What is the connection between physical and mental exercise? Do they have additive effects on brain health? Are they redundant?
Let’s start by reviewing what we know about the effects of physical exercise on the brain.
The effect of physical exercise on cognitive performance
Early studies compared groups of people who exercised to groups of people who did not exercise much. Results showed that people who exercised usually had better performance in a range of cognitive tasks compared to non-exercisers.
Laurin and colleagues (2001) even suggested that moderate and high levels of physical activity were associated with lower risk for Alzheimer’s disease and other dementias.
The problem with these studies is that the exercisers and the non-exercisers may differ on other factors than just exercise. The advantage that exerciser show may not come from exercising but from other factors such as more resources, better brain health to start with, better diet, etc.
The solution to this problem is to randomly assigned people to either an aerobic training group or a control group. If the exerciser group and the non-exerciser group are very similar to start with and if the exerciser group shows less decline or better performance over time than the non-exerciser group, then one can conclude that physical exercise is beneficial for brain health.
In 2003, Colcombe and Kramer, analyzed the results of 18 scientific studies published between 2000 and 2001 that were conducted in the way described above.
The results of this meta-analysis clearly showed that fitness training increases cognitive performance in healthy adults between the ages of 55 and 80.
Another meta-analysis published in 2004 by Heyn and colleagues shows similar beneficial effects of fitness training on people over 65 years old who had cognitive impairment or dementia.
What is the effect of fitness training on the brain itself?
Research with animals has shown that in mice, increased aerobic fitness (running) can increase the number of new cells formed in the hippocampus (the hippocampus is crucial for learning and memory). Increased exercise also has a beneficial effect on mice’s vascular system.
Only one study has used brain imaging to look at the effect of fitness on the human brain. In 2006, Colcombe and colleagues randomly assigned 59 older adults to either a cardiovascular exercise group, or a nonaerobic exercise control group (stretching and toning exercise). Participants exercised 3h per week for 6 months. Colcombe et al. scanned the participants’ brains before and after the training period.
After 6 months, the brain volume of the aerobic exercising group increased in several areas compared to the other group. Volume increase occurred principally in frontal and temporal areas of the brain involved in executive control and memory processes. The authors do not know what underlying cellular changes might have caused these volume changes. However they suspect, based on animal research, that volume changes may be due to an increased number of blood vessels and an increased number of connections between neurons.
How does physical exercise compare to mental exercise?
Very few studies have tried to compare the effect of physical exercise and mental exercise on cognitive performance.
When looking at each domain of research one notices the following differences:
- The effects of cognitive or mental exercise on performance seem to be very task specific, that is trained tasks benefit from training but the benefits do not transfer very well to tasks in which one was not trained.
- The effects of physical exercise on performance seem broader. However they do not generalize to all tasks. They benefit mostly tasks that involve executive-control components (that is, tasks that require planning, working memory, multitasking, resistance to distraction).
To my knowledge only one study tried to directly compare cognitive and fitness training:
By doing a little reading on your great website I understand there is a great emphasis on how to keep the brain sharp and I am must admit many great tips. However in my opinion physical exercise appears to give more value to better brain health in general than doing mental exercises. This is because when doing mental exercise it is virtually minimal to see a positive transfer affect other than the task you training in.
With physical exercise there is general transfer effect and until proved otherwise there should be more emphasis on physical exercise than mental stimulation.
Thanks for the comment. Given the existing evidence, we have decided in favor of a multi-pronged approach, that highlights the benefits of physical exercise, mental stimulation, stress management and good nutrition.
This approach is consistent with excellent recent public health efforts led by the Alzheimer’s Association and the Dana Foundation For Brain Initiatives, both of which are grounded on four close-to-identical pillars or factors.
Why a multi-pronged approach vs. a “one size fits all”?
Because different bodies of research suggest the benefits of different approaches, and there is few research contrasting their interactions directly (as Dr. Michelon points above).
For example, advocating that “there should be more emphasis on physical exercise than mental stimulation” would ignore a large body of Cognitive Reserve research on the benefits of lifelong education and mental stimulation to reduce the probability of developing Alzheimer’s symptoms, very solid large-scale clinical trials such as ACTIVE, and many controlled trials that show the benefits of well-directed mental exercise like meditation, cognitive therapy, computerized cognitive training, for specific populations and goals.
Another example on why a “one size fits all” is not the best approach: the benefits of physical exercise are mostly based on moving people from Sedentary to Slightly Active. Now, there are many people who are not Sedentary, who may benefit from other approaches.
So, I would turn the tables, and say that, right now, most brain health public education efforts are based on a multi-pronged approach and if anyone wants to focus exclusively on one factor for everyone and everything will have to prove a more solid case than the one availabe on existing data today.
Mental exercises that would have a positive transfer effect to other mental tasks
are exercises in attention and concentration.
Meditation is the simplest example of this.
Scott Hagwood says
Does physical exercise, in humans, contribute to neurogenesis? If so, would cognitive exercise then nurture the new cells creating brain volume?
Scott, very well put, that seems to be the case.
Now, it is perhaps not “volume” that grows (our skulls limit overall volume) but density and weight, overall and in specific brain structures. Pretty amazing, isn’t it?
Very well written! I’ll keep these in mind.
Perfect explanation and good to read and getting good tips like this will help me in my routine of exercises..It will be more effective with the help of Aerobic dance too..
As a Physical Educator, it’s great to have this information available. Do you have any research similar to Colcombe and Kramer that supports similar findings in children and youth?
Please keep up the great work.
Joe Herzog says
The research gathered by Dr. Ratey (Spark, A User’s Guide to The Brain, Dr. John Medina (Brain Rules) and Dr. Carla Hannaford (Smart Moves) among others gives physical educators a wealth of evidence to present to school administrations about the value of quality physical education. It should also motivate the entire physical education community to take a hard look at current curriculum and the need to make changes that brings it more in line with students long term needs, social, emotional, physical and cognitive.