Time-Dependent Effects of Cardiovascular Exercise on Memory

Effects of an aerobic fitness test on short- and long-term memory in elementary-aged children

Meta-analytic evidence supports that exercise has benefits for short-term memory (STM) and long-term memory (LTM). However, only three studies with children have tested the differential effects of exercise on STM and LTM. The purpose of this study was to examine the effects of an aerobic fitness test on STM and LTM and to consider the moderating effects of grade level. Children (7-13 years of age) were randomly assigned to either perform an aerobic fitness test before (exercise prior) or after (exercise post) performing the Rey Auditory Verbal Learning Test (RAVLT) to assess memory. Memory was tested again after approximately 24 hours. There were significant differences in memory performance as a function of grade with 4^th and 6^th graders consistently outperforming 2^nd graders. For learning, Day 1 Retention, 24-hr recall, and Day 2 Retention, the exercise prior group performed better than the exercise post group. It is concluded that an aerobic fitness test performed prior to a declarative memory test benefits LTM as compared to when the aerobic fitness test is performed after the memory test.

Effects of acute cardiovascular exercise on motor memory encoding and consolidation: A systematic review with meta-analysis

Emerging evidence indicates that acute bouts of cardiovascular exercise promote motor memory formation. In this preregistered meta-analysis (CRD42018106288) we synthesize data from 22 studies published until February 2020, including a total of 862 participants. We calculated standardized mean differences (SMDs) with 95 % confidence intervals (CIs) to assess exercise effects on motor memory encoding and consolidation, respectively. The pooled data indicate that exercise mainly benefits the consolidation of memories, with exercise prior to motor practice improving early non-sleep consolidation (SMD, 0.58; 95 % CI, 0.30-0.86; p < 0.001), and post-practice exercise facilitating sleep-dependent consolidation (SMD, 0.62; 95 % CI, 0.34-0.90; p < 0.001). Strongest effects exist for high exercise intensities, and motor task nature appears to be another relevant modulator. We demonstrate that acute cardiovascular exercise particularly promotes the consolidation of acquired motor memories, and exercise timing, and intensity as well as motor task nature seem to critically modulate this relationship. These findings are discussed within currently proposed models of motor memory formation and considering molecular and systemic mechanisms of neural plasticity.

Performance on an Associative Memory Test Decreases 8 hr After Cardiovascular Exercise

This study was designed to assess the effects of acute exercise on performance of a paired associate learning (PAL) test, an operationalization of hippocampal-dependent associative memory. Participants performed a PAL test and then ran on a treadmill (exercise group, n = 52) or solved Sudoku puzzles (control group, n = 54). Participants returned 2, 5, or 8 hr later to perform a second, different, PAL test. PAL scores for the control group did not change over time. Similarly, scores on tests taken 2 and 5 hr after exercise were not different from baseline or control data. Scores on tests taken 8 hr after exercise, however, fell significantly below baseline (by 8.6%) and control (by 9.8%) scores. These data demonstrate that acute exercise can negatively affect the encoding and retrieval of new information even hours after the exercise bout, which should be a consideration when designing exercise programs to enhance, and not hinder, learning.

Cognitive-Motor Dual Task Interference Effects on Declarative Memory: A Theory-Based Review

Bouts of exercise performed either prior to or immediately following study periods enhance encoding and learning. Empirical evidence supporting the benefits of interventions that simultaneously pair physical activity with material to be learned is not conclusive, however. A narrative, theory-based review of dual-task experiments evaluated studies in terms of arousal theories, attention theories, cognitive-energetic theories, and entrainment theories. The pattern of the results of these studies suggests that cognitive-motor interference can either impair or enhance memory of semantic information and the manner in which physical activity impacts working memory within executive processing appears to explain disparate outcomes. The integration and timing of physical movements in concert with the type of information to be encoded and remembered appears to be a critical requirement for learning. These observations have implications for the role of physical activity in education, rehabilitation, and gerontological settings.

Acute physical exercise promotes the consolidation of emotional material

Physical exercise can improve cognitive functions and promote learning and memory, especially when performed in close temporal proximity to the encoding of information. This benefit may occur due to circulating stress hormones released in response to acute exercise. When administered after encoding, acute stress typically enhances the consolidation of emotional stimuli. However, whether acute exercise also selectively modulates emotional memories remains to be explored. Likewise, the potential role of sex in moderating these effects has not been addressed so far. Here, we tested whether a single bout of aerobic exercise after learning boosts the consolidation and thus long-term memory for emotional versus neutral visuospatial stimuli. Healthy men and women learned an object-location task and subsequently were exposed to a vigorous-treadmill running task or control intervention. Memory was assessed 24 h later. Acute exercise significantly increased heart rate and salivary cortisol in both sexes and selectively facilitated the consolidation of emotional stimuli. In particular, we found improved memory for negative items in women and better recall of positive items in men following exercise exposure. This memory benefit was positively related to the increase in heart rate and cortisol in both men and women, suggesting that the favorable effects of acute exercise on emotional memory may be mediated via a co-activation of the sympathetic nervous system and the hypothalamus-pituitary-adrenocortical axis. Our findings thereby provide first evidence for the improvement of emotional memory consolidation by acute physical exercise that appears to rely on similar neuroendocrine mechanisms as psychosocial stressors. Given that exercise is healthy, cost-effective and practical in nature, it constitutes an ideal behavioral intervention strategy for boosting memory in clinical and educational settings alike.

Acute Effects of Aerobic Exercise on Cognitive Attention and Memory Performance: An Investigation on Duration-Based Dose-Response Relations and the Impact of Increased Arousal Levels

Current evidence indicates that acute aerobic exercise might increase domain-specific cognitive performance. However, only a small number of studies deduced the impact on lower and higher cognitive functions systematically or analyzed dose-response relationships and the underlying mechanisms. This study aimed to expose the dose-response relationships by investigating the influence of exercise duration on subjective and objective arousal, cognitive attention and visual recognition memory tasks. Nineteen participants (eight female; 25.69 ± 3.11 years) were included in a randomized, three-armed intervention study in a cross-over design. The participants completed three different interventions consisting of either 15, 30 or 45 min of cycling at 60-70% VO₂max. Arousal and cognitive measurements were taken before and immediately after (<2 min) exercise. All three interventions led to significant but comparable effects on self-perceived arousal, heart rate (HR) and rating of perceived exertion (RPE) (p < 0.05). Analysis of variance (ANOVA) indicated significant effects of exercise duration on visual recognition memory accuracy. Reaction times for higher and lower cognitive tasks did not change after exercise. Fifteen minutes of aerobic exercise was feasible to induce beneficial changes in self-perceived arousal. Processing speed of visual recognition memory and attention remained unaltered. Exercise exceeding fifteen minutes seemed to negatively impact visual recognition memory accuracy.

