Over the adult years spanning age 20 to age 90, cardiac output falls by up to 50%. As a result, oxygen and nutritional flow to all of the tissues of the body decline significantly, resulting in reduced metabolic activity. This decline is not due to heart failure, but to the atrophy of the soleus muscles.

The soleus muscles are deep postural muscles located in the lower legs and are responsible for pumping fluid from the lower body back up to the heart. The fatigue resistant contractile ability of these muscles is maintained through sustained use during activities such as squatting or toe standing. While children and young people commonly perform these types of activities, older individuals seldom undertake these types of activities. The result is that, as we age, our soleus muscles lose their ability to perform their critical pumping function.

When the soleus muscles no longer function properly, body fluids (blood and interstitial fluid) body fluids pool into our legs when we are sitting or standing, rather than being returned to the heart. As a result, cardiac output decreases, and the blood pressure in our vascular system declines. Steep drops in blood pressure when sitting or standing (postural hypotension) is very common among older adults, and leads to reduced blood flow to the brain.

Reduced brain blood flow results in memory loss, muscle coordination difficulties, deficits in executive function (ability to plan, make decisions, concentrate on a task, follow directions)- a set of symptoms commonly referred to as “age-related cognitive decline.” Cognitive impairment progresses over time and can result in dementia if the individual has a sufficiently long life. With the aging of the American population, dementia is approaching epidemic status.