Myokines are released into the bloodstream when muscles contract, create new cells, or perform other metabolic activities. When they reach the brain, they also regulate physiological and metabolic responses there. As a result, myokines have the ability to affect cognition, mood, and emotional behavior. Exercise further stimulates what scientists call “cross-talk” between muscle and brain, and these myokin messengers help determine specific beneficial responses in the brain. These may include the formation of new neurons and increased synaptic plasticity, both of which increase learning and memory.
Thus, strong muscles are essential for healthy brain function.
In young muscle, a small amount of exercise triggers molecular processes that signal the muscle to grow. Muscle fibers are damaged by tension and stress, and then repair themselves by fusing together and increasing in size and mass. Muscles become stronger by surviving each series of small tears, allowing for regeneration, rejuvenation and growth. As we age, the signal sent by exercise becomes much weaker. Although it is more difficult for older people to gain and maintain muscle mass, it is still possible to do so, and this maintenance is critical to supporting the brain.
Even moderate exercise can increase metabolism in brain regions important for learning and memory in older adults. And the brain itself has been found to respond to exercise in surprisingly physical ways. The hippocampus, a brain structure that plays an important role in learning and memory, shrinks in late adulthood; this can lead to an increased risk of dementia. Exercise training has been shown to increase the size of the hippocampus, even in late life, protecting against age-related loss and improving spatial memory.