Effects of acute interval handgrip exercise on cognitive performance

Higher handgrip strength is linked to higher salience ventral attention functional network segregation in older adults

Converging evidence suggests that handgrip strength is linked to cognition in older adults, and this may be subserved by shared age-related changes in brain function and structure. However, the interplay among handgrip strength, brain functional connectivity, and cognitive function remains poorly elucidated. Hence, our study sought to examine these relationships in 148 community-dwelling older adults. Specifically, we examined functional segregation, a measure of functional brain organization sensitive to ageing and cognitive decline, and its associations with handgrip strength and cognitive function. We showed that higher handgrip strength was related to better processing speed, attention, and global cognition. Further, higher handgrip strength was associated with higher segregation of the salience/ventral attention network, driven particularly by higher salience/ventral attention intra-network functional connectivity of the right anterior insula to the left posterior insula/frontal operculum and right midcingulate/medial parietal cortex. Importantly, these handgrip strength-related inter-individual differences in salience/ventral attention network functional connectivity were linked to cognitive function, as revealed by functional decoding and brain-cognition association analyses. Our findings thus highlight the importance of the salience/ventral attention network in handgrip strength and cognition, and suggest that inter-individual differences in salience/ventral attention network segregation and intra-network connectivity could underpin the handgrip strength-cognition relationship in older adults.

The neuromodulatory role of dopamine in improved reaction time by acute cardiovascular exercise

Acute cardiovascular physical exercise improves cognitive performance, as evidenced by a reduction in reaction time (RT). However, the mechanistic understanding of how this occurs is elusive and has not been rigorously investigated in humans. Here, using positron emission tomography (PET) with [11 C]raclopride, in a multi-experiment study we investigated whether acute exercise releases endogenous dopamine (DA) in the brain. We hypothesized that acute exercise augments the brain DA system, and that RT improvement is correlated with this endogenous DA release. The PET study (Experiment 1: n = 16) demonstrated that acute physical exercise released endogenous DA, and that endogenous DA release was correlated with improvements in RT of the Go/No-Go task. Thereafter, using two electrical muscle stimulation (EMS) studies (Experiments 2 and 3: n = 18 and 22 respectively), we investigated what triggers RT improvement. The EMS studies indicated that EMS with moderate arm cranking improved RT, but RT was not improved following EMS alone or EMS combined with no load arm cranking. The novel mechanistic findings from these experiments are: (1) endogenous DA appears to be an important neuromodulator for RT improvement and (2) RT is only altered when exercise is associated with central signals from higher brain centres. Our findings explain how humans rapidly alter their behaviour using neuromodulatory systems and have significant implications for promotion of cognitive health. KEY POINTS: Acute cardiovascular exercise improves cognitive performance, as evidenced by a reduction in reaction time (RT). However, the mechanistic understanding of how this occurs is elusive and has not been rigorously investigated in humans. Using the neurochemical specificity of [11 C]raclopride positron emission tomography, we demonstrated that acute supine cycling released endogenous dopamine (DA), and that this release was correlated with improved RT. Additional electrical muscle stimulation studies demonstrated that peripherally driven muscle contractions (i.e. exercise) were insufficient to improve RT. The current study suggests that endogenous DA is an important neuromodulator for RT improvement, and that RT is only altered when exercise is associated with central signals from higher brain centres.

