Handgrip Task Research Articles

Concurrent brain endurance training improves endurance exercise performance

ObjectivesMental fatigue impairs endurance exercise. Brain endurance training (BET) – engaging in cognitively fatiguing tasks during exercise - can develop resilience to mental fatigue and improve physical performance over physical training alone. The mechanism for this effect is unknown.This experiment examines if BET enhances performance over physical training and investigates potential underlying physiological mechanisms. DesignA mixed design randomised control trial. MethodsPre- and post-testing: 36 participants completed dynamic rhythmic muscular endurance handgrip tasks requiring generation of as much force as possible once a second for 300s, performed under 3 counterbalanced conditions: following 600s of a 2-back memory/attention task (subsequent); while performing a 2-back task (concurrent); and on its own (solo). Cardiac activity, electromyographic forearm activity, pre-frontal cerebral haemodynamics (near infrared spectroscopy), and force were recorded. Training: Participants (randomised to a Control or BET group) completed 24 (6 weeks) submaximal hand contractions sessions. The BET group also completed concurrent cognitive tasks (2-back, Stroop). Measures of motivation, physical and mental exertion and mental fatigue were collected throughout. ResultsEndurance performance, across the 3 tasks, improved more following BET (32%) than Control (12%) (p<0.05). The better performance following BET occurred with a higher pre-frontal oxygenation during the post-training physical tasks over time relative to Control (p<0.05). ConclusionsConcurrent BET improved endurance performance over physical training alone. This was accompanied by a training-induced maintenance of pre-frontal oxygenation, suggestive of reduced mental effort during physical activity.

Exploring the relationship between effort perception and poststroke fatigue.

ObjectiveTo test the hypothesis that poststroke fatigue, a chronic, pathologic fatigue condition, is driven by altered effort perception.MethodsFifty-eight nondepressed, mildly impaired stroke survivors with varying severity of fatigue completed the study. Self-reported fatigue (trait and state), perceived effort (PE; explicit and implicit), and motor performance were measured in a handgrip task. Trait fatigue was measured with the Fatigue Severity Scale-7 and Neurologic Fatigue Index. State fatigue was measured with a visual analog scale (VAS). Length of hold at target force, overshoot above target force, and force variability in handgrip task were measures of motor performance. PE was measured with a VAS (explicit PE) and line length estimation, a novel implicit measure of PE.ResultsRegression analysis showed that 11.6% of variance in trait fatigue was explained by implicit PE (R = 0.34; p = 0.012). Greater fatigue was related to longer length of hold at target force (R = 0.421, p < 0.001). A backward regression showed that length of hold explained explicit PE in the 20% force condition (R = 0.306, p = 0.021) and length of hold and overshoot above target force explained explicit PE in the 40% (R = 0.399, p = 0.014 and 0.004) force condition. In the 60% force condition, greater explicit PE was explained by higher force variability (R = 0.315, p = 0.017). None of the correlations were significant for state fatigue.ConclusionTrait fatigue, but not state fatigue, correlating with measures of PE and motor performance, may suggest that altered perception may lead to high fatigue mediated by changes in motor performance. This finding furthers our mechanistic understanding of poststroke fatigue.

Effects of the unilateral dynamic handgrip on resting cortical activity levels: A replication and extension

Previous studies have linked unilateral hand contractions to subsequent changes in hemispheric asymmetric activity, as reflected in the electroencephalographic alpha (8–12 Hz) range in each hemisphere. However, debate continues regarding the state of asymmetry induced by unilateral contractions. We have previously found a bilateral enhancement of alpha amplitude that occurs after contractions, reflecting cortical downregulation instead of changes in asymmetric activity. To corroborate our observations, we examined the effects of 45 s of unilateral dynamic handgrip contractions on subsequent resting alpha activity. Twenty-two right-handed participants were recruited (M = 25 years, 17 female). The study used a within-subjects design consisting of a pre- and post-test (2 min resting; eyes open) for the intervention (dynamic handgrip; at a self-determined pace of approximately twice a second for 45 s for each hand). Following the handgrip task, an increase in alpha amplitude above the baseline was observed over the entire cortex, which was greater after left-hand squeezing. This observation confirms our previous findings and we have extended them by adding more electrodes to gain further insights into the handgrip exercise as an external brain stimulator. Moreover, we grouped electrodes according to scalp regions to facilitate the visualization of the effects on the frequency spectrum. Our findings can be used to develop targeted interventions aimed at modifying behavioral outcomes affected by alpha activity.

