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Mental Fatigue Can Affect Physical EnduranceFindings could become research model to help those with chronic fatigue
BETHESDA, Md. (Feb. 24, 2009) − When participants performed a mentally fatiguing task prior to a difficult exercise test, they reached exhaustion more quickly than when they did the same exercise when mentally rested, a new study finds.
The study also found that mental fatigue did not cause the heart or muscles to perform any differently. Instead, our “perceived effort” determines when we reach exhaustion. The researchers said the next step is to look at the brain to find out exactly why people with mental fatigue perceive exercise to be more difficult.
Samuele M. Marcora, Walter Staiano and Victoria Manning of Bangor University, Wales, the United Kingdom, did the study, “Mental fatigue impairs physical performance in humans.” The study will appear in the March print edition of the Journal of Applied Physiology. The American Physiological Society published the study.
The study
The 16 participants rode a stationary bicycle to exhaustion under two conditions: once when they were mentally fatigued and once when they were mentally rested. The trials took place in the laboratory on different days. The participants got the same amount of sleep, drank the same amount and had the same meal before each of the sessions.
The mental fatigue sessions began with a challenging 90-minute mental task that required close attention, memory, quick reaction and an ability to inhibit a response. After undergoing this session, participants reported being tired and lacking energy. The control session consisted of watching neutral documentaries for 90 minutes and was not mentally fatiguing.
After each of the 90-minute sessions – mentally fatiguing or non-fatiguing – the participants did an intense bout of exercise on a stationary bicycle. They rode until exhaustion, defined as the point when they could not maintain a cadence of at least 60 revolutions per minute for more than five seconds.
Throughout both exercise sessions, the researchers tracked a variety of physiological measures, such as oxygen consumption, heart rate, cardiac output, blood pressure, ventilation, and blood lactate levels. The participants completed surveys to measure their motivation and perceived effort. The researchers offered monetary prizes for the best performance on the exercise and mental tasks as a way to keep motivation high.
Results
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The participants stopped exercising 15% earlier, on average, when they were mentally fatigued.
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The participants stopped at the same perceived effort level in both the fatigued and non-fatigued trial. However, mentally fatigued participants started at a higher level of perceived effort and reached the endpoint sooner.
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The cardio-respiratory and musculo-energetic measurements did not vary between the two trials when compared at specific points in time. However, because the non-fatigued trials went longer, heart rate and blood lactate levels were higher at the end of those trials.
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Motivation was the same in both trials and was not a factor.
The researchers speculate that the perception of effort occurs in the brain. Dr. Marcora said his team is considering two possibilities:
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mental fatigue lowers the brain’s inhibition against quitting, or
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mentally fatigue affects dopamine, a brain chemical that plays a role in motivation and effort
One interesting note is that demanding mental tasks activate the anterior cingulate cortex of the brain. Previous research has shown that rats with a lesion in the anterior cingulate cortex would not work as hard for a reward compared to rats with no lesion. This area of the brain may be where perception of effort originates, Dr. Marcora said.
Applying the results
This research could provide a way to study chronic fatigue syndrome, Dr. Marcora said. People with chronic fatigue report they lack energy and experience “brain fog,” just like the mentally fatigued participants in this study. In addition, as in this study, people with chronic fatigue perceive exercise to be more difficult despite physiological responses considered normal during exercise.
The research model may also be helpful for military personnel. They do physically demanding tasks after long period of vigilance. Vigilance produces mental fatigue.
Finally, the study suggests that people doing high intensity training, such as competitive athletes, should do their training while mentally rested. However, people who exercise after work should continue doing so, even if mentally fatigued. Most people work out at a moderate intensity, which still gives plenty of physiological and psychological benefit, including relief from stress and improved mental performance.
NOTE TO EDITORS: To interview Dr. Marcora, please contact Christine Guilfoy at (301) 634-7253 or at cguilfoy@the-aps.org.
Funding: School of Sport, Health and Exercise Science, Bangor University, Wales, U.K.
Time Pressure Is What You Make It | Psych Central NewsWednesday, Feb 11 (Psych Central) --
Ask anyone working on a project, and the biggest complaint one hears is, “There’s not enough time.”
But instead of more time, maybe what they need is a change of perception.
“Research has shown that it’s not necessarily the time pressure, but it’s the perception of that time pressure that affects you,” says Michael DeDonno, from Case Western Reserve University.
“If you feel you don’t have enough time to do something, it’s going to affect you.”
DeDonno recently studied 163 subjects performing the Iowa Gambling Task (IGT), a popular psychological assessment tool, to investigate the effect of perceived time pressure on a learning-based task.
His study, the first to look at the relationship between perceived time pressure and IGT performance, was published in the December issue of Judgment and Decision Making.
