The Effect of Prolonged Light Intensity Exercise in the Heat on Executive Function

Acute improvement in the attention network with repetitive transcranial magnetic stimulation in Parkinson's disease

PURPOSE

To investigate the effect of two weeks of repetitive transcranial magnetic stimulation (rTMS) on the attention network in Parkinson's disease (PD) patients.

MATERIALS AND METHODS

Sixty PD patients were randomly divided into equal-sized active- and sham-rTMS groups. Executive function was assessed by neuropsychological tests including the Trail-Making Test (TMT), word fluency test, digit span, Wisconsin Card Sorting Test (WCST) and Stroop test. The attention network was evaluated by the attention network test (ANT). rTMS (5 Hz) was applied over the left dorsolateral prefrontal cortex (DLPFC) in the active-rTMS group, and the sham-rTMS group underwent sham stimulation, both for two weeks. All tests were performed before and after rTMS.

RESULTS

After active rTMS, nonparametric analysis revealed significant improvements in categories completed (CC) (p < 0.001) in the WCST and reaction times (RTs) in part 3 (p = 0.002) and the Stroop interference effect (SIE) (p < 0.001) in the Stroop test. Regarding the ANT, the RTs of the executive control network were significantly reduced (p < 0.001). There was no significant change after sham rTMS.

CONCLUSIONS

In the short term, in PD patients, rTMS improved the executive control network involved in resolving conflicting information. However, it showed milder effects on neuropsychological test outcomes assessing executive function, which may involve different neuromechanisms.Implications for rehabilitationCognitive impairment is common in patients with Parkinson's disease (PD), and it is related to functional disability and reduced quality of life.Attention is a main component of the cognitive system, and attention deficits are responsible for disability.This study demonstrates that rTMS is beneficial for cognitive rehabilitation in PD, as patients showed improved performance on the attention network test and neuropsychological tests.

Effects of heat strain on cognitive function among a sample of miners

Heat stress is associated with workplace injuries, likely through a combination of fatigue, reduced cognitive function, and thermal discomfort. The purpose of this study was to evaluate four cognitive tasks for sensitivity to heat stress. Eight participants performed treadmill exercise followed by assessments of serial reaction time (RT), Stroop effect, verbal delayed memory, and continuous performance working memory in an environmental chamber. A control (21.1 °C) trial, and "Hot 1" and "Hot 2" (both 37.8 °C) trials were run sequentially on two separate days to evaluate the four cognitive tasks. Heat strain (comparing Hot 1 and Hot 2 with the control trial) resulted in impairments in the serial RT test response and Stroop accuracy. Delayed memory was impacted only in the Hot 2 trial compared with the control trial. Given the demonstrated impact of heat on cognitive processes relevant to workers' real-world functioning in the workplace, understanding how to assess and monitor vigilant attention in the workplace is essential.

Simultaneous assessment of motor and cognitive tasks reveals reductions in working memory performance following exercise in the heat

This study tested the hypothesis that, following exercise in the heat, motor task performance will be impaired when assessed simultaneously with a cognitive task. In a randomized, crossover and counterbalanced design, twelve healthy adults (23 ± 2 years, 5 women) completed four 10-minute exercise circuits involving upper and lower body exercise in a moderate (18.1 ± 1.7°C, 38 ± 10% relative humidity) and a hot (40.3 ± 1.1°C, 26 ± 5% relative humidity) environment. Experimental testing was completed in a temperate thermal environment before exercise (~25°C) and in either the moderate or hot environment following exercise. The 3 Back test (a test of working memory) was used as the cognitive task and postural sway was used as the motor task. Cognitive and motor task performance assessments were conducted both individually (solo) and simultaneously (dual). At the end of exercise, core temperature (by 0.4 ± 0.3°C, P < 0.001), heart rate (by 12 ± 18 bpm, P = 0.025), and mean skin temperature (by 7.6 ± 0.8°C, P < 0.001) were higher in the Hot trial compared to Moderate. During solo testing, postural sway increased from pre- to post-exercise in the Hot (P ≤ 0.028), but not the Moderate (P ≥ 0.261) trial. During dual testing, postural sway did not differ between trials (P ≥ 0.065) or over time (P ≥ 0.094). During solo testing, 3 Back performance did not differ between trials (P = 0.810) or over time (P = 0.707), but during dual testing 3 Back performance following exercise was reduced in the Hot compared to the Moderate trial (P = 0.028). Simultaneous assessment of motor and cognitive tasks reveals that motor performance is reduced following exercise in the heat. .

