Physical activity levels determine exercise-induced changes in brain excitability

Exercise effects on cortical excitability in pain populations: A systematic review and meta-analysis

BACKGROUND

Transcranial Magnetic Stimulation (TMS) studies examining exercise-induced neuroplasticity in pain populations have produced contradictory findings. We conducted a systematic review to explore how exercise impacts cortical excitability in pain populations using TMS metrics. This review aims to summarize the effect sizes and to understand their sources of heterogeneity.

METHODS

We searched multiple databases from inception to December 2022. We included randomized controlled trials (RCTs) with any type of pain population, including acute and chronic pain; exercise interventions were compared to sham exercise or other active interventions. The primary outcomes were TMS metrics, and pain intensity was the secondary outcome. Risk of bias assessment was conducted using the Cochrane tool.

RESULTS

This review included five RCTs (n = 155). The main diagnoses were fibromyalgia and cervical dystonia. The interventions included submaximal contractions, aerobic exercise, physical therapy, and exercise combined with transcranial direct current stimulation. Three studies are considered to have a high risk of bias. All five studies showed significant pain improvement with exercise. The neurophysiological data revealed improvements in cortical excitability measured by motor-evoked potentials; standardized mean difference = 2.06, 95% confidence interval 1.35-2.78, I2 = 19%) but no significant differences in resting motor threshold. The data on intracortical inhibition/facilitation (ICI/ICF) was not systematically analyzed, but one study (n = 45) reported higher ICI and lower ICF after exercise.

CONCLUSIONS

These findings suggest that exercise interventions positively affect pain relief by modifying corticospinal excitability, but their effects on ICI/ICF are still unclear. While the results are inconclusive, they provide a basis for further exploration in this area of research; future studies should focus on establishing standardized TMS measurements and exercise protocols to ensure consistent and reliable findings. A large-scale RCT that examines various exercise interventions and their effects on cortical excitability could offer valuable insights to optimize its application in promoting neuroplasticity in pain populations.

Impact of Acute High-intensity Interval Training on Cortical Excitability, M1-related Cognitive Functions, and Myokines: A Randomized Crossover Study

High-intensity interval training (HIIT) is a time-efficient, safe, and feasible exercise type that can be utilized across different ages and health status. This randomized cross-over study aimed to investigate the effect of acute HIIT on cortical excitability, M1-related cognitive functions, cognition-related myokines, brain-derived neurotrophic factor (BDNF), and Cathepsin B (CTSB). Twenty-three sedentary young adults (mean age: 22.78 years ± 2.87; 14 female) participated in a cross-over design involving two sessions: either 23 min of HIIT or seated rest. Before and after the sessions, cortical excitability was measured using transcranial magnetic stimulation, and M1-related cognitive functions were assessed by the n-back test and mental rotation test. Serum levels of BDNF and CTSB were assessed using the ELISA method before and after the HIIT intervention. We demonstrated that HIIT improved mental rotation and working memory, and increased serum levels of BDNF and CTSB, whereas cortical excitability did not change. Our findings provide evidence that one session of HIIT is effective on M1-related cognitive functions and cognition-related myokines. Future research is warranted to determine whether such findings are transferable to different populations, such as cognitively at-risk children, adults, and older adults, and to prescribe effective exercise programs.

Non-invasive brain stimulation and vision rehabilitation: a clinical perspective

Non-invasive brain stimulation techniques allow targeted modulation of brain regions and have emerged as a promising tool for vision rehabilitation. This review presents an overview of studies that have examined the use of non-invasive brain stimulation techniques for improving vision and visual functions. A description of the proposed neural mechanisms that underpin non-invasive brain stimulation effects is also provided. The clinical implications of non-invasive brain stimulation in vision rehabilitation are examined, including their safety, effectiveness, and potential applications in specific conditions such as amblyopia, post-stroke hemianopia, and central vision loss associated with age-related macular degeneration. Additionally, the future directions of research in this field are considered, including the need for larger and more rigorous clinical trials to validate the efficacy of these techniques. Overall, this review highlights the potential for brain stimulation techniques as a promising avenue for improving visual function in individuals with impaired vision and underscores the importance of continued research in this field.

Acute aerobic exercise at different intensities modulates inhibitory control and cortical excitability in adults with attention-deficit hyperactivity disorder (ADHD)

BACKGROUND

This study aimed to investigate the effects of different aerobic exercise intensities on inhibitory control and cortical excitability in adults with attention-deficit/hyperactivity disorder (ADHD).

METHODS

The study was conducted in a within-subject design. Twenty-four adults with ADHD completed a stop signal task and received cortical excitability assessment by transcranial magnetic stimulation (TMS) before and after a single session of low-, moderate-, high-intensity aerobic exercise or a control intervention.

RESULTS

Acute moderate-, and high-intensity aerobic exercise improved inhibitory control in adults with ADHD. Moreover, the improving effect was similar between moderate-, and high-intensity aerobic exercise conditions. As shown by the brain physiology results, short interval intracortical inhibition was significantly increased following both, moderate- and high-intensity aerobic exercise intervention conditions. Additionally, the alteration of short interval intracortical inhibition and inhibitory control improvement were positively correlated.

CONCLUSIONS

The moderate-, and high-intensity aerobic exercise-dependent alterations of cortical excitability in adults with ADHD might partially explain the inhibitory control-improving effects of aerobic exercise in this population.

Reducing motor evoked potential amplitude variability through normalization

Background

Transcranial Magnetic Stimulation (TMS) is used for in vivo assessment of human motor cortical excitability, with application of TMS pulses over the motor cortex resulting in muscle responses that can be recorded with electromyography (EMG) as Motor Evoked Potentials (MEPs). These have been widely explored as potential biomarkers for neuropsychiatric disorders but methodological heterogeneity in acquisition, and inherent high variability, have led to constraints in reproducibility. Normalization, consisting in scaling the signal of interest to a known and repeatable measurement, reduces variability and is standard practice for between-subject comparisons of EMG. The effect of normalization on variability of MEP amplitude has not yet been explored and was assessed here using several methods.

Methods

Three maximal voluntary isometric contractions (MVICs) and 40 MEPs were collected from the right hand in healthy volunteers, with a retest session conducted 4 to 8 weeks later. MEP amplitude was normalized using either external references (MVICs) or internal references (extreme MEPs). Iterative re-sampling of 30 normalized MEPs per subject was repeated 5,000 times to define, for each normalization method, distributions for between-subject coefficients of variation (CV) of the mean MEP amplitude. Intra-class correlation coefficients (ICC) were used to assess the impact of normalization on test–retest stability of MEP amplitude measurements.

Results

In the absence of normalization, MEPs collected from the right hand of 47 healthy volunteers were within reported values regarding between-subject variability (95% confidence intervals for the CV: [1.0567,1.0577]) and showed good temporal stability (ICC = 0.77). Internal reference normalization substantially reduced between-subject variability, by values of up to 64%, while external reference normalization had no impact or increased between-subject variability. Normalization with the smallest references reduced test–retest stability, with use of the largest references resulting in slight reduction or improvement of ICCs. Internal reference normalization using the largest MEPs was found to be robust to several sensitivity analyses.

Conclusion

Internal, but not external, reference normalization reduces between-subject variability of MEP amplitude, and has a minimal impact on within-subject variability when conducted with the largest references. Additional research is necessary to further validate these normalization methods toward potential use of MEPs as biomarkers of neuropsychiatric disorders.

