Symptomatic knee osteoarthritis is a condition that nearly everyone reading this article can relate to – either on a personal or professional level. Functionally, knee osteoarthritis is characterized by a loss of knee range of motion, pain during exercise and decreased ability to perform activities of daily living such as walking, climbing up/down stairs and getting up out of a chair. 

A lack of quadriceps strength has been linked to not only a risk factor for symptomatic disease status, but poor functional capacity to perform ADLs.  Improving quadriceps strength can help those individuals with symptomatic osteoarthritis reclaim their life and get back to doing the activities they love to do! 

Current recommendations for improving muscle strength involve lifting weights with greater than 70% of the 1-repetition maximum (1RM). However, knee pain during and following exercise is a common clinical complaint when working with individuals that have symptomatic knee osteoarthritis. Finding alternatives to promote muscle strength in this population is important to promote an active lifestyle and reduce the need for surgery.

Blood flow restriction is a new tool in rehabilitation that can be used to promote similar gains in muscle performance as heavier load strength training. Blood flow restriction, or BFR, uses a cuff calibrated by technology to restrict arterial flow and completely occlude venous return. This restriction increases muscle oxygen demand, causing the muscles to work harder to generate a contraction, allowing lighter weights to be used to promote muscle mass and strength gains. Restrictive pressures are commonly set relative to the individual (which is known as the individual’s limb occlusion pressure, or LOP) which increases safety and allows for an objective measurement of how much blood flow is being restricted during exercise. 

This randomized-controlled study by Ferraz et al. (2018) compared the effects of BFR to high-intensity (HI) loading on thigh muscle mass and strength, function, pain and quality of life in a cohort of 48 women (~60 years old). Each woman was randomized into either HI group (80% 1RM, 4-5 sets x10 reps), BFR group (30% 1RM, 70% LOP, 4-5×15 reps, cuff width 17.5cm) and non-BFR light load training (LI, same as BFR group) and performed bilateral leg press and knee extension twice per week for 12 weeks. 

Outcome measures were quadriceps strength and cross-sectional area (CSA), physical function (30 second sit to stand test and timed up and go) and self-reported quality of life tests (WOMAC and SF-36). 

Results from the 12-week study show improved quadriceps muscle strength in HI and BFR groups only (+26%/+33% in leg-press BFR/HI and +23%/+22% in leg extensions BFR/HI) with both groups showing significantly greater increases than LI group with no between-group differences. Quadriceps muscle mass improved similarly in BFR/HI at +7/+8% with no significant changes in the LI group.

Physical function tests showed increases in scores in HI and BFRT group during the 30-second chair stand task (+7/+14% BFR/HI) with no changes pre- to post- observed in the LI group. Timed up and go tests were not changed in any group. 

Self-reported outcomes highlighted some important considerations with the different training approaches. Perceived improvements in physical function were shown in the WOMAC (Western Ontario and McMaster Universities Arthritis Index) of +49/42% in the BFR/HI group suggesting both forms of training improved self-efficacy in day-to-day tasks. WOMAC pain scores improved +45/39% in the BFR/LI group only, highlighting that BFR/LI can reduce perceived pain during functional activities, allowing individuals to maintain an active lifestyle.  HI group did not appear to exhibit the same magnitude of reduction in perceived pain. Last, 25% of the HI group withdrew from the study due to knee pain during or following exercise while the BFR/LI group did not experience any withdrawals or adverse events. This highlights a major issue with HI loading within this population in that while HI is commonly prescribed for improving muscle strength in individuals with knee osteoarthritis, it may not be optimal for long-term adherence due to the higher levels of self-reported pain performing the exercise. The BFR group was the only group to improve their muscle strength, muscle mass, functional tests and perceived function with high levels of pain reduction. 

This study shows that BFR training can help improve muscle size, strength and physical function to a similar degree as HI training with superior decreases in pain and potentially better long-term adherence. 

If you’re interested in learning more about how BFR can help your patients and clients suffering from Knee OA, check out our course listings to see if The BFR Pros are coming to a city near you! Already certified? We would love to hear about how you and your knee OA patients or clients achieved their goals with BFR and are now able to experience the joy of pain-free movement. Comment with your success story for a chance to be featured on our Instagram!

SOURCE: Ferraz et al. (2018). Benefits of resistance training with blood flow restriction in knee osteoarthritis.  Med Sci Sports Exerc. DOI: 10.1249/MSS.0000000000001530

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