What is blood flow restriction exercise?
Blood flow restriction (BFR) exercise involves the occlusion of the active limbs during regular resistance or aerobic exercise. By using a tourniquet to provide occlusion during exercise, there is restriction of the arterial blood flow to the working muscle and the venous return of blood flow back to the heart. It appears that the addition of BFR to light-intensity exercise can provide numerous benefits including increases in muscle strength and hypertrophy similar to high-load resistance exercise, muscular endurance, and aerobic metabolism. Most notably, our preliminary research has helped support the growing body of evidence reporting remarkable improvements in aerobic capacity (5-10%) resulting from BFR exercise, even after just 4-6 weeks of training (~15 light-intensity walking or cycling sessions; See Figure 1 for an example of our BFR walking exercise protocol).
What is the secret behind these adaptations and how does BFR really impact our bodies?
While this phenomenon is not yet fully understood, our research seeks to investigate the possibility of these adaptions occurring centrally (changes in blood volume, cardiac output, etc.) rather than peripherally (changes in capillarization or mitochondrial content). With this in mind, some of our recent work discovered that post-BFR hormonal changes, specifically those related to fluid retention [antidiuretic (ADH; released in a 1:1 ratio with copeptin hormone) and renin], may hold the key to understanding how BFR truly affects our bodies. A pilot study that we presented at the Canadian Society of Exercise Physiology examining the use of BFR exercise showed that copeptin and renin hormones increased dramatically (copeptin: 6.7±3.2 to 41.0±31.8pmol/L, renin: 19.0±9.3 to 42.6±24.5ng/L), even after a single 19-min bout of BFR walking (Figure 2). It is unclear whether this occurrence is responsible for any of the benefits reported with BFR exercise, but it has led us to the question of whether this unique model could provide a solution for athletes that need to retain fluid by manipulating specific fluid retention hormones (e.g., fluid loading protocols).
What’s next?
To answer this question and provide a potential solution, some of our next work will look to further examine the BFR-induced hormone response and determine whether there are changes in body fluid retention in the 24 hours following exercise. Stay tuned for participant recruitment and more of our research that is currently under review.
Alexander Gamble, PhD is a University Teacher in Sport and Exercise Sciences in the Department of Physical Education and Sport Sciences at the University of Limerick. Alex teaches across several sport science disciplines in PESS and continues his research collaborations with Associate Professor Jamie Burr, PhD Candidate Kyle Thompson, and the rest of the team in the Human Performance and Health Research Laboratory at the University of Guelph in Canada. The research currently presented in this blog is some of the pilot data that we have collected over the past two years.
Contact: alexander.gamble@ul.ie. Follow on twitter: @agmble73. Research Profiles: ResearchGate, LinkedIn
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