Motor behavior-induced prefrontal cortex activation and episodic memory function.

BACKGROUND: The objective of this paper was to evaluate the potential individual and combined effects of acute exercise coupled with bilateral interhemispheric activation on episodic memory function. Six experiments were conducted. METHODS: Experiment 1 was a within-subject, counterbalanced experiment. Participants completed four visits, including 1) exercise and saccadic eye movements, 2) exercise only, 3) saccadic eye movements only, and 4) no exercise and no saccadic eye movements (control). A word-list memory assessment was employed, including a long-term (20-min delay) memory evaluation. In Experiment 2, we evaluated the effects of saccadic eye movements on prefrontal cortex oxygenation, a proxy for neuronal activity. Similarly, in our third experiment, we evaluated the effects of acute exercise on prefrontal cortex oxygenation. Thus, experiments 2 and 3 were employed to provide mechanistic insights from the results shown in experiment 1. Experiment 4 replicated Experiment 1, but instead of increasing prefrontal cortex activation via saccadic eye movements, we used a fist clenching protocol. Experiment 5 evaluated the effects of fist clenching on prefrontal cortex oxygenation. RESULTS: Collectively, these 5 experimental studies showed that acute exercise (Experiment 1), saccadic eye movements (Experiment 1), and fist clenching (Experiment 4) enhanced memory function, and that acute exercise (Experiment 3), saccadic eye movements (Experiment 2) and fist clenching (Experiment 5) all increased prefrontal cortex oxygenation. Experiment 6 demonstrated that prefrontal cortex oxygenation was positively associated with episodic memory function. CONCLUSION: These six experiments suggest that several behaviors, such as acute exercise, saccadic eye movements and fist clenching may improve memory function and may, potentially, do so via increases in prefrontal cortex oxygenation.

The Temporal Effects of Acute Exercise on Episodic Memory Function: Systematic Review with Meta-Analysis.

BACKGROUND: Accumulating research demonstrates that the timing of exercise plays an important role in influencing episodic memory. However, we have a limited understanding as to the factors that moderate this temporal effect. Thus, the purpose of this systematic review with meta-analysis was to evaluate the effects of study characteristics (e.g., exercise modality, intensity and duration of acute exercise) and participant attributes (e.g., age, sex) across each of the temporal periods of acute exercise on episodic memory (i.e., acute exercise occurring before memory encoding, and during memory encoding, early consolidation, and late consolidation). Methods: The following databases were used for our computerized searches: Embase/PubMed, Web of Science, Google Scholar, Sports Discus and PsychInfo. Studies were included if they: (1) Employed an experimental design with a comparison to a control group/visit, (2) included human participants, (3) evaluated exercise as the independent variable, (4), employed an acute bout of exercise (defined as a single bout of exercise), (5) evaluated episodic memory as the outcome variable (defined as the retrospective recall of information either in a spatial or temporal manner), and (6) provided sufficient data (e.g., mean, SD, and sample size) for a pooled effect size estimate. Results: In total, 25 articles met our inclusionary criteria and were meta-analyzed. Acute exercise occurring before memory encoding (d = 0.11, 95% CI: -0.01, 0.23, p = 0.08), during early memory consolidation (d = 0.47, 95% CI: 0.28, 0.67; p < 0.001) and during late memory consolidation (d = 1.05, 95% CI: 0.32, 1.78; p = 0.005) enhanced episodic memory function. Conversely, acute exercise occurring during memory encoding had a negative effect on episodic memory (d = -0.12, 95% CI: -0.22, -0.02; p = 0.02). Various study designs and participant characteristics moderated the temporal effects of acute exercise on episodic memory function. For example, vigorous-intensity acute exercise, and acute exercise among young adults, had greater effects when the acute bout of exercise occurred before memory encoding or during the early memory consolidation period. Conclusions: The timing of acute exercise plays an important role in the exercise-memory interaction. Various exercise- and participant-related characteristics moderate this temporal relationship.

Experimental Evaluation of the Joint Effects of Exercise and Sedentary Behavior on Cognitive Function.

BACKGROUND: The objective of this study was to evaluate the potential joint effects of sedentary behavior and exercise on cognitive function. METHODS: Participants (Mage = 20 yrs) were randomly assigned to one of three experimental groups. The No Exercise Group (n = 19) was instructed to reduce steps to less than 5000/day and were not allowed to exercise for one-week; the Reduced MVPA (moderate-to-vigorous PA) Group (n = 18) was instructed to reduce steps to less than 5000/day but exercised for 50% of their previously reported vigorous PA for one-week; and the Control Group (n = 20) maintained normal activity for one-week. Cognitive functions (via Stroop and Trail Making tasks) were assessed at baseline, post-intervention, and after one week of resumed normal activity for the intervention groups. RESULTS: Statistically significant main effects for time were observed for Stroop Congruent (Ftime = 11.7, p < 0.001, η 2 p = 0.18), Stroop Incongruent (Ftime = 19.4, p < 0.001, η 2 p = 0.26), Stroop Control (Ftime = 54.4, p > 0.001, η 2 p = 0.50), Trail Making-A (Ftime = 19.1, p < 0.001, η 2 p = 0.26) and Trail Making-B (Ftime = 13.8, p < 0.001, η 2 p = 0.21) tasks. However, there were no statistically significant group x time interactions (all p's > 0.05) for any of the cognitive parameters. CONCLUSION: These experimental findings do not suggest an interaction effect between sedentary behavior and physical activity on cognitive function.

