Exercise Dependent Neuroplasticity
I recently re-read one of my favorite research articles discussing neuroplasticity, Exercise Dependent Neuroplasticity. It was published back in 2008, but I consider it an oldie but goodie.
As with many of my favorite articles, I love sharing the tidbits with my colleagues and students. I have even made it required reading for my students (yes, I am that kind of mentor 😊)
I have the honor to serve a wide variety of people with various neurologic conditions. But one thing that they all have in common is the ability to make neuroplastic changes to our brain.
Neuroplasticity is the term for "the mechanism by which the brain encodes experience and learns new behaviors." Neuro = brain and neural connections; Plastic = adapt, mold and change.
Every moment, every memory, and every experience we have with our world constantly impacts our brain's wiring (neural connections). It helps us better adjust and adapt to the world around us.
As a physical therapist, I can significantly impact the brain through movement and exercise.
Kleim and Jones highlighted 10 principles that are critical when attempting to drive neuroplasticity after brain damage.
1. Use It or Lose It: "Failure to drive specific brain functions can lead to functional degradation."
This may feel like a "no-brainer," but our brain is constantly trying to work as efficiently as possible. So if there is a skill, movement, or task that we are not readily using, our brain stops working to build new neural connections in that area, and the neural tissue degrades. This has both positive and negative implications.
Our brain and body have a finite amount of energy and resources each day, and since we are beautifully crafted, our brain and body will focus those resources on the areas we need/use/require the most. This can be a great thing because if there is a skill or task that we do not use or need, then our brain frees up our "brain power" for something else. This can have negative implications if there has been an injury to the brain that has subsequently caused a lack of function or movement. We don't actively work to require that skill or movement from the brain, frequently, then tissue degradation can begin to happen. But don't fret; even years after there has been tissue degradation, there is often still a chance for potential brain/neural connectivity, as long as we require it to utilize it.
2. Use It and Improve It "Training that drives a specific brain function can lead to an enhancement of that function."
This piggybacks on the last point. When we want to improve a skill or movement, the more focused attention we give to it, the better we become. Even the best athlete, without training and practice, would eventually plateau or be overtaken by a competitor determined to refine their skill/craft/or sport.
3. Specificity "The nature of the training experience dictates the nature of the plasticity."
All exercise is not created equal! Although it is recommended for just about everyone to have at least 30 min of moderate-intensity exercise for overall health, especially cardiovascularly. All exercise does not necessarily translate to improvements in specific neuroplastic changes. We have to be clear and specific on what we want the brain to learn and what skill or movement we want to improve. If I want to get better at writing with my left hand, then using only a device like an arm bike as my exercise will not do the trick. I have to practice that specific writing skill with my left hand to make a change at that skill. Now there can be plenty of variability to the craft of writing, and of course, training on the arm bike to increase my blood flow to my brain and the rest of the body is beneficial to prepare me for the task. Still, nothing can replace doing the exercise, other than doing it!
4. Repetition Matters" Induction of plasticity requires sufficient repetition."
So how many repetitions are enough repetitions? Well— it depends. (The most infamous answer to every single question I had in graduate school for physical therapy, but it is the best answer.) Depending on the complexity of the task, the number of repetitions can feel daunting. A 2019 study by Duret, Grosmaire, and Krebs, looked at the effects of the robot- assist therapy intervention. This study suggests at least 300-400 repetitions per therapy session are necessary to see neuroplastic changes. For walking, it can be much greater. So, although there is no magic number, the consensus is— the more repetitions, the better.
5. Intensity Matters: "Induction of plasticity requires sufficient training intensity."
If it feels easy, it's probably not making a difference. When we want to make changes, the intensity should challenge us either aerobically or muscularly or both. It's only with that level of intensity that we are even able to "get the attention" of our brain to form new neural connections.
Photo/Animation Credit: Chris Guyon: https://dribbble.com/shots/4990080-Train-Your-Brain
6. Time Matters: "Different forms of plasticity occur at different times during training."
While the brain is still very plastic to the changes, there are windows of time that are more supportive to learning than others. In the case of an acute brain injury such as a stroke, the first couple of days are not ideal for any high-intensity activity due to the critical nature of the injury. After a few days, however, the brain is very susceptible to neuroplastic changes. As time passes from the initial injury by months and years, the brain can still make changes, but not at the rate at which it could do so in those initial weeks following the injury. With chronic progressive diseases, the earlier a person achieves positive neuroplastic interventions in the disease progress, the more impactful the change can be on longer-term effects. So if you have passed that critical window, there is still so much hope. And if you are in that crucial window, then work hard, and build neural pathways!
7. Salience Matters "The training experience must be sufficiently salient to induce plasticity."
Salience = the quality of being particularly noticeable or significant; prominence
Have you ever been on a plane, and they start the safety information presentation, and you completely zone out. You know the information is essential, but it didn't draw you in or matter to you at the moment? I have to confess, I have! I have flown thousands of times, so it has become white noise to me. Once, however, I was flying, and on the Delta flight, they played a goofy 1980s style video with a lot of corny 80s puns. I laughed and watched every bit. The video's humor caught my attention and made me recognize that something important in the subject matter, captivating and essential, needed my attention at that moment. When training our brain for neuroplastic moments, the same rule applies. Make the experience meaningful to you. As a therapist, this can often be hard for me to find essential activities for my client. Still, I try to collaborate with them to make every experience noteworthy and meaningful to their lives. My goal is to encourage them to carry it over in their daily life (through more repetitions and remember — what we said earlier — repetitions matter.)
8. Age Matters "Training-induced plasticity occurs more readily in younger brains."
This one is pretty self-explanatory, but I think it's notable. However, even if age is not in your favor, you can still make changes, but it may take a little more time, intensity, and repetitions.
9. Transference "Plasticity in response to one training experience can enhance the acquisition of similar behaviors."
We discussed aerobic activity as a primer for functional activity earlier. Generalized aerobic training before or in conjunction with functional activity increases cardiovascular benefits and prepares the brain to respond to the active task better. This is exciting to consider in the injured and uninjured brain. Not only can the functional movement, task, or skill improve with specific training, but it may "warm-up" not only my body but also my brain for improved neuroplasticity. :)
10. Interference "Plasticity in response to one experience can interfere with the acquisition of other behaviors."
The cautionary tale. We have discussed all the positive benefits of neuroplasticity, but we have to recognize our brain learns what is good for us and can also know what is not suitable for us if exposed to it. Our brain can learn compensation, poor habits, and back movement mechanics if it receives sufficient repetition of the movement that is greater than what is received in therapy. This can pose a double whammy for the recovery process. Still, now the brain not only has root relearn the correct movement impact by the brain injury or disease process but now must "unlearn" the compensatory behavior creating a significant uphill battle. So remember, the brain is constantly learning in the uninjured and after a Brian injury or disease, but what we consistently expose and train the brain to respond to determine our future.
Key takeaway:
Meaningful, consistent learning environments that foster the movement or skill you would like to create while minimizing compensation will drive neuroplasticity.
References and Resources:
Kleim, JA, Jones, TA. (2008). Principles of experience-dependent neural plasticity: Implications for rehabilitation after brain damage. Journal of Speech, Language, and Hearing Research, 51, S225-S239.
