Existem várias evidências científicas mostrando que o exercício físico pode melhorar a capacidade de uma pessoa em raciocinar melhor. Mas também existem evidências que mostram que a fadiga e o excesso de treinamento físico não provocam esse efeito positivo. O exercício realizado de forma adequada melhora o estado de humor, o bem-estar, a ansiedade e depressão, assim como ajuda o indivíduo a lidar melhor com o estresse.
Um estudo na Universidade de Georgia USA, revisou publicações dos últimos 30 anos sobre os efeitos do exercício no cérebro e demonstrou que o exercício físico fornece muitos benefícios para a saúde mental, isto é, o exercício afeta de forma positiva o desempenho de várias tarefas mentais. Portanto, qual tipo de exercício poderá melhorar esse desempenho? Diferentes testes psicológicos e mentais mostraram que o exercício aeróbio apresenta melhores resultados quanto à capacidade de resolver problemas e tomar decisões mais rápidas e precisas. O exercício físico aeróbio de intensidade moderada provoca a liberação de hormônios e neurotransmissores (substâncias químicas presentes no cérebro) envolvidos em vários processos cognitivos, como a memória e aprendizagem. No entanto, apesar desses estudos serem muito estimulantes e promissores, ainda existem muitas questões a serem respondidas. Por exemplo, não se sabe ao certo qual seria a duração dos benefícios do exercício após a interrupção de um programa de treinamento físico ou mesmo qual seria a quantidade de exercício necessária para recuperar os benefícios adquiridos.De toda forma, o exercício físico adequado pode aprimorar não somente os aspectos relacionados ao desempenho mental, assim como reduzir os riscos do déficit da cognição relacionada à idade.
Study is first to confirm link between exercise and changes in brain
CHAMPAIGN, Ill. -- Three key areas of the brain adversely affected by aging show the greatest benefit when a person stays physically fit. The proof, scientists say, is visible in the brain scans of 55 volunteers over age 55. The idea that fitness improves cognition in the aging is not new. Animal studies have found that aerobic exercise boosts cellular and molecular components of the brain, and exercise has improved problem-solving and other cognitive abilities in older people. A new study in the February issue of the Journal of Gerontology: Medical Sciences, however, is the first to show -- using high-resolution magnetic resonance imaging -- anatomical differences in gray and white matter between physically fit and less fit aging humans.
Gray matter consists of thin layers of tissue of cell bodies such as neurons and support cells that are critically involved in learning and memory. White matter is the myelin sheath containing the nerve fibers that transmit signals throughout the brain.
"As people age, especially after age 30, these tissues shrink in a pattern closely matched by declines in cognitive performance." Kramer said. "We found differences in three areas of the brain, the frontal, temporal and parietal cortexes. There were very distinct differences particularly in two types of tissue, the gray matter and white matter. Nobody has reported this before."
A second Kramer-led study -- a meta-analysis (comprehensive data review) of 18 previous studies -- that will be published in March in Psychological Science, suggests that older women, especially those on hormone-replacement therapy, benefit more cognitively than do men from increased physical activity as they age.
The Journal of Gerontology study involved well-educated men and women aged 55 to 79. Their fitness ranged from sedentary to very fit, competitive-ready athletes. Fitness was measured by results of one-mile-walking and treadmill stress tests. Three-dimensional scans of the participants' brains were done using MRI equipment at Carle Foundation Hospital in Urbana. Applying voxel-based morphometry, researchers estimated tissue atrophy in a point-by-point fashion in the targeted regions of the brain.
"Interestingly, we found that fitness per se didn't have any influence on brain density," said Kramer, a professor of psychology and member of the Beckman Institute for Advanced Science and Technology at Illinois. "It is fitness as it interacts with age that has the positive effects. Older adults show a real decline in brain density in white and gray areas, but fitness actually slows that decline."
In the study, most other potential negative attributes -- smoking, diabetes, drinking, dieting, etc. -- were factored out of the data equation, Kramer said.
