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Background: Blood flow restriction (BFR) is a process of using inflatable cuffs to create vascular occlusion within a limb during exercise. The technique can stimulate muscle hypertrophy and improve physical function; however, most of these studies have enrolled healthy, young men with a focus on athletic performance. Furthermore, much of the information on BFR comes from studies with small samples sizes, limited follow-up time, and varied research designs resulting in greater design, selection, and sampling bias. Despite these limitations, BFR's popularity is increasing as a clinical rehabilitation tool for aging patients. It is important for practitioners to have a clear understanding of the reported effects of BFR specifically in older adults while simultaneously critically evaluating the available literature before deciding to employ the technique.

Questions/purposes: (1) Does BFR induce skeletal muscle hypertrophy in adults older than 50 years of age? (2) Does BFR improve muscle strength and/or physical function in adults older than 50 years?

Methods: Using PubMed, Google Scholar, Web of Science, and Science Direct, we conducted a systematic review of articles using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to assess the reported effects of BFR on skeletal muscle in older adults. Included articles enrolled participants 50 years of age or older and used BFR in conjunction with exercise to study the effects of BFR on musculoskeletal outcomes and functionality. The following search terms were used: "blood flow restriction" OR "KAATSU" OR "ischemic training" AND "clinical" AND "elderly." After duplicates were removed, 1574 articles were reviewed for eligibility, and 30 articles were retained with interventions duration ranging from cross-sectional to 16 weeks. Sample sizes ranged from 6 to 56 participants, and exercise tasks included passive mobilization or electrical stimulation; walking; resistance training using machines, free weights, body weight, or elastic bands; and water-based activities. Furthermore, healthy participants and those with cardiovascular disease, osteoarthritis, osteoporosis, sporadic inclusion body myositis, spinal cord injuries, and current coma patients were studied. Lastly, retained articles were assigned a risk of bias score using aspects of the Risk of Bias in Nonrandomized Studies of Interventions and the Cochrane Collaboration's tool for assessing the risk of bias in randomized trials.

Results: BFR, in combination with a variety of exercises, was found to result in muscle hypertrophy as measured by muscle cross-sectional area, thickness, volume, mass, or circumference. Effect sizes for BFR's ability to induce muscle hypertrophy were calculated for 16 of the 30 papers and averaged 0.75. BFR was also shown to improve muscle strength and functional performance. Effect sizes were calculated for 21 of the 30 papers averaging 1.15.

Conclusions: Available evidence suggests BFR may demonstrate utility in aiding rehabilitation efforts in adults older than 50 years of age, especially for inducing muscle hypertrophy, combating muscle atrophy, increasing muscle strength, and improving muscle function. However, most studies in this systematic review were at moderate or high risk of bias; that being so, the findings in this systematic review should be confirmed, ideally using greater sample sizes, randomization of participants, and extended follow-up durations.

Level of evidence: Level II, systematic review.