Running During Encoding Improves Word Learning for Children

The learning of new information is an important task in everyday life, especially at a young age. Acute physical exercise can facilitate cognitive processes in multiple ways, and previous studies have shown that memory can profit from physical exercise before and during the encoding of vocabulary. The current study investigates the interplay of movement and vocabulary learning and also addresses lifespan differences in these effects. Participants were recruited in a recreational basketball club. Children (n = 24, M_age = 12.3 years; 13 girls), young adults (n = 30, M_age = 21.5 years; 17 women), and older adults (n = 24, M_age = 59.3 years; 9 women) learned 20 new pseudo-words, which corresponded to a German word. In a between-subjects design, encoding took place either while standing, while running, or while running and dribbling a basketball. Recall was assessed three times throughout the learning session and on the following day. In children, more words could be remembered in the running condition compared to the standing condition. There were no differences between conditions for the young and older adults. Age-dependent reasons for this pattern of results are discussed and embedded into the literature of physical exercise. Our result suggests that implementing learning activities into children’s physical education or exercise activities could be beneficial.

Acute Exercise Protects Newly Formed Motor Memories Against rTMS-induced Interference Targeting Primary Motor Cortex

Acute cardiovascular exercise can promote motor memory consolidation following motor practice, and thus long-term retention, but the underlying mechanisms remain sparsely elucidated. Here we test the hypothesis that the positive behavioral effects of acute exercise involve the primary motor cortex and the corticospinal pathway by interfering with motor memory consolidation using non-invasive, low frequency, repetitive transcranial magnetic stimulation (rTMS). Forty-eight able-bodied, young adult male participants (mean age = 24.8 y/o) practiced a visuomotor accuracy task demanding precise and fast pinch force control. Following motor practice, participants either rested or exercised (20 min total: 3 × 3 min at 90% VO_2peak) before receiving either sham rTMS or supra-threshold rTMS (115% RMT, 1 Hz) targeting the hand area of the contralateral primary motor cortex for 20 min. Retention was evaluated 24 h following motor practice, and motor memory consolidation was operationalized as overnight changes in motor performance. Low-frequency rTMS resulted in off-line decrements in motor performance compared to sham rTMS, but these were counteracted by a preceding bout of intense exercise. These findings demonstrate that a single session of exercise promotes early motor memory stabilization and protects the primary motor cortex and the corticospinal system against interference.

Effects of Physical Exercise on Working Memory and Attention-Related Neural Oscillations

Cognitive functions, such as working memory (WM) and attention, have been shown to benefit from physical exercise. Quantifying frequency-band-specific neural oscillatory patterns during the use of such cognitive functions can provide insight into exercise-induced benefits in the brain. Specifically, we investigated whether a 4-month physical exercise training influenced theta and alpha power measured in visual WM and attention tasks. The delayed match-to-sample (DMS) task required mnemonic discrimination of similar visual stimuli, akin to pattern separation, while the visual-attention search (VAS) task required detecting the presence of a specific object (i.e., target) in an image. Behavioral and electroencephalographic data were acquired during a DMS visual WM task and VAS task both before and after the intervention. Forty-three sedentary young adults (19–34 years) were pseudorandomly assigned to a training group (indoor treadmill, n = 20) or to a control group (n = 23). Compared to the preintervention baseline, the exercise group showed increased frontal alpha power (9–12 Hz) during the VAS task after the intervention. In addition, alpha power changes correlated positively with fitness changes. Behaviorally, there were no exercise-related effects on reaction times or accuracy in either task. Our findings substantiate that aerobic training of sedentary young adults may influence neural dynamics underlying visual attention rather than visual WM and mnemonic discrimination.

Acute exercise on memory function: open vs. closed skilled exercise

Background: Previous studies suggest that acute exercise may improve memory function. Few studies, however, have investigated the differential effect of the acute exercise movement patterns on memory. Such an effect is plausible, as research demonstrates that open-skilled exercise (e.g.,racquetball) may have a greater effect on memory-related neurotrophins (e.g., brain-derived neurotrophic factors) when compared to closed-skilled exercise (e.g. treadmill exercise). A key distinction between open- and closed-skilled exercise is that open-skilled exercises are those that require an individual to react in a dynamic way to a changing, unpredictable environment. Our aim in this study was to assess wether retrospective and prospective memory are differentially influenced from open- and closed-skilled acute exercise. Methods: A within-subject design was employed. Participants (Mage = 20.6 years; 69% female)completed two visits, in a counterbalanced order. The two experimental conditions included open-skilled acute exercise (racquetball) and closed-skilled acute exercise (treadmill exercise),each lasting 30-minute at 60% of heart rate reserve (HRR). During both experimental conditions,participants completed short- and long-term assessments of retrospective and prospective memory function. Retrospective memory was evaluated across multiple word-list trials (e.g.,Trials 1-6, 20-minute delay, 24-hour delay). Results: No significant effect of exercise was found on prospective memory. For retrospective memory, there was a significant main effect for condition, F(1, 57) = 5.33, P = 0.02, η2 = 0.004,main effect for trial, F(4.12, 234.9) = 227.85, P < 0.001, η2 = 0.46, but no condition by trial interaction, F(4.63, 264.08) = 1.022, P = 0.40, η2 = 0.002. Conclusion: Retrospective memory was greater after closed-skilled exercise (treadmill) when compared to open-skilled exercise (racquetball).

The Immediate Effects of Acute Aerobic Exercise on Cognition in Healthy Older Adults: A Systematic Review

BACKGROUND

Age-related cognitive decline is a worldwide challenge, highlighting the need for safe, effective interventions that benefit cognition in older adults. Harnessing the immediate and long-term pleiotropic effects of aerobic exercise is one approach that has gained increasing interest.

OBJECTIVE

The aim of this review is to provide knowledge on the immediate effects of acute aerobic exercise on cognitive function of healthy older adults and to assess the methodological quality of studies investigating these effects.

METHODS

A database search in PubMed, CINAHL, Cochrane Central Register of Controlled Trials, Embase, PsycINFO, Web of Science, ClinicalTrials.gov and Google Scholar was conducted using a systematic search strategy.

RESULTS

Fifteen studies were identified and cognitive domains investigated included executive function and visual perception. Results from 14 of 15 studies showed that an acute bout of aerobic exercise can enhance at least one subsequent cognitive performance of healthy older adults when measured within 15 min post-exercise.

