Post activation potentiation (PAP) is a phenomenon whereby strength is acutely increased following a conditioning contraction. This effect is purported to be small and specific to the contraction history of the muscle (local), however, a potential cross-over effect in PAP has not been ruled out. PURPOSE: To determine if PAP is specific to the muscle being conditioned or if it is also observed within the homologous muscles of the contralateral limb. METHODS: 56 men and women participated in a four-visit study. Visit 1 included baseline measurements and familiarization of the unilateral biceps contractions (isometric and isokinetic for each arm)). Visits 2-4 included the completion of one of the three experimental conditions: 1) control, 2) same side PAP, and 3) cross over PAP in a randomized order. Each visit included a warm up followed by three maximal isokinetic contractions at 210°/second (baseline). The control condition then rested eight minutes prior to completing three more maximal isokinetic contractions (post). The other two conditions completed the pretest followed five minutes later by a six-second maximal isometric contraction on the same side as the baseline isokinetic test (same side PAP) or on the opposite side (cross over PAP) followed by three additional maximal isokinetic contractions (post) three minutes after conditioning stimulus. The variable of interest was the change from baseline in isokinetic strength. Three hypotheses were compared using Bayesian Informative Hypothesis Evaluation (BAIN). The hypotheses were as follows: H1) same > cross = control; H2) same > cross > control; H3) same = cross = control. RESULTS: Torque produced during the potentiating stimulus was similar between PAP conditions (same: 47 Nm vs. cross: 45 Nm). The change [mean (95% credible interval)] in isokinetic strength for each condition was: control = -0.41 (-0.91, 0.07) Nm; same side PAP = 0.48 (-0.20, 1.16) Nm, and cross PAP = -0.03 (-0.67, 0.60) