There are a number of possible reasons. If you have just completed a hard workout, your muscles will be fatigued in the short term, leading to a lower score (even though hard workouts are good for balance overall). Also, any small movement during the test will count as a pertubation – did you fidget, scratch an itch, cough, move your head? If so, try doing the test again. Also, make sure you’ve answered the questions for the Balance Profile for how you feel today, and the type of exercise you have done this week. It makes a big difference.