Aerobic Exercise
Exercise and in particular aerobic exercise has been shown to have wide ranging health benefits reducing the risks of such diseases as heart disease, diabetes and cancer. More recently the effects of exercise on the brain have been studied showing that it also has wide ranging effect here. There are numerous human based studies examining how exercise effects cognition. Several of these studies show that groups performing aerobic exercise consistently demonstrated improvements in different facets of cognitive function compared to that of control groups. Other studies support this conclusion showing that regular exercise results in larger grey and white matter volume as well as reduced severity of age related cognitive degeneration. The one possible area where exercise may show a negative effect on at least some facets of cognition is during the exercise itself. This was demonstrated in several studies. Aerobic exercise as a cognitive enhancing strategy is extremely well supported and has virtually no negative side effects. A note that aerobic exercise involves increasing the heart rate. Generally the higher and longer the heart rate is raised the more pronounced the effect.
Most beneficial for - Both healthy individuals and those with cognitive problems have demonstrated benefit.
Effective dose - at least 3 time a week of brisk walking. Higher intensity has demonstrated better results.
Length of action - Benefits have been reported directly following exercise.
Safety - Muscular injuries are a potential risk
Type cognition effected - reasoning, working memory, audio and visual reaction time, visual sensitivity, planning, task switching and short term memory have all shown improvement in scientific studies.
Enhancers - demonstrated synergistic effect when combined with omega 3 fatty acids (DHA).
Supporting Human Studies
Relationships between physical exercise and cognitive abilities in older adults (Clarkson-Smith et al, 1989)
Sixty two elderly men and women who had exercised vigorously were compared to 62 sedentary elderly men and women on a series of cognitive tests. Analysis of test results allowing for age and education variation showed that those performing the vigorous exercise performed significantly better on reasoning, working memory and reaction time tasks compared to the sedentary group.
Age and fitness effects on EEG, ERPs, visual sensitivity, and cognition (Dustman et al, 1990)
Thirty young and 30 older healthy men were divided into groups of high and low fitness according to their VO2max scores during a maximal exercise test. Measures of EEG, event-related potentials (ERPs), visual sensitivity, and cognition were then obtained. Compared to low fit men, the physically active men had shorter ERP latencies, stronger central inhibition, better neurocognitive performance, and better visual sensitivity.
Changes in Cognition and Mortality in Relation to Exercise in Late Life: A Population Based Study (Middleton et al, 2008)
This study took measurements of cognition and exercise frequency of 8403 older Canadian adults and re-examined them after 5 years. Higher frequency exercisers (3 times per week with a minimum intensity of walking) had higher and more stable cognition compared to low/no exercisers. People who did not exercise were more likely to die in this study also.
Effects of aerobic exercise and gender on visual and auditory P300, reaction time, and accuracy (Yagi et al, 1999)
Twenty Four healthy volunteers were tested for both audio and visual reaction times before, during and after aerobic exercise. Reaction times for both audio and visual test decreased during exercise compared to both before, after and a control group. Error rates however increased during the exercise compared to the other conditions.
The effect of exercise-induced arousal on cognitive task performance: A meta-regression analysis (Lambourne et al, 2010)
Using meta-regression analysis techniques the effects of acute exercise on cognition were examined. Cognitive tasks performed during the first 20 minutes were shown to generally be inhibited. Following exercise metal speed and memory performance were enhanced by both steady state and exhaustive exercise regimes. Cycling was shown to enhance cognition more strongly than running.
Effects of Aerobic Exercise on Overweight Children’s Cognitive Functioning (Davis et al, 2007)
Ninety-four sedentary, overweight but otherwise healthy children (mean age = 9.2 years) were randomized to a low-dose (20 min/day exercise), high-dose (40 min/day exercise), or control condition. Exercise sessions met 5 day/wk for 15 weeks. The Cognitive Assessment System (CAS), a standardized test of cognitive processes, was administered individually before and following intervention. Planning scores on the CAS were significantly higher in the high dose group compared to the low exercise group.
