Lay summary by Ryan Cen
Edited by Crystal Han
What is the cardiovascular system and why is it important?
The cardiovascular (CV) system consists of a closed network of blood vessels and the heart, a specialized muscle that pumps blood to the entire body. This system is most important for circulating blood and oxygen throughout the the body, as well as delivering nutrients and shuttling waste from tissues. Therefore, the healthy of the CV system is critically important for one’s long-term health and wellbeing.
In the case of spinal cord injuries (SCI), however, not only is there a loss of control of movements below the level of injury (LOI), but the SCI can also impact the nervous system’s control of the CV system. Together, these effects can ultimately prevent the individual from getting enough exercise or even activating the CV system, which can lead to undesirable changes for the heart and blood vessels. Importantly, SCI has been associated with 3-4 fold increased odds of cardiovascular disease, indicating how important adequate exercise may be for people with SCI.
What was the purpose of this study?
The goal of this study was to examine the effects of a tailored, community-based physical activity (PA) regimen on cardiovascular health in those with an SCI. Specifically, the study explored the effects of 8 weeks of this “ProACTIVE” PA program on the structure and function of the heart and blood vessels in individuals with SCI.
How was the study conducted?
In total, 28 participants completed the study, which was a randomized control trial, meaning that the 28 individuals were randomly assigned to one of two groups, each with 14 people. In the PA group, participants worked with the researchers to achieve or exceed the exercise goals set by the SCI PA guidelines, while in the other group (control or no intervention), the subjects did not participate in the community-based PA regimen until after the study was complete.
All PA was done in a community setting, such as the gym, at home, or in a community centre. At the end of the 9 week study, a variety of cardiovascular tests and measurements were taken from both groups, and compared to see if the participation in PA impacted measures of heart and blood vessel structure and function.
What were the results of the study?
There were notable improvements in peak power and oxygen uptake in the group who underwent PA. Despite this, there were not significant changes in the structure and function of the heart or blood vessels in the full group of participants with SCI.
However, upon further analysis, there were differences seen based on the level of injury. Participants in the PA group with a lower level of injury (ie below the T6 vertebrae, which is just below the level of the shoulder blades near the stomach) had changes to their heart structure following physical activity. In particular, there was evidence of alterations in the left ventricle, the chamber of the heart responsible for pumping blood to the rest of the body. Such changes are thought to reflect an increase in volume of blood that the ventricle can hold due to the PA intervention. These changes were not seen in individuals with higher levels of injury (ie. at or above the T6 vertebrae), potentially because they are not able to activate the nervous system or musculature as much as those with lower injury levels.
Why are these findings important?
Until this study, most research looking at the impacts of PA participation focused on highly trained athletes with SCI using laboratory-based exercise methods. As a result, the findings of those studies were not widely representative of the general SCI population. Furthermore, the lab-based exercising methods used are not widely accessible to the general public in their local communities, which was another barrier to the applicability of those studies.
Therefore, this study was the first to examine community-based PA interventions, and its effects on both the structure and function of the heart and blood vessels in individuals with an SCI. This study has shown that an individualized PA regimen may promote improved heart function more readily in those with a lower-level SCI compared to those with higher levels of injury, who may require other techniques to help activate neural signalling or musculature in the lower body to see such effects.