Delving into the relationship between regular physical exercise and cardiac interoception in two cross-sectional studies.

Cardiac interoception, the ability to sense and process cardiac afferent signals, has been shown to improve after a single session of acute physical exercise. However, it remains unclear whether repetitive engagement in physical exercise over time leads to long-term changes in cardiac interoceptive accuracy. It is also unknown whether those changes affect the neural activity associated with the processing of afferent cardiac signals, assessed by the heart-evoked potential (HEP). In this study, we aimed to investigate this hypothesis through two cross-sectional studies, categorizing participants as active or inactive based on physical fitness (Study I; N = 45) or self-reported physical activity levels (Study II; N = 60). Interoception was assessed at rest using the HEP (Studies I and II), the Heartbeat Counting task (Study II), and the Rubber Hand Illusion (RHI) (Study II). Study I showed strong evidence of better cardiovascular fitness in the active group than in the inactive group as well as robust between-group differences in electrocardiogram (ECG) recordings. Study 2 replicated the clear differences in ECG as a function of regular physical activity. Those results were expected due to clear differences in physical activity habits. In contrast, our analysis revealed no robust differences between groups across cardiac interoception tasks and the RHI, although the direct relevance of these measures to interoception remains under investigation. In sum, our results do not provide convincing evidence to support a strong version of the notion that regular physical exercise is associated with an enhanced in cardiac interoception.

An umbrella review of randomized control trials on the effects of physical exercise on cognition.

Extensive research links regular physical exercise to an overall enhancement of cognitive function across the lifespan. Here we assess the causal evidence supporting this relationship in the healthy population, using an umbrella review of meta-analyses limited to randomized controlled trials (RCTs). Despite most of the 24 reviewed meta-analyses reporting a positive overall effect, our assessment reveals evidence of low statistical power in the primary RCTs, selective inclusion of studies, publication bias and large variation in combinations of pre-processing and analytic decisions. In addition, our meta-analysis of all the primary RCTs included in the revised meta-analyses shows small exercise-related benefits (d = 0.22, 95% confidence interval 0.16 to 0.28) that became substantially smaller after accounting for key moderators (that is, active control and baseline differences; d = 0.13, 95% confidence interval 0.07 to 0.20), and negligible after correcting for publication bias (d = 0.05, 95% confidence interval -0.09 to 0.14). These findings suggest caution in claims and recommendations linking regular physical exercise to cognitive benefits in the healthy human population until more reliable causal evidence accumulates.

Test-Retest Reliability of the Timed Up and Go Test in Subjects with Parkinson's Disease: Implications for Longitudinal Assessments.

BACKGROUND: Despite the frequent use of the Timed Up and Go (TUG) test in clinical trials, evaluation of longitudinal test-retest reliability is generally lacking and still inconclusive for patients with Parkinson's disease (PD). OBJECTIVE: We aimed to further investigate long-term reliability and sensitivity of the TUG test among this population. Furthermore, we explored alternative assessment strategies of the test aimed at elucidating whether the inclusion or combination of timed trials may have potential implications on outcome measure. METHODS: Relative and absolute reliability of the TUG performance were obtained in forty-three subjects with PD over three timed trials in two different testing sessions separated by a two-months period. RESULTS: Our results reported excellent intra-session and moderate inter-session reliability coefficients. The use of different assessment strategies of the TUG was found to have an important impact on outcome measure, highlighting the averaging of several timed trials in each testing session as a recommended alternative to minimize measurement error and increase reliability in longitudinal assessments. Nevertheless, beyond acceptable reliability, poor trial-to-trial stability of the measure appears to exist, since the ranges of expected variability upon retesting were wide and the incidence of spurious statistical effects was not negligible, especially in longitudinal repeated testing. CONCLUSION: Limitations may exist in the interpretation of the TUG outputs as part of longitudinal assessments aimed at evaluating treatment effectiveness in PD population. Researchers and practitioners should be aware of these concerns to prevent possible misrepresentations of functional ability in patients for a particular intervention.

Key Factors Associated with Adherence to Physical Exercise in Patients with Chronic Diseases and Older Adults: An Umbrella Review.