Response to experimental cold-induced pain discloses a resistant category among endurance athletes, with a distinct profile of pain-related behavior and GABAergic EEG markers: a case-control preliminary study

Pain is a major public health problem worldwide, with a high rate of treatment failure. Among promising non-pharmacological therapies, physical exercise is an attractive, cheap, accessible and innocuous method; beyond other health benefits. However, its highly variable therapeutic effect and incompletely understood underlying mechanisms (plausibly involving the GABAergic neurotransmission) require further research. This case-control study aimed to investigate the impact of long-lasting intensive endurance sport practice (≥7 h/week for the last 6 months at the time of the experiment) on the response to experimental cold-induced pain (as a suitable chronic pain model), assuming that highly trained individual would better resist to pain, develop advantageous pain-copying strategies and enhance their GABAergic signaling. For this purpose, clinical pain-related data, response to a cold-pressor test and high-density EEG high (Hβ) and low beta (Lβ) oscillations were documented. Among 27 athletes and 27 age-adjusted non-trained controls (right-handed males), a category of highly pain-resistant participants (mostly athletes, 48.1%) was identified, displaying lower fear of pain, compared to non-resistant non-athletes. Furthermore, they tolerated longer cold-water immersion and perceived lower maximal sensory pain. However, while having similar Hβ and Lβ powers at baseline, they exhibited a reduction between cold and pain perceptions and between pain threshold and tolerance (respectively -60% and - 6.6%; -179.5% and - 5.9%; normalized differences), in contrast to the increase noticed in non-resistant non-athletes (+21% and + 14%; +23.3% and + 13.6% respectively). Our results suggest a beneficial effect of long-lasting physical exercise on resistance to pain and pain-related behaviors, and a modification in brain GABAergic signaling. In light of the current knowledge, we propose that the GABAergic neurotransmission could display multifaceted changes to be differently interpreted, depending on the training profile and on the homeostatic setting (e.g., in pain-free versus chronic pain conditions). Despite limitations related to the sample size and to absence of direct observations under acute physical exercise, this precursory study brings into light the unique profile of resistant individuals (probably favored by training) allowing highly informative observation on physical exercise-induced analgesia and paving the way for future clinical translation. Further characterizing pain-resistant individuals would open avenues for a targeted and physiologically informed pain management.

Acute Aerobic Exercise at Different Intensities Modulates Motor Learning Performance and Cortical Excitability in Sedentary Individuals

Converging evidence indicates the beneficial effects of aerobic exercise on motor learning performance. Underlying mechanisms might be an impact of aerobic exercise on neuroplasticity and cortical excitability. Evidence suggests that motor learning and cortical excitability alterations correlate with the intensity of aerobic exercise and the activity level of participants. Thus, this study aims to investigate the effects of different aerobic exercise intensities on motor learning and cortical excitability in sedentary individuals. The study was conducted in a crossover and double-blind design. Twenty-six healthy sedentary individuals (13 women and 13 men) performed a motor learning task and received a cortical excitability assessment before and after a single session of low-, moderate-, and high-intensity aerobic exercise or a control intervention. The study revealed that motor learning performance and cortical excitability were significantly enhanced in the moderate-intensity aerobic exercise, compared with the other conditions. These findings suggest aerobic exercise intensity-dependent effects on motor learning in sedentary adults. The underlying mechanism might be an exercised-induced alteration of cortical excitability, specifically a reduction of GABA activity.

[Movement as a Neuromodulator: How Physical Activity Influences the Physiology of Adolescent Depression]

Movement as a Neuromodulator: How Physical Activity Influences the Physiology of Adolescent Depression Abstract: In the context of adolescent depression, physical activity is becoming increasingly recognized for its positive effects on neuropathology. Current scientific findings indicate that physical training affects the biological effects of depression during adolescence. Yet the pathophysiology of adolescent depression is not yet fully understood. Besides psychosocial and genetic influences, various neurobiological factors are being discussed. One explanation model describes a dysfunction of the hypothalamus-pituitary-adrenal axis (HPA axis) with a sustained elevation in cortisol concentration. Recent studies highlight neuroimmunological processes and a reduced concentration of growth factors as causative factors. These changes appear to lead to a dysregulation of the excitation and inhibition balance of the cerebral cortex as well as to cerebral morphological alterations. Regular physical training can potentially counteract the dysregulation of the HPA axis and normalize cortisol levels. The release of proinflammatory cytokines is inhibited, and the expression of growth factors involved in adult neurogenesis is stimulated. One should ensure the synergistic interaction of biological and psychosocial factors when designing the exercise schedule (endurance or strength training, group or individual sports, frequency, duration, and intensity). Addressing these open questions is essential when integrating physical activity into the guidelines for treating depressive disorders in children and adolescents.

Physiological, Anatomical and Metabolic Correlates of Aerobic Fitness in Human Primary Motor Cortex: A Multimodal Study

Physical activity (PA) has been shown to benefit various cognitive functions and promote neuroplasticity. Whereas the effects of PA on brain anatomy and function have been well documented in older individuals, data are scarce in young adults. Whether high levels of cardiorespiratory fitness (CRF) achieved through regular PA are associated with significant structural and functional changes in this age group remains largely unknown. In the present study, twenty young adults that engaged in at least 8 hours per week of aerobic exercise during the last 5 years were compared to twenty sedentary controls on measures of cortical excitability, white matter microstructure, cortical thickness and metabolite concentration. All measures were taken in the left primary motor cortex and CRF was assessed with VO_2max. Transcranial magnetic stimulation (TMS) revealed higher corticospinal excitability in high- compared to low-fit individuals reflected by greater input/output curve amplitude and slope. No group differences were found for other TMS (short-interval intracortical inhibition and intracortical facilitation), diffusion MRI (fractional anisotropy and apparent fiber density), structural MRI (cortical thickness) and magnetic resonance spectroscopy (NAA, GABA, Glx) measures. Taken together, the present data suggest that brain changes associated with increased CRF are relatively limited, at least in primary motor cortex, in contrast to what has been observed in older adults.

Synaptic Plasticity 101: The Story of the AMPA Receptor for the Brain Stimulation Practitioner

The fields of Neurobiology and Neuromodulation have never been closer. Consequently, the phrase "synaptic plasticity" has become very familiar to non-basic scientists, without actually being very familiar. We present the "Story of the AMPA receptor," an easy-to-understand "10,000 ft" narrative overview of synaptic plasticity, oriented toward the brain stimulation clinician or scientist without basic science training. Neuromodulation is unparalleled in its capacity to both modulate and probe plasticity, yet many are not comfortable with their grasp of the topic. Here, we describe the seminal discoveries that defined the canonical mechanisms of long-term potentiation (LTP), long-term depression (LTD), and homeostatic plasticity. We then provide a conceptual framework for how plasticity at the synapse is accomplished, describing the functional roles of N-methyl-d-aspartate (NMDA) receptors and calcium, their effect on calmodulin, phosphatases (ie, calcineurin), kinases (ie, calcium/calmodulin-dependent protein kinase [CaMKII]), and structural "scaffolding" proteins (ie, post-synaptic density protein [PSD-95]). Ultimately, we describe how these affect the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor. More specifically, AMPA receptor delivery to (LTP induction), removal from (LTD), or recycling within (LTP maintenance) the synapse is determined by the status of phosphorylation and protein binding at specific sites on the tails of AMPA receptor subunits: GluA1 and GluA2. Finally, we relate these to transcranial magnetic stimulation (TMS) treatment, highlighting evidences for LTP as the basis of high-frequency TMS therapy, and briefly touch on the role of plasticity for other brain stimulation modalities. In summary, we present Synaptic Plasticity 101 as a singular introductory reference for those less familiar with the mechanisms of synaptic plasticity.

The size and behavior of virtual objects have influence on functional exercise and motivation of persons with multiple sclerosis: a randomized study

The consequences of multiple sclerosis are problems with limb movement, coordination, and vision. Heretofore a combination of therapy and additional medications can alter the course of the disease and reduce upper extremity disability. We developed a virtual environment for pick-and-place tasks as a supportive tool to address the problem of challenging task in occupational therapy. The primary objective of the study was to investigate the influence of size and bounce on proximal and fine motor performance and intrinsic motivation. The secondary objective was to examine how the absence of challenge may decrease intrinsic motivation and heart rate. The randomized trial involved 84/107 eligible inpatients with multiple sclerosis. They were divided into 4 groups by computer randomization: Group 1 small and bouncing, Group 2 small and non-bouncing, Group 3 large and bouncing, and Group 4 large and non-bouncing virtual cubes. Each participant completed 50 sessions of up to 2 min each in approximately 14 days. Before commencement of the study the participants completed visuospatial and cognitive tests. Participants' subjective experiences were assessed daily using the intrinsic motivation inventory. Before and after the study, the box and block test and the 9-hole peg test were administered. Kinematic analysis showed significant differences between groups (average manipulation time p = 0.008, inserted cubes p = 0.004). Group 4 was the most successful (inserted cubes > 9) and the fastest (63.4 SD 25.8 s), but had low pressure/tension and heart rate. Group 1 was the slowest (88.9 SD 28.2 s) but had increased interest/enjoyment in the task under higher pressure/tension. There were substantial differences in intrinsic motivation between the 1st and last sessions within groups (Cohen's U3 < 0.3 or > 0.8). The size and behavior of virtual objects may be important for training proximal movements and fine motor skills in people with multiple sclerosis. Furthermore, the demonstrated approach proved to be effective and may reduce upper extremity disability in the long term if intrinsic motivation can be sustained longer with a challenging task.Trial registration The small scale randomized pilot trial has been registered at ClinicalTrials.gov Identifier: NCT04266444, 12/02/2020, https://clinicaltrials.gov/ct2/show/NCT04266444 .