Acute hypoxia impairs posterior cerebral bioenergetics and memory in man

Hypoxia has the potential to impair cognitive function; however, it is still uncertain which cognitive domains are adversely affected. We examined the effects of acute hypoxia (∼7 h) on central executive (Go/No-Go) and non-executive (memory) tasks and the extent to which impairment was potentially related to regional cerebral blood flow and oxygen delivery (CDO2 ). Twelve male participants performed cognitive tasks following 0, 2, 4 and 6 h of passive exposure to both normoxia and hypoxia (12% O2 ), in a randomized block cross-over single-blinded design. Middle cerebral artery (MCA) and posterior cerebral artery (PCA) blood velocities and corresponding CDO2 were determined using bilateral transcranial Doppler ultrasound. In hypoxia, MCA DO2 was reduced during the Go/No-Go task (P = 0.010 vs. normoxia, main effect), and PCA DO2 was attenuated during memorization (P = 0.005 vs. normoxia) and recall components (P = 0.002 vs. normoxia) in the memory task. The accuracy of the memory task was also impaired in hypoxia (P = 0.049 vs. normoxia). In contrast, hypoxia failed to alter reaction time (P = 0.19 vs. normoxia) or accuracy (P = 0.20 vs. normoxia) during the Go/No-Go task, indicating that selective attention and response inhibition were preserved. Hypoxia did not affect cerebral blood flow or corresponding CDO2 responses to cognitive activity (P > 0.05 vs. normoxia). Collectively, these findings highlight the differential sensitivity of cognitive domains, with memory being selectively vulnerable in hypoxia. NEW FINDINGS: What is the central question of this study? We sought to examine the effects of acute hypoxia on central executive (selective attention and response inhibition) and non-executive (memory) performance and the extent to which impairments are potentially related to reductions in regional cerebral blood flow and oxygen delivery. What is the main finding and its importance? Memory was impaired in acute hypoxia, and this was accompanied by a selective reduction in posterior cerebral artery oxygen delivery. In contrast, selective attention and response inhibition remained well preserved. These findings suggest that memory is selectively vulnerable to hypoxia.

Association between muscle strength and executive function in Tibetan adolescents at high altitude in China: Results from a cross-sectional study at 16-18 years of age

BACKGROUND

In recent years, adolescents have shown a trend of decreasing muscle strength, especially in the upper limbs, and it affects the development of executive functions. However, few studies have been conducted on Tibetan adolescents in high-altitude regions of China. To this end, this study investigated upper limb muscle strength and executive function in Tibetan adolescents in Tibetan regions of China and analyzed the association between them.

METHODS

A three-stage stratified whole-group sampling method was used to test and investigate grip strength, executive function, and basic information in 1093 Tibetan adolescents from Tibet, a high-altitude region of China. A chi-square test and one-way ANOVA were used to compare the basic status and executive function of Tibetan adolescents with different muscle strength. Multiple linear regression analysis and logistic regression analysis were used to analyze the correlations that existed between muscle strength and each sub-function of executive function.

RESULTS

The differences between the inconsistently and congruent reaction times of Tibetan adolescents with different grip strength levels (P75 ) at high altitude in China were statistically significant (F-values of 32.596 and 31.580, respectively; P-values <.001). The differences between the 1-back and 2-back response times for the refresh memory function were also statistically significant (F-values of 9.055 and 6.610, respectively; P-values <.01). Linear regression analysis showed that after adjusting for the relevant covariates, the 1-back reaction time of Tibetan adolescents in the grip strength < P25 group increased by 91.72 ms (P < .01); the 2-back reaction time of Tibetan adolescents in the grip strength < P25 group increased by 105.25 ms (P < 0.01), using grip strength > P75 as the reference group. Logistic regression analysis showed that, after adjusting for relevant covariates, Tibetan adolescents in the grip strength < P25 group had a higher risk of developing 2-back dysfunction (OR = 1.89, 95% CI: 1.24,2.88), using grip strength >P75 as the reference group (P < .01). The risk of cognitive flexibility dysfunction (OR = 1.86, 95% CI: 1.16, 2.98) was also increased (P < .05).

CONCLUSION

There was a significant correlation between grip strength and executive function of refresh memory function and cognitive flexibility in Tibetan adolescents in high altitude areas of China. Those with higher upper limb muscle strength had shorter reaction time, that is, better executive function. In the future, we should focus on improving the upper limb muscle strength of Tibetan adolescents at high altitude in China to better promote the development of executive function.

