A friend lent me her 65 cm ball which is a gym ball not designated birth ball. Everyone has told me they are the same thing but even though I am 5'6 and so it should be fine, when I sit on it my hips seem in line with my knees which I don't think is right.
It seems to push down quite a bit when I sit on it - I am overweight but also read this shouldn't affect this?
So my question is, is this just a crappy ball and do I need a new one? If so should I buy a 65cm one or a 75cm one? I need to sort this urgently as have left a bit late!!
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