Neuroplasticity is defined as an increase or decrease in the strength of synaptic connections between neurons in the brain in response to various experiences. Every time we learn a new skill, travel to exotic places, and form long-term memories, our brains literally rewire themselves in order to be more adapted to novel situations. The better a person’s neuroplasticity is, the better equipped they are at facing challenges in life.
Studies have shown that regular aerobic exercise enhances memory, cognitive control, executive function, and attention. These associations have been reported across diverse populations and using different exercise protocols, cementing the notion that aerobic exercise enhances brain performance.
However, the underlying mechanisms that govern this relationship are still poorly understood.
What we know so far is that aerobic exercise may improve cognitive performance through the upregulation or neurotrophic factors (biomolecules that regulate the proliferation, survival, migration, and differentiation of cells in the nervous system). Examples of such biomolecules include the brain-derived neurotrophic factor (BDNF), cortisol, and lactate.
Studies carried out on both animals and humans suggest that BDNF promotes and modulates neuroplasticity. It is plausible that neurochemistry alterations to neuroplasticity induced by exercise could translate into changes in cognition.
Researchers from the University of South Australia performed a systematic review of the existing literature investigating the link between acute aerobic exercise and neuroplasticity. They included eight studies in their meta-analysis, which utilized a non-invasive brain stimulation technique to induce neuroplasticity and transcranial magnetic stimulation (TMS) to determine neuroplasticity outcomes.
The exercises included in the meta-analysis were not hypertrophy-inducing bodybuilding exercises and workouts, for example, such as 6 x Mr Olympia Dorian Yates’s back workout, this type of exercise is distinctly different. Rather aerobic exercises like cycling and treadmill were linked to neuroplasticity. Their intensity ranged from low but continuous exercise to high-intensity interval training (HIIT), with the participants’ heart rates varying from 50% to 90% of their maximum.
“We already know that engaging in regular aerobic exercise is good for the brain, improving memory, attention and learning,” says co-author Dr. Ashleigh Smith of the University of South Australia. “However, we need to understand why it is so beneficial and what the best exercise, intensity and duration is.”
Measurements of neuroplasticity performed before and after the exercises using TMS suggest that the most profound changes occur following 20 minutes of HIIT or 25 minutes of continuous moderate aerobic exercise.
What’s more, the research team also found that the stress hormone cortisol acts like a major mediating factor between aerobic exercise and changes in neuroplasticity. High levels of cortisol in the blood can block neuroplastic responses, the researchers reported in the Journal of Science and Medicine in Sport. Changing the tempo during HIIT sessions seems to allow cortisol levels to return to baseline levels, they added.