Handgrip exercise does not alter CO2 -mediated cerebrovascular flow-mediated dilation

Handgrip exercise (HG), a small muscle exercise, improves cognitive function and is expected to provide a useful exercise mode to maintain cerebral health. However, the effect of HG on cerebral blood flow regulation is not fully understood. The present study aimed to examine the effect of acute HG on cerebral endothelial function as one of the essential cerebral blood flow regulatory functions. Thirteen healthy young participants performed interval HG, consisting of 4 sets of 2 min HG at 25% of maximum voluntary contraction with 3 min recovery between each set. Cognitive performance was evaluated before and at 5 and 60 min after interval HG using the Go/No-Go task (reaction time and accuracy). The diameter and blood velocity of the internal carotid artery (ICA) were measured using a duplex Doppler ultrasound system. To assess cerebral endothelial function, hypercapnia (30 s of hypercapnia stimulation, end-tidal partial pressure of CO2 : +9 mmHg)-induced cerebrovascular flow-mediated dilatation (cFMD) was induced, calculated as relative peak dilatation from baseline diameter. The shear rate (SR) was calculated using the diameter and blood velocity of the ICA. As a result, cognitive performance improved only at 5 min after interval HG (reaction time, P = 0.008; accuracy, P = 0.186), whereas ICA SR during interval HG and cFMD after interval HG were unchanged (P = 0.313 and P = 0.440, respectively). These results suggest that enhancement in cerebral endothelial function is not an essential mechanism responsible for acute HG-induced cognitive improvement. NEW FINDINGS: What is the central question of this study? Does handgrip exercise, a small muscle exercise, improve cerebral endothelial function? What is the main finding and its importance? Acute interval isometric handgrip exercise (2 min of exercise at 25% maximum voluntary contraction, followed by 3 min of recovery, repeated for a total of 4 sets) did not improve cerebral endothelial function. Since the cerebrovascular shear rate did not change during exercise, it is possible that acute handgrip exercise is not sufficient stimulation to improve cerebral endothelial function.

Point/counterpoint: Arterial blood pressure response to exercise does relate to exercise-induced improvement in cognitive function

Exercise is a beneficial intervention to prevent cognitive dysfunction. However, an optimal exercise prescription for preventing dementia has not been established because the physiological mechanism(s) of exercise-induced improvements in cognitive function remains unclear. Interestingly, our recent study demonstrated that individuals with a higher exercise pressor response exhibit less exercise-induced cognitive improvement, suggesting that individual differences in cardiovascular responses to exercise or its associated physiological factors, may be related to exercise-induced alterations in cognitive function. Therefore, consideration of individual cardiovascular responses is warranted to develop appropriate exercise prescriptions for a given individual to prevent cognitive dysfunction.

Point/counterpoint: Arterial blood pressure response to exercise does not relate to exercise-induced improvement in cognitive function

Acute exercise has been shown to transiently improve specific aspects of cognitive function, however the mechanism governing these effects remain unclear. Blood pressure responses during exercise have been hypothesized to be a primary contributing factor, in part through its influence on cerebral blood flow. In this counterpoint, we highlight the inconsistent and weak associations between changes in blood pressure, cerebral blood flow and cognitive responses during and following acute exercise. Despite sound theoretical foundation, cognitive responses to exercise do not appear strongly related to blood pressure and more likely stem from a complex integration of multiple mechanisms.

Effects of Acute Resistance Exercise on Executive Function: A Systematic Review of the Moderating Role of Intensity and Executive Function Domain

BACKGROUND

Research has demonstrated that there is a beneficial effect of acute exercise on cognitive function; however, the moderators of the acute resistance exercise (RE) effect on executive function (EF) are underestimated. This systematic review aims to clarify the effects of acute RE on EF by examining the moderating effect of exercise intensity (light, moderate, and vigorous) and EF domains (inhibitory control, working memory, and cognitive flexibility), as well as their interactions.