The Combined Influences of Exercise, Diet and Sleep on Neuroplasticity

Neuroplasticity refers to the brain’s ability to undergo structural and functional adaptations in response to experience, and this process is associated with learning, memory and improvements in cognitive function. The brain’s propensity for neuroplasticity is influenced by lifestyle factors including exercise, diet and sleep. This review gathers evidence from molecular, systems and behavioral neuroscience to explain how these three key lifestyle factors influence neuroplasticity alone and in combination with one another. This review collected results from human studies as well as animal models. This information will have implications for research, educational, fitness and neurorehabilitation settings.

Can exercise shape your brain? A review of aerobic exercise effects on cognitive function and neuro-physiological underpinning mechanisms

It is widely accepted that physical exercise can be used as a tool for the prevention and treatment of various diseases or disorders. In addition, in the recent years, exercise has also been successfully used to enhance people's cognition. There is a large amount of research that has supported the benefits of physical exercise on human cognition, both in children and adults. Among these studies, some have focused on the acute or transitory effects of exercise on cognition, while others have focused on the effects of regular physical exercise. However, the relation between exercise and cognition is complex and we still have limited knowledge about the moderators and mechanisms underlying this relation. Most of human studies have focused on the behavioral aspects of exercise-effects on cognition, while animal studies have deepened in its possible neuro-physiological mechanisms. Even so, thanks to advances in neuroimaging techniques, there is a growing body of evidence that provides valuable information regarding these mechanisms in the human population. This review aims to analyze the effects of regular and acute aerobic exercise on cognition. The exercise-cognition relationship will be reviewed both from the behavioral perspective and from the neurophysiological mechanisms. The effects of exercise on animals, adult humans, and infant humans will be analyzed separately. Finally, physical exercise intervention programs aiming to increase cognitive performance in scholar and workplace environments will be reviewed.

Acute Effects of High-Intensity Aerobic Exercise on Motor Cortical Excitability and Inhibition in Sedentary Adults

Transcranial magnetic stimulation studies have demonstrated increased cortical facilitation and reduced inhibition following aerobic exercise, even when examining motor regions separate to the exercised muscle group. These changes in brain physiology following exercise may create favorable conditions for adaptive plasticity and motor learning. One candidate mechanism behind these benefits is the increase in brain-derived neurotropic factor (BDNF) observed following exercise, which can be quantified from a venous blood draw. The aim of this study was to investigate changes in motor cortex excitability and inhibition of the upper limb, and circulating BDNF, following high-intensity interval training (HIIT) on a stationary bicycle. Nineteen sedentary adults participated in a randomized crossover design study involving a single bout of high-intensity interval cycling for 20 min or seated rest. Venous blood samples were collected, and transcranial magnetic stimulation (TMS) was used to stimulate the extensor carpi radialis (ECR), where motor evoked potentials (MEP) were recorded pre- and post-condition. Following exercise, there was a significant increase (29.1%, p < 0.001) in corticospinal excitability measured at 120% of resting motor threshold (RMT) and a reduction in short-interval cortical inhibition (SICI quantified as 86.2% increase in the SICI ratio, p = 0.002). There was a non-significant (p = 0.125) 23.6% increase in BDNF levels. Collectively, these results reflect a net reduction in gamma aminobutyric acid (GABA)ergic synaptic transmission and increased glutamatergic facilitation, resulting in increased corticospinal excitability. This study supports the notion that acute high-intensity exercise provides a potent stimulus for inducing cortical neuroplasticity, which may support enhanced motor learning.

EU health co-design policies to counteract the covid-19 pandemic effect promoting physical activity

BACKGROUND

The research is placed in the context of interdisciplinary medical-legal studies on the importance of promoting physical activity as a public health tool.

OBJECTIVE

The aim was to highlight the tools that can be used by EU members for planning interventions aimed at overcoming the consequences of the COVID-19 pandemic and for responding to a future crisis.

METHODS

First, the medical resources relating to the indirect and direct effects of the COVID-19 pandemic are analysed. Then, the results are compared with the measures of the EU bodies to verify the correspondence of the scientific arrests, with the political-regulatory interventions.

RESULTS

It was found that the prolonged closure of sports centres and the contagion from COVID-19 produce affects the body in a way that can only be recovered by motor activity. However, in the EU, there does not exist a regulatory harmonization about health issues that can directly impose the Members to implement their legislation to promote motor activity.

CONCLUSIONS

The signing of the Rome Declaration at the Global Health Summit on 21 May 2021 constitutes an important and concrete commitment for the exchange in the medical-scientific field, and for an effective co-design of intervention strategies for the relaunch of physical activity within projects such as EU4Health and the two-year HealthyLifestyle4All campaign.

Use-dependent corticospinal excitability is associated with resilience and physical performance during simulated military operational stress

Simulated military operational stress (SMOS) provides a useful model to better understand resilience in humans as the stress associated with caloric restriction, sleep deficits, and fatiguing exertion degrades physical and cognitive performance. Habitual physical activity may confer resilience against these stressors by promoting favorable use-dependent neuroplasticity, but it is unclear how physical activity, resilience, and corticospinal excitability (CSE) relate during SMOS. To examine associations between corticospinal excitability, physical activity, and physical performance during SMOS. Fifty-three service members (age: 26 ± 5 yr, 13 women) completed a 5-day and -night intervention composed of familiarization, baseline, SMOS (2 nights/days), and recovery days. During SMOS, participants performed rigorous physical and cognitive activities while receiving half of normal sleep (two 2-h blocks) and caloric requirements. Lower and upper limb CSE were determined with transcranial magnetic stimulation (TMS) stimulus-response curves. Self-reported resilience, physical activity, military-specific physical performance (TMT), and endocrine factors were compared in individuals with high (HIGH) and low CSE based on a median split of lower limb CSE at baseline. HIGH had greater physical activity and better TMT performance throughout SMOS. Both groups maintained physical performance despite substantial psychophysiological stress. Physical activity, resilience, and TMT performance were directly associated with lower limb CSE. Individual differences in physical activity coincide with lower (but not upper) limb CSE. Such use-dependent corticospinal excitability directly relates to resilience and physical performance during SMOS. Future studies may use noninvasive neuromodulation to clarify the interplay among CSE, physical activity, and resilience and improve physical and cognitive performance.NEW & NOTEWORTHY We demonstrate that individual differences in physical activity levels coincide with lower limb corticospinal excitability. Such use-dependent corticospinal excitability directly relates to resilience and physical performance during a 5-day simulation of military operational stress with caloric restriction, sleep restriction and disruption, and heavy physical and cognitive exertion.

Acute High-Intensity Interval Exercise Modulates Corticospinal Excitability in Older Adults

INTRODUCTION

Acute exercise can modulate the excitability of the non-exercised upper-limb representation in the primary motor cortex (M1). Measures of M1 excitability using transcranial magnetic stimulation (TMS) are modulated following various forms of acute exercise in young adults, including high intensity interval training (HIIT). However, the impact of HIIT on M1 excitability in older adults is currently unknown. Therefore, the purpose of the current study was to investigate the effects of lower-limb cycling HIIT on bilateral upper-limb M1 excitability in older adults.

METHODS

We assessed the impact of acute lower-limb HIIT or rest on bilateral corticospinal excitability, intracortical inhibition and facilitation, and interhemispheric inhibition of the non-exercised upper-limb muscle in healthy older adults (aged 66 ± 8). We used single and paired-pulse TMS to assess motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI), intracortical facilitation (ICF) and the ipsilateral silent period (iSP). Two groups of healthy older adults completed either HIIT exercise or seated rest for 23 min, with TMS measures performed pre (T0), immediately post (T1) and 30 min post (T2) HIIT/rest.

RESULTS

MEPs were significantly increased after HIIT exercise at T2 compared to T0 in the dominant upper-limb. Contrary to our hypothesis we did not find any significant change in SICI, ICF or iSP following HIIT.

