Why Is My Exercise Not Working

[Otilia Mojarro]

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Background: This systematic and meta-analytic review aimed to investigate the effects of physical exercise on the working memory of older adults, and to identify the moderators of these effects.

Methods: We searched six electronic databases for randomized controlled trials on the effects of physical exercise on working memory that were published before or on May 15, 2020. The PEDro scale was used to evaluate the methodological quality of the included studies. Stata 14.0 software was used to perform the meta-analysis, subgroup analysis, and publication bias testing.

Results: A total of 28 studies and 2156 participants were included. The methodological quality of the included studies was fair to excellent, and there was no publication bias. Overall, we found that physical exercise had a significant effect on working memory in older adults (standardized mean difference = 0.30, p Conclusion: Physical exercise can effectively improve the working memory of older adults. The recommended physical exercise is multi-component exercise or mind-body exercise of moderate intensity for 45-60 min 3 times a week, for more than 6 months.

Figure 1. The working-memory experimental paradigm (A) is a DMS task (120 trials). A sample stimulus (encoding) and a probe stimulus (retrieval) were presented with a stimulus delay of 5 s (maintenance). Participants were instructed to respond to whether the sample stimulus was either private or public and to memorize the image. The probe stimulus was either the same (repeat item) or had small changes in the image (lure items) that needed to be detected. (B) The VAS task (60 trials). During this task, subjects were instructed to detect whether a target (i.e., ball) was present. The background image remained the same throughout the visual-attention paradigm.

Figure 4. (A) Correlation between theta power in frontal regions and performance (corrected hit rate) during the maintenance phase (delay). Higher scores for corrected hit rates revealed a more prominent event-related desynchronization (ERD) for theta. (B) Correlation between theta power in frontal regions and RT (lure stimuli) during the maintenance phase. Shorter RTs for detecting lure items revealed greater ERD for theta during the maintenance phase (delay).

Figure 6. (A) Correlation between changes in alpha power in frontal regions and fitness score. A higher fitness score was related to a greater increase in alpha power. (B) Correlation between change in alpha power in frontal regions and correct response during the VAS (target absent trials) task.

Copyright 2020 Chaire, Becke and Dzel. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Emily Cronkleton is a certified yoga teacher and has studied yoga in the United States, India, and Thailand. Her passion for yoga has laid the foundation for a healthy and inspired life, while her teachers and practice have helped shape her life experience in many ways.

Dr. Grant Tinsley is a tenured associate professor at Texas Tech University and the director of the Energy Balance & Body Composition Laboratory. He has published more than 75 peer-reviewed journal articles in intermittent fasting, body composition assessment, and sports nutrition. He is also a certified strength and conditioning specialist and a certified sports nutritionist.

Regular exercise is excellent for boosting energy and reducing fatigue. When you work out, oxygen and nutrients travel to your heart and lungs. This improves your cardiovascular system, endurance, and overall stamina.

In the study, participants completed a round of 8-hour days of prolonged sitting with and without a 30-minute morning walk on the treadmill. On some days, they also took 3-minute walking breaks every 30 minutes.

In the study, 10 young men exercised in the morning, afternoon, and evening over separate sessions. The researchers found that 24-hour fat burn was highest when they exercised in the morning before breakfast.

A 2015 study published in the Journal of Diabetes Science and Technology found that morning exercise lowers that risk. In the study, 35 adults with T1DM did two separate sessions of morning and afternoon treadmill workouts.

The researchers think cortisol may be at play. Aside from increasing alertness, cortisol also helps control blood sugar. Lower levels, which occur later in the day, could make it easier for hypoglycemia to develop.

In the United States, 1 in 3 adults have hypertension, or high blood pressure. Physical activity is one of the best ways to naturally control hypertension. But according to a small 2014 study published in Vascular Health and Risk Management, exercising in the morning may be the best move.

Also, different times of day may be best for different types of exercise. For example, an intense spin class may be ideal in the morning, while a relaxing yoga routine might be more practical at night.

