Prefrontal Cortex Activity Predicts Mental Fatigue in Young and Elderly Men During a 2 h “Go/NoGo” Task

Background: Although the effects of mental fatigue on cognitive–motor function and psychological state in young adults are well-documented, its effects in the elderly are not completely understood. The aim of this study was to estimate the effect of prolonged cognitive load on the indicators of psychological, cognitive, and motor functions.Methods: Fifteen young and 15 elderly men were asked to perform a 2 h “Go/NoGo” task. Psychological state (mood and motivation), cognitive (prefrontal cortex activity and cognitive performance), and motor (motor cortex excitability and grip strength) functions were measured before and after the task. During the 2 h task, both groups had a significantly similar increase in the number of “Incorrect NoGo” errors. Only in young men reaction time (RT) of “Incorrect NoGo” and intraindividual variability of RT of “Incorrect NoGo” significantly increased during task. After the task, handgrip strength decreased for the young men, whereas latency of motor evoked potentials prolonged both groups. Nevertheless, both groups indicated that they felt fatigue after the 2 h task; we observed that mental demand increased, whereas intrinsic motivation and mood decreased only in young men. Prolonged task decreased the switching/rest ratio of oxygenated hemoglobin for the young and the elderly men; however, greater for elderly than young men. Interestingly, the more the prefrontal cortex was activated before the 2 h task during the switching task, the fewer of “Incorrect NoGo” errors made by the young men and the greater the number of errors made by the elderly men.Conclusion: Because of the greater mental load and (possibly) greater activation of prefrontal cortex during the 2 h “Go/NoGo” task, there was greater mental and neuromuscular performance fatigue in young men than in elderly men

Cold stress induced sex-specific physiological responses

It has been suggested that one of the factors that affects response to thermal stress is sex. Women experience a faster core cooling rate than men during cold water immersion, however it is not clear if faster core cooling would induce differences at neuroendocrine response, motor and cognitive performance between men and women. Furthermore, it was established that when core temperature was above 36˚C there were no differences in physiological adjustments strategies to cold stress in men and women, however it is not clear if more extreme core cooling induces differences in responses between men and women. Thus, the aim of the research was to identify if there were any sex-specific differences in neuroendocrine response, physiological adjustments to cold stress strategies, cognitive performance, and motor performance due to whole body immersion at cold water-induced stress. The present study indicated that despite the similar level of cold stress in men and women, men exhibited greater neuroendocrine response of the hypothalamic-pituitary-adrenal (cortisol) axis and sympathetic-adrenomedulary (epinephrine) axis, greater perturbations in cognitive function, decrease in brief maximal voluntary contraction (MVC) and sustained 2-min MVC fatigability. Besides, physiological adjustments to cold stress also differed; women were more reliant on insulative response, and men were more reliant on metabolic response, particularly shivering. Thus, whole body cooling-induced sex-specific differences in physiological responses

Cold stress induced sex-specific physiological responses

It has been suggested that one of the factors that affects response to thermal stress is sex. Women experience a faster core cooling rate than men during cold water immersion, however it is not clear if faster core cooling would induce differences at neuroendocrine response, motor and cognitive performance between men and women. Furthermore, it was established that when core temperature was above 36˚C there were no differences in physiological adjustments strategies to cold stress in men and women, however it is not clear if more extreme core cooling induces differences in responses between men and women. Thus, the aim of the research was to identify if there were any sex-specific differences in neuroendocrine response, physiological adjustments to cold stress strategies, cognitive performance, and motor performance due to whole body immersion at cold water-induced stress. The present study indicated that despite the similar level of cold stress in men and women, men exhibited greater neuroendocrine response of the hypothalamic-pituitary-adrenal (cortisol) axis and sympathetic-adrenomedulary (epinephrine) axis, greater perturbations in cognitive function, decrease in brief maximal voluntary contraction (MVC) and sustained 2-min MVC fatigability. Besides, physiological adjustments to cold stress also differed; women were more reliant on insulative response, and men were more reliant on metabolic response, particularly shivering. Thus, whole body cooling-induced sex-specific differences in physiological responses

Changes in gait after severe traumatic brain injury during post-acute rehabilitation