CONCLUSION

The small number of studies available, the limited domains of cognition investigated, the great variability between research protocols, and the low overall quality rating limits the conclusions that can be drawn. More comprehensive randomised controlled trials are needed to address these limitations and verify the potential benefits of acute aerobic exercise.

Experimental Effects of Acute High-Intensity Resistance Exercise on Episodic Memory Function: Consideration for Post-Exercise Recovery Period

Background

The present experiments evaluated the effects of acute high-intensity resistance exercise on episodic memory.

Methods

Two experiments were conducted. For Experiment 1, participants (N = 40; M_age = 21.0 years) were randomized into one of two groups, including an experimental exercise group and a control group (seated for 20 min). The experimental group engaged in an acute bout of resistance exercises (circuit style exercises) for 15 minutes, followed by a 5-min recovery period. Memory function was subsequently assessed using a multiple trial (immediate and delay), word-list episodic memory task (Rey Auditory Verbal Learning Test, RAVLT), and then followed by a comprehensive, computerized assessment of episodic memory (Treasure Hunt task, THT). The THT involved a spatio-temporal assessment of what, where, and when components of episodic memory. Experiment 2 evaluated if altering the recovery period would influence the potential negative effects of high-intensity resistance exercise on episodic memory function. For Experiment 2, participants (N = 51) were randomized into the same acute resistance exercise protocol but either with a 10-min recovery period, 20-min recovery period, or a control group.

Results

For Experiment 1, for RAVLT, the exercise group performed worse (F_{group × time} = 3.7, p = .001, η ²p = .09). Across nearly all THT outcomes, the exercise group had worse spatio-temporal memory than the control group. These results suggest that high-intensity resistance exercise (with a 5-min recovery) may have a detrimental effect on episodic memory function. For Experiment 2, for RAVLT, the exercise with 10-min recovery group performed better (F_{group × time} = 3.1, p = .04, η ²p = .11). Unlike Experiment 1, exercise did not impair spatio-temporal memory, with the 20-min exercise recovery group having the best "where" component of episodic memory.

Conclusion

Collectively, the results from these two experiments suggest that acute high-intensity resistance exercise may impair episodic memory when a short exercise recovery period (e.g., 5-min) is employed, but with a longer recovery period (10+ min), acute high-intensity resistance exercise may, potentially, enhance episodic memory.

Effect of a Single Bout of Acute Aerobic Exercise at Moderate-to-Vigorous Intensities on Motor Learning, Retention and Transfer

Acute exercise influences human cognition, and evidence suggests that learning can be improved. According to the cognitive–energetic approach towards exercise cognition, exercise represents a stressor that elevates physiological arousal, which, in turn, increases the availability of mental resources. However, the degree of arousal is hypothesized to have optimal and suboptimal states, and moderate intensity exercise is thus considered to be favorable compared to low intensity and vigorous exercise. The current evidence for such a moderating effect of exercise intensity on motor learning, however, appears somewhat mixed. Therefore, the purpose of this study was to explore the effect of aerobic exercise conducted with different exercise intensities on immediate practice, transfer, and 24-h retention of a motor skill. To this end, young adults (n  =  40, mean (SD) age: 23.80 (1.98) years) were randomized to exercise at either 50% or 75% of age-predicted maximal heart rate according to the Karvonen formulae. Immediately after exercising, participants practiced a high-precision golf putting task in a blocked design. Retention and transfer of skill were assessed after 24 h. Results indicated that both groups demonstrated motor learning, retention, and transfer at a similar level. Further works are thus needed to establish the specific relationship between exercise and learning and establish the factors that have an influence.

Experimental Investigation Examining the Effects of Acute Exercise on Implicit Memory Function

Emerging work suggests that acute exercise can enhance explicit memory function. Minimal research, however, has examined whether acute exercise is associated with implicit memory, which was the purpose of this study. Three separate experimental studies were computed (N = 120; Mean age = 21). In Experiment 1, participants were randomly assigned to either a moderate-intensity bout of acute exercise (15-minute) or engaged in a seated control task (15-minute), followed by the completion of a word-fragmentation implicit memory task. Experiment 2 replicated Experiment 1, but instead employed a higher-intensity exercise protocol. For Experiment 3, participants were randomly assigned to either a moderate-intensity bout of acute exercise (15-minute) or engaged in a seated control task (15-minute), followed by the completion of a real world, 3-dimensional implicit memory task. For Experiment 1, the exercise and control groups, respectively, had an implicit memory score of 7.0 (0.5) and 7.5 (0.6) (t(38) = 0.67, p = .51). For Experiment 2, the exercise and control groups, respectively, had an implicit memory score of 6.9 (1.9) and 7.8 (2.4) (t(38) = 1.27, p = .21). These findings suggest that exercise, and the intensity of exercise, does not alter implicit memory from a word fragmentation task. For Experiment 3, the exercise and control groups, respectively, had a discrimination implicit memory index score of 0.48 (0.18) and 0.29 (0.32) (t(38) = 2.16, p = .03). In conclusion, acute exercise does not influence a commonly used laboratory-based assessment of implicit memory but may enhance real world-related implicit memory function.

Unfolding the Effects of Acute Cardiovascular Exercise on Neural Correlates of Motor Learning Using Convolutional Neural Networks

Cardiovascular exercise is known to promote the consolidation of newly acquired motor skills. Previous studies seeking to understand the neural correlates underlying motor memory consolidation that is modulated by exercise, have relied so far on using traditional statistical approaches for a priori selected features from neuroimaging data, including EEG. With recent advances in machine learning, data-driven techniques such as deep learning have shown great potential for EEG data decoding for brain-computer interfaces, but have not been explored in the context of exercise. Here, we present a novel Convolutional Neural Network (CNN)-based pipeline for analysis of EEG data to study the brain areas and spectral EEG measures modulated by exercise. To the best of our knowledge, this work is the first one to demonstrate the ability of CNNs to be trained in a limited sample size setting. Our approach revealed discriminative spectral features within a refined frequency band (27–29 Hz) as compared to the wider beta bandwidth (15–30 Hz), which is commonly used in data analyses, as well as corresponding brain regions that were modulated by exercise. These results indicate the presence of finer EEG spectral features that could have been overlooked using conventional hypothesis-driven statistical approaches. Our study thus demonstrates the feasibility of using deep network architectures for neuroimaging analysis, even in small-scale studies, to identify robust brain biomarkers and investigate neuroscience-based questions.

