Effects of Mental Fatigue on Exercise Intentions and Behavior

Neurophysiological and biosignal data for investigating occupational mental fatigue: MEFAR dataset

The prevalence of mental fatigue is a noteworthy phenomenon that can affect individuals across diverse professions and working routines. This paper provides a comprehensive dataset of physiological signals obtained from 23 participants during their professional work and questionnaires to analyze mental fatigue. The questionnaires included demographic information and Chalder Fatigue Scale scores indicating mental and physical fatigue. Both physiological signal measurements and the Chalder Fatigue Scale were performed in two sessions, morning and evening. The present dataset encompasses diverse physiological signals, including electroencephalogram (EEG), blood volume pulse (BVP), electrodermal activity (EDA), heart rate (HR), skin temperature (TEMP), and 3-axis accelerometer (ACC) data. The NeuroSky MindWave EEG device was used for brain signals, and the Empatica E4 smart wristband was used for other signals. Measurements were carried out on individuals from four different occupational groups, such as academicians, technicians, computer engineers, and kitchen workers. The provision of comprehensive metadata supplements the dataset, thereby promoting inquiries about the neurophysiological concomitants of mental fatigue, autonomic activity patterns, and the repercussions of a cognitive burden on human proficiency in actual workplace settings. The accessibility of the aforementioned dataset serves to facilitate progress in the field of mental fatigue research while also laying the groundwork for the creation of customized fatigue evaluation techniques and interventions in diverse professional domains.

Boosts for walking: how humorous messages increase brisk walking among cognitively fatigued individuals

BACKGROUND

A well-studied internal barrier to regular physical activity, and more specifically brisk walking, is cognitive fatigue. However, thus far little research examined how cognitively fatigued individuals can be motivated to exercise, more specifically to engage in brisk walking. This study investigates whether humorous intervention messages might be an effective strategy to motivate cognitively fatigued individuals to brisk walk, and through which underlying processes.

METHODS

An online experiment was performed in which variation in cognitive fatigue was induced through mental arithmetic questions. Afterwards, participants (n = 250) recruited through Prolific, randomly received either humorous or non-humorous intervention messages related to brisk walking. Potential mediators of the relations between physical activity, humour and cognitive fatigue were measured, were self-efficacy, self-control, and motivation.

RESULTS

First, regression analyses confirmed that cognitive fatigue negatively influences brisk walking intentions and that the perceived humour of the intervention messages moderated this relationship. Second, results showed that self-control and self-efficacy are mediators explaining the relationship between cognitive fatigue and brisk walking intentions. Lastly, this study found that perceived humour of the intervention messages moderated the relationship between cognitive fatigue and self-control, indicating that perceptions of self-control were positively changed after receiving messages that were perceived as humorous compared to messages that were not perceived as humorous, subsequently increasing brisk walking intentions.

CONCLUSIONS

This study is the first to unravel the underlying relationship between humorous intervention messages and brisk walking intentions through positive changes in perceptions of self-control within a cognitively fatigued sample. Results of this study suggest that existing smartphone applications monitoring and promoting brisk walking should integrate tailored message strategies within their cues to brisk walk by implementing humour as a strategy to motivate users when they are cognitively fatigued.

Assessing the Evidential Value of Mental Fatigue and Exercise Research

It has often been reported that mental exertion, presumably leading to mental fatigue, can negatively affect exercise performance; however, recent findings have questioned the strength of the effect. To further complicate this issue, an overlooked problem might be the presence of publication bias in studies using underpowered designs, which is known to inflate false positive report probability and effect size estimates. Altogether, the presence of bias is likely to reduce the evidential value of the published literature on this topic, although it is unknown to what extent. The purpose of the current work was to assess the evidential value of studies published to date on the effect of mental exertion on exercise performance by assessing the presence of publication bias and the observed statistical power achieved by these studies. A traditional meta-analysis revealed a Cohen's dz effect size of - 0.54, 95% CI [- 0.68, - 0.40], p < .001. However, when we applied methods for estimating and correcting for publication bias (based on funnel plot asymmetry and observed p-values), we found that the bias-corrected effect size became negligible with most of publication-bias methods and decreased to - 0.36 in the more optimistic of all the scenarios. A robust Bayesian meta-analysis found strong evidence in favor of publication bias, BFpb > 1000, and inconclusive evidence in favor of the effect, adjusted dz = 0.01, 95% CrI [- 0.46, 0.37], BF10 = 0.90. Furthermore, the median observed statistical power assuming the unadjusted meta-analytic effect size (i.e., - 0.54) as the true effect size was 39% (min = 19%, max = 96%), indicating that, on average, these studies only had a 39% chance of observing a significant result if the true effect was Cohen's dz = - 0.54. If the more optimistic adjusted effect size (- 0.36) was assumed as the true effect, the median statistical power was just 20%. We conclude that the current literature is a useful case study for illustrating the dangers of conducting underpowered studies to detect the effect size of interest.

