Segal NA, Williams GN, Davis M, Wallace RB, Mikesky A. PM&R. 2015;7(4):376-384
Abstracted by: Ariana Domke, SPT from Missouri State University, Springfield, MO
This double-blinded, randomized controlled study evaluated the effectiveness of blood flow restriction during low-load resistance training, as a means to improve quadriceps strength and volume in women with risk factors for symptomatic knee osteoarthritis. Forty-five women between the ages of 45-65 volunteered to participate in the study, meeting at least one of the following inclusion criteria: Body Mass Index greater than or equal to 25 kg/m2, a history of knee joint injury or surgery, knee symptoms on most of the last 30 days, or previously informed of having radiographic knee osteoarthritis. Exclusion criteria included participation in resistance training in the three months prior to the study and the presence of any condition preventing safety during exercise intervention.
Four components were measured before and after the four-week trial and included isotonic bilateral leg press strength, isokinetic knee extensor strength, quadriceps volume by Magnetic Resonance Imaging, and knee pain (assessed using the Knee Osteoarthritis Outcome Score). The participants’ one-repetition maximum was based on the isotonic leg press and was determined by the equation: 1RM = (Number of Repetitions)0.01 x Resistance.
Each participant performed 4 sets of bilateral leg presses at 30% of their one-repetition maximum, 3 times a week for 4 weeks, using the instrumented leg press. The exercise protocol consisted of 30 repetitions for the first set and 15 repetitions for the following three sets, with a thirty second rest between each set. Twenty-four participants served as a control group. Twenty-one participants completed training using a blood flow restriction device. For the first training session the cuffs were inflated to an initial pressure of 30 mmHg and were tightened to 40 mmHg during following sessions. With the cuff in place, the incremental inflation pressure was raised from 100mmHG to 160mmHg for Week 1-3, 120-180mmHg for Week 2, and 120-200mmHg for Week 3.
The results showed significant improvement in isotonic one-repetition maximum and isokinetic knee extensor strength in the blood flow restriction group compared to the control group. Neither group reported any increase in knee-specific pain.
Personal Commentary:
Knee pain is a very common complaint from individuals seeking physical therapy. This pain can emerge due to several disorders, such as osteoarthritis and patellofemoral pain syndrome. Typically, the rehab protocols for these conditions include strengthening of the supportive musculature (Kisner and Colby, 2012). However, due to the patient’s pain, resistive exercises tend to be aggravating, and strengthening is limited to isometric or low-load open chain exercises. Based on anecdotal evidence, while these exercises are effective they are also slow to progress. Blood flow restrictive therapy may be an alternative method than can be used for this patient population by allowing greater strength gain while maintaining the low-load that these patients tolerate. In a case study performed by Hylden et al (2015), seven individuals suffering from chronic quadriceps and hamstring weakness three months’ post-surgery, received blood flow restriction therapy. Significant gains in strength were measured for all seven patients, after just two weeks of treatment.
Although this type of therapy has been around for a while, these past few years have brought increasing popularity in its use, and the evidence supporting this therapy is beginning to grow. In addition, blood flow restrictive therapy seems to be relatively safe. In a review performed by Loenneke et al (2011), different safety measures were compared between blood flow restriction therapy and regular exercise. This review concluded that early evidence supports that the effects of blood flow restrictive therapy on peripheral blood flow response, coagulation activity, oxidative stress, muscle damage, and chronic nerve conduction velocity are comparable to regular exercise. While more long term evidence is still needed, the current research is very promising for the use of blood flow restrictive therapy as a safe and effective technique for patients requiring alternative ways to gain strength.
References:
Hylden, C., Burns, T., Stinner, D., & Owens, J. (2015). Blood flow restriction rehabilitation for extremity weakness: a case series. J Spec Oper Med, 15(1), 50-6.
Kisner, C., & Colby, L. A. (2012). Therapeutic exercise: foundations and techniques. Fa Davis.
Loenneke, J. P., Wilson, J. M., Wilson, G. J., Pujol, T. J., & Bemben, M. G. (2011). Potential safety issues with blood flow restriction training. Scandinavian journal of medicine & science in sports, 21(4), 510-518.