A single high-intensity exercise bout during early consolidation does not influence retention or relearning of sensorimotor locomotor long-term memories

A single exercise bout has been found to improve the retention of a skill-based upper extremity motor task up to a week post-practice. This effect is the greatest when exercise intensity is high and exercise is administered immediately after motor practice (i.e., early in consolidation). Whether exercise can affect other motor learning types (e.g., sensorimotor adaptation) and tasks (e.g., walking) is still unclear as previous studies have not optimally refined the exercise parameters and long-term retention testing. Therefore, we investigated whether a single high-intensity exercise bout during early consolidation would improve the long-term retention and relearning of sensorimotor adaptation during split-belt treadmill walking. Twenty-six neurologically intact adults attended three sessions; sessions 2 and 3 were 1 day and 7 days after session 1, respectively. Participants were allocated either to Rest (REST) or to Exercise (EXE) group. In session 1, all groups walked on a split-belt treadmill in a 2:1 speed ratio (1.5:0.75 m/s). Then, half of the participants exercised for 5 min (EXE), while the other half rested for 5 min (REST). A short exercise bout during early consolidation did not improve retention or relearning of locomotor memories one or seven days after session 1. This result reinforces previous findings that the effect of exercise on motor learning may differ between sensorimotor locomotor adaptation and skilled-based upper extremity tasks; thus, the utility of exercise as a behavioral booster of motor learning may depend on the type of motor learning and task.

Acute high-intensity football games can improve children's inhibitory control and neurophysiological measures of attention

Recent studies suggest that a single bout of exercise can lead to transient performance improvements in specific cognitive domains in children. However, more knowledge is needed to determine the key exercise characteristics for obtaining these effects and how they translate into real-world settings. In the present study, we investigate how small-sided football games of either high- or moderate-intensity affect measures of inhibitory control in a school setting. Eighty-one children (mean age 11.8, 48 boys) were randomly allocated to three groups performing 20-minute of high-intensity small-sided real football games (SRF), moderate-intensity small-sided walking football games (SWF) or resting (RF). Behavioral measures of inhibitory control and neurophysiological measures of attention (P300 latency and amplitude) were obtained during a flanker task performed at baseline and 20 minutes following the intervention. Retention of declarative memory was assessed in a visual memory task 7 days after the intervention. Measures of inhibitory control improved more in children performing SRF compared to SWF 19 ms, 95% CI [7, 31 ms] (P = 0.041). This was paralleled by larger increases in P300 amplitudes at Fz in children performing SRF compared both to RF in congruent (3.54 μV, 95% CI [0.85, 6.23 μV], P = 0.039) and incongruent trials (5.56 μV, 95% CI [2.87, 8.25 μV], P < 0.001) and compared to SWF in incongruent trials (4.10 μV, 95% CI [1.41, 6.68 μV], P = 0.010). No effects were found in measures of declarative memory. Together this indicates that acute high-intensity small-sided football games can transiently improve measures of inhibitory control and neurophysiological correlates of attention. Intense small-sided football games are easily implementable and can be employed by practitioners, for example, during breaks throughout the school day.

Enhancing Children's Motor Memory Retention Through Acute Intense Exercise: Effects of Different Exercise Durations

Physical exercise has been proposed as a viable means to stimulate motor learning. Exercise characteristics, including intensity and duration, may play a role in modulating the exercise effect on motor learning. While some evidence exists regarding the benefits of intense and relatively long exercise, little is known about the effect of short exercise bouts on motor learning, especially in children. This study aimed to assess the effect of long versus short intense exercise bouts on the adaptation and consolidation of a rotational visuomotor adaptation task. The participants were 71 healthy children from two sites divided into three groups: long exercise bout (LONG), short exercise bout (SHORT), and no exercise (CON). Children performed a rotated (clockwise 60° rotation) motor task on four different occasions: an adaptation set and 1 h, 24 h, and 7 days delayed retention sets. Exercise bouts were performed prior to the adaptation set. Results showed a group effect during motor adaptation [F(2,68) = 3.160; p = 0.049; η p 2 = 0.087], but no statistical differences were found between groups. Regarding retention tests, both exercise groups (LONG and SHORT) showed superior retention compared to CON group [F(2,68) = 7.102; p = 0.002; η p 2 = 0.175]. No differences were found between exercise groups, indicating similar benefits for the two exercise interventions. Overall, whether the exercise duration was long or short, exercise improved motor memory retention as an estimate of memory consolidation process. The use of short exercise bouts may be suitable to improve children's motor memory consolidation in environments where time constraints exist.

Acute Physical Exercise Can Influence the Accuracy of Metacognitive Judgments

Acute exercise generally benefits memory but little research has examined how exercise affects metacognition (knowledge of memory performance). We show that a single bout of exercise can influence metacognition in paired-associate learning. Participants completed 30-min of moderate-intensity exercise before or after studying a series of word pairs (cloud-ivory), and completed cued-recall (cloud-?; Experiments 1 & 2) and recognition memory tests (cloud-? spoon; ivory; drill; choir; Experiment 2). Participants made judgments of learning prior to cued-recall tests (JOLs; predicted likelihood of recalling the second word of each pair when shown the first) and feeling-of-knowing judgments prior to recognition tests (FOK; predicted likelihood of recognizing the second word from four alternatives). Compared to no-exercise control conditions, exercise before encoding enhanced cued-recall in Experiment 1 but not Experiment 2 and did not affect recognition. Exercise after encoding did not influence memory. In conditions where exercise did not benefit memory, it increased JOLs and FOK judgments relative to accuracy (Experiments 1 & 2) and impaired the relative accuracy of JOLs (ability to distinguish remembered from non-remembered items; Experiment 2). Acute exercise seems to signal likely remembering; this has implications for understanding the effects of exercise on metacognition, and for incorporating exercise into study routines.

H-reflex conditioning during locomotion in people with spinal cord injury

Key points

In people or animals with incomplete spinal cord injury (SCI), changing a spinal reflex through an operant conditioning protocol can improve locomotion.

All previous studies conditioned the reflex during steady‐state maintenance of a specific posture. By contrast, the present study down‐conditioned the reflex during the swing‐phase of locomotion in people with hyperreflexia as a result of chronic incomplete SCI. The aim was to modify the functioning of the reflex in a specific phase of a dynamic movement.

This novel swing‐phase conditioning protocol decreased the reflex much faster and farther than did the steady‐state protocol in people or animals with or without SCI, and it also improved locomotion.

The reflex decrease persisted for at least 6 months after conditioning ended.

The results suggest that conditioning reflex function in a specific phase of a dynamic movement offers a new approach to enhancing and/or accelerating recovery after SCI or in other disorders.