He divided the study’s participants into two groups: an experimental group that was informed the time allotted to perform the task was insufficient and the control group which was told they had typically sufficient time to complete the task.
In the IGT, participants choose from among four decks of cards with the goal of making as much money as possible. Two of the decks are “good decks,” yielding a positive utility, and two are “bad decks,” with a negative utility.
The idea is to figure out which decks are good decks in the quickest amount of time to maximize profit over the course of the task.
Both groups were actually given sufficient time to complete the task, which involved 100 trials for each participant. However, each of the two groups was further broken down into subgroups, with one subgroup being given less time between card selections to think about the task.
But results show that participants who were advised the time was insufficient performed worse than those who were told they had enough time, regardless of the actual time allotted.
“If I told you that you didn’t have enough time, your performance was low regardless if you had ample time or not,” DeDonno says. “If you were told you had enough time, in both scenarios, they out performed those who were told they didn’t. ”
DeDonno says there are plenty of real-world benefits to understanding the effects of perceived time pressure on decision-making performance. He cited project team members who perceived a high degree of time pressure had lower job satisfaction. He also noted standardized tests, like the ACT or LSAT, have a high rate of test anxiety by test takers due mostly to time constraints.
He also wants to further the study to examine time perception with HMO physicians in relation to time spent with patients and diagnostic accuracy. Will a perception of time being insufficient by HMO physicians lead to inappropriate medications or an increase in diagnostic error?
While it remains to be determined why perceived time pressure can impair performance, DeDonno says that there are ways to combat it.
“Decision-making can be emotion based, keep your emotions in check. Have confidence in the amount of time you do have to do things. Try to focus on the task and not the time. We don’t control time, but we can control our perception. It’s amazing what you can do with a limited amount of time.
“Time is relevant. Just have the confidence with the time you’re given. I tell my students ‘Do the best you can in the time allotted. When it ends, it ends.’”
Color Wars: Do Hues Enhance Performance?For those who think people who worry about color schemes are fussy decorator types, think again. New research has shown that certain colors can inspire caution or creativity in problem solving.
"Everybody has a hunch about how color affects our behavior and cognition," said Juliet Zhu, co-author of the study and assistant professor of marketing at the Sauder School of Business at the University of British Columbia in Vancouver, British Columbia. "But there is not much research done in a scientific manner."
Zhu and co-author Ravi Mehta tested more than 600 participants over one year on a variety of problem-solving tasks, including solving anagrams and memorizing lists of words. The tasks were done against either a red, blue or white (neutral) screen, usually on computers.
When presented with a red background, the participants solved tasks that required attention to detail faster than when presented with a blue background.
Conversely, when presented against a blue background, participants offered superior solutions to problems that required a high degree of creativity, such as building a toy out of small parts or the many ways to use a brick.
Previous research on color and cognition often show conflicting results in which either red or blue is shown to enhance performance on cognitive tasks. Zhu and Mehta's efforts to reconcile that conflict led them to divide the cognitive tasks into those that required attention and those that required creativity.
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Zhu and Mehta's results suggested that a red background enhances performance on detail-oriented tasks and a blue background enhances performance on tasks that require creative thinking. The study appeared today in Science Express.
Seeing Red, Blue
Mehta, a doctoral student at the University of British Columbia, said they picked red and blue because they were at opposite ends of the color spectrum, in the warmest and coolest color groups, respectively. But red and blue also have strong meanings, or learned associations, attached to them.
Red is often associated with danger and mistakes -- stop signs, for example -- and promotes avoidance behavior. Consequently, people become more alert and detail oriented.
"That is part of being careful," Mehta said.
Blue, on the other hand, is associated with calmness, openness and images of oceans and sky, giving the perception of safety. In a safe environment, people are more comfortable taking risks and exploring creative ideas while solving problems.
For example, when asked to come up with different ways to use a brick, those in the blue group suggested an animal scratching post, chalk or an object in a museum to symbolize hard work.
Participants in the red group, on the other hand, offered suggestions such as using the brick as part of a house or a road or a wall.
When presented with a neutral, white background, Mehta said participant performance fell in between that of the red and blue groups, proving that certain colors can be beneficial, depending on the task.
Color Wars
But Zhu and Mehta's study showed that people are largely unaware of the impact color can have on cognitive ability.
"There are no common cultural expectations about what those colors are gong to do for them," said Ronald Friedman, assistant professor of psychology at the University at Albany, State University of New York, who has researched creativity and was not associated with this study. "People do not have any lay theories [that could make this] a placebo effect."
When participants were told they would be presented with a task that either required attention or creativity, and to select the color they believed would enhance their performance on that task, the participants overwhelmingly chose blue. Some 66 percent of participants chose blue when confronted with a creative task, and 74 percent chose blue when confronted with a detail-oriented task.
"That was the most surprising finding," Zhu said. "People are totally unaware of this effect."
