Active Voice: A Novel Therapeutic Exercise Mode for Managing Knee Osteoarthritis
By Hamilton Roschel, Ph.D.
Viewpoints presented in SMB commentaries reflect opinions of the authors and do not necessarily represent positions or policies of ACSM.
Dr. Hamilton Roschel is a professor at University of Sao Paulo, Brazil. He is the head of the Applied Physiology and Nutrition Research Group, and his research focuses mainly on the impact of nutrition and exercise in chronic diseases and with aging. He also investigates the influences of nutrition on training-induced adaptations and physical performance.
This commentary presents Dr. Roschel’s views on the topic of a research article that he co-authored with other colleagues. Their article appears in the May 2018 issue of Medicine & Science in Sports & Exercise® (MSSE).
Osteoarthritis (OA) is the single most common cause of disability in older adults. Even though its development is closely associated with aging, several modifiable and non-modifiable risk factors — such as obesity, trauma, sedentary behavior and gender — may contribute to its development. Thus, these risk factors can further increase the number and the profile of individuals with OA.
Knees and hips are the most prevalent joints affected by OA and are considered a direct cause of pain and physical impairment, deeply and negatively impacting quality of life for patients. The evolution of OA is characterized by a vicious cycle that encompasses pain, sedentary behavior, loss of muscle mass and strength, disability and disease progression. Thus, common practices for management of OA include activities that strengthen and promote hypertrophy of the thigh muscles. Despite the scientifically supported relevance of resistance exercise in knee OA, clinical practice is not always that straight forward. Classically, to induce significant gains in muscle strength and mass, a relatively high external load must be employed which, in many cases, results in overt pain, thus hampering this conventional approach.
A novel low-load exercise mode has, however, challenged this concept. Blood flow restriction training (BFRT) combines low-intensity exercise (external loads of approximately 30 percent of the individual’s maximum dynamic strength) with partial blood flow restriction to the working muscle via inflatable air cuffs. This exercise mode has been shown effective in increasing muscle adaptation (despite the low load) to comparable levels of those observed after conventional high-intensity resistance training. Discussion of the proposed mechanisms are beyond the scope of this commentary, but its therapeutic application, especially in conditions marked by pain and disabilities, is of great clinical relevance.
In our study, as presented in the May 2018 issue of MSSE, we investigated whether an alternative approach to conventional high-intensity resistance exercise would induce similar benefits in knee OA patients. Forty-eight women with knee OA were assigned to one of three groups for 12 weeks of resistance exercise training of the lower limbs. The groups completed one of the following protocols: 1) conventional high-intensity exercise (80 percent), 2) a low-load exercise (30 percent) with BFRT, or 3) a low-load exercise (30 percent) without BFRT. Results showed that, as expected, low loads without BFRT had little to no effect on clinically relevant parameters such as muscle mass, strength and functionality. However, similar and significant improvements were found between low load with BFRT and high-intensity exercises on lower-limb strength and muscle mass, and both objectively and subjectively measured functionality. It is also important to highlight that subjective pain was reduced only after low-load with BFRT training. Furthermore, conventional high-intensity resistance exercise, despite improving several outcome measures, induced a significant amount of pain. This led to 25 percent of the subjects in that group withdrawing from the intervention.
Exercise-induced pain is not a new issue in clinical management of OA. As pain often limits OA patients from exercising with high external loads, interventions focused on rescuing muscle mass and strength are limited. Consequently, therapy has shifted attention to more general mobility-focused activities (water-based activities, yoga, stretching, etc.).
Given the impact that increased muscle strength and mass may have on clinical parameters in knee OA, the search for alternative therapeutic strategies continues to be of great interest, with low-load with BFRT training emerging as a promising approach. Though the results from our study are encouraging, its viability in population-based scenarios is intriguing and requires further attention.