"This, to our knowledge, is the first human data providing a potential anatomical account of the cognitive effects that we and others have found over the years," Kramer said. "Our data also suggest that more research is clearly needed to actually do a thorough examination of brain structure and functioning, and the impact of interventions such as fitness and cognitive training."
In 1999, Kramer and colleagues reported in the journal Nature that previously sedentary people over age 60 who walked rapidly for 45 minutes three days a week can significantly improve mental-processing abilities that decline with age, and particularly tasks that rely heavily on the frontal lobes of the brain.
For their meta-analysis paper, researchers reviewed 18 intervention studies done between 1966 and 2001 and involving hundreds of participants ages 55 and older. Fitness training was found to show "robust but selective benefits for cognition, with the largest fitness-induced benefits occurring for executive-control processes."
Few studies done in the early part of the time included women, but as data were analyzed from later studies, Kramer said, "We found that gender had a large effect; men simply don't benefit as much, so we went back through our own data and asked why."
In previous studies of mice whose ovaries had been removed, they noted a decline in exercise and a drop in production of brain-derived neurotropin. When mice were put back on estrogen, production of the brain molecule increased and so did exercise activity.
In women, Kramer said, the data showed a similar trend: Women on estrogen replacement therapy benefited more than women not on it.
Other main conclusions from the meta-analysis: Exercise programs involving both aerobic exercise and strength training produced better results on cognitive abilities than either one alone.
Older adults benefit more than younger adults do, possibly, Kramer said, because older adults have more to gain as age-related declines become more prevalent.
More than 30 minutes of exercise per session produce the greatest benefit, a finding consistent with many existing guidelines for adults. The studies were funded by the National Institute on Aging (National Institutes of Health) and the New York-based Institute for the Study of Aging.
"These intriguing data suggest there may be one more possible benefit from regular exercise," said Molly V. Wagster, program director for the Neuropsychology of Aging, Neuroscience and Neuropsychology of Aging Program of the NIA, which supported the work. "The study emphasizes the importance of continued research on the potential role that exercise might play in reducing cognitive decline with age."
Illinois contributors to the Journal of Gerontology paper were Kramer; postdoctoral researcher Stanley J. Colcombe; doctoral student Kirk I. Erickson; Andrew G. Webb, professor of electrical and computer engineering; Neal Cohen, professor of psychology; and Edward McAuley, professor of kinesiology. Naftali Raz of Wayne State University in Detroit also was a co-author. Colcombe and Kramer performed the meta-analysis study.
Source: University of Illinois at Urbana-Champaign 28 Jan 2003
How does exercise improve mental health?
One theory for some of the benefits of exercise included the fact that exercise triggers the production of endorphins. These natural opiates are chemically similar to morphine. They may be produced as natural pain-relievers in response to the shock that the body receives in exercise. Researchers are beginning to question whether these substances improve mood. Studies show that endorphins do not cross the blood-brain barrier easily. Their ability to relieve pain probably occurs at the level of the spinal cord, leaving some other mechanism responsible for the mental health effects of exercise.
Recent studies have found that exercise boosts activity in the brain's frontal lobes and the hippocampus. We don't really know how or why this occurs. Animal studies have found that exercise increases levels of serotonin, dopamine and norepinephrine. These neurotransmitters have been associated with elevated mood, and it is thought that antidepressant medications like Prozac also work by boosting these chemicals.
Exercise has also been found to increase levels of "brain-derived neurotrophic factor" (BDNF). This substance is thought to improve mood, and it may play a role in the beneficial effects of exercise. BDNF's primary role seems to be to help brain cells survive longer; so this may also explain some of the beneficial effects of exercise on dementia.
The bottom line is that most of us feel good after exercise, and it's probably not from endorphins. Physical exercise is good for our mental health and for our brains. Someday we will understand it all better - but we can start exercising today.