Effect Of Mental Fatigue Induced By A Cognitive Task On A Subsequent Handgrip Endurance Exercise

Mental fatigue is commonly observed when using the sequential task protocol. In this protocol, participants perform a first task that requires effortful control or that does not. Then, they have to perform a second task that systematically requires effortful control. Participants generally give up earlier the second task when they have exerted effortful control in the first task. Despite an extensive literature on this phenomenon, researchers still debate about its real existence and failed to define its conditions of occurrence. PURPOSE: To replicate the mental fatigue effect with a long cognitive task tapping executive functions on a subsequent effortful physical task. METHODS: Fifty-five young adults completed 4 sessions separated by a minimum of 48h. The first session was a learning session in which participants familiarize with the Stroop task and the handgrip task. During the second session, participants only performed the endurance handgrip task at 13% voluntary maximal contraction until exhaustion. During the third and fourth sessions, participants performed a 30-min cognitive task (modified Stroop task vs. Video task) followed by the same handgrip task than in the 2nd session. The order of sessions 2 and 3 were counterbalanced across participants. RESULTS: As expected, participants squeezed the handgrip during a shorter time (5.36 min) after the Stroop task than after watching an emotionally neutral movie (5.82 min). In addition, there was a significant difference between the performance of the second session (5.80 min) and the performance after the Stroop task. CONCLUSION: This study clearly shows that a long task overloading execution functions leads to an early disengagement of mental effort in a subsequent effortful physical task. The cause of this earlier dropout is explained in different ways: (1) a quicker depletion of brain resources, (2) energetic and computational costs higher than the benefits associated with the achievement of the task goal, or (3) a reorientation of attention and intention to more pleasant tasks. Further studies are needed to confront these different explanations and manipulate the difficulty of the first task (duration and effortful control load) to determine the conditions of occurrence necessary to induce mental fatigue.

Cutaneous warmth, but not touch, increases muscle sympathetic nerve activity during a muscle fatigue hand-grip task

In homeostasis, somatosensory C fibre afferents are hypothesised to mediate input to the brain about interactions with external stimuli and sympathetic efference provides the output that regulates bodily functions. We aimed to test this hypothesis and whether different types of innocuous somatosensory input have differential effects. Healthy volunteers performed a muscle fatigue (hand-grip) task to exhaustion, which produces increased muscle sympathetic nerve activity (MSNA), as measured through microneurography. Participants completed the muscle fatigue task without concurrent cutaneous sensory stimulation (control) or we applied skin warming (heat pack) as a C fibre stimulation, slow brush stroking as C and Aβ fibre stimulation, or vibration as Aβ fibre stimulation, to the participant’s forearm. We also measured heart rate, the duration of the hand-grip task, and ratings of pain at the end of the task. Concurrent skin warming showed increased MSNA compared to the other conditions. Tactile stimuli (brushing, vibration) were not significantly different to the control (no intervention) condition. Warming increased the pain from the muscle contraction, whereas the tactile stimuli did not. We interpret the effect of warming on MSNA as providing relevant afferent information during muscle contraction, which needed to be counteracted via vasoconstriction to maintain homeostasis. Brushing and vibration were less homeostatically relevant stimuli for the muscle contraction and hence had no significant effect. The findings add sensory specificity to our current understanding of homeostatic regulation through somatosensory afferent and sympathetic efferent pathways.

Differences in Net Information Flow and Dynamic Connectivity Metrics Between Physically Active and Inactive Subjects Measured by Functional Near-Infrared Spectroscopy (fNIRS) During a Fatiguing Handgrip Task.

