Briefly, much like a blood pressure machine, a cuff is fastened on the proximal end of either an arm or a leg, depending on the limb requiring the strengthening exercise. Then, each individual’s personalized tourniquet pressure is carefully measured to ensure a safe and efficacious restriction of blood flow. Once a prescribed level of occlusion is achieved, the patient performs low-intensity resistance exercises that are between 20% and 30% of maximal effort. But how does BFR-LIX improve muscle strength and tone? During aerobic exercises, muscles use oxygen shuttled by the blood. But when the activity is strenuous, the metabolic demand of the muscle increases. To cope, muscles start to generate energy using anaerobic mechanisms, whereby glucose is converted into lactate, releasing energy. But if pressure is applied to the vascular system and the blood flow is limited to the exercised muscles, even low-resistance training can deprive muscles of sufficient oxygen, triggering anaerobic energy production and a buildup of metabolites near the cuff. “What happens is lactate and hydrogen ions that are normally only produced when you're lifting heavy weights or when you're sprinting are generated with blood flow restriction,” said Hedt. “When the cuff is removed, these metabolites get flushed, and the body thinks it did something hard and strength has to be restored in that area.” The paper also highlights putative biochemical signaling pathways that are evoked by BFR-LIX, including those regulated by hormones, such as insulin, growth factors and immune molecules. While the positive outcomes of BFR-LIX for muscles distal to the occlusion site have been known for some time, the authors noted that there is emerging evidence of the benefits of the technique in proximal muscles, such as those in the hip or shoulder, bone and connective tissue. For example, researchers from Houston Methodist were the first to show that compared to healthy, untrained adults who only did low-intensity strength training, patients who received blood flow restriction along with rotator cuff training had improved muscle mass and isometric strength of the shoulder muscles. The authors noted that the current clinical applications of BFR-LIX include preventing muscle injury, speeding recovery after injury, modulating pain post-surgery, reducing muscle weakness due to neurological conditions and improving muscle strength for aerobic fitness. However, future applications of BFR-LIX will aim to encompass a wider variety of clinical conditions and patients. “We at Houston Methodist were likely the first system in the state, if not one of the first in the nation, to recognize its benefits and start using it with our patients,” said Hedt.