Abstract

In animals and people with incomplete spinal cord injury, appropriate operant conditioning of a spinal reflex can improve impaired locomotion. In all previous conditioning studies, the reflex was conditioned during steady‐state maintenance of a stable posture; this steady‐state protocol aimed to change the excitability of the targeted reflex pathway; reflex size gradually changed over 8–10 weeks. The present study introduces a new protocol, comprising a dynamic protocol that aims to change the functioning of the reflex pathway during a specific phase of a complex movement. Specifically, we down‐conditioned the soleus H‐reflex during the swing‐phase of locomotion in people with hyperreflexia as a result of chronic incomplete SCI. The swing‐phase H‐reflex, which is absent or very small in neurologically normal individuals, is abnormally large in this patient population. The results were clear. With swing‐phase down‐conditioning, the H‐reflex decreased much faster and farther than did the H‐reflex in all previous animal or human studies with the steady‐state protocol, and the decrease persisted for at least 6 months after conditioning ended. The H‐reflex decrease was accompanied by improvements in walking speed and in the modulation of locomotor electromyograph activity in proximal and distal muscles of both legs. These results provide new insight into the factors controlling spinal reflex conditioning; they suggest that the conditioning protocols targeting reflex function in a specific movement phase provide a promising new opportunity to enhance functional recovery after SCI or in other disorders.

In people or animals with incomplete spinal cord injury (SCI), changing a spinal reflex through an operant conditioning protocol can improve locomotion.

All previous studies conditioned the reflex during steady‐state maintenance of a specific posture. By contrast, the present study down‐conditioned the reflex during the swing‐phase of locomotion in people with hyperreflexia as a result of chronic incomplete SCI. The aim was to modify the functioning of the reflex in a specific phase of a dynamic movement.

This novel swing‐phase conditioning protocol decreased the reflex much faster and farther than did the steady‐state protocol in people or animals with or without SCI, and it also improved locomotion.

The reflex decrease persisted for at least 6 months after conditioning ended.

The results suggest that conditioning reflex function in a specific phase of a dynamic movement offers a new approach to enhancing and/or accelerating recovery after SCI or in other disorders.

A single bout of hard RPE-based cycling exercise increases salivary alpha-amylase

Exercise exerts beneficial effects on cognition, in part by stimulating an arousal response that includes the release of catecholamines. Sympathetic nervous system arousal and activation of the noradrenergic system in particular may enhance cognitive performance. Measurement of salivary alpha-amylase, a non-invasive biomarker of central noradrenergic activity, is a promising avenue for characterizing the arousal-mediated effects of exercise on cognition. However, the effectiveness of high-intensity acute exercise, and the time course of sAA concentrations following exercise, has not been clearly described. The purpose of this study was to determine the effects of 20 min of perceived exertion-based high-intensity cycling exercise on salivary alpha-amylase levels in healthy young adults. We utilized a repeated-measures design to examine the sAA response to cycling exercise, rest, and an emotional picture viewing task. Thirty-two participants between the ages of 18-30 viewed pleasant, neutral, and unpleasant pictures from the International Affective Picture System. Before and after the task, participants completed either 20 min of seated rest or cycling exercise at an intensity corresponding to 15 ("hard") on Borg's Ratings of Perceived Exertion scale. Salivary alpha-amylase was assessed at time points immediately before and after rest, exercise, and the picture viewing task. Exercise elicited a robust increase in salivary alpha-amylase approximately six times higher than that induced by emotional picture viewing. Importantly, the observed exercise-induced increase in salivary alpha-amylase returned to a level comparable to baseline after ten minutes. These findings have meaningful implications for future work characterizing the relationship between exercise and arousal-mediated effects on cognitive performance.

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.

An integrated model of acute exercise on memory function

Memory is a complex cognition that plays a critical role in daily functioning. This review discusses the dynamic effects of acute exercise on memory function, via a hypothesized exercise-memory interaction model, taking into consideration multiple memory systems and exercise parameters.

Association between habitual physical activity on episodic memory strategy use and memory controllability

Background: The primary objective of this study was to evaluate the association between habitual physical activity engagement and perceived controllability of memory function. Secondary objectives included the evaluation of physical activity on memory strategy use, and whether the latter mediates the relationship between physical activity on memory controllability. Methods: Two-hundred and nine young adults (M_age=25 y) completed a brief survey evaluating physical activity (Physical Activity Vital Signs Questionnaire), memory strategy use (Memory Functioning Questionnaire), and memory controllability (Memory Controllability Inventory). Results: Physical activity was not associated with memory strategy use (β=0.68; 95% CI: -1.25,2.62; P=0.48), nor was memory strategy use associated with memory controllability. Physical activity was consistently associated with various attributes of memory controllability, including Present Ability (β=1.10; 95% CI: 0.07, 2.12; P=0.03), Potential Improvement (β=0.84; 95% CI:0.05, 1.63; P=0.03), Effort Utility (β=0.87; 95% CI: 0.11, 1.61; P=0.02), Inevitable Decrement (β=-1.19; 95% CI: -2.19, -0.19; P=0.02) and Alzheimer's likelihood (β=-1.21; 95% CI: -2.29,-0.12; P=0.02). Conclusion: Physical activity is consistently associated with greater perceptions of memory controllability. Future longitudinal and experimental work on this topic is warranted to evaluate if physical activity can foster an individual's ability to modify their behavior and cognitions to enhance and preserve memory 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.

Hypothesized mechanisms through which acute exercise influences episodic memory

Emerging research demonstrates that exercise is favorably associated with several cognitive outcomes, including episodic memory function. The majority of the mechanistic work describing the underlying mechanisms of this effect has focused on chronic exercise engagement. Such mechanisms include, e.g., chronic exercise-induced neurogenesis, gliogenesis, angiogenesis, cerebral circulation, and growth factor production. Less research has examined the mechanisms through which acute (vs. chronic) exercise subserves episodic memory function. The purpose of this review is to discuss these potential underlying mechanisms, which include, e.g., acute exercise-induced (via several pathways, such as vagus nerve and muscle spindle stimulation) alterations in neurotransmitters, synaptic tagging/capturing, associativity, and psychological attention.