Twenty-three young adults (4 Females, 25.13 ± 3.72 years) performed an intermittent maximal handgrip force task using their dominant hand for 20 min (3.5 s squeeze/6.5 s release, 120 blocks) with concurrent cortical activity imaging by functional Near-Infrared Spectroscopy (fNRIS; OMM-3000, Shimadzu Corp., 111 channels). Subjects were grouped as physically active (n = 10) or inactive (n = 12) based on a questionnaire (active-exercise at least four times a week, inactive- exercise less than two times a week). We explored how motor task fatigue affected the vasomotion-induced oscillations in ΔHbO as measured by fNIRS at each hemodynamic frequency band: endothelial component (0.003–0.02 Hz) associated to microvascular activity, neurogenic component (0.02–0.04 Hz) related to intrinsic neuronal activity, and myogenic component (0.04–0.15 Hz) linked to activity of smooth muscles of arterioles. To help understand how these three neurovascular regulatory mechanisms relate to handgrip task performance we quantified several dynamic fNIRS metrics, including directional phase transfer entropy (dPTE), a computationally efficient and data-driven method used as a marker of information flow between cortical regions, and directional connectivity (DC), a means to compute directionality of information flow between two cortical regions. The relationship between static functional connectivity (SFC) and functional connectivity variability (FCV) was also explored to understand their mutual dependence for each frequency band in the context of handgrip performance as fatigued increased. Our findings ultimately showed differences between subject groups across all fNIRS metrics and hemodynamic frequency bands. These findings imply that physical activity modulates neurovascular control mechanisms at the endogenic, neurogenic, and myogenic frequency bands resulting in delayed fatigue onset and enhanced performance. The dynamic cortical network metrics quantified in this work for young, healthy subjects provides baseline measurements to guide future work on older individuals and persons with impaired cardiovascular health.

The effect of mild whole-body cold stress on isometric force control during hand grip and key pinch tasks.

Prolonged exposure to cold can impair manual performance, which in turn can affect work task performance. We investigated whether mild whole-body cold stress would affect isometric force control during submaximal hand grip and key pinch tasks. Twelve male participants performed isometric hand grip and key pinch tasks at 10% and 30% of maximal voluntary contraction (MVC) for 30 and 10 s respectively, in cold (8 °C) and control (25 °C) conditions. Finger temperature decreased significantly by 18.7 ± 2.1 °C and continuous low-intensity shivering in the upper trunk increased significantly in intensity and duration during cold exposure. Rectal temperature decreased similarly for the 8 °C and 25 °C exposures. Force variability (FCv) was <2% for the hand grip tasks, and <3% for the key pinch tasks. No significant changes in FCv or force accuracy were found between the ambient temperatures. In conclusion, isometric force control during hand grip and key pinch tasks was maintained when participants experienced mild whole-body cold stress compared with when they were thermally comfortable.

Investigating prismatic adaptation effects in handgrip strength and in plantar pressure in healthy subjects

BackgroundPrismatic Adaptation (PA) is a visuomotor procedure inducing a shift of the visual field that has been shown to modulate activation of a number of brain areas, in posterior (i.e. parietal cortex) and anterior regions (i.e. frontal cortex). This neuromodulation could be useful to study neural mechanisms associated with either postural measures such as the distribution of plantar pressure or to the generation of muscle strength. Indeed, plantar pressure distribution is associated to activation of high-level cognitive mechanisms taking place within the posterior regions of the brain dorsal stream, especially of the right hemisphere. Conversely, hand force mostly rely on sensorimotor mechanisms, fulfilled by anterior regions of the brain and involving both hemispheres. Research questionSince PA effects have been reported to affect both sensorimotor and higher level cognitive processes, is it possible to hypothesize a modulation of both hands strenght and plantar pressure after PA? MethodsForty-six healthy subjects (male = 23; mean age = 25 ± 3 years) were randomly divided into two groups: a leftward prismatic adaptation group (l-PA) and a rightward prismatic adaptation group (r-PA). Hand strength and plantar pressure were assessed, immediately before and after PA, using the handgrip task and baropodometric measurement, respectively. ResultsBoth l-PA and r-PA induced a significant decrease of strength in the hand contralateral to the lenses deviation side. Only r-PA was associated with an increase of the forefoot plantar pressure in both feet. Modulation of interhemispheric inhibitory processes at sensorimotor and higher cognitive level may account for the present results. SignificancePA exerts effects on body posture and hand strength relying on different mechanisms. The PA effects on hand strength are probably related to the modulation of interhemispheric inhibition of sensorimotor processes, involving both hemispheres. The PA effects on body posture are probably related to modulation of body representation, involving mainly the right hemisphere.

Mapping cortical network effects of fatigue during a handgrip task by functional near-infrared spectroscopy in physically active and inactive subjects.

