The Adaptive Nervous System: Exercise Enrichment for Cognitive Resilience

The concept of “environmental enrichment” comes from the field of animal behaviour studies and is not a term that is typically heard in exercise and physical activity circles. But I think that it should be.

In a nutshell, we know that mammals kept in captivity (whether in a zoo, domestic, or laboratory setting) do not do well when they are deprived of physical and mental stimulation. Environmental enrichment aims to enhance the wellbeing of kept animals by “enriching” their environment with stimulating objects, activities, and experiences. Successful environmental enrichment promotes activities that are concurrently physically and cognitively stimulating. The best enrichment is at a level which is stimulating enough to be interesting, but not so over-stimulating as to be stressful.1

 In a natural setting, an animal would typically encounter myriad interactions with things in the environment: the landscape, food sources, predators, social interactions and play. Survival very much depends on the ability to use the body and brain together to navigate and respond to a complex and ever-changing environment. 

 The bodies and brains of animals - including humans - evolved in a complex natural environment, and the ability to effectively meet the complexities of that environment is directly linked to survival. You have to be constantly moving, constantly learning, constantly adapting. It is not surprising then, that good health outcomes are tightly entwined with behaviours that would have been beneficial in these natural environments. It is exactly why exercise and physical activity is so good for our overall health.

For nerdy eyes interested in looking at the role of exercise in health through an evolutionary biology lens, I recommend a paper by David Raichlen and Gene Alexander, called Adaptive Capacity: An evolutionary-neuroscience model linking exercise, cognition and brain health. The paper is open access and available online - reference below.2

The idea that exercise and cognitive function is linked through our evolutionary history is a theory, but a solid one in my opinion. Our body and brain evolved in an environment that demanded high levels of skilled motor control, learning/memory, endurance, navigation, strength, and decision-making. Tasks such as foraging and hunting require broad levels of both physical and cognitive capacity. 

Our modern environment is certainly not devoid of cognitive tasks, but these tasks are primarily sedentary. They do not engage the body and brain together in the same way a natural environment would. And so, we need our exercise to do that for us. More and more research is pointing to physical activity as a key component of maintaining brain health and cognition into older age.3,4 This beneficial impact appears to be enhanced even further when the exercise is cognitively engaging.5 Combining a physical task with a cognitive task is sometimes referred to as “dual-tasking”, but I think of cognitively engaging exercise more broadly as exercise enrichment. This term includes dual tasking but covers a broader ground.

The Adaptive Nervous System.

Neural plasticity is the ability of the nervous system - and the brain in particular - to change and adapt in response to environmental stimuli. This adaptive capacity allows the nervous system to “learn” from experience. There is an abundance of research studies in non-human animals outlining how environmental enrichment and exercise affect both the anatomy and physiology of the mammalian brain.1

 Of particular interest is research around the generation of new neurons and other neural structures like glial cells, as well as the ability of the brain to form new connections between neurons.

This is important because the cognitive decline seen with ageing is strongly associated with neurodegeneration - the loss of brain volume and decrease in connections between neurons. Preventing cognitive decline, from Mild Cognitive Impairment through to Alzheimer’s disease, is a matter of preserving the health and structure of the ageing brain as best as we possibly can.6

It used to be assumed that neurodegeneration seen with ageing was purely a consequence of biological ageing. The concept that the adult brain could generate new neural connections, let alone new neurons, was neuroscience heresy - until recently. Whilst the evidence for adult neurogenesis* in the strict sense - i.e., the generation of new neurons - in humans is still not very strong, there is strong evidence that the adult brain can, and does, adapt in many ways in response to exercise.

[*Technically, neurogenesis refers specifically to the generation of new neurons, but the term is being used - for the sake of simplicity - to refer more broadly to the generation of all new brain tissues: new neurons, new glial cells, new synaptic connections between cells etc.]

  In addition to promoting neurogenesis, exercise increases blood flow to the brain, improves the number and quality of blood vessels, enhances the metabolic health of brain tissue, positively impacts hormone levels, and raises levels of certain chemicals, called neurotrophic factors, which are associated with good brain health and cognitive function.

We know without a doubt that exercise results in positive anatomical and physiological adaptions in the brain, and that these changes are associated with better outcome measures for cognitive functions including attention/concentration, working memory and executive functioning.  Exercise is strongly protective against cognitive decline into older age.7,8

We also know that for optimal brain health and cognitive benefits, exercise should be enriched with a cognitive load. So, what does this look like in practice?