CONCLUSIONS

Our findings demonstrate that corticospinal excitability of the non-exercised upper-limb is increased following HIIT in healthy older adults. Our results indicate that acute HIIT exercise impacts corticospinal excitability in older adults, without affecting intracortical or interhemispheric circuitry. These findings have implications for the development of exercise strategies to potentiate neuroplasticity in healthy older and clinical populations.

A Single Bout of High-Intensity Cardiovascular Exercise Does Not Enhance Motor Performance and Learning of a Visuomotor Force Modulation Task, but Triggers Ipsilateral Task-Related EEG Activity

Acute cardiovascular exercise (aCE) seems to be a promising strategy to improve motor performance and learning. However, results are heterogeneous, and the related neurophysiological mechanisms are not well understood. Oscillatory brain activitiy, such as task-related power (TRPow) in the alpha and beta frequencies, are known neural signatures of motor activity. Here, we tested the effects of aCE on motor performance and learning, along with corresponding modulations in EEG TRPow over the sensorimotor cortex. Forty-five right-handed participants (aged 18-34 years) practiced a visuomotor force-matching (FM) task after either high-intensity (HEG), low-intensity (LEG), or no exercise (control group, CG). Motor performance was assessed immediately, 15 min, 30 min, and 24 h after aCE/control. EEG was measured during the FM task. Results of frequentist and Bayesian statistics revealed that high- and low-intensity aCE had no effect at the behavioral level, adding to the previous mixed results. Interestingly, EEG analyses showed an effect of aCE on the ipsilateral sensorimotor cortex, with a stronger decrease in β-TRPow 15 min after exercise in both groups compared to the CG. Overall, aCE applied before motor practice increased ipsilateral sensorimotor activity, while motor learning was not affected; it remains to be seen whether aCE might affect motor learning in the long run.

Acute Exercise Modulates the Excitability of Specific Interneurons in Human Motor Cortex

Acute exercise can modulate the excitability of the non-exercised upper-limb representation in the primary motor cortex (M1). Accumulating evidence demonstrates acute exercise affects measures of M1 intracortical excitability, with some studies also showing altered corticospinal excitability. However, the influence of distinct M1 interneuron populations on the modulation of intracortical and corticospinal excitability following acute exercise is currently unknown. We assessed the impact of an acute bout of leg cycling exercise on unique M1 interneuron excitability of a non-exercised intrinsic hand muscle using transcranial magnetic stimulation (TMS) in young adults. Specifically, posterior-to-anterior (PA) and anterior-to-posterior (AP) TMS current directions were used to measure the excitability of distinct populations of interneurons before and after an acute bout of exercise or rest. Motor evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) were measured in the PA and AP current directions in M1 at two time points separated by 25 min of rest, as well as immediately and 30 min after a 25-minute bout of moderate-intensity cycling exercise. Thirty minutes after exercise, MEP amplitudes were significantly larger than other timepoints when measured with AP current, whereas MEP amplitudes derived from PA current did not show this effect. Similarly, SICI was significantly decreased immediately following acute exercise measured with AP but not PA current. Our findings suggest that the excitability of unique M1 interneurons are differentially modulated by acute exercise. These results indicate that M1 interneurons preferentially activated by AP current may play an important role in the exercise-induced modulation of intracortical and corticospinal excitability.

Cognition and Exercise: GENERAL OVERVIEW AND IMPLICATIONS FOR CARDIAC REHABILITATION

Performance of endurance exercise is associated with a broad range of cognitive benefits, with notable improvements shown across a wide variety of populations including healthy populations as well as those with impaired cognition. By examining the effects of exercise in general populations, as well in populations where cognitive deficits are pronounced, and critical to self-care, we can learn more about using exercise to ameliorate cognitive issues and apply that knowledge to other patient populations, such as those eligible for cardiac rehabilitation (CR). Cognitive challenges are a concern within CR, as management of a chronic disease is cognitively taxing, and, as expected, deficits in cognition predict worse outcomes, including lower attendance at CR. Some subsets of patients within CR may be particularly at high risk for cognitive challenges including those with heart failure with low ejection fraction, recent coronary bypass surgery, multiple chronic conditions, and patients of lower socioeconomic status. Attendance at CR is associated with cognitive gains, likely through the progressive exercise component, with larger amounts of exercise over longer periods having greater benefits. Programs should identify at-risk patients, who could gain the most from completing CR, and provide additional support to keep those patients engaged. While engaged in CR, patients should be encouraged to exercise, at least at moderate intensity, and transitioned to a long-term exercise regimen. Overall, CR programs are well-positioned to support these patients and make significant contributions to their long-term well-being.

Physical activity, motor performance and skill learning: a focus on primary motor cortex in healthy aging

Participation in physical activity benefits brain health and function. Cognitive function generally demonstrates a noticeable effect of physical activity, but much less is known about areas responsible for controlling movement, such as primary motor cortex (M1). While more physical activity may support M1 plasticity in older adults, the neural mechanisms underlying this beneficial effect remain poorly understood. Aging is inevitably accompanied by diminished motor performance, and the extent of plasticity may also be less in older adults compared with young. Motor complications with aging may, perhaps unsurprisingly, contribute to reduced physical activity in older adults. While the development of non-invasive brain stimulation techniques have identified that human M1 is a crucial site for learning motor skills and recovery of motor function after injury, a considerable lack of knowledge remains about how physical activity impacts M1 with healthy aging. Reducing impaired neural activity in older adults may have important implications after neurological insult, such as stroke, which is more common with advancing age. Therefore, a better understanding about the effects of physical activity on M1 processes and motor learning in older adults may promote healthy aging, but also allow us to facilitate recovery of motor function after neurological injury. This article will initially provide a brief overview of the neurophysiology of M1 in the context of learning motor skills, with a focus on healthy aging in humans. This information will then be proceeded by a more detailed assessment that focuses on whether physical activity benefits motor function and human M1 processes.

Correlation of exercise style to mental health and social adaptability of college students

BACKGROUND

Talents are the basis of all development and comprehensive strength of a country. As college students who are about to contact the society, their mental health and social adaptability are the most critical factors for their entry into society.

OBJECTIVE

Therefore, this study explores the correlation of exercise style to mental health and social adaptability of college students.

METHODS

Based on the sample processing of college students in 4 universities in a city, 1,000 students are selected for research on the correlation of exercise style to mental health and social adaptability. In addition, the impacts of college students participating in sports activities on their mental health and social adaptability are analyzed.

RESULTS

When the duration of a single sports activity is 30-60 min, the mental health of students reaches optimal. On the contrary, when the duration of a single sports activity exceeds 90 min, the mental health of students is low. This indicates that the more students participate in sports activities, the stronger the social adaptability is. When the intensity of sports activities for students is moderate, the average scores of interpersonal communication ability of students are the highest. When the duration of a single sports activity is 60-90 min, the average scores of living adaptability of students are the highest. If students keep the appropriate duration and intensity of sports activities, their social adaptability will be improved notably.

CONCLUSION

The social adaptability of students is related to the number of times they participate in sports activities, the duration of a single sports activity, and the intensity of sports activities. However, while exercising, students should plan the duration of sports activities to avoid excessively prolonged exercise time. In addition, students should beware their exercise intensity of sports activities. The optimal choice of exercise intensity is moderate or slightly tired.

The effect of acute aerobic exercise on the consolidation of motor memories

Acute aerobic exercise performed prior to training may assist with motor skill acquisition through enhancement of motor cortical plasticity. In addition, high-intensity exercise performed after training improves retention, although the mechanisms of this are unclear. We hypothesized that acute continuous moderate-intensity exercise performed post-motor training would also assist with motor skill retention and that this behavioral change would be positively correlated with neural markers of training-related cortical adaptation. Participants [n = 33; assigned to an exercise (EXE) or control (CON) group] completed a single visuomotor training session using bilateral wrist movements while movement-related cortical potentials (MRCPs) were collected. After motor training, the EXE group exercised for 20 min [70% of heart rate reserve (HRR)] and the CON group read for the same amount of time. Both groups completed two post-training tests after exercise/rest: 10 min and ~ 30 min once heart rate returned to resting level in EXE. Retention and transfer tests were both completed 1 and 7 days later. MRCPs measured training-related neural adaptations during the first visit and motor performance was assessed as time and trajectory to the target. The EXE group had better performance than CON at retention (significant 7 days post-training). MRCP amplitudes increased from early to late motor training and this amplitude change was correlated with motor performance at retention. Results suggest that moderate-intensity exercise post-motor training helps motor skill retention and that there may be a relationship with motor training-related cortical adaptations that is enhanced with post-motor training exercise.