Aerobic Exercise Training Increases Brain Volume in Aging Humans (Colcombe et al, 2006)
Fifty-nine healthy but sedentary community-dwelling volunteers, aged 60–79 years, participated in the 6-month randomized clinical trial. Half the group did aerobic training while the other half only tone and stretching exercises. Magnetic resonance images (MRI) of the subject brains were taken before and after the experiment. Maximum oxygen uptakes (VO2) were also evaluated. The group doing the aerobic training showed significant increases in brain volume (both white and grey matter) compared to the stretching group and a group of young controls.
Does active leisure protect cognition? Evidence from a national birth cohort (Richards et al, 2003)
In this study several long term studies were examined where people had been followed over many years since birth or early childhood. Those doing more physical activity were shown to have improved memory performance at 43 years of age. Those that were regularly exercising at 36 years showed a much slower decline in memory over the rest of their life.
Effects of Aerobic Exercise on Mild Cognitive Impairment (Baker et al, 2010)
Thirty three elderly adults with mild cognitive impairments were randomised into a aerobic training or stretching group. The aerobic group performed for 45-60 minute 4 time per week at 75 to 85% of maximum heart rate. The stretching group followed the same schedule only at or below 50% of max heart rate. This continued for 6 months. Several cognitive tests were performed at the end of the experiment. In women those doing the aerobic exercise showed significant improvements in executive function. Men on the aerobic exercise regimen showed improvements in trails B tests (testing visual attention and task switching).
Aerobic exercise, mood states and menstrual cycle symptoms (Aganoff et al, 1994)
A group of female regular exercisers (N = 97), and a second group of female non-exercisers (N = 159), completed the Differential Emotions Scale (DES-IV) premenstrually, menstrually and intermenstrually. The regular exercisers obtained significantly lower scores on impaired concentration, negative affect, behaviour change and pain.
The influence of aerobic fitness on cerebral white matter integrity and cognitive function in older adults: Results of a one-year exercise intervention (Voss et al,2012)
Elderly Adults underwent a one year intervention where they were assigned aerobic exercise. White matter integrity, executive function and short term memory were measured throughout the study. No overall group difference was seen before or after the intervention. However those participants that showed an improvements in cardiovascular fitness did show improved white matter integrity in the frontal and temporal lobes as well as short term memory.
Supporting animal Studies
Aerobic fitness relates to learning on a virtual Morris Water Task and hippocampal volume in adolescents (Herting et al, 2012)
Adolescent rats underwent aerobic exercise and were tested for hippocampal size and learning and memory. Results showed that higher aerobic fitness predicted better learning on a morris water maze and larger hippocampal volume. The exercise did not effect global brain volume or verbal learning.
Exercise improves cognition and hippocampal plasticity in APOE ε4 mice (Nichol et al, 2009)
Sedentary mutant mice performed much better in a water maze after exercise for 4 weeks. The exercise was shown to increase the levels of brain derived neurotrophic factor, tyrosine kinase b receptors and synaptophysin. All these factors are involved in neuron growth and plasticity.
Brain-derived neurotrophic factor functions as a metabotrophin to mediate the effects of exercise on cognition (Gomez-Pnilla et al, 2008)
Rats performed one week of voluntary exercise and then had the hippocampal brain region examined. The exercise itself was found to enhance memory and leaning. Higher levels of brain-derived neurotrophic factor (BDNF) were linked with exercise as were higher levels of other energy production molecules (AMPK, uMtCK, IGF-1, ghrelin). Blocking of BDNF eliminated the memory and learning benefits from the exercise.