Investigating real-time physical activity behavior using ecological momentary assessment: Effects of mental fatigue and benefit-cost valuations

BACKGROUND

Current research investigating the relationship between mental fatigue and physical activity behaviors relies on laboratory-based, experimental studies which lack ecological validity.

OBJECTIVE

This study used ecological momentary assessment (EMA) to assess feelings of mental fatigue and subjective evaluations (benefits and costs) as predictors of moderate-to-vigorous intensity physical activity in the everyday lives of young adults.

METHODS

One hundred participants (n = 22 males, n = 78 females, Mage = 20.60 years, 70% meeting or exceeding physical activity guidelines) responded to digital survey prompts up to four times a day and wore an accelerometer for seven consecutive days. Moderate-to-vigorous intensity physical activity in the 180-min time window following each survey prompt was recorded. Data from the 28 survey-moderate-to-vigorous intensity physical activity epochs were analyzed using multilevel mixed-effects linear modelling.

RESULTS

Higher levels of mental fatigue than one's average level were associated with engaging in fewer moderate-to-vigorous intensity physical activity minutes (p = .004) and lower benefit vs. cost scores (p = .001). Higher benefit vs. cost scores than one's average level were associated with engaging in more minutes of moderate-to-vigorous intensity physical activity (p < .001).

CONCLUSIONS

Results are the first to demonstrate outside the lab, that mental fatigue experienced in everyday life may amplify the perceived costs of moderate-to-vigorous intensity physical activity, with both factors playing a potential role in moderate-to-vigorous intensity physical activity decision-making. Future research may apply insights gained from this study in design and testing of real-time interventions promoting moderate-to-vigorous intensity physical activity.

Discrimination and Health Among First-Generation Hispanic/Latinx Immigrants: the Roles of Sleep and Fatigue

INTRODUCTION

A growing literature documents the associations between discrimination and health. Emerging evidence suggests that among Hispanic/Latinx immigrants, discrimination leads to the deterioration of health outcomes over time. While sleep has been proposed as an important mediator of the relationship between discrimination and health, few studies have explicitly investigated this pathway, particularly among Hispanic/Latinx populations.

OBJECTIVE

To investigate the relationships between racial/ethnic discrimination, sleep, and physical and mental health among Hispanic/Latinx immigrants in the USA. Data and Methods Using data from a parent study of first-generation Hispanic/Latinx immigrants in the southeastern USA, we conducted sequential mediation analyses using the bootstrapping method to investigate whether self-reported sleep duration, sleep quality, and fatigue mediate the relationship(s) between self-reported discrimination, as measured by the discrimination subscale of the Riverside Acculturative Stress Inventory, and self-reported physical and mental health.

RESULTS

Nocturnal awakenings, fatigue, and sleep quality were statistically significant sequential mediators of the relationship between discrimination and physical health (b = -.001, SE = .001, CI [-.0027, -.0001]); fatigue alone also mediated this relationship (b = -.01, SE = .01, CI [-.0279, -.0003]). Nocturnal awakenings, fatigue, and sleep quality were also significant sequential mediators of the relationship between discrimination and mental health (b = -.001, SE = .001, CI [-.0031, -.0001]).

CONCLUSION

Sleep and fatigue play an important role in linking discrimination and health among first-generation Hispanic/Latinx immigrants. The development and implementation of interventions that focus on reducing fatigue among this population could mitigate the effects of unfair treatment on health outcomes.

