This never occurred to me until yesterday; you are mostly on the balls of your feet except during lunges. Since I used to play nearly every day and was actually IN shape my feet wouldn't be tired or ache. But I just played a 3 hour session and right now I am OUT of shape and today my feet were tired/sore. I know in ballet you have to strengthen the muscles in the foot; so I was wondering if this occurs in badminton. Looking back when I played everyday my feet never really was tired/sore, it had injuries though but not muscles tiredness. Plus I never heard anyone say you need to strengthen your foot in badminton.