| This result is consistent with the hypothesis that the coefficient relating DP 1 to DP 2 , at constant a . p . d . of the first test pulse ( AP 1 ) , is an index of the proportion of the activator of contraction stored during relaxation of test beat 1 which is released again on beat 2 . ^^^ In order to determine the relationship between DP 2 and AP 1 it was necessary to carry out multiple regression analysis because DP 2 was already known to be strongly dependent on DP 1 ( point 3 above ) , i . e . ^^^ DP 2 = BDP ( DP 1 ) + BAP ( AP 1 D ) . ^^^ |