A plausible link between the time-on-task effect and the sequential task effect

Mental fatigue can be studied by using either the time-on-task protocol or the sequential task protocol. In the time-on-task protocol, participants perform a long and effortful task and a decrease in performance in this task is generally observed over time. In the sequential task protocol, a first effortful or control task is followed by a second effortful task. The performance in the second task is generally worse after the effortful task than after the control task. The principal aim of the present experiment is to examine the relationship between these two decrements in performance while concomitantly using a sequential task protocol and assessing the performance of the first effortful task as a function of time-on-task. We expect a positive correlation between these two decrements in performance. A total of 83 participants performed a 30-min fatiguing mental task (i.e., a modified Stroop task) or a control task followed by a time-to-exhaustion handgrip task. As expected, this protocol combining the time-on-task and sequential task protocols allowed us to observe (1) a decrease in performance over time during the Stroop task, (2) a worst performance in the handgrip task after the Stroop task by comparison to the control task, (3) a positive correlation between these two effects. The decrease in performance during the Stroop task also correlated with the subjective measures of boredom and fatigue, whereas the detrimental effect observed in the handgrip task did not. Our findings suggest that the two fatigue-related phenomena share a common mechanism but are not completely equivalent.

Health Status Stability of Patients in a Medical Rehabilitation Program: What Are the Roles of Time, Physical Fitness Level, and Self-efficacy?

BACKGROUND

Individuals' physical and mental health, as well as their chances of returning to work after their ability to work is damaged, can be addressed by medical rehabilitation.

AIM

This study investigated the developmental trends of mental and physical health among patients in medical rehabilitation and the roles of self-efficacy and physical fitness in the development of mental and physical health.

DESIGN

A longitudinal design that included four time-point measurements across 15 months.

SETTING

A medical rehabilitation center in Germany.

POPULATION

Participants included 201 patients who were recruited from a medical rehabilitation center.

METHODS

To objectively measure physical fitness (lung functioning), oxygen reabsorption at anaerobic threshold (VO2AT) was used, along with several self-report scales.

RESULTS

We found a nonlinear change in mental health among medical rehabilitation patients. The results underscored the importance of medical rehabilitation for patients' mental health over time. In addition, patients' physical health was stable over time. The initial level of physical fitness (VO2AT) positively predicted their mental health and kept the trend more stable. Self-efficacy appeared to have a positive relationship with mental health after rehabilitation treatment.

CONCLUSIONS

This study revealed a nonlinear change in mental health among medical rehabilitation patients. Self-efficacy was positively related to mental health, and the initial level of physical fitness positively predicted the level of mental health after rehabilitation treatment.

CLINICAL REHABILITATION

More attention could be given to physical capacity and self-efficacy for improving and maintaining rehabilitants' mental health.

Distractibility and impulsivity neural states are distinct from selective attention and modulate the implementation of spatial attention

In the context of visual attention, it has been classically assumed that missing the response to a target or erroneously selecting a distractor occurs as a consequence of the (miss)allocation of attention in space. In the present paper, we challenge this view and provide evidence that, in addition to encoding spatial attention, prefrontal neurons also encode a distractibility-to-impulsivity state. Using supervised dimensionality reduction techniques in prefrontal neuronal recordings in monkeys, we identify two partially overlapping neuronal subpopulations associated either with the focus of attention or overt behaviour. The degree of overlap accounts for the behavioral gain associated with the good allocation of attention. We further describe the neural variability accounting for distractibility-to-impulsivity behaviour by a two dimensional state associated with optimality in task and responsiveness. Overall, we thus show that behavioral performance arises from the integration of task-specific neuronal processes and pre-existing neuronal states describing task-independent behavioral states.

Failing to detect relevant information has been assumed to be a consequence of misallocation of attention. Here, the authors present findings showing that optimal behavioral performance results from the absence of interference between internal neural states and attention control.