Passive heat acclimation does not modulate processing speed and executive functions during cognitive tasks performed at fixed levels of thermal strain

PURPOSE

This study evaluated if passive controlled hyperthermia heat acclimation (HA) modulates cognitive performance during passive heat stress.

METHODS

Eight healthy adults (25 ± 4 years) underwent 7 consecutive days of hot water immersion (core temperature ≥38.6°C) and a 7-day time-control period. On days 1 and 7 of HA, participants performed a digital Stroop test at baseline, when core temperature reached 38.6°C, and after 60 minutes at a core temperature ≥38.6°C to evaluate reaction time during tasks targeting processing speed (reading and counting) and executive functions (inhibition and switching). On days 1 and 7 of the time-control intervention, participants performed the Stroop test with equivalent amounts of time separating each task as for HA.

RESULTS

During day 1 of HA, reaction time was quicker during the reading (-44 ms [-71, -17], P<0.01) and counting (-39 ms [-76, -2], P=0.04) tasks when rectal temperature reached 38.6°C, but after a further 60 minutes of heat exposure, reaction time only remained quicker during the reading task (-56 ms [-83, -29], P<0.01). Changes in reaction time during heat exposure were unaffected by subsequent HA (interaction, all P≥0.09).

CONCLUSION

Seven days of HA does not modulate processing speed and executive functions during passive heat exposure. Novelty: - Whether heat acclimation (HA) to improve cognitive performance during heat exposure remains understudied. - We tested the hypothesis that HA modulates reaction time during cognitive tasks performed at matched levels of thermal strain. - Despite classical signs of HA, reaction time during heat exposure was unaffected by HA.

Physiological interactions with personal-protective clothing, physically demanding work and global warming: An Asia-Pacific perspective

The Asia-Pacific contains over half of the world's population, 21 countries have a Gross Domestic Product <25% of the world's largest economy, many countries have tropical climates and all suffer the impact of global warming. That 'perfect storm' exacerbates the risk of occupational heat illness, yet first responders must perform physically demanding work wearing personal-protective clothing and equipment. Unfortunately, the Eurocentric emphasis of past research has sometimes reduced its applicability to other ethnic groups. To redress that imbalance, relevant contemporary research has been reviewed, to which has been added information applicable to people of Asian, Melanesian and Polynesian ancestry. An epidemiological triad is used to identify the causal agents and host factors of work intolerance within hot-humid climates, commencing with the size dependency of resting metabolism and heat production accompanying load carriage, followed by a progression from the impact of single-layered clothing through to encapsulating ensembles. A morphological hypothesis is presented to account for inter-individual differences in heat production and heat loss, which seems to explain apparent ethnic- and gender-related differences in thermoregulation, at least within thermally compensable states. The mechanisms underlying work intolerance, cardiovascular insufficiency and heat illness are reviewed, along with epidemiological data from the Asia-Pacific. Finally, evidence-based preventative and treatment strategies are presented and updated concerning moisture-management fabrics and barriers, dehydration, pre- and post-exercise cooling, and heat adaptation. An extensive reference list is provided, with >25 recommendations enabling physiologists, occupational health specialists, policy makers, purchasing officers and manufacturers to rapidly extract interpretative outcomes pertinent to the Asia-Pacific.

