Although it has previously been suggested that skeletal muscle size and strength only increase during high resistance training that exceeds 65% of an individual’s one-repetition maximum (1-RM), recent studies have noted that low to moderate-intensity resistance exercise training combined with partial vascular occlusion (PVO) can increase muscle size and strength similarly to high-intensity resistance exercise alone.1
This may benefit patients with knee osteoarthritis (OA), who are often limited in their ability to participate in high intensity exercise secondary to knee pain and functional limitation.
To investigate if women with knee OA participating in a physical therapy (PT) program consisting of low-load exercises combined with PVO had developed similar quadriceps strength as compared to women performing high-load exercises without PVO, Flavio Fernandes Bryck, PT, MS, and colleagues from Irmandade da Santa Casa de Misericórdia, São Paulo, Brazil designed a randomized clinical trial and recruited 31 women with knee OA to participate in a 6 week PT program .2
The study participants, who had an average age of 61, were randomly assigned to either the conventional (high-load exercise) treatment group or the PVO group for 6-weeks of supervised quadriceps strengthening and stretching. The women assigned to the conventional treatment group (n=17) exercised a load of approximately 70% of their 1-RM.
In the occlusion treatment group, PVO was induced using a pressure cuff applied to the upper third of the thigh inflated to 200 mm Hg. The PVO treatment group then participated in the same program as the conventional group, with the exception of only targeting strength exercises to approximately 30% of their 1-RM.
Outcomes were measured at baseline and at the end of the 6 week study period using the 11-point Numerical Pain Rating Scale (NPRS), Lequesne questionnaire, Timed-Up and Go (TUG) test, and muscle strength as measured by a dynamometer. Pain, using the NPRS, was also assessed during active exercise activity.
The researchers found that women in both treatment groups had a higher level of function (P<.05, as measured by the Lequesne and TUG test), less pain (P<.05, as measured by NPRS), and increased quadriceps strength (P<.05, as measured by dynamometer readings) when compared to baseline.
Most notably, women being treated in the PVO group had less anterior knee discomfort during the treatment sessions (P<.05).
Summary and Clinical Applicability
There were no differences in quadriceps strength in women with knee OA receiving conventional therapy with high-load exercises compared with women who performed low-load exercise combined with PVO. 2 This is clinically significant as quadriceps strengthening exercises have been shown to relieve symptoms associated with knee OA3, but many patients report that exercises can themselves cause knee pain, limiting PT and rehabilitation.
Low to moderate-intensity resistance exercise training combined with partial vascular occlusion (PVO) may therefore be a way for patients with knee OA to participate in quadriceps strengthening.
These findings are primarily limited by the small study size and lack of long-term follow up. Additionally, this study included only women who were not post-operative from knee surgery, thus limiting the extent of generalizability.
1. Abe T, Kearns CF, Sato Y. Muscle size and strength are increased following walk training with restricted venous blood flow from the leg muscle, Kaatsu-walk training. J Appl Physiol .2006; 100: 1460-1466.
2. Bryk FF, Dos reis AC, Fingerhut D, et al. Exercises with partial vascular occlusion in patients with knee osteoarthritis: a randomized clinical trial. Knee Surg Sports Traumatol Arthrosc. 2016; Epub ahead of print March 12, 2016.
3. Segal NA, Glass NA, Felson DT, et al. Effect of quadriceps strength and proprioception on risk for knee osteoarthritis. Med Sci Sports Exerc. 2010;42(11):2081-8.