The Counteractive Effect of Self-Regulation-Based Interventions on Prior Mental Exertion: A Systematic Review of Randomised Controlled Trials

Background: Many investigations have been performed on the effects of mental exertion that consumes self-regulatory resources and then affects physical and/or cognitive performance later on. However, the effect of manipulating self-regulation and interventions to attenuate this negative effect remains unclear. Moreover, there is continuous controversy regarding the resource model of self-regulation. Objective: We conducted a systematic review to assess the literature on manipulating self-regulation based on four ingredients (standard, monitoring, strength, and motivation) in order to counter mental exertion and improve physical and/or cognitive performance. The results provide more insight into the resource model. Method: A thorough search was conducted to extract the relevant literature from several databases, as well as Google Scholar, and the sources from the references were included as grey literature. A self-regulation intervention compared to a control condition, a physical and/or cognitive task, and a randomised controlled trial were selected. Result: A total of 39 publications were included. Regarding the four components of self-regulation, the interventions could mainly be divided into the following: (i) standard: implementation intervention; (ii) monitoring: biofeedback and time monitoring; (iii) strength: repeated exercise, mindfulness, nature exposure, and recovery strategies; (iv) motivation: autonomy-supportive and monetary incentives. The majority of the interventions led to significant improvement in subsequent self-regulatory performance. In addition, the resource model of self-regulation and attention-restoration theory were the most frequently used theories and supported relevant interventions. Conclusion: In line with the resource model, manipulating the four components of self-regulation can effectively attenuate the negative influence of mental exertion. The conservation proposed in the strength model of self-regulation was supported in the current findings to explain the role of motivation in the self-regulation process. Future studies can focus on attention as the centre of the metaphorical resource in the model.

Mental Fatigue Prior to Aerobic Exercise Reduces Exercise Pleasure and Negatively Affects Implicit Attitudes Toward Future Exercise

We investigated the effects of mental fatigue (MF) on affective responses during an aerobic exercise session at moderate intensity. We submitted 12 insufficiently active adults (50% women; M age = 24.9 years, SD = 3.0; M BMI = 24.3 kg/m2; SD = 2.6) to two 30-minute pre-exercise conditions: an MF condition (Stroop Color-Word task) and a control condition (watching a documentary) prior to their performance of 20 minutes of aerobic treadmill exercise at 40–59% of heart rate reserve. The minimum washout interval between conditions was two days. Perceived MF and motivation to perform physical exercise were assessed before and after conditions with a visual analog scale of 100 mm. We assessed participants’ affective and exertion responses with the Feeling Scale, Rating of Perceived Exertion (RPE) and heart rate during every two minutes of physical exercise. Implicit attitudes toward physical exercise were assessed by the Implicit Association Test before the MF and control conditions and after the physical exercise session. The participants in the MF condition reported lower pleasure ( M difference = −1.57, 95% CI = −2.64 to −0.50, d = 0.93, p = .008) and higher exertion (RPE) ( M difference = 1.16, 95% CI = 0.04 to 2.27, d = 0.66, p = .043) compared to those in the control condition. Participants who experienced MF also reported a more negative implicit attitude toward physical exercise than in the control condition ( β = −0.47, 95% CI= −0.73 to −0.21, d = 1.41, p < .001). While these findings should be cross-validated in subsequent research with a larger and more diverse participant sample, there appears to be value in minimizing pre-exercise mental fatigue to avoid negative MF effects on the exercisers’ affective experience.

The Effect of Music Tempo on Fatigue Perception at Different Exercise Intensities

Background: This study aimed to clarify the effect of music tempo on runners’ perception of fatigue at different exercise intensities and while listening to music of different tempos through running experiments. Methods: This study used a within-subject two-factor experimental design with music tempo (fast music, slow music, no music) and exercise intensity (high intensity, low intensity) as independent variables and the time to fatigue perception (TFP), the difference in heart rate (HR) and the difference in the median frequency (MF) of surface electromyography (sEMG) signals as observation indexes. Eighteen participants completed a total of 108 sets of running experiments. Results: (1) The main effect of music tempo on the TFP was significant (p < 0.001). (2) The main effect of exercise intensity on the TFP was significant (p < 0.001), and the main effect on the difference in HR was significant (p < 0.001). (3) The interaction effect of music tempo and exercise intensity on the TFP was significant (p < 0.05). Conclusions: Exercisers’ subjective perception of fatigue was affected by music tempo and the interaction between music tempo and exercise intensity, and exercisers’ objective fatigue perception was influenced mostly by exercise intensity. The findings of this study provide guidance for runners’ choice of music at different intensities of exercise. Whether it is low-intensity exercise or high-intensity exercise, listening to fast music while exercising can help runners perform better mentally and physically during their runs.