.The temporal evolution of cortical activation and connectivity patterns during a fatiguing handgrip task were studied by functional near-infrared spectroscopy (fNIRS). Twenty-three young adults (18 to 35 years old) were recruited to use a handheld force sensor to perform intermittent handgrip contractions with their dominant hand at their personal maximum voluntary contraction force level for 3.5 s followed by 6.5 s of rest for 120 blocks. Subjects were divided into self-reported physically active and inactive groups, and their hemodynamic activity over the prefrontal and sensory-motor cortices (111 channels) was mapped while they performed this task. Using this fNIRS setup, a more detailed time sequence of cortical activation and connectivity patterns was observed compared to prior studies. A temporal evolution sequence of hemodynamic activation patterns was noted, which was different between the active and the inactive groups. Physically active subjects demonstrated delayed fatigue onset and significantly longer-lasting and more spatially extended functional connectivity (FC) patterns, compared to inactive subjects. The observed differences in activation and FC suggested differences in cortical network adaptation patterns as fatigue set in, which were dependent on subjects’ physical activity. The findings of this study suggest that physical activity increases FC with regions involved in motor task control and correlates to extended fatigue onset and enhanced performance.

Can the Stereotype Threat and Lift Phenomenon Be Applicable to a Muscular Endurance Task?

ABSTRACTPurpose. Inducing a negative stereotype toward women usually leads to a decrease in women performance and an increase in men performance. These effects were observed during technical tasks. The purpose of the present study was to investigate the effect of this sex stereotype during a non-technical muscular endurance task. The perception of effort, closely related to endurance performance, was also recorded. Based on the type of task and the mere effort account, we predicted that both men and women in the negative stereotype toward women condition would perform better than participants in the two other groups. Method. Seventy-seven participants (38 women and 39 men) were randomly assigned to a negative stereotype toward women, a nullified-stereotype, or a control condition. Then, they performed a submaximal handgrip task until exhaustion at 50% of their maximal strength. Results. This study showed that performance at T2 was reduced for men and women in the nullified-stereotype and control conditions, but not in the negative stereotype toward women condition, revealing that participants in the negative stereotype toward women condition performed better than participants in the other conditions. No significant difference was observed concerning the perception of effort according to the conditions. Conclusion. As compared to technical tasks, inducing a negative stereotype toward women increased women’s performance. The perception of effort could be responsible for this performance improvement. However, more research is needed to investigate the mechanisms involved. Concerning men, in line with the stereotype lift phenomenon, a performance increase was observed in this same condition.

Analgesia-enhancing effects of repetitive transcranial magnetic stimulation on neuropathic pain after spinal cord injury:An fNIRS study.

Repetitive transcranial magnetic stimulation (rTMS) is a promising treatment for chronic intractable neuropathic pain in patients with spinal cord injury (SCI). However, the analgesia-enhancing effects of rTMS on conventional interventions (e.g., medications), and the underlying mechanisms remain poorly understood. To investigate the enhancement of analgesia and change of cortex activation by rTMS treatment on neuropathic pain following SCI. A double-blind, sham-controlled, clinical trial was performed. Twenty-one patients with neuropathic pain after SCI were randomized (2:1) to receive a session of rTMS (10 Hz, a total of 1200 pulses at an intensity of 80% resting motor threshold) or sham treatment over the left primary motor cortex (M1) corresponding to the hand area daily for six weeks with a one-day interval per week. At T0 (before rTMS treatment), T1 (after the first session rTMS), T2 (after one week), T3 (after two weeks), T4 (after four weeks) and T5 (after six weeks), activations in the bilateral M1, primary somatosensory cortex (S1), premotor cortex (PMC) and prefrontal cortex (PFC) during the handgrip task were measured using functional near-infrared spectroscopy (fNIRS). In addition, the numerical rating scale (NRS) was used to assess pain. The pain intensity or activation in PFC, PMC, M1 or S1 was not remarkably changed at T1. Along with the time, the pain intensity gradually decreased in both the rTMS and sham groups. The real rTMS, compared with the sham, showed more pain relief from two weeks (T3) to six weeks (T5), and the activations of the motor-related areas M1 and PMC were remarkably suppressed. The findings of this preliminary study with a small patient sample suggest that the analgesia-enhancing effects of high-frequency rTMS might be related with the amelioration of M1 and PMC hypersensitivity, shedding light upon the clinical treatment of SCI-related neuropathic pain.

The Interplay of Achievement Motive-Goal Incongruence and State and Trait Self-Control: A Pilot Study Considering Cortical Correlates of Self-Control.