The Experimental Effects of Acute Exercise on Long-Term Emotional Memory

Emerging work suggests that acute, moderate-intensity aerobic exercise may help to subserve episodic memory of neutral stimuli. Less investigated, however, is whether acute exercise is associated with enhanced memory recognition of emotional stimuli, which was the purpose of this experiment. A parallel-group randomized controlled experiment was employed. Participants (mean age = 20 yr) were randomized into an exercise (n = 17) or control group (n = 17). The exercise group engaged in a 15-min bout of moderate-intensity treadmill walking. Emotional memory recognition was assessed via images from the International Affective Picture System, including assessments of varying degrees of valence and arousal. Memory recognition was assessed at 1 day, 7 days, and 14 days post-memory encoding. We observed a significant main effect for time (F(2) = 104.2, p < 0.001, η²_p = 0.77) and a significant main effect for valence–arousal classification (F(4) = 21.39, p < 0.001, η²_p = 0.40), but there was no significant time by group interaction (F(2) = 1.09, p = 0.34, η²_p = 0.03), classification by group interaction (F(4) = 0.12, p = 0.97, η²_p = 0.01), time by classification interaction (F(8) = 1.78, p = 0.08, η²_p = 0.05), or time by classification by group interaction (F(8) = 0.78, p = 0.62, η²_p = 0.02). In conclusion, emotional memory recognition decreased over the 14-day follow-up period and this rate of memory decay was not altered by acute moderate-intensity exercise engagement. We discuss these findings in the context of exercise intensity and the temporal effects of exercise.

Intensity-specific effects of acute exercise on human memory function: considerations for the timing of exercise and the type of memory

Background: The purpose of this review was to evaluate whether acute exercise intensities have unique effects on memory function, and whether this is influenced by memory type as well as the temporality of the acute exercise bout.

Methods: A systematic review was employed, using several databases (PubMed, PsychInfo,Sports Discus, Google Scholar, Embase).

Results: In total, 9 articles met the study criteria. All 9 studies evaluated either working memory capacity or episodic-related memory function. The main findings across these studies were 1) when acute exercise occurs before the memory task, high-intensity exercise may be less favorable for working memory but may favor episodic memory; 2) when acute exercise occurs during the memory task, high-intensity exercise may be less favorable for working memory capacity; and 3) high-intensity exercise may not associate with long-term memory function when it occurs shortly after memory encoding.

Conclusion: The relationship between acute exercise and memory is complex and may vary based on the intensity of exercise, the temporality of exercise, and the memory type evaluated.

A Single Bout of Aerobic Exercise Improves Motor Skill Consolidation in Parkinson's Disease

Background: Motor learning is impaired in Parkinson’s disease (PD), with patients demonstrating deficits in skill acquisition (online learning) and consolidation (offline learning) compared to healthy adults of similar age. Recent studies in young adults suggest that single bouts of aerobic exercise (AEX), performed in close temporal proximity to practicing a new motor task, may facilitate motor skill learning. Thus, we aimed at investigating the effects of a single bout of aerobic cycling on online and offline learning in PD patients.

Methods: 17 PD patients (Hoehn and Yahr 1 – 2.5, age: 64.4 ± 6.2) participated in this crossover study. Immediately prior to practicing a novel balance task, patients either performed 30 min of (i) moderate intensity (60–70% VO_2max) aerobic cycling, or (ii) seated rest (order counterbalanced). The task required patients to stabilize a balance platform (stabilometer) in a horizontal position for 30 s. For each experimental condition, patients performed 15 acquisition trials, followed by a retention test 24 h later. We calculated time in balance (platform within ± 5° from horizontal) for each trial, and analyzed within- and between-subjects differences in skill acquisition (online learning) and skill retention (offline learning) using mixed repeated-measures ANOVA.

Results: We found that the exercise bout had no effect on performance level or online gains during acquisition, despite affecting the time course of skill improvements (larger initial and reduced late skill gains). Aerobic cycling significantly improved offline learning, as reflected by larger 24-h skill retention compared to the rest condition.

Conclusion: Our results suggest that a single bout of moderate-intensity AEX is effective in improving motor skill consolidation in PD patients. Thus, acute exercise may represent an effective strategy to enhance motor memory formation in this population. More work is necessary to understand the underlying mechanisms, the optimal scheduling of exercise, and the applicability to other motor tasks. Further, the potential for patients in later disease stages need to be investigated. The study was a priori registered at ClinicalTrials.gov (NCT03245216).

Experimental Investigation of the Time Course Effects of Acute Exercise on False Episodic Memory

Previous experimental work suggests that acute exercise may positively influence the accurate recall of past episodic events. However, few studies have examined whether acute exercise also reduces the number of false episodic memories. We evaluated this paradigm in conjunction with an examination of the temporal effects of acute exercise, which have previously been shown to play an important role in subserving episodic memory function. Twenty young adults participated in three experimental visits, including a non-exercise control visit, a visit involving an acute bout (20 min) of moderate-intensity exercise occurring prior to the memory task, and a visit involving an acute bout of exercise occurring during the encoding of the memory task. All visits were counterbalanced and occurred at least 24 h apart. The Deese–Roediger–McDermott (DRM) Paradigm, involving a separate word list trial for each visit, was employed to assess accurate and false episodic memory recall. For each visit, a short-term (immediate recall) and a long-term (25-min delay) memory recall was assessed. For both time points, the visit that involved exercise prior to encoding resulted in better short-term and long-term memory function (F(2) = 11.56, p < 0.001, η²_p = 0.38). For both time points, the control visit resulted in a greater number of false memories. These findings suggest that acute moderate-intensity exercise may help to increase the accurate recall of past episodic memories and may help to reduce the rate of false memories.

Experimental Effects of Acute Exercise on Iconic Memory, Short-Term Episodic, and Long-Term Episodic Memory

The present experiment evaluated the effects of acute exercise on iconic memory and short- and long-term episodic memory. A two-arm, parallel-group randomized experiment was employed (n = 20 per group; Mage = 21 year). The experimental group engaged in an acute bout of moderate-intensity treadmill exercise for 15 min, while the control group engaged in a seated, time-matched computer task. Afterwards, the participants engaged in a paragraph-level episodic memory task (20 min delay and 24 h delay recall) as well as an iconic memory task, which involved 10 trials (at various speeds from 100 ms to 800 ms) of recalling letters from a 3 × 3 array matrix. For iconic memory, there was a significant main effect for time (F = 42.9, p < 0.001, η²p = 0.53) and a trend towards a group × time interaction (F = 2.90, p = 0.09, η²p = 0.07), but no main effect for group (F = 0.82, p = 0.37, η²p = 0.02). The experimental group had higher episodic memory scores at both the baseline (19.22 vs. 17.20) and follow-up (18.15 vs. 15.77), but these results were not statistically significant. These findings provide some suggestive evidence hinting towards an iconic memory and episodic benefit from acute exercise engagement.