Effect of a Prolonged Maximal Bout of Exercise on Visual Performance

Background: Despite it being purported that acute, prolonged maximal periods of exercise may impair visual performance, little/no research on this topic is forthcoming. In fact, research has demonstrated that sub-maximal and maximal acute exercise may actually improve cognitive and sensory tasks and thus possibly improve visual performance. Objectives: This study aimed to ascertain the influence of an acute, prolonged maximal bout of exercise on visual performance. Methods: A quantitative study was undertaken with 60 untrained males being divided into a control group (CON; n = 30) or treatment group (TRE; n = 30). Both groups completed a baseline vision test battery consisting of accommodation facility, saccadic eye movement, speed of recognition, peripheral awareness, visual memory, and hand-eye coordination using the following tests; Hart Near Far Rock, saccadic eye movement, evasion, accumulator, flash memory and Ball Wall Toss tests. Two weeks later, participants returned for follow-up testing using the same vision test battery, with the TRE participants first engaging in a standardized incremental maximal treadmill protocol immediately prior to their vision testing. Results: Following the incremental maximal treadmill protocol, statistical analyses indicated that statistically significant (P ≤ 0.05) differences existed for accommodation facility, saccadic eye movements, speed of recognition, hand-eye coordination, peripheral awareness, and visual memory between pre-test and after the aerobic treatment (P = 0.00 for all measures). Conclusions: This study indicates that an acute, prolonged maximal bout of running improves visual performance. As such, an appropriate prolonged maximal warm-up may be required as opposed to a standardized and general warm-up when preparing an athlete for visual skills training or for participation in an athletic event that requires optimal visual performance.

Mental fatigue increases across a 16-week pre-season in elite female athletes

OBJECTIVES

To examine potential changes in mental and physical fatigue across an elite netball pre-season training phase and relationships between mental fatigue, physical fatigue, salivary cortisol (sCort) and alpha-amylase (sAA).

DESIGN

Observational with repeated measures.

METHODS

Across a 16-week pre-season, 10 elite female netballers (25.3 ± 3.7y) rated their physical fatigue, mental fatigue and readiness to perform on 100-mm visual analogue scales, and provided salivary samples for sCort and sAA analyses.

RESULTS

Linear mixed model analyses revealed elevated (p < 0.05) ratings of mental fatigue for weeks 12, 14 and 15 v 1; 12, 14 and 15 v 4 and 14 v 7. Higher (p < 0.05) ratings of physical fatigue were reported on weeks 6, 10, 11 and 12-16 compared to week 4; and 10 and 13 compared to week 7. Moderate and large ES differences were found between multiple weeks. Mental and physical fatigue demonstrated a shared variance of 14.3% (r = 0.38, p < 0.001) and an inverse relationship was observed between mental fatigue and readiness to perform (r = -0.50; p < 0.001). Changes in sCort nor sAA were not related to changes in mental or physical fatigue.

CONCLUSIONS

Mental fatigue fluctuated across the 16-week pre-season phase with elevated ratings observed in the later weeks. Whilst value remains in identifying subjective tools to assess mental fatigue; salivary biomarkers do not appear to be a suitable objective indicator of mental fatigue in the applied sporting environment. Practitioners should work to identify and manage mental fatigue with the same level of importance given to the periodisation of physical fatigue.

