Figure: The cardio-postural system. When a person stands, blood pools in the lower legs and this leads to a drop in blood pressure. The body’s blood pressure sensors (baroreceptors) detect the drop in blood pressure and relay this information to the brain where: 1) the blood pressure reflex (arterial baroreflex) increases heart rate and causes blood vessels in the limbs to constrict (vasoconstriction), and 2) the posture system is activated and muscles in the legs contract (skeletal muscle pump), forcing pooled blood in the leg veins back to the heart. To an observer this would be seen as body sway. Together, these two physiological actions cause the blood pressure to return to normal.

Preventing falls: A balancing act between posture and blood pressure control

The motivation – The investigation of falls has focused on two areas: 1) fainting due to cardiovascular disease; and, 2) slips, trips and loss of balance due to problems with posture control and gait. Although research in these areas has yielded some solutions to prevent falls, particularly in the elderly, a large number of incidents remain unpredictable.

The discovery – Based on observations that returning astronauts have problems with both balance and fainting, the Blaber Group at Simon Fraser University proposed that cardiovascular and postural control are part of one integrated system. This paper is the result of a 10-year investigation based on this hypothesis.  With the results of this study in hand, there is definitive evidence that these two systems are interrelated. Using causality analysis, Blaber’s group provides evidence of the existence and activity of a cardio-postural system that enables humans to stand upright for long periods. In particular, this cardio-postural system allows the body to respond to blood pressure changes in the following way: blood pressure change affects the activation of muscles in the legs and alters posture, which then affects blood pressure through the skeletal muscle pump (see figure). The authors also show that the effectiveness of postural control on blood pressure decreases with age, a physiological change that may contribute to falls occurring more frequently among the elderly.

Its significance – Falls and the fear of falling are major contributors to reducing mobility as we age. As the average age of Canadians increases, a greater effort is being invested into maintaining active health among seniors. Preventive and rehabilitative medicine has treated posture and blood pressure control independently. However, with these results showing that they are two components of one integrated cardio-postural system, we can initiate an approach to fall prevention that is informed by their interactions. Along with aspects of aging, the authors are investigating how this new knowledge can benefit other health concerns, including multiple sclerosis, recovery from stroke and concussion, as well as recovery from long term bed rest, and exercise and rehabilitation of astronauts.

Read the paper – “Skeletal Muscle Pump Drives Control of Cardiovascular and Postural Systems” by Verma, AK; Garg, A; Xu, D; Bruner, M; Fazel-Rezai, R; Blaber, AP; Tavakolian, K. Scientific Reports 7:45301 (2017).  DOI: 10.1038/srep45301.

Website article compiled by Jacqueline Watson with Theresa Kitos