Research object: gait dynamic after severe traumatic brain injury during post-acute rebailitation. Traumatic brain injury (TBI) is one of the major health problems throughout the world, which undergo more than 2 million people every year (Preikšaitis ir Ročka, 2007). In recent years particular attention increased on gait after TBI. Changes in gait after TBI are very important for evaluation, clinical reasoning and for intervention programs (Williams et al., 2009). Most studies analyze walking function during acute phase (William et al., 2007), but there is lack of information during post-acute period. The aim of the research was to determine gait changes during post-acute TBI rehabilitation. Research goals: 1. To observe spatiotemporal and kinematic gait changes. 2. To observe kinetic gait changes. 3. To observe muscles electrical activity amplitude changes. 4. To observe legs reaction time, movement speed and accuracy changes. Male (21 years old) participated in the research after 2 years severe TBI. Studies show that subjects with chronic and stable motor dysfunctions improve only during specialized and intensive programs (Kunkel et al., 1999; Fasoli et al., 2003). Our participant undergone 5 weeks intensive rehabilitation program composed of 15 physiotherapy, 12 motor control and 10 yoga procedures. Physiotherapy was composed of stretching, coordination, balance and weight-bearing exercises. During motor control participant performed „accuracy“ task which helps to improve legs reaction time, movement speed and accuracy. Yoga was performed to built core stability, train flexibility and diminish muscle tone. Gait changes were observed during 3D gait analysis. Force plate was placed in the middle of walkway. Electromyographic and DPA-1 dynamic movement parameters analysis was also performed. Research hypothesis: intensive rehabilitation improves gait changes after severe TBI during post-acute period. After research several conclusions were made: 1. After rehabilitation shortened stance and swing phase’s time, lengthened step, increased velocity and cadence, changed lower extremities joint angles and center of mass amplitude (p < 0.05). 2. After rehabilitation improved bilateral weight-bearing during gait (p < 0.05). Initial contact force was stronger compared to push-off (p < 0.05). 3. After rehabilitation reduced maximal electrical amplitude of soleus muscles and rectus femoris during stance phase (p < 0.05). 4. After rehabilitation shortened legs reaction time and improved movement accuracy (p < 0.05), but no changes were observed during maximal speed

The effects of the Nirvana Fitness exercise programme on perceived stress and cognition

Background. Mind and body exercise programmes, such as Tai Chi, Yoga and Pilates, can be successfully applied for stress reduction and cognitive function enhancement, however Nirvana Fitness training effects on perceived stress and cognition remain equivocal. The aim. To determine the effects of Nirvana Fitness training on perceived stress and cognition. Methods. The study included 20 women. They were randomly assigned to a control (n=10) or experimental (n=10) group. Participants in the experimental group participated in the Nirvana Fitness exercise programme, which consisted of a 50-minute class twice a week for 8 weeks. Participants in the control group were asked to maintain their daily routines. Changes in perceived stress and cognitive performance were evaluated. Results. The Nirvana Fitness exercise programme significantly decreased (p<0.05) perceived stress and improved (p<0.05) inhibitory control and cognitive flexibility, whereas spatial and working memory remained unchanged. Conclusion. The Nirvana Fitness programme can be used as an effective method to decrease stress and improve attention in women

Sex-related differences in attention and memory

Background and objectives: The sex differences and similarities in cognitive abilities is a continuing topic of major interest. Besides, the influences of trends over time and possible effects of sex steroid and assessment time on cognition have expanded the necessity to reevaluate differences between men and women. Therefore, the aim of this study was to compare cognitive performance between men and women in a strongly controlled experiment. Materials and methods: In total, 28 men and 25 women were investigated. Variables of body temperature and heart rate were assessed. A cognitive test battery was used to assess attention (visual search, unpredictable task switching as well as complex visual search and predictable task switching tests) and memory (forced visual memory, forward digit span and free recall test). Results: The differences in heart rate and body temperatures between men and women were not significant. There were no differences in the mean values of attention and memory abilities between men and women. Coefficients of variation of unpredictable task switching response and forward digit span were lower (P < 0.05) in men. Coefficients of variation positively correlated (P < 0.05) with attention task incorrect response and negatively correlated (P < 0.05) with correct answers in the memory task. Conclusions: Current study showed no sex differences in the mean values of cognition, whereas higher intra-individual variability of short-term memory and attention switching was identified in women, indicating that their performance was lower on these cognitive abilities