The Impact of Cognitive and Physical Effort Exertion on Physical Effort Decisions: A Pilot Experiment

Research suggests that cognitive fatigue has a negative impact on physical activity participation. However, the mechanisms underlying this effect are yet unclear. Using an effort-based decision-making paradigm, we examined whether individuals weigh physical effort-costs more strongly when they are cognitively or physically fatigued. Twenty university students visited the lab on three occasions. On each visit, participants underwent a manipulation that was designed to either induce cognitive fatigue (i.e., 2-back task), physical fatigue (i.e., handgrip exercise), or served as a control condition (i.e., documentary watching). After the manipulations, participants performed an effort-based decision-making task in which they decided for 125 offers whether they accepted the offer to exert the required level of physical effort to obtain rewards that varied in value. The probability to accept offers declined with increasing effort requirements whereas the general probability to accept offers was not reduced by any of the experimental conditions. As expected, the decline in accepted offers with increasing effort requirements was stronger after prolonged exertion of physical effort compared to the control condition. Unexpectedly, this effect was not found after exerting cognitive effort, and exploratory analyses revealed that the impact of physical effort exertion on physical effort-based decisions was stronger than that of cognitive effort exertion. These findings suggest that people weight future physical effort-costs more strongly after exerting physical effort, whereas we could not find any evidence for this after exerting cognitive effort. We discuss multiple explanations for this discrepancy, and outline possibilities for future research.

Sedentary work and participation in leisure-time physical activity

Objective

Demanding psychosocial work characteristics, such as high job demands, can have a detrimental impact on leisure–time physical activity (LTPA), with adverse consequences for employee health and well-being. However, the mechanisms and moderators of this crossover effect are still largely unknown. We therefore aimed to identify and test potential mediating and moderating factors from within and outside the work environment. Based on the previous research, we expected job demands to be negatively related to LTPA through fatigue. In addition, we expected that job control and worktime control would attenuate the relationship between job demands and fatigue. Furthermore, we hypothesized that autonomous exercise motivation and spontaneous action planning would attenuate the relationship between fatigue and LTPA. In addition to these cross-sectional hypotheses, we expected the same effects to predict a change in LTPA in the following year.

Methods

To investigate these assumptions, a preregistered longitudinal survey study was conducted among a large sample of Dutch employees in sedentary jobs. Participants reported on the constructs of interest in 2017 and 2018 (N = 1189 and 665 respectively) and the resulting data were analyzed using path analyses.

Results

Our cross-sectional analyses confirm a weak indirect, negative association between job demands and LTPA, via fatigue. However, this finding was not observed in our longitudinal analyses and none of the other hypotheses were confirmed.

Conclusion

This study shows that, among employees with relatively healthy psychosocial work characteristics (i.e., high job control), the evidence for an impact of these work characteristics on participation in LTPA is limited.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00420-021-01750-7.

Investigating the Effects of Mental Fatigue on Resistance Exercise Performance

Mental fatigue can impart negative effects on subsequent physical performance, although the mechanisms underlying these effects are not well understood. This study examined whether mental fatigue confers negative carryover effects on the performance of a set of biceps curls, while also investigating physiological and psychological mechanisms proposed to explain the predicted effect. A randomized, cross-over design was employed. On visit 1, participants (N = 10) performed a barbell biceps curl one-repetition maximum (1RM) test. On visits 2-3, participants performed 20 biceps curls at 50% of their 1RM, followed by their respective 10 min experimental manipulation (high vs. low cognitive exertion) and then a second set of biceps curls to exhaustion. Ratings of perceived exertion and electromyography of the biceps brachii, triceps brachii, upper trapezius, thoracic erector spinae and lumbar erector spinae were recorded during the physical task. The total number of repetitions completed was similar across the conditions. Results also failed to show between-condition differences for muscle activation and perceptions of exertion. Future research is needed to build an adequate knowledge base to determine whether there is an effect of mental fatigue on dynamic resistance-based task performance and, if so, identify the mechanisms explaining how and why.

Mental Fatigue Might Be Not So Bad for Exercise Performance After All: A Systematic Review and Bias-Sensitive Meta-Analysis

There is an ongoing debate in the scientific community regarding whether a state of mental fatigue may have a negative effect upon a range of objective and subjective measures of human performance. This issue has attracted attention from several fields, including sport and exercise sciences. In fact, a considerable body of literature in the sport science field has suggested that performing a long and demanding cognitive task might lead to a state of mental fatigue, impairing subsequent exercise performance, although research in this field has shown contradictory results. Here, we performed a meta-analysis to investigate these inconsistent findings. The analysis yielded small-to-medium effects of mental fatigue on exercise performance, d _z = 0.50, and RPE, d _z = 0.21. However, a three-parameter selection model also revealed evidence of publication or reporting biases, suggesting that the bias-corrected estimates might be substantially lower (0.08 and 0.10, respectively) and non-significant. In sum, current evidence does not provide conclusive support for the claim that mental fatigue has a negative influence on exercise performance.

