Researchers studied two groups: (1) maintained a consistent routine prior to free throws; (2) those who didn't. The results of this study indicate that athletes in the Maintaining Routine Group (MRG - maintained the same routine during successive free throws 90% or more of the time) made 74% (214 of 290) of the free throws. While, athletes in the Non-Maintaining Routine Group (NMRG - maintained a routine less than 0-30% of the time) made 68% (166 of 240) of attempted free throws. Moreover, the NMRG had a lower shooting percentage, 65%-70%, from the first free throw to the second, while the MRG shot 65% and 82% on the first and second attempts, respectively.
Czech, D.R., Ploszay, A.R., & Burke, K.L. (2004). An Examination of the Maintenance of Preshot Routines in Basketball Free Throw Shooting. Journal of Sport Behavior, Vol. 27, Issue 4
Joe Slowinski