Hippocampal BDNF mediates the efficacy of exercise on synaptic plasticity and cognition (Vaynman et al, 2004)
Exercise in rats had previously been shown to improve their performance on water mazes and increase brain-derived neurotrophic factor (BDNF). In this experiment rats undergoing voluntary exercise were injected with a chemical that blocks the activity of BDNF. Results demonstrated that by blocking the BDNF the rats performance on a water maze mirrored that of sedentary control rats. Other factors affected by blocking BDNF were reduced levels of cAMP response element binding protein (CREB) and synapsin I. These were shown to be raised by exercise in previous studies and are thought to be involved in neuro-plasticity.
Spatial learning and physical activity contribute to the induction of fibroblast growth factor: neural substrates for increased cognition associated with exercise (Gomez-Pinilla et al, 1998)
Rats underwent aerobic training in the morris water maze. Tests showed that this activity increased the levels of fibroblast growth factor. The more the maze was repeated the higher the levels of fibroblast growth factor became. The addition of a learning and memory component to the water maze further elevated the fibroblast growth factor levels. The higher fibroblast growth factor levels were associated with increased astrocyte density in the hippocampus of the rats.
Contradictory Studies
The effects of exercise on spatial learning and anxiety-like behavior are mediated by an IGF-I-dependent mechanism related to hippocampal neurogenesis (Trejo et al, 2007)
Mice that were genetically altered to produce reduced levels of insulin like growth factor I that resulted in reduced hippocampal neurogenesis and impaired spatial learning were exercised to see if it would reverse these deficits. The exercise did not have any effect on IGF-I, hippocampal neurogenesis or spatial learning. Exercise did reduce some aspects of anxiety however.
Endurance exercise selectively impairs prefrontal-dependent cognition (Deitricht et al, 2004)
In this experiment, athletes who exercised at a sustained, moderate pace were compared to sedentary controls on two neuropsychological tests, one that is generally regarded as heavily dependent on prefrontal cognition and one that is relatively insensitive to prefrontal operation. Results showed that during exercise performance on tests demanding prefrontal-dependent cognition was impaired, while at the same time, cognitive processes requiring little prefrontal activity were unaffected.
Combinational Studies
Docosahexaenoic acid dietary supplementation enhances the effects of exercise on synaptic plasticity and cognition (Wu et al, 2008)
Rats on a DHA diet (1.25%) received exercise or no exercise for 12 days. Compared to a control group the DHA diet significantly increased spatial learning ability, and these effects were further enhanced by exercise. The DHA diet also increased levels of brain derived neurotrophic factor (BDNF), CREB, Akt, CaMKII and synapsin I with further increases with the addition of exercise. These molecules are all involved in synaptic plasticity, memory and learning.
Most beneficial for - Both healthy individuals and those with cognitive problems have demonstrated benefit.
Effective dose - at least 3 time a week of brisk walking. Higher intensity has demonstrated better results.
Length of action - Benefits have been reported directly following exercise.
Safety - Muscular injuries are a potential risk
Type cognition effected - reasoning, working memory, audio and visual reaction time, visual sensitivity, planning, task switching and short term memory have all shown improvement in scientific studies.
Enhancers - demonstrated synergistic effect when combined with omega 3 fatty acids (DHA).
Supporting Human Studies
Relationships between physical exercise and cognitive abilities in older adults (Clarkson-Smith et al, 1989)
Sixty two elderly men and women who had exercised vigorously were compared to 62 sedentary elderly men and women on a series of cognitive tests. Analysis of test results allowing for age and education variation showed that those performing the vigorous exercise performed significantly better on reasoning, working memory and reaction time tasks compared to the sedentary group.
Age and fitness effects on EEG, ERPs, visual sensitivity, and cognition (Dustman et al, 1990)
Thirty young and 30 older healthy men were divided into groups of high and low fitness according to their VO2max scores during a maximal exercise test. Measures of EEG, event-related potentials (ERPs), visual sensitivity, and cognition were then obtained. Compared to low fit men, the physically active men had shorter ERP latencies, stronger central inhibition, better neurocognitive performance, and better visual sensitivity.
