Strength is an envied and sought after quality in a variety of populations. Athletes want to improved their muscle mass and muscle production in order to run faster, jump higher and move with more precision and power. The general population is told that strength will influence a whole host of factors in overall wellness. Elderly individuals are instructed to avoid frailty at all costs and to prevent catastrophic injury by being as strong as possible. In fact, longevity expert Peter Attia references grip strength as a primary indicator of how long someone might live in the later years of his or her life. Many want additional strength but few know how to achieve it.
Traditional Strength Training Recommendations and Limitations
The American College of Sports Medicine recommends that individuals seeking strength gains should engage in strength training of at least 8-10 exercises 2-3 times per week, which seems manageable at face value. It goes on to recommend that these exercises be performed loaded, moving more than 65% of one’s one-rep maximum (1RM); furthermore, if hypertrophy is desired, the resistance training load should exceed 70% of the 1RM. Practically speaking, this is a heavy load. This substantiates the opinions of exercise physiologists, strength and conditioning coaches and athletic trainers everywhere that have been cautioning individuals against engaging in body weight exercises exclusively. In order for true strength to be gained, there must be a heavy load applied so that the tissues react during the time under deformation and build back stronger in response to the stress of the activity. Strength, and specifically muscle hypertrophy, occurs through a variety of different mechanisms including but not limited to metabolic stress and therefore metabolite accumulation, cell swelling and hormone responses.
In some individuals, either due to acute injury or chronic disease process, this type of loading cannot be achieved. No physical therapist would load an acutely post-operative patient who has had an ACL reconstruction in a loaded squat rack. No client with end stage arthritis in the shoulder is going to tolerate a heavy lat pull downs or reverse fly exercises. An elderly person with decreased bone mass likely won’t tolerate a heavy compressive load on the spine without risking some sort of serious injury. It would be grossly negligent to ask a person with a neurological condition such as multiple sclerosis to tolerate such a rigorous exercise program. So how can these individuals hope to gain strength? How can their bodies be prepared to tolerate an appropriate load at some stage, if ever?
Blood Flow Restriction (BFR) Training: A Viable Alternative
Blood flow restriction (BFR) therapy is an excellent option. It works by placing a torniquet cuff around a limb or limbs and inflating the cuff to a certain percentage of the total limb occlusion pressure (LOP). The individual then engages in exercise with a load, but lighter load such as 20-30% of 1 RM while the cuff is engaged. Depending on tolerance and desired effect these exercises can have a concentric and eccentric component, can be purely concentric, can focus on cardiovascular conditioning and can be used throughout the entire exercise or deflated in between sets. This therapy is extremely safe as the precise calculation of the LOP allows the practitioner to confidently provide the dose for the patient in order to achieve the desired results. Often times the question of clotting risk arises- there has been no direct effect shown between blood flow restriction therapy and clot formation. In fact, according to DeJong et al (2006)- “An acute bout of resistance training improves fibrinolytic potential without elevating thrombotic potential”. More clearly stated, the release of the cuff and the circulation increased caused by it seems to have an anti-thrombolytic effect. Other concerns seem to be cardiac in nature due to the increased stroke volume and increase in blood pressure that occurs; however, this is similar to the effect seen in traditional exercise so if a patient is cleared medically to exercise, there should be no exception to BFR.
How does Blood Flow Restriction work?
There are several pathways to which the literature points. The primary mechanisms appear to be increased fiber type recruitment, accumulation of metabolites such as lactate and growth hormone, activation of muscle protein synthesis and cell swelling. When blood is occluded to a limb and more specifically the blood previously present in the limb is trapped there, there is an accumulation of lactate. This lactate accumulation causes increased motor unit recruitment and therefor increased muscle activation. With more activation, there is an increased production of growth hormone and IGF-1. This leads to a stimulus of satellite cells and therefore increased in cellular repair/ rejuvenation and overall muscle/ bone/ tissue growth. An adjunct to the repair of the tissue appears to be vascular endothelial growth factor (VEGF) as well which is responsible for angiogenesis which has an effect on the cellular oxygen consumption (and therefore VO2 max) and increased permeability of capillary beds. This process specifically addresses the benefit to those afflicted with osteoporosis or osteopenia- according to the Lambert ACL clinical trial, the individuals who trained with BFR noted prevention of muscle mass loss and preserved bone mineral density compared to controls who exhibited bone loss at week 6 and 12 post operatively, per data collection. When looking at bone density specifically Linero and Choi (2020) found that individuals who trained at a low intensity with BFR had an increase in muscle strength, lactate concentration and bone formation markers when compared with those who engaged in low intensity resistance training in a traditional sense. These effects are seen in populations who might have previously been excluded from strength training, such as the aforementioned group: patients with multiple sclerosis. In a study focused on this population, patients who engaged in low intensity resistance training with BFR demonstrated improved balance and improved gait speed after 6 weeks of training AND these effects were still noted 6 weeks after training had stopped. This suggests the carryover from treatment is strong so training in acute bouts might be recommended.
It is worth saying that when comparing blood flow restriction training to high load training, bigger gains are seen in the high load training groups. Plainly put, if you can lift heavy, you should! However, BFR can be used in the programs of athletes who are engaging in heavy training as a recovery tool, to train around an injury, as a way of adding training volume when under-recovered from previous sessions or as a supplement to ensure sufficient fatigue with a decreased risk of technical failure due to loss of form. And for those individuals who cannot lift heavy loads, for whatever reason, BFR may be a gateway to achieving strength gains that were previously impossible. Under the supervision of licensed professionals, it has been shown to be a safe and reliable method for priming individuals for strength gains, attenuating muscle atrophy and improving function, which comes with improved quality of life and activity satisfaction.