METHODS

The search strategy was conducted in four databases (PubMed, Scopus, PsycARTICLES, and Cochrane Library) prior to January 29, 2022. Included studies had to: (1) investigate acute RE in adults with normal cognition and without diagnosed disease; (2) include a control group or control session for comparison; (3) include outcomes related to the core EF domains; and (4) be published in English. The methodological quality of the included studies was judged according to the PEDro scale guidelines.

RESULTS

Nineteen studies were included which included a total of 692 participants. More than half of the outcomes (24/42, 57.14%) indicate that acute RE had a statistically significant positive effect on overall EF. In terms of RE intensity and EF domain, moderate intensity acute RE benefited EF more consistently than light and vigorous intensity acute RE. Acute RE-induced EF benefits were more often found for inhibitory control than for working memory and cognitive flexibility. When considering moderators simultaneously, measuring inhibitory control after light or moderate intensity RE and measuring working memory or cognitive flexibility after moderate intensity RE most often resulted in statistically significant positive outcomes.

CONCLUSION

Acute RE has a beneficial effect on EF, observed most consistently for inhibitory control following moderate intensity RE. Future studies should include all exercise intensities and EF domains as well as investigate other potential moderators to enable a better understanding of the benefits of acute RE on EF.

Effect of isometric handgrip exercise on cognitive function: Current evidence, methodology, and safety considerations

Cognitive function is essential for most behaviors of daily living and is a critical component in assessing the quality of life. Mounting prospective evidence supports the use of isometric handgrip exercise (IHE) as a small muscle mass practice to promote health-related outcomes in clinical and healthy populations. The aim of the present review was to systematically investigate whether IHE is effective in improving the cognitive function of adults (aged ≥18 years). Studies were identified by searching five databases (CINAHL, MEDLINE, SPORTDiscus, PsychINFO, and Web of Science). Eight out of 767 studies met the inclusion criteria, including three types of studies: 1) acute effect for IHE with various intensity protocols (n = 4); 2) acute effect for IHE with one set exhaustion protocol (n = 2); and 3) chronic effect of IHE on cognitive function (n = 2). To assess the methodological quality of studies, the PEDro scale was used (mean score = 6.75). The evidence on whether IHE exerts acute positive effects on cognitive performance is currently rather inconclusive. However, a trend was discernible that implementing IHE can generate a beneficial chronic effect on cognitive function, although the results should be interpreted with caution. The clinical relevance of IHE as a time-efficient type of physical exercise to improve cognitive function warrants further investigation. Methodology and safety considerations were discussed.

Systematic Review Registration: (https://osf.io/gbzp9).

Effect of intermittent isometric handgrip exercise protocol with short exercise duration on cognitive performance

The handgrip exercise, a small muscle exercise, is useful for exercise therapy, particularly in the elderly and bedridden patients. The isometric handgrip (IHG) exercise has been utilized in training programs to reduce resting blood pressure; however, the acute effects of the IHG exercise on cognitive performance are not fully understood. The present study aimed to investigate the effect of an intermittent IHG exercise protocol with short exercise duration, which minimizes the arterial blood pressure response to exercise, on cognitive performance. Twenty-two young healthy subjects performed the intermittent IHG exercise protocol, which consisted of 30-s IHG and 45-s recovery × 16 trials; the exercise intensity of the IHG exercise was 30% of the maximal voluntary contraction. Cognitive performance was evaluated before and after the exercise with the Go/No-Go and memory recognition tasks. Specifically, the reaction time (RT) and performance accuracy were measured. The intermittent IHG exercise protocol did not change the RT or performance accuracy of either the Go/No-Go task (P = 0.222 and P = 0.260, respectively) or the memory recognition task (P = 0.427 and P = 0.245, respectively). These findings suggest that the intermittent IHG exercise protocol with short exercise duration may not provide enough stimulation to improve cognitive performance despite being useful as a safe exercise therapy in the elderly and in patients with cardiovascular disease.