Physical inactivity is a major concern and poor adherence to exercise programs is often reported. The aim of this paper was to systematically review published reviews on the study of adherence to physical exercise in chronic patients and older adults and to identify those adherence-related key factors more frequently suggested by reviews for that population. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. Results were classified considering the target population and participants' characteristics to identify the most repeated factors obtained for each condition. Fifty-five articles were finally included. Fourteen key factors were identified as relevant to increase adherence to physical exercise by at least ten reviews: (a) characteristics of the exercise program, (b) involvement of professionals from different disciplines, (c) supervision, (d) technology, (e) initial exploration of participant's characteristics, barriers, and facilitators, (f) participants education, adequate expectations and knowledge about risks and benefits, (g) enjoyment and absence of unpleasant experiences, (h) integration in daily living, (i) social support and relatedness, (j) communication and feedback, (k) available progress information and monitoring, (l) self-efficacy and competence, (m) participant's active role and (n) goal setting. Therefore, adherence to physical exercise is affected by several variables that can be controlled and modified by researchers and professionals.

An Integrative Clustering Approach to tDCS Individual Response Variability in Cognitive Performance: Beyond a Null Effect on Working Memory.

Despite the growing interest in the use of transcranial direct current stimulation (tDCS) for the modulation of human cognitive function, there are contradictory findings regarding the cognitive benefits of this technique. Inter-individual response variability to tDCS may play a significant role. We explored the effects of anodal versus sham tDCS over the left prefrontal cortex (LPFC) on working memory performance, taking into account the inter-individual variability. Twenty-nine healthy volunteers received an 'offline' anodal tDCS (1.5 mA, 15 min) to the left prefrontal cortex (F3 electrode site) in an intra-individual, cross-over, sham-controlled experimental design. n-back and Sternberg task performance was assessed before (baseline), immediately after tDCS administration (T1) and 5 min post-T1 (T2). We applied an integrative clustering approach to characterize both the group and individual responses to tDCS, as well as identifying naturally occurring subgroups that may be present within the total sample. Anodal tDCS failed to improve working memory performance in the total sample. Cluster analysis identified a subgroup of 'responders' who significantly improved their performance after anodal (vs. sham) stimulation, although not to a greater extent than the best baseline or sham condition. The proportion of 'responders' ranged from 15% to 59% across task conditions and behavioral outputs. Our findings show a high inter-individual variability of the tDCS response, suggesting that the use of tCDS may not be an effective tool to improve working memory performance in healthy subjects. We propose that the use of clustering methods is more suitable in identifying 'responders' and for evaluating the efficacy of this technique.

Exercise practice associates with different brain rhythmic patterns during vigilance.

Cardiovascular fitness has repeatedly been associated to enhanced cognitive and brain functioning, generally in the form of differences in reaction time and response accuracy, as well as in event-related potentials (ERPs) and blood-oxygen-level-dependent imaging while participants performed executive demanding tasks. However, the evidence regarding potential differences in oscillatory neural activity, an inherent characteristic of brain functioning, is scarce. To fill this gap, here, we extracted and analysed (using a data-driven exploratory approach) brain oscillatory activity, both tonic (overall electroencephalographic - EEG - oscillatory activity) and transient (event related spectral perturbation [ERSP] and inter-trial coherence [ITC]), from a previous published dataset (Luque-Casado et al. 2016), where we showed different behavioural and ERP patterns during a vigilance/sustained attention task as a function of cardiovascular fitness in young adults. The ERSP results of the current study revealed increased theta (4-8 Hz) and upper beta (20-40 Hz) power and reduced lower beta (14-20 Hz) suppression after the target stimulus presentation in the higher-fit group compared to their lower-fit peers, but these differences disappeared in the second part of the task. ITC results mimicked the ERSP pattern within theta (4-8 Hz), while no differences were observed for the remaining frequency bands. Interestingly, the overall time-dependent effect in transient oscillatory activity followed the reaction time pattern of results. The analysis of the overall EEG oscillatory (tonic) dynamics did not show significant differences between groups. In sum, cardiorespiratory fitness was related to a brain oscillatory differential response pattern over a wide range of the frequency spectrum and spatio-temporal distribution, which seems to underlie the positive relationship between aerobic fitness and behavioural performance in a sustained attention task. Future studies are warranted to study the causal nature (beyond mere association) of these findings.

Exploring the effects of Transcranial Direct Current Stimulation over the prefrontal cortex on working memory: A cluster analysis approach.