Objective: This study utilized different theoretical perspectives to better understand motor performance. We refered to concepts of achievement motive-goal incongruence and assessed cortical correlates of self-control. We assumed that more self-control is required when people act in conformance with an incongruent goal which, in turn, results in impaired performance. We considered the activation of a brain area associated with self-control (dorsolateral prefrontal cortex, dLPFC) as a consequence of motive-goal incongruence. Furthermore, we analyzed whether trait self-control buffers the negative effects of achievement motive—goal incongruence.Method: Twenty-eight participants (17 women, mean age: 24 years), whose implicit achievement motives were assessed at the beginning of the study, performed a handgrip task in an achievement goal condition and in three incongruent conditions, while their dLPFC oxygenation was monitored continuously (using functional near-infrared spectroscopy, fNIRS).Results: None of the two-way interactions (motive × goal condition) reached significance. A significant three-way interaction (motive × trait self-control × goal condition) showed that trait self-control buffered the detrimental effects of incongruence on motor performance. The nature of the three-way interaction predicting dLPFC oxygenation was unexpected.Conclusions: Although our results have to be treated with caution due to a small sample size, we see them as an encouraging starting point for further research on the interplay between motive-goal incongruence and trait and cortical correlates of state self-control that we assume to be important to understand performance in strenuous tasks.

HEART AUTONOMIC CONTROL DURING STATIC SUBMAXIMAL CONTRACTIONS: INFLUENCE OF TASK FEATURES

Background: Isometric exercise is important to cardiac rehabilitation, but understanding how different tasks can interfere with the Heart Rate Variability (HRV) still needs some clarification. Objective: To compare the Autonomic Nervous System (ANS) behavior during submaximal isometric tasks involving different muscle groups. Methods: Six healthy males ([Formula: see text] years old) performed two submaximal isometric tasks (30%) of knee extension and handgrip, sustained for 3[Formula: see text]min each, using visual feedback to maintain force levels. Successive RR intervals were recorded along the task, as well as for 5[Formula: see text]min before the task. Linear and nonlinear methods were used to obtain HRV parameters from successive RR intervals. Student [Formula: see text] test was used to compare the data with significant level set as [Formula: see text]. Results: Time domain parameters as well as the nonlinear parameters were significantly higher during the handgrip task. Conclusions: Submaximal isometric handgrip task is associated with a lower vagal withdrawal, when compared to submaximal isometric knee extension, suggesting that handgrip task promotes greater cardioprotection during exercise, while the isometric knee extension task could induce better adaptations to training.

Neural effects of hand-grip-activity induced fatigue sensation on appetite: a magnetoencephalography study

It has been reported that physical activity not only increases energy expenditure, but also affects appetite. However, little remains known about the effects of physical activity-induced fatigue sensation on appetite. In the present study, classical conditioning related to fatigue sensation was used to dissociate fatigue sensation from physical activity. The participants were 20 healthy male volunteers. After overnight fasting, on day 1, the participants performed hand-grip task trials for 10 min with listening to a sound. The next day, they viewed food images with (target task) and without (control task) listening to the sound identical to that used on day 1, and their neural activity during the tasks were recorded using magnetoencephalography. The subjective levels of appetite and fatigue sensation were assessed using a visual analog scale. The subjective level of fatigue increased and that of appetite for fatty foods showed a tendency toward increase in the target task while the subjective level of fatigue and that of appetite for fatty foods were not altered in the control task. In the target task, the decrease of theta (4–8 Hz) band power in the supplementary motor area (SMA), which was observed in the control task, was suppressed, and the suppression was positively correlated with appetite for fatty foods, suggesting hand grip activity-induced fatigue sensation may increase the appetite for fatty food; this increase could be related to neural activity in the SMA. These findings are expected to contribute to the understanding of the neural mechanisms of appetite in relation to fatigue.