Exposure to acute noxious heat evokes a cardiorespiratory shock response in humans

Background: Noxious acute cold stimuli cause cold shock via the sympathetic nervous system. However, no studies have investigated respiratory “heat shock” in response to noxious acute heat stimuli (≥ 42 °C). Methods: In the present study, we examined whether short-duration whole-body immersion (for 5 min) in noxious hot water (45 °C) is a sufficient stimulus to induce a respiratory acute shock response. Results and conclusion: Our results indicate that short-duration whole-body immersion in noxious 45 °C water produces a significantly greater body temperature, heart rate, and perceptual and respiratory strain than immersion in innocuous warm 37 °C water (p < .05). The initial first minute of hot water immersion (HWI) at 45 °C (vs. immersion at 37 °C) caused a cardiorespiratory shock response, which manifested as acute hyperventilation, and increased ventilatory tidal volume, respiratory exchange ratio, and heart rate (p < .05). Adjustment to this initial respiratory heat shock response within the first minute of immersion was observed as compared with remaining HWI time (1–5 min). Intriguingly, the time-course kinetics of breathing frequency, oxygen uptake, and carbon dioxide washout did not differ between whole-body immersion at 37 °C and immersion at 45 °C, but were higher than in control thermoneutral conditions of an empty bath (p < .05). This may be because of events initiated not only by the water temperature but also by the change in the hydrostatic pressure acting upon the body when immersed in the water bath

Age-Related Difference in Cognitive Performance under Severe Whole-Body Hyperthermia Parallels Cortisol and Physical Strain Responses

Background and Objectives: To date, understanding age-related changes in cognitive processes during heat exposure still needs to be better-understood. Thus, the main aim of the current study was to evaluate the effects of whole-body hyperthermia (WBH), i.e., a ≈ 2.5 °C increase in rectal temperature (Tre) from overnight-fast baseline value, on cognitive functioning in old and young men and to explore factors, such as stress and thermophysiological strain, that could influence such changes. Materials and Methods: Ten young (19–21 years of age) and nine old (61–80 years of age) healthy men underwent an experimental trial with passive lower-body heating in hot water immersion (HWI) at 43 °C (HWI–43 °C) until Tre reached 39 °C in old adults and 39.5 °C in young adults. Cognitive performance and cortisol concentration were assessed before and after HWI, and the physiological strain index (PSI) was assessed during HWI–43 °C. Results: PSI was lower and cortisol concentration was greater after HWI–43 °C in the old group compared with the young group (p Conclusions: A ≈ 2.5 °C increase in rectal temperature can improve executive function in old adults, and this increase parallels the increased cortisol concentration and the lower thermophysiological strain under severe WBH conditions

Modulation of neuromuscular excitability in response to acute noxious heat exposure has no additional effects on central and peripheral fatigability

Background: Whole-body hyperthermia (WBH) has an adverse effect on the nervous system and neurophysiological performance. In the present study, we examined whether short-duration whole-body immersion in 45°C water (HWI-45°C), which produces a strong neural and temperature flux without inducing WBH, can increase or impair neurophysiological performance in humans. Methods: Fifteen men (aged 25 ± 6 years) were enrolled in this study and participated in three experiments: 1) a brief (5-min) immersion of the whole body in 37°C water (WI-37°C); 2) a brief (5-min) HWI-45°C; and 3) a control trial in a thermoneutral condition at an ambient temperature of 24°C and 60% relative humidity. Before and after the immersions, neuromuscular function (electromyographic activity, reflexes, electrically and voluntary induced torque production, voluntary muscle activation level) were tested. To provoke central inhibition, the participants performed a sustained 2-min maximal voluntary contraction (MVC). Results: Thermophysiological strain was greater after HWI-45°C than after WI-37°C. Electrophysiological modulations of motor drive transmission and peripheral modulations of muscle contractility properties in response to HWI-45°C seemed to have little effect on central activation of the exercising muscles and no effect on MVC production. Conclusion: Although exposure to acute noxious heat was effective in evoking neuromuscular excitability, the increases in core temperature (∼0.2°C) and muscle temperature (∼0.6°C) did not induce moderate or severe WBH. These changes did not seem to affect central structures; that is, there were no additional increases in central and/or peripheral fatigue during a sustained 2-min MVC