BACKGROUND: The interest in the use of anodal transcranial direct current stimulation (tDCS) for the enhancement of cognitive functioning has increased significantly in recent years. However, the efficacy of this technique remains to be established. OBJECTIVE: The current study explored the effects of anodal vs. sham tDCS over the left dorsolateral prefrontal cortex (DLPFC) during the performance of the digit span backwards task. METHODS: 30 healthy participants received 'offline' anodal tDCS (1.5 mA, 15 min) to the left DLPFC in an intra-individual, cross-over, sham-controlled experimental design. Memory span performance was assessed before (baseline), immediately after tDCS administration (T1) and 10 min post-T1 (T2). We applied cluster analysis in order to characterize individual responses to tDCS, and in order to identify naturally occurring subgroups that may be present. RESULTS: Analysis of all the subjects showed that anodal tDCS failed to improve memory span performance. Cluster analysis revealed the presence of a subgroup of 'responders' that significantly improved their performance after anodal (vs. sham) tDCS in T1 (47%) and T2 (46%). However, there was no significant improvement in performance after anodal tDCS compared to the best baseline performance. CONCLUSION: Our findings suggest that tDCS does not improve memory span performance and highlights the need for better ways to optimize methodological approaches in order to account for inter-individual variability and accurately assess the evidential value of tDCS-linked cognitive outcomes.

Associations between accommodative dynamics, heart rate variability and behavioural performance during sustained attention: A test-retest study.

This study evaluated the time-on-task effect of a sustained attention task on the accommodative response, explored the link between ocular accommodation, cardiac autonomic regulation and behavioral performance, and tested the inter-session repeatability of these results by performing the same experimental procedure on different days. The accommodative response was measured in 25 university students using a WAM-5500 autorefractor, while participants performed a 10-minute psychomotor vigilance task at 50 cm. There were no time-on-task effects for the lag of accommodation, whereas the microfluctuations of accommodation and reaction time were modulated as a function of time-on-task, observing a progressive increment of both variables over time. Multiple regression analysis revealed that the microfluctuations of accommodation were a reasonably good predictor of behavioral performance. Analysis of inter-session repeatability showed that ocular accommodation, heart rate variability and reaction time had a low to moderate level of repeatability between two measurements. The microfluctuations of accommodation were sensitive to time-on-task effects during sustained attention, with a lower stability of accommodation being linked to reduced behavioral performance. The predictive capacity of the variability of accommodation for behavioral performance might be explained by the brain mechanisms shared by the ocular dynamics and attentional state; however, future studies would be required to elucidate this association. The low to moderate inter-session repeatability indicated that results in two measurement periods cannot be considered interchangeable, and therefore, the results of this study should be interpreted cautiously in this regard.

The relationship between vigilance capacity and physical exercise: a mixed-effects multistudy analysis.

A substantial body of work has depicted a positive association between physical exercise and cognition, although the key factors driving that link are still a matter of scientific debate. Here, we aimed to contribute further to that topic by pooling the data from seven studies (N = 361) conducted by our research group to examine whether cardiovascular fitness (VO2), sport type participation (externally-paced (e.g., football or basketball) and self-paced (e.g., triathlon or track and field athletes) vs. sedentary), or both, are crucial factors to explain the association between the regular practice of exercise and vigilance capacity. We controlled for relevant variables such as age and the method of VO2 estimation. The Psychomotor Vigilance Task was used to measure vigilance performance by means of reaction time (RT). The results showed that externally-paced sport practice (e.g., football) resulted in significantly shorter RT compared to self-paced sport (e.g., triathlon) and sedentary condition, depicting larger effects in children and adolescents than in adults. Further analyses revealed no significant effect of cardiovascular fitness and self-paced sport practice, in comparison to the sedentary condition, on RT. Our data point to the relevance of considering the type of sport practice over and above the level of cardiovascular fitness as crucial factor to explain the positive association between the regular practice of exercise and vigilance capacity.

Oscillatory brain activity during acute exercise: Tonic and transient neural response to an oddball task.

Intense physical exercise exerts measurable changes at various physiological levels that are well documented in the literature. However, despite the key role of the brain in processing inputs from internal organ systems and the external environment to coordinate and optimize behavior, little is known about brain dynamics during exercise. The present study investigates tonic and transient oscillatory brain activity in a group of participants performing an oddball task during a single bout of aerobic exercise. Twenty young males (19-32 years) were recruited for two experimental sessions on separate days. EEG activity was recorded during a session of cycling at 80% (moderate-to-high intensity) of VO2max (maximum rate of oxygen consumption) while participants responded to infrequent targets (red square and big blue circle) presented among frequent nontargets (small blue circle). This was compared to a (baseline) light intensity session (30% VO2max ) to control any potential effect of dual tasking (i.e., pedaling and performing the oddball task). A cluster-based nonparametric permutations test revealed an increase in power across the entire frequency spectrum during the moderate-to-high intensity exercise compared to light intensity. Furthermore, the more salient target (red square) elicited a lower increase in (stimulus-evoked) theta power in the 80% VO2max than in the light intensity condition. Alpha and lower beta power decreased less in the standard trials (small blue circle) during the moderate-to-high exercise condition than in the light exercise condition. The present study unveils, for the first time, a complex brain activity pattern during vigorous exercise while attending to task-relevant stimuli.