Transcranial Magnetic Stimulation to Assess Exercise-Induced Neuroplasticity

Aerobic exercise facilitates neuroplasticity and has been linked to improvements in cognitive and motor function. Transcranial magnetic stimulation (TMS) is a non-invasive technique that can be used to quantify changes in neurophysiology induced by exercise. The present review summarizes the single- and paired-pulse TMS paradigms that can be used to probe exercise-induced neuroplasticity, the optimal stimulation parameters and the current understanding of the neurophysiology underlying each paradigm. Further, this review amalgamates previous research exploring the modulation of these paradigms with exercise-induced neuroplasticity in healthy and clinical populations and highlights important considerations for future TMS-exercise research.

A Single Bout of High-intensity Interval Exercise Increases Corticospinal Excitability, Brain-derived Neurotrophic Factor, and Uncarboxylated Osteolcalcin in Sedentary, Healthy Males

Exercise induces neuroplasticity in descending motor pathways facilitating motor learning, and as such it could be utilized as an intervention in neurorehabilitation, for example when re-learning motor skills after stroke. To date, however, the neurophysiological and molecular mechanisms underlying exercise-induced neuroplasticity remain largely unknown impeding the potential utilization of exercise protocols as 'motor learning boosters' in clinical and non-clinical settings. Here, we assessed corticospinal excitability, intracortical facilitation (ICF) and short-interval intracortical inhibition (SICI) using transcranial magnetic stimulation (TMS) and serum biochemical markers including brain-derived neurotrophic factor (BDNF), total and precursor cathepsin B (tCTSB, proCTSB), uncarboxylated and carboxylated osteocalcin (unOCN, cOCN) and irisin using ELISA. Measurements were carried out in sedentary, healthy males before and after a single session of high-intensity interval exercise (HIIE) or in individuals who rested and did not perform exercise (No Exercise). We found that HIIE increased corticospinal excitability, BDNF and unOCN, and decreased cOCN. We also determined that greater increases in BDNF were associated with increases in unOCN and irisin and decreases in cOCN only in participants who underwent HIIE, suggesting that unOCN and irisin may contribute to exercise-induced BDNF increases. Conversely, no changes other than a decrease in serum unOCN/tOCN were found in No Exercise participants. The present findings show that a single session of HIIE is sufficient to modulate corticospinal excitability and to increase BDNF and unOCN in sedentary, healthy males.

Aerobic exercise and aerobic fitness level do not modify motor learning

Motor learning may be enhanced when a single session of aerobic exercise is performed immediately before or after motor skill practice. Most research to date has focused on aerobically trained (AT) individuals, but it is unknown if aerobically untrained (AU) individuals would equally benefit. We aimed to: (a) replicate previous studies and determine the effect of rest (REST) versus exercise (EXE) on motor skill retention, and (b) explore the effect of aerobic fitness level (AU, AT), assessed by peak oxygen uptake (VO2peak), on motor skill retention after exercise. Forty-four participants (20-29 years) practiced a visuomotor tracking task (acquisition), immediately followed by 25-min of high-intensity cycling or rest. Twenty-four hours after acquisition, participants completed a motor skill retention test. REST and EXE groups significantly improved motor skill performance during acquisition [F(3.17, 133.22) = 269.13, P = 0.001], but had no group differences in motor skill retention across time. AU-exercise (VO2peak = 31.6 ± 4.2 ml kg-1 min-1) and AT-exercise (VO2peak = 51.5 ± 7.6 ml kg-1 min-1) groups significantly improved motor skill performance during acquisition [F(3.07, 61.44) = 155.95, P = 0.001], but had no group differences in motor skill retention across time. Therefore, exercise or aerobic fitness level did not modify motor skill retention.

Reliability of corticospinal excitability estimates for the vastus lateralis: Practical considerations for lower limb TMS task selection

Transcranial magnetic stimulation (TMS) is increasingly used to examine lower extremity corticospinal excitability (CSE) in clinical and sports research. Because CSE is task-specific, there is growing emphasis on the use of ecological tasks. Nevertheless, the comparative reliability of CSE measurements during established (e.g. knee extensions; KE) and more recent ecological (e.g. squats; SQT) lower extremity tasks has received less attention. The aim of this study was to compare the test-retest reliability of CSE, force, and muscle activity (EMG) during isometric SQT and KE. 19 right-footed men (age: 25 ± 5 yrs) with similar fitness and body composition performed SQT (N = 7) or KE (N = 12) on two consecutive days. Force and EMG were recorded during maximum voluntary isometric contractions (MVC). Corticospinal excitability was determined in the dominant leg during light (15% MVC) contractions based on motor evoked potential (MEP) stimulus-response-curves (SRC). Test-retest reliability, absolute agreement, and consistency were determined for force, EMG, and SRC MEP maximum (MEPMAX) and rising phase midpoint (V50). As a secondary analysis, all outcomes were compared between groups with mixed-methods ANCOVAs (Task × Time, covariate: body-fat-percentage). Compared with SQT, KE displayed better test-retest reliability and agreement for MEPMAX whereas V50, force, and EMG were similarly reliable. Force (p = 0.01) and MEPMAX (p = 0.02) were also greater during KE despite a similar V50 (p = 0.11). Differences in test-retest reliability, absolute agreement, and between-group comparisons highlight the need to carefully select lower limb TMS assessment tasks and encourage future efforts to balance ecological validity with statistical sensitivity.

Determining the Intracortical Responses After a Single Session of Aerobic Exercise in Young Healthy Individuals: A Systematic Review and Best Evidence Synthesis

ABSTRACT

Alibazi, RJ, Pearce, AJ, Rostami, M, Frazer, AK, Brownstein, C, and Kidgell, DJ. Determining the intracortical responses after a single session of aerobic exercise in young healthy individuals: a systematic review and best evidence synthesis. J Strength Cond Res 35(2): 562-575, 2021-A single bout of aerobic exercise (AE) may induce changes in the excitability of the intracortical circuits of the primary motor cortex (M1). Similar to noninvasive brain stimulation techniques, such as transcranial direct current stimulation, AE could be used as a priming technique to facilitate motor learning. This review examined the effect of AE on modulating intracortical excitability and inhibition in human subjects. A systematic review, according to PRISMA guidelines, identified studies by database searching, hand searching, and citation tracking between inception and the last week of February 2020. Methodological quality of included studies was determined using the Downs and Black quality index and Cochrane Collaboration of risk of bias tool. Data were synthesized and analyzed using best-evidence synthesis. There was strong evidence for AE not to change corticospinal excitability and conflicting evidence for increasing intracortical facilitation and reducing silent period and long-interval cortical inhibition. Aerobic exercise did reduce short-interval cortical inhibition, which suggests AE modulates the excitability of the short-latency inhibitory circuits within the M1; however, given the small number of included studies, it remains unclear how AE affects all circuits. In light of the above, AE may have important implications during periods of rehabilitation, whereby priming AE could be used to facilitate motor learning.

Impact of the number of conditioning pulses on motor cortex excitability: a transcranial magnetic stimulation study

Conditioning transcranial magnetic stimulation (TMS) with subthreshold conditioning stimulus followed by supra-threshold test stimulus at inter-stimulus intervals (ISI) of 1–5 ms results in inhibition (SICI), while ISI at 10–15 ms results in facilitation (ICF). One concerning issue, applying ICF/SICI protocols on patients is the substantial protocol variability. Here, we hypothesized that increasing the number of CS could result in more robust ICF/SICI protocols. Twenty healthy subjects participated in the study. Motor-evoked potentials (MEP) were obtained from conditioning TMS with a varying number of conditioning stimuli in 3, 4, 10, and 15 ms ISI over the primary motor cortex. MEP amplitudes were then compared to examine excitability. TMS with 3, 5, and 7 conditioning stimuli but not with one conditioning stimulus induced ICF. Moreover, 10 ms ISI produced stronger ICF than 15 ms ISI. Significant SICI was only induced with one conditioning stimulus. Besides, 3 ms ISI resulted in stronger SICI than 4 ms ISI. Only a train of conditioning stimuli induced stable ICF and may be more advantageous than the classical paired pulse ICF paradigm.