Temporal dynamics of sitting behavior at work

Sitting for prolonged periods of time impairs people's health. Prior research has mainly investigated sitting behavior on an aggregate level, for example, by analyzing total sitting time per day. By contrast, taking a dynamic approach, here we conceptualize sitting behavior as a continuous chain of sit-to-stand and stand-to-sit transitions. We use multilevel time-to-event analysis to analyze the timing of these transitions. We analyze ∼30,000 objectively measured posture transitions from 156 people during work time. Results indicate that the temporal dynamics of sit-to-stand transitions differ from stand-to-sit transitions, and that people are quicker to switch postures later in the workday, and quicker to stand up after having been more active in the recent hours. We found no evidence for associations with physical fitness. Altogether, these findings provide insights into the origins of people's stand-up and sit-down decisions, show that sitting behavior is fundamentally different from exercise behavior, and provide pointers for the development of interventions.

Heart rate variability mediates motivation and fatigue throughout a high-intensity exercise program

High-intensity exercise interventions are often promoted as a time-efficient public health intervention to combat chronic disease. However, increased physical effort and subsequent fatigue can be barriers to long-term maintenance of high-intensity exercise programs. The purpose of the present study was to determine if heart rate variability (HRV) mediated state traits related to exercise program adherence. Fifty-five healthy men and women (ages 19-35 years) used a commercially available smartphone application to monitor daily HRV status throughout a 6-week high-intensity exercise intervention. Participants reported state motivation to exercise and global physical fatigue immediately prior to each exercise session. Temporary shifts toward increased parasympathetic reactivation (p = 0.030) resulted in significant increases in daily fatigue (p < 0.001) and decreases in motivation to exercise (p = 0.028). Through modulation of exercise volume, in response to these temporary shifts in HRV, these effects were reversed (p < 0.001) via increased parasympathetic withdrawal (p = 0.018). For the first time, these data demonstrate a mediating effect of HRV on adherence-related trait states throughout a high-intensity exercise program. Applied strategies, such as appropriately timed exercise volume moderation, may be able to leverage this effect and help facilitate long-term exercise program maintenance. Novelty These data establish a link between expected shifts in HRV throughout high-intensity exercise programs with motivation to participate and physical fatigue. Modulation of training volume, in response to these shifts, can optimize adherence-related behavioral responses during high-exercise programs.

Relationship Between Physical Activity and Motor Vehicle Crashes Among Older Adult Drivers

Background: There are approximately 42 million licensed drivers aged 65 years or older in the United States, who face unique age-related risks while driving. While physical activity affects several chronic conditions thought to be associated with motor vehicle crashes (MVCs), it is unclear if increased physical activity leads to fewer MVCs. This study explores whether self-reported vigorous and moderate physical activity is associated with MVCs in the previous year. Methods: Using cross-sectional data from the LongROAD study, a large multisite prospective cohort study of 2990 older adult drivers, we examined variables related to physical activity and performed a multivariate regression analysis to examine the association of physical activity health behaviors with self-reported MVCs. Results: Overall, 41.2% of participants reported vigorous and 69.6% of participants reported moderate exercise at least once per week. Eleven percent of participants reported at least 1 MVC in the previous year. Neither vigorous nor moderate physical activity was significantly associated with self-reported MVCs in the previous year. Select variables that were significantly associated with self-reported MVC included self-reported unsafe driving practices (odds ratio [OR] 1.55, confidence interval [CI] 1.05-2.29), and fall in the past 12 months (OR 1.46, CI 1.14-1.85). Conclusions: We were unable to detect a significant association between self-reported physical activity and MVCs in the past year among this group of older drivers. Use of objective measures of activity may better clarify this relationship.