Skin Temperature Measurement Using Contact Thermometry: A Systematic Review of Setup Variables and Their Effects on Measured Values

Background: Skin temperature (T_skin) is commonly measured using T_skin sensors affixed directly to the skin surface, although the influence of setup variables on the measured outcome requires clarification. Objectives: The two distinct objectives of this systematic review were (1) to examine measurements from contact T_skin sensors considering equilibrium temperature and temperature disturbance, sensor attachments, pressure, environmental temperature, and sensor type, and (2) to characterise the contact T_skin sensors used, conditions of use, and subsequent reporting in studies investigating sports, exercise, and other physical activity. Data sources and study selection: For the measurement comparison objective, Ovid Medline and Scopus were used (1960 to July 2016) and studies comparing contact T_skin sensor measurements in vivo or using appropriate physical models were included. For the survey of use, Ovid Medline was used (2011 to July 2016) and studies using contact temperature sensors for the measurement of human T_skinin vivo during sport, exercise, and other physical activity were included. Study appraisal and synthesis methods: For measurement comparisons, assessments of risk of bias were made according to an adapted version of the Cochrane Collaboration's risk of bias tool. Comparisons of temperature measurements were expressed, where possible, as mean difference and 95% limits of agreement (LoA). Meta-analyses were not performed due to the lack of a common reference condition. For the survey of use, extracted information was summarised in text and tabular form. Results: For measurement comparisons, 21 studies were included. Results from these studies indicated minor (<0.5°C) to practically meaningful (>0.5°C) measurement bias within the subgroups of attachment type, applied pressure, environmental conditions, and sensor type. The 95% LoA were often within 1.0°C for in vivo studies and 0.5°C for physical models. For the survey of use, 172 studies were included. Details about T_skin sensor setup were often poorly reported and, from those reporting setup information, it was evident that setups widely varied in terms of type of sensors, attachments, and locations used. Conclusions: Setup variables and conditions of use can influence the measured temperature from contact T_skin sensors and thus key setup variables need to be appropriately considered and consistently reported.

Skin Temperature Measurement Using Contact Thermometry: A Systematic Review of Setup Variables and Their Effects on Measured Values

Background: Skin temperature (Tskin) is commonly measured using Tskin sensors affixed directly to the skin surface, although the influence of setup variables on the measured outcome requires clarification. Objectives: The two distinct objectives of this systematic review were (1) to examine measurements from contact Tskin sensors considering equilibrium temperature and temperature disturbance, sensor attachments, pressure, environmental temperature, and sensor type, and (2) to characterise the contact Tskin sensors used, conditions of use, and subsequent reporting in studies investigating sports, exercise, and other physical activity. Data sources and study selection: For the measurement comparison objective, Ovid Medline and Scopus were used (1960 to July 2016) and studies comparing contact Tskin sensor measurements in vivo or using appropriate physical models were included. For the survey of use, Ovid Medline was used (2011 to July 2016) and studies using contact temperature sensors for the measurement of human Tskinin vivo during sport, exercise, and other physical activity were included. Study appraisal and synthesis methods: For measurement comparisons, assessments of risk of bias were made according to an adapted version of the Cochrane Collaboration's risk of bias tool. Comparisons of temperature measurements were expressed, where possible, as mean difference and 95% limits of agreement (LoA). Meta-analyses were not performed due to the lack of a common reference condition. For the survey of use, extracted information was summarised in text and tabular form. Results: For measurement comparisons, 21 studies were included. Results from these studies indicated minor (<0.5°C) to practically meaningful (>0.5°C) measurement bias within the subgroups of attachment type, applied pressure, environmental conditions, and sensor type. The 95% LoA were often within 1.0°C for in vivo studies and 0.5°C for physical models. For the survey of use, 172 studies were included. Details about Tskin sensor setup were often poorly reported and, from those reporting setup information, it was evident that setups widely varied in terms of type of sensors, attachments, and locations used. Conclusions: Setup variables and conditions of use can influence the measured temperature from contact Tskin sensors and thus key setup variables need to be appropriately considered and consistently reported.

Hydration: The New FIFA World Cup's Challenge for Referee Decision Making?

Various continental sporting events have exposed team sports referees to different environmental conditions. Several studies have focused on strategies to prevent athlete performance impairment induced by heat or warm (or both) conditions, but few authors have investigated the effect of heat on referees' performance. In a thermoneutral environment, referees' physical activity induced mild 2.0% dehydration, which was responsible for reductions in physical, psychomotor, and cognitive performances. Therefore, the hydration status of referees should be taken into account to reduce referees' errors and misjudgments in the heat.