A chest-based continuous cuffless blood pressure method: Estimation and evaluation using multiple body sensors

Blood pressure (BP) is a critical vital sign in health, measured millions of times per day worldwide. Current BP measurement requires cumbersome tools, is painful and can be inconvenient. Non-invasive cuffless BP measurement based on pulse arrival time (PAT) techniques allow an alternative way of monitoring BP in healthcare settings with refined wearability and user-friendly features. PAT extraction requires at least two measurements, one as a time reference and another to obtain time delay; there are several approaches to calculate the PAT from various sensors placed on the body. Commonly used signals are electrocardiography (ECG) and photoplethysmography (PPG), which can be recorded from a patients body using more than two separate sensors attachment set-ups. In this work, cuffless BP calculation based on five different PAT readings using Bio-impedance (BImp) at the shoulder as an alternative to PPG, has been investigated. Sensor placement is on the patients chest; which hides them beneath the patient’s clothes making them more suitable for ambulatory monitoring systems. Technology performance was assessed using different postures, exercises and Glyceryl Trinitrate (GTN) spray doses; which provided stable, rising and falling BPs for evaluation. Data were collected from 41 participants who were sitting, standing and supine. Twenty-four of 41 participants undertook experiments including a handgrip task (isometric exercise), three periods of cycling on an exercise bike with light, moderate and heavy resistance settings and an observed rest period at the end. The remaining 17 of 41 subjects received GTN spray for predefined times with variable recovery periods afterwards. Different methods of PAT extraction from BImp data were compared for accuracy. Comparisons were made between PAT readings alone and PAT combined with Heart Rate and the combination model performed better when calculating BP. Simultaneously, data were collected using PPG-based PATs compared to BImp-based PATs. BImp-based PATs proved 3% more accurate than PPG-based PATs, demonstrating the potential superiority of BImp-based BP calculations.

Effect of a Combined Exercise and Dietary Intervention on Self-Control in Obese Adolescents.

ObjectiveThe aim of this study was to determine whether a combined exercise and dietary intervention improved cognitive and physical self-control and whether pre-to-post interventional changes in self-control were mediated by changes in body mass index (BMI) and maximal grip strength (MGS), in a sample of obese adolescents.MethodsForty-four obese adolescents were randomly assigned to a combined exercise and dietary program or to a waitlist control group; the data from 36 participants (n = 18 for each group) were analyzed. The combined exercise and dietary program was performed over 6 weeks and was supervised by qualified trainers in a closed boot camp. The exercise consisted primarily of typical aerobic training, sports, outdoor training, yoga, and resistance training. Participants were placed on moderate dietary restriction according to individual target body weight (30 kcal/kg × target weight). The primary outcomes of this study were metrics based on cognitive and physical self-control, assessed by the Stroop task and a handgrip task, respectively. Secondary outcomes included BMI and MGS.ResultsThe combined exercise and dietary intervention significantly improved both cognitive and physical self-control. Similar positive effects were also found for reduced BMI and enhanced MGS. Correlation analyses showed that the reduced BMI and enhanced MGS were significantly closely associated with improved cognitive and physical self-control. The mediation analyses revealed that the pre-to-post intervention changes in BMI and MGS significantly mediated physical self-control, but did not mediate cognitive self-control.ConclusionOur combined exercise and dietary intervention is an effective approach to improve multiple aspects of self-control, reduce BMI, and strengthen MGS among obese adolescents. These findings also suggest that reduced BMI and enhanced MGS mediate specific aspects of self-control.

Effect of repetitive transcranial magnetic stimulation combined with robot-assisted training on wrist muscle activation post-stroke

ObjectiveTo compare the effects of active assisted wrist extension training, using a robotic exoskeleton (RW), with simultaneous 5 Hz (rTMS + RW) or Sham rTMS (Sham rTMS + RW) over the ipsilesional extensor carpi radialis motor cortical representation, on voluntary wrist muscle activation following stroke. MethodsThe two training conditions were completed at least one week apart in 13 participants >1-year post-stroke. Voluntary wrist extensor muscle activation (motor unit (MU) recruitment thresholds and firing rate modulation in a ramp-hold handgrip task), ipsilesional corticospinal excitability (motor evoked potential [MEP] amplitude) and transcallosal inhibition were measured Pre- and Post-training. ResultsFor MUs active both Pre and Post training, greater reductions in recruitment thresholds were found Post rTMS + RW training (p = 0.0001) compared to Sham rTMS + RW (p = 0.16). MU firing rate modulation increased following both training conditions (p = 0.001). Ipsilesional MEPs were elicited Pre and Post in only 5/13 participants. No significant changes were seen in ipsilesional corticospinal excitability and transcallosal inhibition measures (p > 0.05). ConclusionsFollowing a single rTMS + RW session in people >1-year post-stroke, changes were found in voluntary muscle activation of wrist extensor muscles. Alterations in ipsilesional corticospinal or interhemispheric excitability were not detected. SignificanceThe effects of rTMS + RW on muscle activation warrant further investigation as post-stroke rehabilitation strategy.