Changes in Cognition and Mortality in Relation to Exercise in Late Life: A Population Based Study (Middleton et al, 2008)
This study took measurements of cognition and exercise frequency of 8403 older Canadian adults and re-examined them after 5 years. Higher frequency exercisers (3 times per week with a minimum intensity of walking) had higher and more stable cognition compared to low/no exercisers. People who did not exercise were more likely to die in this study also.
Effects of aerobic exercise and gender on visual and auditory P300, reaction time, and accuracy (Yagi et al, 1999)
Twenty Four healthy volunteers were tested for both audio and visual reaction times before, during and after aerobic exercise. Reaction times for both audio and visual test decreased during exercise compared to both before, after and a control group. Error rates however increased during the exercise compared to the other conditions.
The effect of exercise-induced arousal on cognitive task performance: A meta-regression analysis (Lambourne et al, 2010)
Using meta-regression analysis techniques the effects of acute exercise on cognition were examined. Cognitive tasks performed during the first 20 minutes were shown to generally be inhibited. Following exercise metal speed and memory performance were enhanced by both steady state and exhaustive exercise regimes. Cycling was shown to enhance cognition more strongly than running.
Effects of Aerobic Exercise on Overweight Children’s Cognitive Functioning (Davis et al, 2007)
Ninety-four sedentary, overweight but otherwise healthy children (mean age = 9.2 years) were randomized to a low-dose (20 min/day exercise), high-dose (40 min/day exercise), or control condition. Exercise sessions met 5 day/wk for 15 weeks. The Cognitive Assessment System (CAS), a standardized test of cognitive processes, was administered individually before and following intervention. Planning scores on the CAS were significantly higher in the high dose group compared to the low exercise group.
Aerobic Exercise Training Increases Brain Volume in Aging Humans (Colcombe et al, 2006)
Fifty-nine healthy but sedentary community-dwelling volunteers, aged 60–79 years, participated in the 6-month randomized clinical trial. Half the group did aerobic training while the other half only tone and stretching exercises. Magnetic resonance images (MRI) of the subject brains were taken before and after the experiment. Maximum oxygen uptakes (VO2) were also evaluated. The group doing the aerobic training showed significant increases in brain volume (both white and grey matter) compared to the stretching group and a group of young controls.
Does active leisure protect cognition? Evidence from a national birth cohort (Richards et al, 2003)
In this study several long term studies were examined where people had been followed over many years since birth or early childhood. Those doing more physical activity were shown to have improved memory performance at 43 years of age. Those that were regularly exercising at 36 years showed a much slower decline in memory over the rest of their life.
Effects of Aerobic Exercise on Mild Cognitive Impairment (Baker et al, 2010)
Thirty three elderly adults with mild cognitive impairments were randomised into a aerobic training or stretching group. The aerobic group performed for 45-60 minute 4 time per week at 75 to 85% of maximum heart rate. The stretching group followed the same schedule only at or below 50% of max heart rate. This continued for 6 months. Several cognitive tests were performed at the end of the experiment. In women those doing the aerobic exercise showed significant improvements in executive function. Men on the aerobic exercise regimen showed improvements in trails B tests (testing visual attention and task switching).
Aerobic exercise, mood states and menstrual cycle symptoms (Aganoff et al, 1994)
A group of female regular exercisers (N = 97), and a second group of female non-exercisers (N = 159), completed the Differential Emotions Scale (DES-IV) premenstrually, menstrually and intermenstrually. The regular exercisers obtained significantly lower scores on impaired concentration, negative affect, behaviour change and pain.
The influence of aerobic fitness on cerebral white matter integrity and cognitive function in older adults: Results of a one-year exercise intervention (Voss et al,2012)
Elderly Adults underwent a one year intervention where they were assigned aerobic exercise. White matter integrity, executive function and short term memory were measured throughout the study. No overall group difference was seen before or after the intervention. However those participants that showed an improvements in cardiovascular fitness did show improved white matter integrity in the frontal and temporal lobes as well as short term memory.
