While the relationship between brain activity (especially cognitive ability) and physical activity is well referenced in literature, the study sought to take a closer look at the effect physical activity might have on neurogenesis and the levels of proliferative progenitor cells in the brain. The study in question was an animal model examining two groups of mice: one group was able to move freely. The other was able to move only the forelimbs, which mimics the effect of being bedridden or in zero gravity.
The differences found between the two groups were quite profound. While it was an animal model, and thus the applications to humans may not be exact, rat/mice models are commonly used as predictors for how certain interventions or situations may apply to humans, and thus the findings are likely to be quite significant. Findings included the following:
All these scientific terms spell out a simple message: a severe reduction in movement or gravity stimuli “exerts an important effect on the human body, altering the activity of many organs including the brain .” Among the potential changes are “alteration in afferent signalling and feedback information from intramuscular receptors, to the cerebral cortex, due to a modification of the reflex organisation in hindlimb muscle groups [3, in 2]. The researchers also noted that prolonged limb suspension (as seen in bed rest) induces nervous system plastic properties in humans, and changes in the memory function, spatial learning and protein expression changes in mice.
Essentially, this means that when we reduce exercise (especially in our lower limbs), we compromise neurological health, making it difficult for our body to produce new neural cells which can help us adapt and cope with stress. We also lower the amount of oxygen in the body “which creates an anaerobic environment and alters metabolism ” which then alters some genes which are important for the health of our mitochondria.
“It is no accident that we are meant to be active: to walk, run, crouch to sit, and use our leg muscles to lift. Neurological health is not a one-way street with the brain telling the muscles ‘lift’, ‘walk’, and so on” said Adami 
“Our study supports the notion that people who are unable to do load-bearing exercises — such as patients who are bed-ridden, or even astronauts on extended travel — not only lose muscle mass, but their body chemistry is altered at the cellular level and even their nervous system is adversely impacted,” lead researcher, Dr. Raffaella Adami, was quoted as saying .
Researchers also noted neurotransmitter changes involving glutamate receptors, and the concentration of serotonin, dopamine, GABA and epinephrine in rats, and pointed to other work that demonstrated inhibition of bone formation . These findings are all significant, making it obvious how traditional medicine needs to change in order to support brain health (especially in conditions like motor neurone disease and multiple sclerosis.) But it also shines a light on the importance of exercise in general health. The more we work the muscles in our legs, the more our brain can produce new cells.
Beyond these initial findings, the study appears to link seamlessly with chiropractic research showing greater muscle strength and less fatigue (to the leg muscles) once study participants were checked and adjusted [4, 5].
If leg muscle strength is important in brain health according to Adami et al, then the fact that the chiropractic adjustment has been found to increase participants to perform maximal leg contractions (with less fatigue over time) is a significant finding. Yes it does represent a circular effect: we boost the brains ability to drive muscles in the leg, and the use of leg muscles boosts the brains ability to create new nerve cells and maintain health throughout the body.
Together, the two studies illustrate the regenerative and mutually beneficial power of the innate intelligence that drives brain and body.
With neurological diseases representing a growing concern as the population ages, these two pieces of research (when read together) provide a powerful impetus to get checked and get moving. We often say that the aim of chiropractic is to add years to life and life to years. Now we can see one mechanism that explains how that might work.