Assessment of Efficacy of Low Intensity Resistance Training in Men at Risk for Symptomatic Knee Osteoarthritis

Over 9.3 million adults over the age of 60 are afflicted with symptomatic knee osteoarthritis (OA) characterized by radiographic findings and consistent knee pain or stiffness. Furthermore, our research has indicated that reduced strength is a risk factor for incident symptomatic knee OA and progressive knee OA in women.1, 3 In light of this finding, there is a need to increase quadriceps strength to attenuate worsening of this disease. Studies and practice have long indicated that high intensity resistance training is the most efficient means of eliciting skeletal muscle hypertrophy and strength gains.2, 4 The American College of Sports Medicine as well as the National Strength and Conditioning Association have indicated that a resistance training intensity of greater than 65% of the one-repetition maximum (1 RM) is the minimum intensity needed to achieve desired muscle hypertrophy and strength gains.2, 4 This is problematic for those suffering from symptomatic knee OA. Loading an already painful joint at 65% of (1 RM) would be poorly tolerated and possibly injurious for an individual already suffering knee pain and stiffness during activities of daily living. With the inability to perform the exercises prescribed to elicit the necessary strength gains, knee OA sufferers find themselves unable to alleviate debilitating pain that can result in significant decreases in quality of life. Fortunately, a method of training, called partial blood flow restriction (PBFR), may offer older adults and particularly those with knee OA, the ability to develop the strength gains necessary to attenuate disease progression without requiring deleterious joint loading. There is mounting evidence that this training modality serves as a stimulator of muscle growth even when performed at relatively low intensities.

PBFR was developed in Japan. Its basic principles involve the restriction of blood flow to the exercising muscle with the purpose of increasing muscle mass. However, participants are able to elicit similar strength gains performing exercises at, for example, only 30% of 1RM to those attained through conventional high intensity resistance training. Current PBFR training methods are the result of 40 years of research and development.5 Recent studies have demonstrated efficacy and some mechanisms for the effect of PBFR training eliciting significant isometric and isokinetic strength gains as well as increasing ability of adults to perform functional tasks.6 Exercising at only 30% 1RM, PBFR training may benefit older adults suffering from knee OA by enabling development of the strength necessary to protect against disease worsening while avoiding the need to load the joint at deleterious levels.

This study is a follow-up study to IRB#201101711 that we completed earlier this year. That study demonstrated tolerance and safety of the protocol. However, the increases in strength were of a smaller magnitude than we hoped to elicit. The protocol for this follow-up study is very similar to the prior study. We have made some changes in an effort to maintain tolerability and safety, while hopefully eliciting a greater clinical benefit. Specifically, we have reduced the study duration from 9 to 4 weeks and have selected a more efficient exercise protocol that will both reduce subject burden while also halving the length of time that the PBFR cuffs will be worn for each exercise session. The prior study was too gentle to strengthen the quadriceps muscles, so we have increased the resistance from 15% of their maximum to 30% of their maximum. This is still low intensity compared with usual weight lifting that would be at >65%. We believe that these changes will increase benefit to participants while reducing the time burden.

Literature cited

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