Understanding the Neurophysiological and Molecular Mechanisms of Exercise-Induced Neuroplasticity in Cortical and Descending Motor Pathways: Where Do We Stand?

Exercise is a promising, cost-effective intervention to augment successful aging and neurorehabilitation. Decline of gray and white matter accompanies physiological aging and contributes to motor deficits in older adults. Exercise is believed to reduce atrophy within the motor system and induce neuroplasticity which, in turn, helps preserve motor function during aging and promote re-learning of motor skills, for example after stroke. To fully exploit the benefits of exercise, it is crucial to gain a greater understanding of the neurophysiological and molecular mechanisms underlying exercise-induced brain changes that prime neuroplasticity and thus contribute to postponing, slowing, and ameliorating age- and disease-related impairments in motor function. This knowledge will allow us to develop more effective, personalized exercise protocols that meet individual needs, thereby increasing the utility of exercise strategies in clinical and non-clinical settings. Here, we review findings from studies that investigated neurophysiological and molecular changes associated with acute or long-term exercise in healthy, young adults and in healthy, postmenopausal women.

Post-COVID-19 Fatigue: Potential Contributing Factors

Much of the spotlight for coronavirus disease 2019 (COVID-19) is on the acute symptoms and recovery. However, many recovered patients face persistent physical, cognitive, and psychological symptoms well past the acute phase. Of these symptoms, fatigue is one of the most persistent and debilitating. In this "perspective article," we define fatigue as the decrease in physical and/or mental performance that results from changes in central, psychological, and/or peripheral factors due to the COVID-19 disease and propose a model to explain potential factors contributing to post-COVID-19 fatigue. According to our model, fatigue is dependent on conditional and physiological factors. Conditional dependency comprises the task, environment, and physical and mental capacity of individuals, while physiological factors include central, psychological, and peripheral aspects. This model provides a framework for clinicians and researchers. However, future research is needed to validate our proposed model and elucidate all mechanisms of fatigue due to COVID-19.

The effect of breaking up prolonged sitting on paired associative stimulation-induced plasticity

Paired associative stimulation (PAS) can induce plasticity in the motor cortex, as measured by changes in corticospinal excitability (CSE). This effect is attenuated in older and less active individuals. Although a single bout of exercise enhances PAS-induced plasticity in young, physically inactive adults, it is not yet known if physical activity interventions affect PAS-induced neuroplasticity in middle-aged inactive individuals. Sixteen inactive middle-aged office workers participated in a randomized cross-over design investigating how CSE and short-interval intracortical inhibition (SICI) were affected by PAS preceded by 3 h of sitting (SIT), 3 h of sitting interrupted every 30 min by 3 min of frequent short bouts of physical activity (FPA) and 2.5 h of sitting followed by 25 min of moderate-intensity exercise (EXE). Transcranial magnetic stimulation was applied over the primary motor cortex (M1) of the dominant abductor pollicis brevis to induce recruitment curves before and 5 min and 30 min post-PAS. Linear mixed models were used to compare changes in CSE using time and condition as fixed effects and subjects as random effects. There was a main effect of time on CSE and planned within-condition comparisons showed that CSE was significantly increased from baseline to 5 min and 30 min post-PAS, in the FPA condition, with no significant changes in the SIT or EXE conditions. SICI decreased from baseline to 5 min post-PAS, but this was not related to changes in CSE. Our findings suggest that in middle-aged inactive adults, FPAs may promote corticospinal neuroplasticity. Possible mechanisms are discussed.

The influence of an acute bout of moderate-intensity cycling exercise on sensorimotor integration

Acute cycling exercise can modulate motor cortical circuitry in the non-exercised upper-limb. Within the primary motor cortex, measures of intracortical inhibition are reduced and intracortical facilitation is enhanced following acute exercise. Further, acute cycling exercise decreases interhemispheric inhibition between the motor cortices and lowers cerebellar-to-motor cortex inhibition. Yet, investigations into the effects of acute exercise on sensorimotor integration, referring to the transfer of incoming afferent information from the primary somatosensory cortex to motor cortex, are lacking. The current work addresses this gap in knowledge with two experimental sessions. In the first session, we tested the exercise-induced changes in somatosensory and motor excitability by assessing somatosensory (SEP) and motor evoked potentials (MEPs). In the second session, we explored the effects of acute cycling exercise on short- (SAI) and long-latency afferent inhibition (LAI), and afferent facilitation. In both experimental sessions, neurophysiological measures were obtained from the non-exercised upper-limb muscle, tested at two time points pre-exercise separated by a 25-min period of rest. Next, a 25-min bout of moderate-intensity lower-limb cycling was performed with measures assessed at two time points post-exercise. Acute lower-limb cycling increased LAI, without modulation of SAI or afferent facilitation. Further, there were no exercise-induced changes to SEP or MEP amplitudes. Together, these results suggest that acute exercise has unique effects on sensorimotor integration, which are not accompanied by concurrent changes in somatosensory or motor cortical excitability.

No changes in corticospinal excitability, biochemical markers, and working memory after six weeks of high-intensity interval training in sedentary males

A single bout of aerobic exercise modulates corticospinal excitability, intracortical circuits, and serum biochemical markers such as brain‐derived neurotrophic factor (BDNF) and insulin‐like growth factor 1 (IGF‐1). These effects have important implications for the use of exercise in neurorehabilitation. Here, we aimed to determine whether increases in cardiorespiratory fitness (CRF) induced by 18 sessions of high‐intensity interval training (HIIT) over 6 weeks were accompanied by changes in corticospinal excitability, intracortical excitatory and inhibitory circuits, serum biochemical markers and working memory (WM) capacity in sedentary, healthy, young males. We assessed motor evoked potential (MEP) recruitment curves for the first dorsal interosseous (FDI) both at rest and during tonic contraction, intracortical facilitation (ICF), and short‐interval intracortical inhibition (SICI) using transcranial magnetic stimulation (TMS). We also examined serum levels of BDNF, IGF‐1, total and precursor (pro) cathepsin B (CTSB), as well as WM capacity. Compared to pretraining, CRF was increased and ICF reduced after the HIIT intervention, but there were no changes in corticospinal excitability, SICI, BDNF, IGF‐1, total and pro‐CTSB, and WM capacity. Further, greater CRF gains were associated with larger decreases in total and pro‐CTSB and, only in Val/Val carriers, with larger increases in SICI. Our findings confirm that HIIT is efficacious in promoting CRF and show that corticospinal excitability, biochemical markers, and WM are unchanged after 18 HIIT bouts in sedentary males. Understanding how aerobic exercise modulates M1 excitability is important in order to be able to use exercise protocols as an intervention, especially in rehabilitation following brain injuries.

Effects of twelve weeks' aerobic training on motor cortex excitability

BACKGROUND

Regular physical activity or aerobic exercise is well known to increase brain plasticity. Recent studies have reported that aerobic exercise enhances neuroplasticity and motor learning. The aim of this study was to investigate if 12 weeks' aerobic training can modify cortical excitability and motor evoked potential (MEP) responses.

METHODS

Fifteen untrained males were recruited. Cortical excitability was investigated using TMS. VO2<inf>max</inf> was estimated using Cooper's test. Aerobic intervention lasted 12 weeks. The subjects performed a 6-week supervised aerobic workout, 3 times a week, at 60-75% of their maximum heart rate (HR<inf>max</inf>). Over the following 6 weeks, they performed a supervised aerobic workout 3 times a week at 70-75% of FC<inf>max</inf>.

RESULTS

After 8 weeks of aerobic training there was a significant increase of distance covered during Cooper's test (P<0.001) and a significant increase of VO2<inf>max</inf> (P<0.001); there was also an improvement in resting motor threshold (rMT decreased from 60.5±6.6% [T0] to 55.8±5.9% [T2]; P<0.001), motor evoked potential latency decreased (from 25.3±0.8 ms [T0] to 24.1±0.8 ms [T2]; P<0.001), and motor evoked potential amplitude increased (from 0.58±0.09 mV [T0] to 0.65±0.08 mV [T2]; P<0.001). Furthermore, after 12 weeks' aerobic training there were improvements in all parameters.

CONCLUSIONS

This study shows that aerobic activity seems to induce changes in cortical excitability if performed for a period longer than 4 weeks, in addition to typical cardiorespiratory benefits in previously untrained males.