Ocular Accommodative Response is Modulated as a Function of Physical Exercise Intensity.

PURPOSE: The present study aimed (1) to examine the impact of two high-intensity interval training (HIIT) protocols differing in exercise intensity (low intensity and high intensity) on the dynamic accommodative response (AR), and (2) to elucidate whether the ocular accommodation changes are associated with the function of the autonomic nervous system during stimulus processing, as measured by the heart rate variability (HRV). METHODS: Twenty physically active university students (9 women; age = 23.9 ± 3.3 years) were tested on three separate sessions. The lag of accommodation and the root mean square of successive R-R interval differences (RMSSD) parameter of HRV were obtained at the beginning and at the end of each testing session, while one of the following protocols was applied in a randomized order between the measurements, low-intensity HIIT (8 sprints with 60 s of rest), high-intensity HIIT (8 sprints with 30 s of rest), and Control (walking for 8 min). RESULTS: Our data demonstrated a higher lag of accommodation after the high-intensity HIIT compared to the low-intensity HIIT (p = 0.006, d = 0.798) and control (p = 0.007, d = 0.741), but no significant differences were observed between the low-intensity HIIT protocol and control condition (p = 0.598, d = 0.12). As expected, lower HRV values were observed with higher exercise intensity, but the changes of AR and HRV were not significantly correlated (p > 0.05 in all cases). CONCLUSIONS: The present findings indicate that the acute effects of exercise on ocular accommodation depend on exercise intensity, showing that highly demanding physical effort induces a greater lag of accommodation, which may be of relevance when performing near activities after physical efforts.

Effect of induced alkalosis on performance during a field-simulated BMX cycling competition.

OBJECTIVES: The aim of the present study was to test the effect of sodium bicarbonate (NaHCO3-) ingestion on performance during a simulated competition on a Bicycle Motocross (BMX) track. DESIGN: Double-blind cross-over study. METHODS: Twelve elite male BMX cyclists (age: 19.2±3.4 years; height: 174.2±5.3cm; body mass: 72.4±8.4kg) ingested either NaHCO3- (0.3g.kg-1 body weight) or placebo 90min prior to exercise. The cyclists completed three races in a BMX Olympic track interspersed with 15min of recovery. Blood samples were collected to assess the blood acid-base status. Performance, cardiorespiratory, heart rate variability (HRV) as well as subjective variables were assessed. RESULTS: The main effect of condition (NaHCO3- vs. placebo) was observed in pH, bicarbonate concentration and base excess (p<0.05), with a significant blood alkalosis. No changes were found in time, peak velocity and time to peak velocity for condition (p>0.05). The HRV analysis showed a significant effect of NaHCO3- ingestion, expressed by the rMSSD30 (root mean square of the successive differences) (p<0.001). There was no effect of condition on oxygen uptake, carbon dioxide production, or pulmonary ventilation (p>0.05). Finally, there was no effect of condition for any subjective scale (p>0.05). CONCLUSIONS: We present here the first field condition study to investigate the effect of bicarbonate ingestion over performance in BMX discipline. The results showed that NaHCO3--induced alkalosis did not improve performance in a simulated BMX competition in elite BMX cyclists, although future studies should consider the effects of NaHCO3- on autonomic function as a component of recovery.

Physical exercise increases overall brain oscillatory activity but does not influence inhibitory control in young adults.

