My podiatrist said that bicycling or using an elliptical would be acceptable for exercise while my tendon is healing. We have an old mini bike that I set up in front of a stool and I can pedal while leaving my hands free to spin yarn! Not as nice as walking outside, but a good podcast makes it a little better. I do switch sides where my drop spindle hangs to balance out, since I can’t hang it straight down. If left to my own devices I will craft and not exercise, so this gets me to actually get some workout in.