apple watch not tracking as exercise when I select take a walk

I have recent injuries and can not walk as fast as I did when I got my watch. It appears it will not track my walk as exercise when I select an outdoor walk. Is there some way to reset it to allow exercise time tracking on the outdoor walk selection? I have resorted to using the "other" open goal, and then it does not track distances. It works just fine for bike rides where I can still get my heart rate up. It appears it has set a higher threshold for "exercise" in my outdoor activity than I can do these days.