The effect of 6 h of running on brain activity, mood, and cognitive performance

Long-duration exercise has been linked with the psychological model of flow. It is expected that the flow experience is characterized by specific changes in cortical activity, especially a transient hypofrontality, which has recently been connected with an increase in cognitive performance post-exercise. Nevertheless, data on neuro-affective and neuro-cognitive effects during prolonged exercise are rare. The cognitive performance, mental state, flow experience, and brain cortical activity of 11 ultramarathon runners (6 female, 5 male) were assessed before, several times during, and after a 6-h run. A decrease in cortical activity (beta activity) was measured in the frontal cortex, whereas no changes were measured for global beta, frontal or global alpha activity. Perceived physical relaxation and flow state increased significantly after 1 h of running but decreased during the following 5 h. Perceived physical state and motivational state remained stable during the first hour of running but then decreased significantly. Cognitive performance as well as the underlying neurophysiological events (recorded as event-related potentials) remained stable across the 6-h run. Despite the fact that women reported significant higher levels of flow, no further gender effects were noticeable. Supporting the theory of a transient hypofrontality, a clear decrease in frontal cortex activity was noticeable. Interestingly, this had no effect on cognitive performance. The fact that self-reported flow experience only increased during the first hour of running before decreasing, leads us to assume that changes in cortical activity, and the experience of flow may not be linked as previously supposed.

The Impact of Different Environmental Conditions on Cognitive Function: A Focused Review

Cognitive function defines performance in objective tasks that require conscious mental effort. Extreme environments, namely heat, hypoxia, and cold can all alter human cognitive function due to a variety of psychological and/or biological processes. The aims of this Focused Review were to discuss; (1) the current state of knowledge on the effects of heat, hypoxic and cold stress on cognitive function, (2) the potential mechanisms underpinning these alterations, and (3) plausible interventions that may maintain cognitive function upon exposure to each of these environmental stressors. The available evidence suggests that the effects of heat, hypoxia, and cold stress on cognitive function are both task and severity dependent. Complex tasks are particularly vulnerable to extreme heat stress, whereas both simple and complex task performance appear to be vulnerable at even at moderate altitudes. Cold stress also appears to negatively impact both simple and complex task performance, however, the research in this area is sparse in comparison to heat and hypoxia. In summary, this focused review provides updated knowledge regarding the effects of extreme environmental stressors on cognitive function and their biological underpinnings. Tyrosine supplementation may help individuals maintain cognitive function in very hot, hypoxic, and/or cold conditions. However, more research is needed to clarify these and other postulated interventions.

Cognitive and perceptual responses during passive heat stress in younger and older adults

We tested the hypothesis that attention, memory, and executive function are impaired to a greater extent in passively heat-stressed older adults than in passively heat-stressed younger adults. In a randomized, crossover design, 15 older (age: 69 ± 5 yr) and 14 younger (age: 30 ± 4 yr) healthy subjects underwent passive heat stress and time control trials. Cognitive tests (outcomes: accuracy and reaction time) from the CANTAB battery evaluated attention [rapid visual processing (RVP), choice reaction time (CRT)], memory [spatial span (SSP), pattern recognition memory (PRM)], and executive function [one touch stockings of Cambridge (OTS)]. Testing was undertaken on two occasions during each trial, at baseline and after internal temperature had increased by 1.0 ± 0.2°C or after a time control period. For tests that measured attention, reaction time during RVP and CRT was slower (P ≤ 0.01) in the older group. During heat stress, RVP reaction time improved (P < 0.01) in both groups. Heat stress had no effect (P ≥ 0.09) on RVP or CRT accuracy in either group. For tests that measured memory, accuracy on SSP and PRM was lower (P < 0.01) in the older group, but there was no effect of heat stress (P ≥ 0.14). For tests that measured executive function, overall, accuracy on OTS was lower, and reaction time was slower in the older group (P ≤ 0.05). Reaction time generally improved during heat stress, but there was no effect of heat stress on accuracy in either group. These data indicate that moderate increases in body temperature during passive heat stress do not differentially compromise cognitive function in younger and older adults.