The Utility of Functional Near-infrared Spectroscopy for Measuring Cortical Activity during Cycling Exercise.

Real-time measurement of dynamic brain activity during exercise can help advance our understanding of the role of exercise upon brain health and function. In exercise science, functional near infrared spectroscopy (fNIRS) has primarily been used to measure the effects of exercise intensity on hemodynamic responses in the cerebral cortex. However, the utility of fNIRS to measure discreet hemodynamic responses underlying brain activation associated with motor and cognitive function during exercise has not been systematically examined. Here, we compared brain activation associated with a motor and cognitive task at rest and during cycling exercise at different intensities. In separate sessions, 13 participants performed cycling exercise on an indoor trainer at a low, moderate and high intensity. We measured changes in oxygenated (HbO) and deoxygenated (HbR) hemoglobin from prefrontal, parietal, and motor regions of the cerebral cortex during a handgrip and working-memory task. Our findings show significant brain activation (a concurrent increase in HbO and decrease in HbR) in contralateral motor cortex during the handgrip task and left prefrontal cortex during the working-memory task at rest and during exercise at low, moderate and high (motor task HbO only) intensities (P < 0.05). Moreover, brain activation during the handgrip and working-memory tasks was not significantly different at rest and during exercise (P > 0.05). This study shows that fNIRS can robustly measure motor and cognitive task-evoked changes in brain activation during cycling exercise comparable to rest. An implication of these new findings is that fNIRS can be used to determine real-time changes in brain function during exercise in healthy and clinical populations.

Synchronous analysis of brain regions based on multi-scale permutation transfer entropy

The coupling of electroencephalographic (EEG) signals reflects the interaction between brain regions, which is of great importance for the assessment of motor function in post-stroke patients. In this study, the measurement of multi-scale permutation transfer entropy (MPTE) was presented and employed to characterize the coupling between the EEG signals measured from the bilateral motor and sensory areas. Post-stroke patients (n = 5) and healthy volunteers (n = 6) were recruited and participated in a hand grip task with different levels of contraction. MPTE values were computed and analyzed across various frequency bands for all subjects. Results showed that, for healthy controls, the coupling between motor and sensory areas was bi-directional and tended to be strongest in beta band. In particular, greater beta-band MPTE was found in the dominant hand and coupling strength decreased as contraction strength increased. Additionally, coupling between the motor and sensory areas of stroke patients exhibited weaker beta-band MPTE than that of healthy controls. Findings suggest that MPTE is able to quantitatively characterize the coupling properties between multiple brain regions, providing a promising approach to study the underlying mechanisms of functional motor recovery.

Fatigue in Multiple Sclerosis: General and Perceived Fatigue Does Not Depend on Corticospinal Tract Dysfunction.

Background: Multiple sclerosis (MS) is an autoimmune disorder of the CNS in which inflammation, demyelination, and axonal damage of the central nervous system coexist. Fatigue is one of the most disabling symptoms in MS and little is known about the neurophysiological mechanisms involved.Methods: To give more mechanistic insight of fatigue in MS, we studied a cohort of 17 MS patients and a group of 16 age-matched healthy controls. Baseline Fatigue Severity Scales and Fatigue Rating were obtained from both groups to check the level of fatigue and to perform statistical correlations with fatigue-induced neurophysiologic changes. To induce fatigue we used a handgrip task. During the fatiguing task, we evaluated fatigue state (using a dynamometer) and after the task we evaluated the Borg Rating of Perceived Exertion Scale. Transcranial magnetic stimulation and peripheral electric stimulation were used to assess corticospinal tract and peripheral system functions before and after the task.Results: Clinically significant fatigue and central motor conduction time were greater in patients than in controls, while motor cortex excitability was decreased and maximal handgrip strength reduced in patients. Interestingly, fatigue state was positively correlated to perceived fatigue in controls but not in patients. Furthermore, in the presence of similar fatigue state over time, controls showed a significant fatigue-related reduction in motor evoked potential (a putative marker of central fatigue) whereas this effect was not seen in patients.Conclusions: in MS patients the pathogenesis of fatigue seems not driven by the mechanisms directly related to corticospinal function (that characterize fatigue in controls) but seems probably due to other “central abnormalities” upstream to primary motor cortex.