Exercise as a preventative against disability arising from arthritis

I read this in a WebMd news article. A Northwestern University study of more than 3500 individuals over the age of 50 has found correlations between the limiting effects of arthritis and the amount of physical activity engaged in by study participants. Those who exercised at least a half hour per day, 5 days per week, were found to be least likely to become disabled as a result of their arthritic