Walking Training Enhances Corticospinal Excitability in Progressive Multiple Sclerosis-A Pilot Study

Background: Inflammatory lesions and neurodegeneration lead to motor, cognitive, and sensory impairments in people with multiple sclerosis (MS). Accumulation of disability is at least partially due to diminished capacity for neuroplasticity within the central nervous system. Aerobic exercise is a potentially important intervention to enhance neuroplasticity since it causes upregulation of neurotrophins and enhances corticospinal excitability, which can be probed using single-pulse transcranial magnetic stimulation (TMS). Whether people with progressive MS who have accumulated substantial disability could benefit from walking rehabilitative training to enhance neuroplasticity is not known.

Objective: We aimed to determine whether 10 weeks of task-specific walking training would affect corticospinal excitability over time (pre, post, and 3-month follow-up) among people with progressive MS who required walking aids.

Results: Eight people with progressive MS (seven female; 29–74 years old) with an Expanded Disability Status Scale of 6–6.5 underwent harness-supported treadmill walking training in a temperature controlled room at 16°C (10 weeks; three times/week; 40 min at 40–65% heart rate reserve). After training, there was significantly higher corticospinal excitability in both brain hemispheres, reductions in TMS active motor thresholds, and increases in motor-evoked potential amplitudes and slope of the recruitment curve (REC). Decreased intracortical inhibition (shorter cortical silent period) after training was noted in the hemisphere corresponding to the stronger hand only. These effects were not sustained at follow-up. There was a significant relationship between increases in corticospinal excitability (REC, area under the curve) in the hemisphere corresponding to the stronger hand and lessening of both intensity and impact of fatigue on activities of daily living (Fatigue Severity Scale and Modified Fatigue Impact Scale, respectively).

Conclusion: Our pilot results support that vigorous treadmill training can potentially improve neuroplastic potential and mitigate symptoms of the disease even among people who have accumulated substantial disability due to MS.

Fitness Level Influences White Matter Microstructure in Postmenopausal Women

Aerobic exercise has both neuroprotective and neurorehabilitative benefits. However, the underlying mechanisms are not fully understood and need to be investigated, especially in postmenopausal women, who are at increased risk of age-related disorders such as Alzheimer’s disease and stroke. To advance our understanding of the potential neurological benefits of aerobic exercise in aging women, we examined anatomical and functional responses that may differentiate women of varying cardiorespiratory fitness using neuroimaging and neurophysiology. A total of 35 healthy postmenopausal women were recruited (59 ± 3 years) and cardiorespiratory fitness estimated (22–70 mL/kg/min). Transcranial magnetic stimulation was used to assess -aminobutyric acid (GABA) and glutamate (Glu) receptor function in the primary motor cortex (M1), and magnetic resonance spectroscopy (MRS) was used to quantify GABA and Glu concentrations in M1. Magnetic resonance imaging was used to assess mean cortical thickness (MCT) of sensorimotor and frontal regions, while the microstructure of sensorimotor and other white matter tracts was evaluated through diffusion tensor imaging. Regression analysis revealed that higher fitness levels were associated with improved microstructure in pre-motor and sensory tracts, and the hippocampal cingulum. Fitness level was not associated with MCT, MRS, or neurophysiology measures. These data indicate that, in postmenopausal women, higher cardiorespiratory fitness is linked with preserved selective white matter microstructure, particularly in areas that influence sensorimotor control and memory.

Light aerobic exercise modulates executive function and cortical excitability

Single bouts of aerobic exercise can modulate cortical excitability and executive cognitive function, but less is known about the effect of light-intensity exercise, an intensity of exercise more achievable for certain clinical populations. Fourteen healthy adults (aged 22 to 30) completed the following study procedures twice (≥7 days apart) before and after 30 min of either light aerobic exercise (cycling) or seated rest: neurocognitive battery (multitasking performance, inhibitory control and spatial working memory), paired-pulse TMS measures of cortical excitability. Significant improvements in response times during multitasking performance and increases in intracortical facilitation (ICF) were seen following light aerobic exercise. Light aerobic exercise can modulate cortical excitability and some executive function tasks. Populations with deficits in multitasking ability may benefit from this intervention.

Acute high-intensity and moderate-intensity interval exercise do not change corticospinal excitability in low fit, young adults

Previous research has demonstrated a lack of neuroplasticity induced by acute exercise in low fit individuals, but the influence of exercise intensity is unclear. In the present study, we assessed the effect of acute high-intensity (HI) or moderate-intensity (MOD) interval exercise on neuroplasticity in individuals with low fitness, as determined by a peak oxygen uptake (VO2peak) test (n = 19). Transcranial magnetic stimulation (TMS) was used to assess corticospinal excitability via area under the motor evoked potential (MEP) recruitment curve before and following training. Corticospinal excitability was unchanged after HI and MOD, suggesting no effect of acute exercise on neuroplasticity as measured via TMS in sedentary, young individuals. Repeated bouts of exercise, i.e., physical training, may be required to induce short-term changes in corticospinal excitability in previously sedentary individuals.

Acute Low-Intensity Aerobic Exercise Modulates Intracortical Inhibitory and Excitatory Circuits in an Exercised and a Non-exercised Muscle in the Primary Motor Cortex

Recent studies have reported that acute aerobic exercise modulates intracortical excitability in the primary motor cortex (M1). However, whether acute low-intensity aerobic exercise can also modulate M1 intracortical excitability, particularly intracortical excitatory circuits, remains unclear. In addition, no previous studies have investigated the effect of acute aerobic exercise on short-latency afferent inhibition (SAI). The aim of this study was to investigate whether acute low-intensity aerobic exercise modulates intracortical circuits in the M1 hand and leg areas. Intracortical excitability of M1 (Experiments 1, 2) and spinal excitability (Experiment 3) were measured before and after acute low-intensity aerobic exercise. In Experiment 3, skin temperature was also measured throughout the experiment. Transcranial magnetic stimulation was applied over the M1 non-exercised hand and exercised leg areas in Experiments 1, 2, respectively. Participants performed 30 min of low-intensity pedaling exercise or rested while sitting on the ergometer. Short- and long-interval intracortical inhibition (SICI and LICI), and SAI were measured to assess M1 inhibitory circuits. Intracortical facilitation (ICF) and short-interval intracortical facilitation (SICF) were measured to assess M1 excitatory circuits. We found that acute low-intensity aerobic exercise decreased SICI and SAI in the M1 hand and leg areas. After exercise, ICF in the M1 hand area was lower than in the control experiment, but was not significantly different to baseline. The single motor-evoked potential, resting motor threshold, LICI, SICF, and spinal excitability did not change following exercise. In conclusion, acute low-intensity pedaling modulates M1 intracortical circuits of both exercised and non-exercised areas, without affecting corticospinal and spinal excitability.

Sex differences in fatigability and recovery relative to the intensity-duration relationship

KEY POINTS

Females demonstrate greater fatigue resistance than males during contractions at intensities relative to maximum force. However, previous studies have not accounted for the influence of metabolic thresholds on fatigability. This study is the first to test whether sex differences in fatigability exist when exercise intensity is normalised relative to a metabolic threshold: the critical intensity derived from assessment of the intensity-duration relationship during intermittent, isometric knee extensor contractions. We show that critical intensity in females occurred at a higher percentage of maximum force compared to males. Furthermore, females demonstrated greater fatigue resistance at exercise intensities above and below this metabolic threshold. Our data suggest that the sex difference was mediated by lesser deoxygenation of the knee extensors during exercise. These data highlight the importance of accounting for metabolic thresholds when comparing fatigability between sexes, whilst emphasising the notion that male data are not generalisable to female populations.