Extant evidence suggests that acute exercise triggers a tonic power increase in the alpha frequency band at frontal locations, which has been linked to benefits in cognitive function. However, recent literature has questioned such a selective effect on a particular frequency band, indicating a rather overall power increase across the entire frequency spectrum. Moreover, the nature of task-evoked oscillatory brain activity associated to inhibitory control after exercising, and the duration of the exercise effect, are not yet clear. Here, we investigate for the first time steady state oscillatory brain activity during and following an acute bout of aerobic exercise at two different exercise intensities (moderate-to-high and light), by means of a data-driven cluster-based approach to describe the spatio-temporal distribution of exercise-induced effects on brain function without prior assumptions on any frequency range or site of interest. We also assess the transient oscillatory brain activity elicited by stimulus presentation, as well as behavioural performance, in two inhibitory control (flanker) tasks, one performed after a short delay following the physical exercise and another completed after a rest period of 15' post-exercise to explore the time course of exercise-induced changes on brain function and cognitive performance. The results show that oscillatory brain activity increases during exercise compared to the resting state, and that this increase is higher during the moderate-to-high intensity exercise with respect to the light intensity exercise. In addition, our results show that the global pattern of increased oscillatory brain activity is not specific to any concrete surface localization in slow frequencies, while in faster frequencies this effect is located in parieto-occipital sites. Notably, the exercise-induced increase in oscillatory brain activity disappears immediately after the end of the exercise bout. Neither transient (event-related) oscillatory activity, nor behavioural performance during the flanker tasks following exercise showed significant between-intensity differences. The present findings help elucidate the effect of physical exercise on oscillatory brain activity and challenge previous research suggesting improved inhibitory control following moderate-to-high acute exercise.

The Role of Exercise-Induced Arousal and Exposure to Blue-Enriched Lighting on Vigilance.

It is currently assumed that exposure to an artificial blue-enriched light enhances human alertness and task performance, but recent research has suggested that behavioral effects are influenced by the basal state of arousal. Here, we tested whether the effect of blue-enriched lighting on vigilance performance depends on participants' arousal level. Twenty-four participants completed four sessions (blue-enriched vs. dim light × low vs. high arousal) at 10 pm on four consecutive days, following a repeated-measures design. Participants' arousal was manipulated parametrically through the execution of a cycling task at two intensities (low vs. moderate), and was checked by monitoring their heart rate. On each session, distal and proximal skin temperatures were recorded as a neuroergonomic index of vigilance, while participants performed a 20-min psychomotor vigilance task (PVT) under either blue-enriched light or dim light conditions. The Positive and Negative Affect Schedule (PANAS), Karolinska Sleepiness Scale (KSS), and Borg Rating of Perceived Exertion Scale (RPE) were used to measure subjective psychological state. The results showed that the exercise-induced manipulation of arousal produced robust alerting effects in most measures, while the lighting manipulation only attenuated subjective sleepiness and enhanced positive affect, but it did not influence behavior or physiology. Acute exposure to a blue-enriched light was practically ineffective when the arousal level was over baseline. The present research favored the use of acute physical exercise over acute exposure to blue-enriched lighting in order to boost humans' alertness when necessary, as in work settings where maintaining optimal levels of attention is difficult (shift work, night-work, vigilance tasks) and necessary to prevent human error and accidents.

Tramadol effects on physical performance and sustained attention during a 20-min indoor cycling time-trial: A randomised controlled trial.

OBJECTIVES: To investigate the effect of tramadol on performance during a 20-min cycling time-trial (Experiment 1), and to test whether sustained attention would be impaired during cycling after tramadol intake (Experiment 2). DESIGN: Randomized, double-blind, placebo controlled trial. METHODS: In Experiment 1, participants completed a cycling time-trial, 120-min after they ingested either tramadol or placebo. In Experiment 2, participants performed a visual oddball task during the time-trial. Electroencephalography measures (EEG) were recorded throughout the session. RESULTS: In Experiment 1, average time-trial power output was higher in the tramadol vs. placebo condition (tramadol: 220W vs. placebo: 209W; p<0.01). In Experiment 2, no differences between conditions were observed in the average power output (tramadol: 234W vs. placebo: 230W; p>0.05). No behavioural differences were found between conditions in the oddball task. Crucially, the time frequency analysis in Experiment 2 revealed an overall lower target-locked power in the beta-band (p<0.01), and higher alpha suppression (p<0.01) in the tramadol vs. placebo condition. At baseline, EEG power spectrum was higher under tramadol than under placebo in Experiment 1 while the reverse was true for Experiment 2. CONCLUSIONS: Tramadol improved cycling power output in Experiment 1, but not in Experiment 2, which may be due to the simultaneous performance of a cognitive task. Interestingly enough, the EEG data in Experiment 2 pointed to an impact of tramadol on stimulus processing related to sustained attention. TRIAL REGISTRATION: EudraCT number: 2015-005056-96.

The relationship between sustained attention and aerobic fitness in a group of young adults.

