Clinical safety of blood flow-restricted training? A comprehensive review of altered muscle metaboreflex in cardiovascular disease during ischemic exercise

Abstract

Blood flow restriction training (BFRT) is an increasingly widespread method of exercise that involves imposed restriction of blood flow to the exercising muscle. Blood flow restriction is achieved by inflating a pneumatic pressure cuff (or a tourniquet) positioned proximal to the exercising muscle before, and during, the bout of exercise (i.e., ischemic exercise). Low-intensity BFRT with resistance training promotes comparable increases in muscle mass and strength observed during high-intensity exercise without blood flow restriction. BFRT has expanded into the clinical research setting as a potential therapeutic approach to treat functionally impaired individuals, such as the elderly, and patients with orthopedic and cardiovascular disease/conditions. However, questions regarding the safety of BFRT must be fully examined and addressed before the implementation of this exercise methodology in the clinical setting. In this respect, there is a general concern that BFRT may generate abnormal reflex-mediated cardiovascular responses. Indeed, the muscle metaboreflex is an ischemia-induced, sympathoexcitatory pressor reflex originating in skeletal muscle, and the present review synthesizes evidence that BFRT may elicit abnormal cardiovascular responses resulting from increased metaboreflex activation. Importantly, abnormal cardiovascular responses are more clearly evidenced in populations with increased cardiovascular risk (e.g., elderly and individuals with cardiovascular disease). The evidence provided in the present review draws into question the cardiovascular safety of BFRT, which clearly needs to be further investigated in future studies. This information will be paramount for the consideration of BFRT exercise implementation in clinical populations.

Hemodynamic and Pressor Responses to Combination of Yoga and Blood Flow Restriction

“…A number of BFR cuffs made up of various materials and widths have been used in the literature, namely elastic knee wraps [31], elastic belts with a pneumatic bag inside [32], nylon pneumatic cuffs [33], or a traditional nylon blood pressure cuff [34]. The type of blood flow restriction cuff has the potential to impact the degree of exaggerated blood pressure response [35]. In previous studies using walking exercises [2,7,30], non-elastic, wide, rigid BFR cuffs (e. g., Hokanson) were used.…”

The physiological, morphological and functional responses to resistance exercise with blood flow restriction: an examination of protocol type and exercise load

“…The acute response of the cardiovascular system to the onset of exercise is intricately coordinated by the autonomic nervous system, which redirects blood flow from inactive vascular beds (e.g. splanchnic) to the active skeletal muscle [68]. Both mechanical and chemical receptors within skeletal muscle relay information back to cardiovascular control areas in the brainstem through a mechanism known as exercise pressor reflex (EPR) [296].…”

“…Despite concerns for excessive stimulation of the muscle metaboreflex during BFR exercise resulting in elevated cardiac demand, this does not appear to increase risk over and above traditional RT [68,309]. Additionally, although there is a potential for excessive muscle damage and rhabdomyolysis [346], this risk is extremely low [330] and can be mitigated by employing submaximal set and repetition schemes and limiting exercise volume in individuals unaccustomed to BFR exercise.…”

Acute physiological responses to arm-cranking with blood flow restriction

“…Vascular and hemodynamic responses to BFR have been primary variables of interest in several reviews aimed at determining the safety of BFR in clinical populations [54,55]. Additionally, BFR acutely increases blood pressure during exercise in healthy and clinical populations compared to the same exercise without BFR; yet, the postexercise hypotensive response is greater following BFR [56,57].…”

“…Several groups [54,55] have expressed concerns regarding the safety of BFR with clinical populations, such as those with cardiovascular disease. To address these concerns, it is critical to monitor changes in hemodynamic responses, such as blood pressure, to evaluate the safety and efficacy of BFR.…”