I'm sorry your RA is so painful. Have you consulted your Podiatrist? You may need more cushioning in your shoes.
I personally take an OTC supplement for joint health, and made with athletes in mind. I had been taking glucosamine chondroitin supplements with some success, until my trainer told me about the supplement. But, please do check with your Rheumatologist before taking any supplements; perhaps have him/her check out the product to see if it would be alright for you to try.
You might try walk/run intervals. For example, walk 3 minutes, run 1.
You might also need some strength.
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