Zhu said this outcome was likely the result of a general preference for blue over red in the population, and that people do not realize that red will, in some cases, enhance their performance more than blue.
Mehta pointed out that further research on colors and cognition could have practical implications, for example, using a red background when filing out tax forms -- a detail oriented task.
Zhu said further research could explore how cognitive responses to color can change depending on the cultural context, in other countries, for example, or as part of athletics.
"Despite the fact that we have these intuitive feelings that environmental cues will affect our behavior, little research has been done," Zhu said.
Cognitive Training Can Alter Biochemistry Of The BrainScienceDaily (Feb. 9, 2009) — Researchers at the Swedish medical university Karolinska Institutet have shown for the first time that the active training of the working memory brings about visible changes in the number of dopamine receptors in the human brain. The study, which is published in the journal Science, was conducted with the help of PET scanning and provides deeper insight into the complex interplay between cognition and the brain's biological structure.
"Brain biochemistry doesn't just underpin our mental activity; our mental activity and thinking process can also affect the biochemistry," says Professor Torkel Klingberg, who led the study. "This hasn't been demonstrated in humans before, and opens up a floodgate of fascinating questions."
The neurotransmitter dopamine plays a key part in many of the brain's functions. Disruptions to the dopamine system can impair working memory, making it more difficult to remember information over a short period of time, such as when problem solving. Impaired working memory has, in its turn, proved to be a contributory factory to cognitive impairments in such disorders as ADHD and schizophrenia.
Professor Klingberg and his colleagues have previously shown that the working memory can be improved with a few weeks' intensive training. Through a collaborative project conducted under the Stockholm Brain Institute, the researchers have now taken a step further and monitored the brain using Positron Emission Tomography (PET scans), and have confirmed that intensive brain training leads to a change in the number of dopamine D1 receptors in the cortex.
Their results can be of significance to the development of new treatments for patients with cognitive impairments, such as those related to ADHD, stroke, chronic fatigue syndrome and ageing.
"Changes in the number of dopamine receptors in a person doesn't give us the key to poor memory," says Professor Lars Farde, one of the researchers who took part in the study. "We also have to ask if the differences could have been caused by a lack of memory training or other environmental factors. Maybe we'll be able to find new, more effective treatments that combine medication and cognitive training, in which case we're in extremely interesting territory."
Positron Emission Tomography is a medical imaging technique based on the decay of radioactive isotopes that is able to produce three-dimensional pictures of the movement of signal substances in the living body. Karolinska Institutet has been able to invest in the world's most powerful PET scanner for brain imaging thanks to a financial contribution by pharmaceutical company AstraZeneca.
A good cry isn't for everyone - International Herald TribuneThey're considered a release, a psychological tonic, and to many a glimpse of something deeper: the heart's own sign language, emotional perspiration from the well of common humanity.
Tears lubricate love songs and love, weddings and funerals, public rituals and private pain, and perhaps no scientific study can capture their many meanings.
"I cry when I'm happy, I cry when I'm sad, I may cry when I'm sharing something that's of great significance to me," said Nancy Reiley, 62, who works at a women's shelter in Tampa, Florida, "and for some reason I sometimes will cry when I'm in a public speaking situation.
"It has nothing to do with feeling sad or vulnerable. There's no reason I can think of why it happens, but it does."
Now, some researchers say that the common psychological wisdom about crying — crying as a healthy catharsis — is incomplete and misleading. Having a "good cry" can and usually does allow people to recover some mental balance after a loss. But not always and not for everyone, argues a review article in the current issue of the journal Current Directions in Psychological Science. Placing such high expectation on a tearful breakdown most likely sets some people up for emotional confusion afterward.
Rapid Thinking Makes People Happy: Scientific AmericanLousy day? Don’t try to think happy thoughts—just think fast. A new study shows that accelerated thinking can improve your mood. In six experiments, researchers at Princeton and Harvard universities made research participants think quickly by having them generate as many problem-solving ideas (even bad ones) as possible in 10 minutes, read a series of ideas on a computer screen at a brisk pace or watch an I Love Lucy video clip on fast-forward. Other participants performed similar tasks at a relaxed speed.
Results suggested that thinking fast made participants feel more elated, creative and, to a lesser degree, energetic and powerful. Activities that promote fast thinking, then, such as whipping through an easy crossword puzzle or brain-storming quickly about an idea, can boost energy and mood, says psychologist Emily Pronin, the study’s lead author.
Pronin notes that rapid-fire thinking can sometimes have negative consequences. For people with bipolar disorder, thoughts can race so quickly that the manic feeling becomes aversive. And based on their own and others’ research, Pronin and a colleague propose in another recent article that although fast and varied thinking causes elation, fast but repetitive thoughts can instead trigger anxiety. (They further suggest that slow, varied thinking leads to the kind of calm, peaceful happiness associated with mindfulness meditation, whereas slow, repetitive thinking tends to sap energy and spur depressive thoughts.)