Experimental effects of exercise on memory function among mild cognitive impairment: systematic review and meta-analysis.

OBJECTIVE: The objective of this study was to evaluate the experimental effects of exercise on memory function among adults with mild cognitive impairment (MCI). METHODS: A systematic review and meta-analysis were employed. Studies were identified using electronic databases, including PubMed, PsychInfo, SPORTDiscus, and Google Scholar. To be eligible for inclusion, studies had to employ an experimental design, be conducted in humans (no animal models) with mild cognitive impairment, include an exercise intervention arm (either acute exercise or chronic training), and measure memory function (any type) as the outcome measure. Comprehensive Meta-Analysis software was used to compute the standardized mean difference effect size (Cohen's d) and 95% CI using a random-effects model. RESULTS: In total, 11 studies met our criteria, contributing to 20 effect size estimates. Among the 20 effect size estimates, 13 contributed to a short-term memory recall, with 7 contributing to a delayed/long-term memory recall. The overall weighted mean effect size was d = 0.30 (95% CI: 0.16-0.44; P < 0.001), indicating a small to medium effect of exercise on improving memory function. For the moderation analysis, there was no evidence of a moderation effect for recall duration (Q = 0.004, df(1), P = 0.95), as exercise (vs. control) demonstrated both short-term (d = 0.31; 95% CI: 0.14-0.47; P < 0.001) and long-term memory (d = 0.29; 95% CI: 0.06-0.53; P = 0.013) benefits. CONCLUSION: Current evidence suggests that exercise may help to improve memory function among those with MCI. Safe and progressive forms of exercise should be promoted among MCI patients.

Experimentally investigating the joint effects of physical activity and sedentary behavior on depression and anxiety: A randomized controlled trial.

OBJECTIVE: To experimentally examine whether increasing sedentary behavior, among a young adult active population, for one week is still associated with increased depression and anxiety symptomology even when allowing for a moderate engagement in physical activity (PA). METHODS: Participants were confirmed as active via self-report and accelerometry during baseline and randomly assigned to one of three experimental groups. The No Exercise Group (n = 19) was instructed to reduce steps to less than 5000/day and were not allowed to exercise for one-week; the Reduced MVPA (moderate-to-vigorous PA) Group (n = 18) was instructed to reduce steps to less than 5000/day but exercised for 50% of their previously reported vigorous PA for one-week; and the Control Group (n = 20) maintained normal activity for one-week. PA, depression, and anxiety levels were assessed at baseline, post-intervention, and after one week of resumed normal activity for the intervention groups. RESULTS: The experiment was successful in altering physical activity levels among the intervention groups and maintaining activity habits in the control group (FInteraction = 16.053, P < 0.001, η2p = 0.391). Anxiety and depression symptomology remained constant across the two time periods in the control group. For both intervention groups (No Exercise Group and Reduced MVPA Group), depression statistically significantly increased during the inactive week and then resumed back to baseline levels after a week of resumed activity. However, there were no differential trends in anxiety (FInteraction = 0.073, P = 0.897, η2p = 0.002) or depression (FInteraction = 0.276, P = 0.760, η2p = 0.008) among these two intervention groups. CONCLUSION: We provide experimental evidence that reducing habitual physical activity causes an increase in depression symptomology among young active adults. We did not, however, observe a joint effect of sedentary behavior and exercise on changes in anxiety and depression. At this point, it is still uncertain as to whether reduced MVPA or increased sedentary behavior were driving the observed changes in psychological function. Future research may help determine if these negative effects are from increased sedentary behavior or a reduction in MVPA.

Randomized controlled trial investigating the experimental effects of reduced habitual physical activity on cardiometabolic profile.

OBJECTIVE: Previous work suggests that reduced habitual physical activity is unfavorably associated with cardiometabolic health. Fewer lifestyle-based, experimental studies on this topic have been conducted. Thus, the purpose of this study was to experimentally reduce habitual physical activity over a one-week period to evaluate its potential effects on cardiometabolic profile. METHODS: Young physically active adults (Mage = 21 yrs) were randomized into a Reduced Activity Group (N = 19) or a Control Group (N = 20). The Reduced Activity group engaged in baseline week of normal activity, then reduced their activity for one week (from approximately 9000 steps/day to approximately 6000 steps/day), followed by resumption of habitual activity for a week. The Control Group maintained their normal active lifestyle for two-weeks. At all time points, the following cardiometabolic parameters were assessed: systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), atherogenic index of plasma (AIP), TC/HDL-C, LDL-C/HDL-C, TG/HDL-C, non-HDL-C, and glucose. RESULTS: The Reduced Activity Group, compared to the Control Group, had an unfavorable change in TG/HDL-C (FInteraction = 4.995, P = 0.03, η2p = 0.14). No other biomarkers were altered CONCLUSION: A one-week period of reduced activity among a young adult, active population, increased TG/HDL-C levels, with no changes observed in any of the other evaluated cardiometabolic parameters. Thus, a temporary lapse in habitual physical activity does not considerably change cardiometabolic outcomes in young, healthy physically active adults.