Supporting animal Studies
Aerobic fitness relates to learning on a virtual Morris Water Task and hippocampal volume in adolescents (Herting et al, 2012)
Adolescent rats underwent aerobic exercise and were tested for hippocampal size and learning and memory. Results showed that higher aerobic fitness predicted better learning on a morris water maze and larger hippocampal volume. The exercise did not effect global brain volume or verbal learning.
Exercise improves cognition and hippocampal plasticity in APOE ε4 mice (Nichol et al, 2009)
Sedentary mutant mice performed much better in a water maze after exercise for 4 weeks. The exercise was shown to increase the levels of brain derived neurotrophic factor, tyrosine kinase b receptors and synaptophysin. All these factors are involved in neuron growth and plasticity.
Brain-derived neurotrophic factor functions as a metabotrophin to mediate the effects of exercise on cognition (Gomez-Pnilla et al, 2008)
Rats performed one week of voluntary exercise and then had the hippocampal brain region examined. The exercise itself was found to enhance memory and leaning. Higher levels of brain-derived neurotrophic factor (BDNF) were linked with exercise as were higher levels of other energy production molecules (AMPK, uMtCK, IGF-1, ghrelin). Blocking of BDNF eliminated the memory and learning benefits from the exercise.
Hippocampal BDNF mediates the efficacy of exercise on synaptic plasticity and cognition (Vaynman et al, 2004)
Exercise in rats had previously been shown to improve their performance on water mazes and increase brain-derived neurotrophic factor (BDNF). In this experiment rats undergoing voluntary exercise were injected with a chemical that blocks the activity of BDNF. Results demonstrated that by blocking the BDNF the rats performance on a water maze mirrored that of sedentary control rats. Other factors affected by blocking BDNF were reduced levels of cAMP response element binding protein (CREB) and synapsin I. These were shown to be raised by exercise in previous studies and are thought to be involved in neuro-plasticity.
Spatial learning and physical activity contribute to the induction of fibroblast growth factor: neural substrates for increased cognition associated with exercise (Gomez-Pinilla et al, 1998)
Rats underwent aerobic training in the morris water maze. Tests showed that this activity increased the levels of fibroblast growth factor. The more the maze was repeated the higher the levels of fibroblast growth factor became. The addition of a learning and memory component to the water maze further elevated the fibroblast growth factor levels. The higher fibroblast growth factor levels were associated with increased astrocyte density in the hippocampus of the rats.
Contradictory Studies
The effects of exercise on spatial learning and anxiety-like behavior are mediated by an IGF-I-dependent mechanism related to hippocampal neurogenesis (Trejo et al, 2007)
Mice that were genetically altered to produce reduced levels of insulin like growth factor I that resulted in reduced hippocampal neurogenesis and impaired spatial learning were exercised to see if it would reverse these deficits. The exercise did not have any effect on IGF-I, hippocampal neurogenesis or spatial learning. Exercise did reduce some aspects of anxiety however.
Endurance exercise selectively impairs prefrontal-dependent cognition (Deitricht et al, 2004)
In this experiment, athletes who exercised at a sustained, moderate pace were compared to sedentary controls on two neuropsychological tests, one that is generally regarded as heavily dependent on prefrontal cognition and one that is relatively insensitive to prefrontal operation. Results showed that during exercise performance on tests demanding prefrontal-dependent cognition was impaired, while at the same time, cognitive processes requiring little prefrontal activity were unaffected.
Combinational Studies
Docosahexaenoic acid dietary supplementation enhances the effects of exercise on synaptic plasticity and cognition (Wu et al, 2008)
Rats on a DHA diet (1.25%) received exercise or no exercise for 12 days. Compared to a control group the DHA diet significantly increased spatial learning ability, and these effects were further enhanced by exercise. The DHA diet also increased levels of brain derived neurotrophic factor (BDNF), CREB, Akt, CaMKII and synapsin I with further increases with the addition of exercise. These molecules are all involved in synaptic plasticity, memory and learning.