The Role of Sex in Memory Function: Considerations and Recommendations in the Context of Exercise

There is evidence to suggest that biological sex plays a critical role in memory function, with sex differentially influencing memory type. In this review, we detail the current evidence evaluating sex-specific effects on various memory types. We also discuss potential mechanisms that explain these sex-specific effects, which include sex differences in neuroanatomy, neurochemical differences, biological differences, and cognitive and affect-related differences. Central to this review, we also highlight that, despite the established sex differences in memory, there is little work directly comparing whether males and females have a differential exercise-induced effect on memory function. As discussed herein, such a differential effect is plausible given the clear sex-specific effects on memory, exercise response, and molecular mediators of memory. We emphasize that future work should be carefully powered to detect sex differences. Future research should also examine these potential exercise-related sex-specific effects for various memory types and exercise intensities and modalities. This will help enhance our understanding of whether sex indeed moderates the effects of exercise and memory function, and as such, will improve our understanding of whether sex-specific, memory-enhancing interventions should be developed, implemented, and evaluated.

A single exercise bout and locomotor learning after stroke: physiological, behavioural, and computational outcomes

KEY POINTS

Previous work demonstrated an effect of a single high-intensity exercise bout coupled with motor practice on the retention of a newly acquired skilled arm movement, in both neurologically intact and impaired adults. In the present study, using behavioural and computational analyses we demonstrated that a single exercise bout, regardless of its intensity and timing, did not increase the retention of a novel locomotor task after stroke. Considering both present and previous work, we postulate that the benefits of exercise effect may depend on the type of motor learning (e.g. skill learning, sensorimotor adaptation) and/or task (e.g. arm accuracy-tracking task, walking).

ABSTRACT

Acute high-intensity exercise coupled with motor practice improves the retention of motor learning in neurologically intact adults. However, whether exercise could improve the retention of locomotor learning after stroke is still unknown. Here, we investigated the effect of exercise intensity and timing on the retention of a novel locomotor learning task (i.e. split-belt treadmill walking) after stroke. Thirty-seven people post stroke participated in two sessions, 24 h apart, and were allocated to active control (CON), treadmill walking (TMW), or total body exercise on a cycle ergometer (TBE). In session 1, all groups exercised for a short bout (∼5 min) at low (CON) or high (TMW and TBE) intensity and before (CON and TMW) or after (TBE) the locomotor learning task. In both sessions, the locomotor learning task was to walk on a split-belt treadmill in a 2:1 speed ratio (100% and 50% fast-comfortable walking speed) for 15 min. To test the effect of exercise on 24 h retention, we applied behavioural and computational analyses. Behavioural data showed that neither high-intensity group showed greater 24 h retention compared to CON, and computational data showed that 24 h retention was attributable to a slow learning process for sensorimotor adaptation. Our findings demonstrated that acute exercise coupled with a locomotor adaptation task, regardless of its intensity and timing, does not improve retention of the novel locomotor task after stroke. We postulate that exercise effects on motor learning may be context specific (e.g. type of motor learning and/or task) and interact with the presence of genetic variant (BDNF Val66Met).

The protective effects of acute cardiovascular exercise on the interference of procedural memory

Numerous studies have reported a positive impact of acute exercise for procedural skill memory. Previous work has revealed this effect, but these findings are confounded by a potential contribution of a night of sleep to the reported exercise-mediated reduction in interference. Thus, it remains unclear if exposure to a brief bout of exercise can provide protection to a newly acquired motor memory. The primary objective of the present study was to examine if a single bout of moderate-intensity cardiovascular exercise after practice of a novel motor sequence reduces the susceptibility to retroactive interference. To address this shortcoming, 17 individuals in a control condition practiced a novel motor sequence that was followed by test after a 6-h wake-filled interval. A separate group of 17 individuals experienced practice with an interfering motor sequence 45 min after practice with the original sequence and were then administered test trials 6 h later. One additional group of 12 participants was exposed to an acute bout of exercise immediately after practice with the original motor sequence but prior to practice with the interfering motor sequence and the subsequent test. In comparison with the control condition, increased response times were revealed during the 6-h test for the individuals that were exposed to interference. The introduction of an acute bout of exercise between the practice of the two motor sequences produced a reduction in interference from practice with the second task at the time of test, however, this effect was not statistically significant. These data reinforce the hypothesis that while there may be a contribution from exercise to post-practice consolidation of procedural skills which is independent of sleep, sleep may interact with exercise to strengthen the effects of the latter on procedural memory.

The feasibility of an acute high-intensity exercise bout to promote locomotor learning after stroke

BACKGROUND

People post-stroke can learn a novel locomotor task but require more practice to do so. Implementing an approach that can enhance locomotor learning may therefore improve post-stroke locomotor recovery. In healthy adults, an acute high-intensity exercise bout before or after a motor task may improve motor learning and has thus been suggested as a method that could be used to improve motor learning in neurorehabilitation. However, it is unclear whether an acute high-intensity exercise bout, which stroke survivors can feasibly complete in neurorehabilitation session, would generate comparable results.

OBJECTIVE

To determine a feasible, high-intensity exercise protocol that could be incorporated into a post-stroke neurorehabilitation session and would result in significant exercise-induced responses.

METHODS

Thirty-seven chronic stroke survivors participated. We allocated subjects to either a control (CON) or one of the exercise groups: treadmill walking (TMW), and total body exercise (TBE). The main exercise-induced measures were: average intensity (% max intensity) and time spent (absolute: seconds; normalized: % total time) at target exercise intensity, and magnitudes of change in serum lactate (mmol/l) and brain-derived neurotrophic factor (BDNF; ng/ml).

RESULTS

Compared to CON, both exercise groups reached and exercised longer at their target intensities and had greater responses in lactate. However, the TBE group exercised longer at target intensity and with greater lactate response than the TMW group. There were no significant BDNF responses among groups.

CONCLUSIONS

An acute high-intensity exercise bout that could be incorporated into a neurorehabilitation learning-specific session and results in substantial exercise-induced responses is feasible post-stroke.

Temporal Effects of Acute Walking Exercise on Learning and Memory Function

PURPOSE

To evaluate the temporal effects of acute exercise on episodic memory.

DESIGN

A quasi-experimental study.

SAMPLE

Eighty-eight college students (N = 22 per group).

MEASURES

Four experimental groups were evaluated, including a control group, exercising prior to memory encoding, exercising during encoding, and exercising during memory consolidation. The exercise stimulus consisted of a 15-minute moderate-intensity walk on a treadmill. Participants completed the Rey Auditory Verbal Learning Test (RAVLT) to assess learning and memory. Prospective memory was assessed via a Red Pen Task. Long-term memory (recognition and attribution) of the RAVLT was assessed 20 minutes and 24 hours after exercise.

