Studies, Guidelines Differ on Extent of Exercise Needed to Stave Off Arthritis
JANUARY 11, 2017
The most recent set of fitness guidelines from the federal Office of Disease Prevention and Health Promotion, entitled 2008 Physical Activity Guidelines for Americans, use 150 minutes of moderate-intensity exercise per week as the benchmark for maintaining good physical health in various groups, from pregnant women to adults with disabilities to older adults.
The agency defines “moderate-intensity aerobic exercise” to be as simple as brisk walking. But for many older adults with painful rheumatic conditions like rheumatoid arthritis or osteoarthritis, such exercise can be quite the tall task.
A new study from Northwestern Medicine suggests, however, that achieving even a third of that 150 minute guideline may be of great benefit to older individuals with arthritis. Using multi-site data from over 1600 individuals in the Osteoarthritis Initiative accelerometer substudy, researchers assessed gait speed and patient-reported outcomes at baseline and two-year follow-up.
According to a news release, the researchers used “sophisticated movement-monitoring accelerometers” for the study, and found that those patients performing 45 minutes or more of moderate physical activity per week were 80 percent more likely to maintain or improve functionality over the course of two years (“gait speed [relative risk (RR)] 1.8, 95% CI: 1.6 to 2.1; PRO physical function RR 1.4, 95% CI: 1.3 to 1.6”, according to the study.) Participants were 49 years of age or older with arthritic symptoms in their lower-body joints, and the improvements based on threshold were consistent across demographics.
Deviating from the federal guidelines’ recommendations, the researchers found that performing exercise blocks of 10 or more minutes was not as important as an aggregate achievement of 45 or more minutes of exercise.
The Osteoarthritis Initiative has produced a number of studies that seek to inform rheumatology’s standards for preventive exercise. At the 2016 American College of Rheumatology Annual Meeting in Washington, DC, researchers from the University of Delaware presented findings using the Initiative based on patients’ capacity for exercise. They said they found that a majority of arthritis patients were more capable than perhaps previously thought.
The authors of that study had previously garnered media attention with a 2014 report that determined 6,000 or more steps per day was a healthy walking regimen for the maintenance of good joint health and reduction of arthritis pain, with at least 3,000 as a minimum target. The study presented at ACR 2016 purported to show that 71% of their osteoarthritis patients met both the speed and endurance thresholds to walk 6,000 steps per day, defining physical capability as being able to walk faster than 2.7 miles per hour, and to be able to walk a quarter mile in under 5 and a half minutes.
Looking at these findings together, there’s a wide chasm: the steps-needed studies from Delaware recommend a healthy minimum with a time commitment significantly higher than 45 minutes per week. In fact, those recommendations go even beyond the federally recommended 150 minutes per week: equating 3,000 steps to 1.5 miles, at a walking speed of three miles per hour, that clocks in at 30 minutes per day and 210 minutes per week.
The only concrete takeaway seems to be that exercise is a good thing. According to Northwestern University professor Dorothy Dunlop, primary author on the new study, "Even a little activity is better than none.”
The paper, titled “Physical activity minimum threshold predicting improved function in adults with lower limb symptoms,” was published online in Arthritis Care and Research on December 28th, 2016.
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