ABSTRACT

Females are less fatigable than males during isometric exercise at intensities relative to maximal voluntary contraction (MVC); however, whether a sex difference in fatigability exists when exercise is prescribed relative to a critical intensity is unknown. This study established the intensity-duration relationship, and compared fatigability and recovery between sexes following intermittent isometric contractions normalised to critical intensity. Twenty participants (10 females) completed four intermittent isometric knee extension trials to task failure to determine critical intensity and the curvature constant (W'), followed by fatiguing tasks at +10% and -10% relative to critical intensity. Neuromuscular assessments were completed at baseline and for 45 min post-exercise. Non-invasive neurostimulation, near-infrared spectroscopy, and non-invasive haemodynamic monitoring were used to elucidate the physiological mechanisms responsible for sex differences. Females demonstrated a greater critical intensity relative to MVC than males (25 ± 3 vs. 21 ± 2% MVC, P = 0.003), with no sex difference for W' (18,206 ± 6331 vs. 18,756 ± 5762 N s, P = 0.850). Time to task failure was greater for females (62.37 ± 17.25 vs. 30.43 ± 12.75 min, P < 0.001) during the +10% trial, and contractile function recovered faster post-exercise (P = 0.034). During the -10% trial females experienced less contractile dysfunction (P = 0.011). Throughout the +10% trial, females demonstrated lesser decreases in deoxyhaemoglobin (P = 0.007) and an attenuated exercise pressor reflex. These data show that a sex difference in fatigability exists even when exercise is matched for critical intensity. We propose that greater oxygen availability during exercise permits females to sustain a higher relative intensity than males, and is an explanatory factor for the sex difference in fatigability during intermittent, isometric contractions.

Advantages of using 3D virtual reality based training in persons with Parkinson's disease: a parallel study

BACKGROUND

Parkinson's disease (PD) is a slowly progressive neurodegenerative disease. There are mixed reports on success of physiotherapy in patients with PD. Our objective was to investigate the functional improvements, motivation aspects and clinical effectiveness when using immersive 3D virtual reality versus non-immersive 2D exergaming.

METHODS

We designed a randomized parallel study with 97 patients, but only 20 eligible participants were randomized in 2 groups; the one using 3D Oculus Rift CV1 and the other using a laptop. Both groups participated in the 10-session 3 weeks training with a pick and place task in the virtual world requiring precise hand movement to manipulate the virtual cubes. The kinematics of the hand was traced with Leap motion controller, motivation effect was assessed with modified Intrinsic Motivation Inventory and clinical effectiveness was evaluated with Box & Blocks Test (BBT) and shortened Unified Parkinson's disease rating scale (UPDRS) before and after the training. Mack-Skilling non-parametrical statistical test was used to identify statistically significant differences (p < 0.05) and Cohen's U3 test to find the effect sizes.

RESULTS

Participants in the 3D group demonstrated statistically significant and substantially better performance in average time of manipulation (group x time, p = 0.009), number of successfully placed cubes (group x time, p = 0.028), average tremor (group x time, p = 0.002) and UPDRS for upper limb (U3 = 0.35). The LCD and 3D groups substantially improved their BBT score with training (U3 = 0.7, U3 = 0.6, respectively). However, there were no statistically significant differences in clinical tests between the groups (group x time, p = 0.2189, p = 0.2850, respectively). In addition the LCD group significantly decreased the pressure/tension (U3 = 0.3), the 3D did not show changes (U3 = 0.5) and the differences between the groups were statistically different (p = 0.037). The 3D group demonstrated important increase in effort (U3 = 0.75) and perceived competences (U3 = 0.9).

CONCLUSIONS

The outcomes of the study demonstrated that the immersive 3D technology may bring increased interests/enjoyment score resulting in faster and more efficient functional performance. But the 2D technology demonstrated lower pressure/tension score providing similar clinical progress. A study with much larger sample size may also confirm the clinical effectiveness of the approaches.

TRIAL REGISTRATION

The small scale randomized pilot study has been registered at ClinicalTrials.gov Identifier: NCT03515746 , 4 May 2018.

Modulation of inhibitory function in the primary somatosensory cortex and temporal discrimination threshold induced by acute aerobic exercise

Acute aerobic exercise beneficially affects brain function. The effect of acute aerobic exercise on the inhibitory mechanism of the primary somatosensory cortex (S1) and somatosensory function remains unclear. We investigated whether acute aerobic exercise modulates S1 inhibitory function and somatosensory function. In Experiment 1, we measured somatosensory evoked potentials (SEP) and paired-pulse inhibition (PPI) in 15 healthy right-handed participants. The right median nerve underwent electrical stimulation (ES). Interstimulus intervals were 5 ms, 30 ms, and 100 ms. In Experiment 2, we assessed the somatosensory function by using a somatosensory temporal discrimination task. Single or paired ES was applied to the distal phalanx of the right index finger. Both the experiments involved three sessions: 20 min of moderate-intensity exercise, 30 min of low-intensity exercise, and 30 min of seated rest. Before and after each session, PPI and somatosensory temporal discrimination task performance were measured. The N20 latency was significantly shortened immediately after moderate exercise. The SEP amplitude was not modulated in any session. The PPI at 30 ms (PPI_30ms) significantly decreased 20 min after moderate exercise, whereas the PPI at 5 ms (PPI_5ms) and PPI at 100 ms (PPI_100ms) did not change. The 50% and 75% thresholds and reaction time did not improve in any session. We found negative relationships between the change in PPI_5ms and the change in the 75% threshold under low-intensity exercise condition. Thus, acute aerobic exercise modulated S1 inhibitory function depending on exercise intensity. The exercise-induced change in PPI was associated with the change in temporal discrimination.

Changes in neurovascular coupling during cycling exercise measured by multi-distance fNIRS: a comparison between endurance athletes and physically active controls

It is well known that endurance exercise modulates the cardiovascular, pulmonary, and musculoskeletal system. However, knowledge about its effects on brain function and structure is rather sparse. Hence, the present study aimed to investigate exercise-dependent adaptations in neurovascular coupling to different intensity levels in motor-related brain regions. Moreover, expertise effects between trained endurance athletes (EA) and active control participants (ACP) during a cycling test were investigated using multi-distance functional near-infrared spectroscopy (fNIRS). Initially, participants performed an incremental cycling test (ICT) to assess peak values of power output (PPO) and cardiorespiratory parameters such as oxygen consumption volume (VO₂max) and heart rate (HRmax). In a second session, participants cycled individual intensity levels of 20, 40, and 60% of PPO while measuring cardiorespiratory responses and neurovascular coupling. Our results revealed exercise-induced decreases of deoxygenated hemoglobin (HHb), indicating an increased activation in motor-related brain areas such as primary motor cortex (M1) and premotor cortex (PMC). However, we could not find any differential effects in brain activation between EA and ACP. Future studies should extend this approach using whole-brain configurations and systemic physiological augmented fNIRS measurements, which seems to be of pivotal interest in studies aiming to assess neural activation in a sports-related context.

Differential effects of aging and physical activity on corticospinal excitability of upper and lower limb muscles

Corticospinal tract excitability can be altered by age, physical activity (PA), and possibly sex, but whether these effects differ between upper and lower limb muscles is unknown. We determined the influence of age, PA, and sex on corticospinal excitability of an upper limb and a lower limb muscle during submaximal contractions by comparing stimulus-response curves of motor evoked potentials (MEPs). Transcranial magnetic stimulation (TMS) was used to evoke stimulus-response curves in active muscles by incrementally increasing the stimulator intensity from below the active motor threshold (AMT) until a plateau in MEP amplitudes was achieved. Stimulus-response curves were analyzed from the first dorsal interosseous (FDI) of 30 young (23.9 ± 3.8 yr) and 33 older (72.6 ± 5.6 yr) men and women and the vastus lateralis (VL) of 13 young (23.2 ± 2.2 yr) and 25 older (72.7 ± 5.5 yr) men and women. Corticospinal excitability was determined by fitting the curves with a four-parameter sigmoidal curve and calculating the maximal slope (slope_max). PA was assessed with triaxial accelerometry, and participants were dichotomized into high-PA (>10,000 steps/day, n = 15) or low-PA (<10,000 steps/day, n = 43) groups. Young adults had larger FDI MEP amplitudes (% maximum amplitude of compound muscle action potential) at higher TMS intensities (120-150% AMT) and greater slope_max than older adults (P < 0.05), with no differences between high- and low-PA groups (P > 0.05). VL MEP amplitudes and slope_max, however, were lower in the high-PA than low-PA participants, with no age or sex differences. These data suggest that aging and PA, but not sex, differentially influence the excitability of the corticospinal tracts projecting to muscles of the upper compared with the lower limb. NEW & NOTEWORTHY Excitability of the corticospinal tract projecting to the first dorsal interosseous assessed with transcranial magnetic stimulation was reduced with age but independent of regular physical activity (steps/day) and sex of the individual. In contrast, corticospinal excitability of the vastus lateralis was not affected by age but was reduced in individuals achieving more than the physical activity recommendations of 10,000 steps/day. Aging and activity differentially affect corticospinal excitability of upper and lower limb muscles.