ANALYSIS

Repeated-measures analysis of variance (ANOVA) assessed the performance of RAVLT scores of trials 1 to 5 across groups. One-way ANOVA assessed the performance of individual trials across groups, whereas χ² assessed the performance of the Red Pen Task across groups.

RESULTS

Regarding learning, the interaction of groups × trial was marginally statistically significant ( F_12,332 = 1.773, P = .05), indicating that the group which exercised before encoding did better than the group that exercised during encoding and consolidation. For both 24-hour recognition and attribution performance, the group that exercised before memory encoding performed significantly better than the group that exercised during consolidation ( P = .05 recognition, P = .006 attribution).

DISCUSSION

Engaging in a 15-minute bout of moderate-intensity walking before a learning task was effective in influencing long-term episodic memory.

Acute physical exercise in humans enhances reconsolidation of emotional memories

Increasing evidence suggests that when a memory is reactivated through retrieval, it becomes temporarily vulnerable to environmental or pharmacological manipulation, which can consequently update or strengthen the memory. Physical exercise has been shown to modulate the maintenance of fear memories in animals following memory reactivation. This study investigated the effect of intense exercise in modulating the reconsolidation of trauma memories. Fifty-four undergraduate students watched a trauma film depicting the aftermath of a highway car crash. Two days later, participants engaged in either (a) 20-25min of incremental cycling following a memory reactivation induction (Reactivation/Exercise), (b) 20-25min of mild cycling (Reactivation/No Exercise) following memory reactivation, or (c) 20-25min of incremental cycling but no memory reactivation (No Reactivation/Exercise). Saliva samples were collected to index salivary amylase and cortisol at baseline and post activity. Participants completed memory questionnaires relating to declarative and intrusive memory recall two days after memory reactivation. Reactivation/Exercise participants recalled more central details of the trauma film relative to other participants. Increased cortisol predicted better total memory recall in the Reactivation/Exercise, but not in the other conditions. These findings suggest that intense exercise during the period of memory reactivation enhances subsequent trauma memory, and provides human evidence consistent with recent findings of exercise-induced fear reconsolidation in animals.

Randomized controlled trial evaluating the temporal effects of high-intensity exercise on learning, short-term and long-term memory, and prospective memory

The broader purpose of this study was to examine the temporal effects of high-intensity exercise on learning, short-term and long-term retrospective memory and prospective memory. Among a sample of 88 young adult participants, 22 were randomized into one of four different groups: exercise before learning, control group, exercise during learning, and exercise after learning. The retrospective assessments (learning, short-term and long-term memory) were assessed using the Rey Auditory Verbal Learning Test. Long-term memory including a 20-min and 24-hr follow-up assessment. Prospective memory was assessed using a time-based procedure by having participants contact (via phone) the researchers at a follow-up time period. The exercise stimulus included a 15-min bout of progressive maximal exertion treadmill exercise. High-intensity exercise prior to memory encoding (vs. exercise during memory encoding or consolidation) was effective in enhancing long-term memory (for both 20-min and 24-h follow-up assessments). We did not observe a differential temporal effect of high-intensity exercise on short-term memory (immediate post-memory encoding), learning or prospective memory. The timing of high-intensity exercise may play an important role in facilitating long-term memory.

Dose-Response Effects of Exercise Duration and Recovery on Cognitive Functioning

We examined the effects of different acute exercise durations and recovery periods on cognitive function in a counterbalanced, cross-over randomized controlled experiment. We placed 352 participants, aged 18 to 35 years into one of 16 experimental groups. Each participant visited the laboratory twice, separated by a 1-week washout period. Either Visit 1 or 2 consisted of an acute bout of moderate-intensity treadmill exercise (10, 20, 30, 45, or 60 minutes) followed by a period of rest (5, 15, or 30 minutes) before taking a set of five cognitive tests; the other visit consisted only of completing the cognitive tests (no exercise). Cognitive tests sampled multiple cognitive parameters, including reasoning, concentration, memory, attention, and planning. We found that a short recovery period (i.e., 5 minutes) may have a less favorable effect on planning ability but may be beneficial for memory. In addition, for various exercise durations and recovery periods, a Group × Time × Resting (nonexercise) A cognitive interaction effect was observed such that for both memory and inhibitory cognitive ability, acute exercise (vs. no exercise) had an enhancement effect for those with lower resting cognitive functioning. The length of the acute exercise recovery period and resting cognitive ability most influenced the association between exercise and cognitive function.

A Single Bout of High-Intensity Interval Training Improves Motor Skill Retention in Individuals With Stroke

BACKGROUND

One bout of high-intensity cardiovascular exercise performed immediately after practicing a motor skill promotes changes in the neuroplasticity of the motor cortex and facilitates motor learning in nondisabled individuals.

OBJECTIVE

To determine if a bout of exercise performed at high intensity is sufficient to induce neuroplastic changes and improve motor skill retention in patients with chronic stroke.

METHODS

Twenty-two patients with different levels of motor impairment were recruited. On the first session, the effects of a maximal graded exercise test on corticospinal and intracortical excitability were assessed from the affected and unaffected primary motor cortex representational area of a hand muscle with transcranial magnetic stimulation. On the second session, participants were randomly assigned to an exercise or a nonexercise control group. Immediately after practicing a motor task, the exercise group performed 15 minutes of high-intensity interval training while the control group rested. Twenty-four hours after motor practice all participants completed a test of the motor task to assess skill retention.

RESULTS

The graded exercise test reduced interhemispheric imbalances in GABA_A-mediated short-interval intracortical inhibition but changes in other markers of excitability were not statistically significant. The group that performed high-intensity interval training showed a better retention of the motor skill.

CONCLUSIONS

The performance of a maximal graded exercise test triggers only modest neuroplastic changes in patients with chronic stroke. However, a single bout of high-intensity interval training performed immediately after motor practice improves skill retention, which could potentially accelerate motor recovery in these individuals.

Adaptive Capacity: An Evolutionary Neuroscience Model Linking Exercise, Cognition, and Brain Health

The field of cognitive neuroscience was transformed by the discovery that exercise induces neurogenesis in the adult brain, with the potential to improve brain health and stave off the effects of neurodegenerative disease. However, the basic mechanisms underlying exercise-brain connections are not well understood. We use an evolutionary neuroscience approach to develop the adaptive capacity model (ACM), detailing how and why physical activity improves brain function based on an energy-minimizing strategy. Building on studies showing a combined benefit of exercise and cognitive challenge to enhance neuroplasticity, our ACM addresses two fundamental questions: (i) what are the proximate and ultimate mechanisms underlying age-related brain atrophy, and (ii) how do lifestyle changes influence the trajectory of healthy and pathological aging?