Also in this issue of Mind
It is unclear why thought speed affects mood, but Pronin and her colleagues theorize that our own expectations may be part of the equation. In earlier research, they found that people generally believe fast thinking is a sign of a good mood. This lay belief may lead us to instinctively infer that if we are thinking quickly we must be happy. In addition, they suggest, thinking quickly may unleash the brain’s novelty-loving dopamine system, which is involved in sensations of pleasure and reward.
The kind of rush that a person gets from rapid-fire thinking may be transient, but “these little bursts of positive emotion add up,” says psychologist Sonja Lyubomirsky of the University of California, Riverside. Studies have demonstrated that happiness yields myriad benefits, including greater productivity, stronger social support and improved immune function, she explains, adding that “even brief periods of heightened mood can lead to upward spirals.”
Stress May Hasten The Growth Of Melanoma Tumors But Common Beta-Blocker Medications Might Slow That ProgressCOLUMBUS, Ohio – For patients with a particularly aggressive form of skin cancer – malignant melanoma – stress, including that which comes from simply hearing that diagnosis, might amplify the progression of their disease.
But the same new research that infers this also suggests that the use of commonly prescribed blood pressure medicines might slow the development of those tumors and therefore improve these patients’ quality of life.
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The study, the third by Ohio State University scientists in the last two years that looked for links between stress hormones and diseases like cancer, is published in the the journal Brain, Behavior and Immunity.
Eric V. Yang, a research scientist at the Institute for Behavioral Medicine Research (IBMR), exposed samples of three melanoma cell lines to the compound norepinephrine, a naturally occurring catecholamine that functions as a stress hormone. In times of increased stress, levels of norepinephrine increase in the bloodstream.
Yang and colleague Ronald Glaser were looking for changes in the levels of three proteins released by the cells. Glaser is a professor of molecular virology, immunology and medical genetics, member of the university’s Comprehensive Cancer Center and director of the IBMR.
One of the proteins – vascular endothelial growth factor, or VEGF – plays a key role in stimulating the growth of new blood vessels needed to feed a growing tumor, a process called angiogenesis. The other two proteins, Interleukin-6 and Interleukin-8, are both involved in fostering tumor growth.
All three of the cell lines were grown from tissues taken from secondary tumors that had metastasized from a primary site and they signify aggressive forms of cancer. But one of them – C8161 – represented the most aggressive and advanced form of melanoma.
“We noticed that all three of these proteins increased in response to the norepinephrine,” Yang explained, adding that in the C8161 cells, “we got a 2,000 percent increase in IL-6. In untreated samples from this cell line, you normally can’t detect any IL-6 at all.
“What this tells us is that stress might have a worse effect on melanoma that is in a very aggressive or advanced stage, and that one marker for that might be increased levels of IL-6,” he said.
The researchers ruled out cell proliferation – an increase in the number of cells present – as a reason for the increase in all three proteins. That meant that the only other answer was that the cells were increasing their expression of the genes responsible for producing these compounds.
The researchers showed that the norepinephrine molecule binds to receptors on the surface of cancer cells and once this linkage occurs, it stimulates the release of the proteins that support angiogenesis and tumor growth.
Yang and Glaser first confirmed that the receptors were present on cells in all three cell lines and then tested what would happen when the receptors were blocked by common blood pressure medicine – the so-called “beta-blockers.”
When the beta-blockers did bind to the receptors, the production of the three proteins reduced significantly, suggesting that in patients with melanoma, using these types of medications might be used to slow the progression of the disease in patients.
While the study was restricted to tumor cell lines, rather than using animal models or human patients, the findings are still exciting. The researchers found strong evidence that the same receptors are expressed on the surface of tumor cells from biopsies that were taken from melanoma patients. That supports the clinical importance of the results.
Two earlier studies on different tumor cell lines – one prepared from a multiple myeloma and the other from a nasopharyngeal carcinoma – also showed that exposure to norepinephrine increased the levels of proteins responsible for accelerating tumor growth.
The research is showing not only that different forms of cancer react differently to stress hormones but also that those reactions can vary within a specific form of the disease, with the possibility of a more aggressive form of the disease reacting more strongly to the stressors.
For melanoma patients, that can be very important since these tumors are able to metastasize, or spread, when they are much smaller than most other solid cancers. The American Cancer Society estimates that nearly 48,000 cases of melanoma are diagnosed each year and nearly 8,000 people are killed each year by the disease.
This research was supported in part by the National Cancer Institute. Other collaborators in the study included Sanford Barsky, professor and chair of pathology; and IBMR members Elise Donovan, Min Chen, Amy Gross, Jeanette Webster Marketon and Seung-jae Kim.