Enriching Exercise for Physical and Cognitive Resilience.

Essentially, enriching exercise is about increasing the complexity of what you do, adding novelty and cognitive challenge.

I am a long-time proponent of complex movement, novel tasks, and movement variation (sometimes called movement variability although these are, technically, two different things. I am pointing this out because I’m a giant geek, not because it has any practical relevance whatsoever. Call it what you want, darling).

Enriching exercise with complexity and novelty builds a broad base of competence and physical resilience. It also builds cognitive resilience. Learning a new exercise or new dance choreography makes demands of motor control patterns, attention/concentration and memory.  Hiking through uneven terrain whilst navigating from a map or looking for specific plants challenges balance and awareness. Introducing an element of play into exercise simultaneously increases both complexity and enjoyment and is a great way to get the heart rate up in novel ways.  Exercises that contain both a physical and cognitive task enhance brain function and learning.

Now it bears saying that The Goldilocks Principle applies here: not too hot, not too cold - just right. There will always be those folks who insist on the more-is-better way of doing things and before you know it, your Instagram feed is full of people juggling kettlebells whilst simultaneously smashing out some new dance moves on a balance board and playing a brain game via a fancy 3D immersive software application. God help me.

Just as there is a sweet spot with the level of stimulation in environmental enrichment, there is a sweet spot with the level of complexity and variability in exercise enrichment. Too little complexity and the exercise is not interesting enough, too much complexity and the exercise becomes stressful and/or dangerous. Where exactly this sweet spot lies is going to be different for different people - finding it is the art of training.

So here are 3 simple things you can try to get started on the road to including more complexity, novelty, and variability into your exercise:

1. Change your environment. Take your exercise outside if you can, preferably into a natural environment, and aim to interact with that environment in some way. Obvious examples include hiking and bouldering. If you can’t get out into the bush, go to a new park and train on the grass, go to a beach and train on the sand. Take advantage of the novel surfaces. If you can’t get outside or you’re allergic to nature, buy a guest pass to a new gym and play with some equipment you haven’t got in your regular gym.

2. Learn a new exercise or new movement. Pick something that is skill-based, requires 3D movement and is complex enough to engage your attention and concentration. If you’re stumped for ideas, go to a random exercise class you’ve never done before. Practice with a spirit of curiosity, and not from the perspective of perfecting the skill. The secret sauce is in the trying of the new thing. If you suck at the new thing, it doesn’t actually matter. You brain thrives on the novelty, not just the performance outcome.

3. Play. Whether by yourself or with someone else, making a game out of an exercise is a great way to increase novelty, engage decision-making and make things more fun. It doesn’t have to be serious business to be beneficial.

1. Gelfo, F et al (2018). The Neuroprotective Effects of Experience on Cognitive Functions: Evidence from Animal Studies on the Neurobiological Bases of Brain Reserve. Neuroscience.

2. Raichlen, DA and Alexander, GE (2017). Adaptive Capacity: An Evolutionary-neuroscience Model Linking Exercise, Cognition, and Brain Health. Trends Neurosci.

3. Gallaway, PJ et al (2017). Physical Activity: A Viable Way to Reduce the Risks of Mild Cognitive Impairment, Alzheimer’s Disease and Vascular Dementia in Older Adults. Brain Sciences. 

 4. Landrigan, J. F et al (2020). Lifting Cognition: A Meta-Analysis of Effects of Resistance Exercise on Cognition. Psychol Res.

 5. Karssemeijer, E et al (2017). Positive Effects of Combined Cognitive and Physical Exercise Training on Cognitive Function in Older Adults with Mild Cognitive Impairment or Dementia: A Meta-Analysis. Ageing Research Reviews.

6. Voss, MW et al (2010). Plasticity of Brain Networks in a Randomised Intervention Trial of Exercise Training in Older Adults. Front. Age Neurosi.

 7. De la Rosa, A et al (2020). Physical Exercise in the Prevention and Treatment of Alzheimer’s Disease. J Sport Health Sci.

 8. Basso, J.C & Suzuki, W.A (2017). The Effects of Acute Exercise on Mood, Cognition, Neurophysiology, and Neurochemical Pathways: A Review. Brain Plast.