of fixed effects yielded a main effect for Condition (p = .04); a main effect for Condition was also observed for the 24-hr recall period (p = .01). For these two assessment periods, memory recall was greater after exercise compared to after rest (Mdiff = .75 to 1.07, p < .05). No main effects for Duration or an interaction between Condition and Duration were observed for memory performance at either recall period (ps > .23). CONCLUSION: Moderate-intensity acute exercise is effective in enhancing long-term episodic memory performance. This effect occurred for shorter and longer durations of acute exercise, countering the predictions of the catecholamine hypothesis.