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Limited studies have examined the effects of acute exercise and caffeine intake on cognition concurrently25, however none to our knowledge have examined acute exercise in comparison to caffeine administration on either cognition or caffeine withdrawal symptoms. By comparing acute exercise directly to caffeine administration, which has well-established mechanistic pathways (i.e., antagonism of adenosine receptors), the mechanisms underlying acute exercise-induced benefits to cognitive function can be further elucidated. Thus, the objectives of the present study were to compare acute aerobic exercise to caffeine administration on cognitive performance and caffeine withdrawal symptoms. The first objective (Phase I) was to determine the effects of an acute bout of moderate intensity aerobic exercise and caffeine administration on WM in both non-caffeine and caffeine consumers. The second objective (Phase II) was to determine whether an acute bout of moderate intensity aerobic exercise and caffeine administration could reduce caffeine withdrawal symptoms and restore WM performance after a 12- hour caffeine deprivation period among the caffeine consumers used in Phase I. It was hypothesized in Phase I that in comparison to baseline WM performance, aerobic exercise and caffeine administration would improve WM comparably in both non-caffeine and caffeine consumers. In Phase II, it was hypothesized that aerobic exercise or caffeine administration would reduce caffeine withdrawal symptoms and restore WM performance comparably following a 12-hour caffeine deprivation period.

Results from the present study indicate that acute aerobic exercise and caffeine administration improved WM accuracy in non-caffeine and caffeine consumers on the most difficult load of the n-back task (3-back). Furthermore, acute aerobic exercise and caffeine administration demonstrated some utility in reducing caffeine withdrawal symptoms induced by a 12-hour caffeine deprivation period. Interestingly, no decrements to WM were detected following a 12-hour caffeine deprivation period. Beyond these overarching findings, several issues warrant further discussion.

In Phase I, acute aerobic exercise and caffeine administration conferred comparable improvements to accuracy (absolute percent difference: 2.62%, 2.29% and relative percent difference: 20.1%, 17.5% respectively). For non-caffeine consumers, caffeine administration conferring a marginal accuracy benefit may be due in part to the novelty of caffeine as a substance. Prior research has suggested non-caffeine consumers display heightened physiological and psychological responses to caffeine26. Furthermore, the non-caffeine consumers in this study reported high physical activity participation (Table 1), suggesting tolerance of a single-bout of aerobic exercise with little fatigue and discomfort27. Previous studies have identified that exercise tolerance is implicated in exercise-cognition investigations as individuals who do not regularly exercise are more likely to experience fatigue, which has been associated with impaired cognitive performance28. It is also important to note that our findings contribute to the body of literature8,14 supporting the notion that caffeine provides net benefits to cognition and does not rely completely on the reversal of withdrawal symptoms, as non-caffeine consumers would not be expected to experience caffeine withdrawal.

Our investigation did not find improvements to WM speed (RT) as a result of acute aerobic exercise or caffeine administration in both non-caffeine and caffeine consumers on the 3-back load. These findings differ from those reported by Haskell et al.30, and McMorris et al.31. Diverging results could be due to the wide range in administered caffeine doses32, type of cognitive task administered, and exercise intensity12,31. Prior work by our group also detected no changes to RT on the n-back task following acute aerobic exercise at a moderate intensity (Fagan et al., unpublished). It is important to note when examining the WM speed and accuracy findings in concert, improved WM was not due to a speed-accuracy trade-off33. In other words, individuals were not committing less errors on the n-back task at a cost to response speed. Prior work has suggested caffeine may improve accuracy in cognitive tasks via increased alertness34 and modulation of neuronal activity in regions associated with attention35. When considering acute aerobic exercise it has been proposed that exercise selectively affects the activation and allocation of attentional resources4,36. Thus, the improved WM accuracy that was observed may be in part due to increased general arousal. A battery of cognitive tests could have aided in elucidating whether the effects were WM-specific or a reflection of global cognitive improvement.

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