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The position of peak-to-peak displacement (PPD) was used and the distance, in cm, between the feet at the base of VP was to (a) 2.5 mm of PPD, 3 cm between the feet; (b) 5.0 mm of PPD, 21 cm between the feet; and in (c) 7.5 mm of PPD, 39 cm between the feet.