BACKGROUND: A growing set of studies has shown a positive relationship between aerobic fitness and a broad array of cognitive functions. However, few studies have focused on sustained attention, which has been considered a fundamental cognitive process that underlies most everyday activities. The purpose of this study was to investigate the role of aerobic fitness as a key factor in sustained attention capacities in young adults. METHODS: Forty-four young adults (18-23 years) were divided into two groups as a function of the level of aerobic fitness (high-fit and low-fit). Participants completed the Psychomotor Vigilance Task (PVT) and an oddball task where they had to detect infrequent targets presented among frequent non-targets. RESULTS: The analysis of variance (ANOVA) showed faster responses for the high-fit group than for the low-fit group in the PVT, replicating previous accounts. In the oddball task, the high-fit group maintained their accuracy (ACC) rate of target detection over time, while the low-fit group suffered a significant decline of response ACC throughout the task. DISCUSSION: Importantly, the results show that the greater sustained attention capacity of high-fit young adults is not specific to a reaction time (RT) sustained attention task like the PVT, but it is also evident in an ACC oddball task. In sum, the present findings point to the important role of aerobic fitness on sustained attention capacities in young adults.

Transient autonomic responses during sustained attention in high and low fit young adults.

Maintaining vigilance over long periods of time is especially critical in performing fundamental everyday activities and highly responsible professional tasks (e.g., driving, performing surgery or piloting). Here, we investigated the role of aerobic fitness as a crucial factor related to the vigilance capacity. To this end, two groups of young adult participants (high-fit and low-fit) were compared in terms of reaction time (RT) performance and event-related heart rate responses in a 60' version of the psychomotor vigilance task. The results showed shorter RTs in high-fit participants, but only during the first 24' of the task. Crucially, this period of improved performance was accompanied by a decelerative cardiac response pattern present only in the high-fit group that also disappeared after the first 24'. In conclusion, high aerobic fitness was related to a pattern of transient autonomic responses suggestive of an attentive preparatory state that coincided with improved behavioural performance, and that was sustained for 24'. Our findings highlight the importance of considering the role of the autonomic nervous system reactivity in the relationship between fitness and cognition in general, and sustained attention in particular.

Differences in Sustained Attention Capacity as a Function of Aerobic Fitness.

PURPOSE: We investigated the relationship between aerobic fitness and sustained attention capacity by comparing task performance and brain function, by means of event-related potentials (ERP), in high- and low-fit young adults. METHODS: Two groups of participants (22 higher-fit and 20 lower-fit) completed a 60-min version of the Psychomotor Vigilance Task (PVT). Behavioral (i.e., reaction time) and electrophysiological (ERP) (i.e., contingent negative variation and P3) were obtained and analyzed as a function of time-on-task. A submaximal cardiorespiratory fitness test confirmed the between-groups difference in terms of aerobic fitness. RESULTS: The results revealed shorter reaction time in higher-fit than in lower-fit participants in the first 36 min of the task. This was accompanied by larger contingent negative variation amplitude in the same period of the task in higher-fit than in lower-fit group. Crucially, higher-fit participants maintained larger P3 amplitude throughout the task compared to lower-fit, who showed a reduction in the P3 magnitude over time. CONCLUSIONS: Higher fitness was related to neuroelectric activity suggestive of better overall sustained attention demonstrating a better ability to allocate attentional resources over time. Moreover, higher fitness was related to enhanced response preparation in the first part of the task. Taken together, the current data set demonstrated a positive association between aerobic fitness, sustained attention, and response preparation.

Heart rate variability and cognitive processing: The autonomic response to task demands.

This study investigated variations in heart rate variability (HRV) as a function of cognitive demands. Participants completed an execution condition including the psychomotor vigilance task, a working memory task and a duration discrimination task. The control condition consisted of oddball versions (participants had to detect the rare event) of the tasks from the execution condition, designed to control for the effect of the task parameters (stimulus duration and stimulus rate) on HRV. The NASA-TLX questionnaire was used as a subjective measure of cognitive workload across tasks and conditions. Three major findings emerged from this study. First, HRV varied as a function of task demands (with the lowest values in the working memory task). Second, and crucially, we found similar HRV values when comparing each of the tasks with its oddball control equivalent, and a significant decrement in HRV as a function of time-on-task. Finally, the NASA-TLX results showed larger cognitive workload in the execution condition than in the oddball control condition, and scores variations as a function of task. Taken together, our results suggest that HRV is highly sensitive to overall demands of sustained attention over and above the influence of other cognitive processes suggested by previous literature. In addition, our study highlights a potential dissociation between objective and subjective measures of mental workload, with important implications in applied settings.