Potential Therapeutic Benefits of Cyclical Blood Flow Restriction Exercise: A Novel Adaptation of Remote Ischemic Preconditioning

Myocardial infarction and stroke are two major causes of death and disability. As such, novel interventions are needed to reduce the incidence and severity of these events, and improve post-event rehabilitation. I have developed a potentially novel therapy by combining two interventions that independently exert neuro- and cardio-protective effects - exercise and remote ischemic preconditioning (RIPC) - in the form of a unique exercise paradigm, cyclical blood flow restriction exercise (cyclical BFRE). I hypothesized that an acute bout of cyclical BFRE would augment the release of factors that mediate the protection associated with exercise and RIPC when performed independently (nitric oxide and cytokines). A concern about clinical application of BFRE is the potential amplification of the exercise pressor reflex, causing an unsafe rise in arterial pressure. To address this, I further hypothesized that exercise-induced elevations in plasma norepinephrine, arterial pressure, and cerebral blood flow would be 1) attenuated with cyclical blood flow restriction resistance exercise, due to the use of lower workloads, but 2) augmented with cyclical blood flow restriction aerobic exercise, due to increased exercise pressor reflex activation. Fifteen healthy human subjects completed 5 experiments: RIPC, aerobic exercise with and without cyclical blood flow restriction, and resistance exercise with and without cyclical blood flow restriction. A standard thigh cuff pressure of 220 mmHg was used for all restriction protocols. The major findings from these studies are: 1) an acute bout of cyclical BFRE does not increase release of nitric oxide and key anti- and pro-inflammatory cytokines when blood sampling is performed immediately post-exercise, 2) there is high inter-subject variability in the degree of blood flow restriction achieved with a standardized cuff pressure, 3) cyclical blood flow restriction resistance exercise elicits an attenuated increase in sympathetic activity compared to conventional resistance exercise, 4) cyclical blood flow restriction aerobic exercise elicits an exaggerated increase in sympathetic activity compared to conventional aerobic exercise, but the cyclical reperfusions resulted in lower arterial pressures. This work has laid the groundwork for future studies utilizing individualized cuff pressures in both healthy and clinical populations, as well as training studies to assess the long term adaptations that may result from cyclical BFRE.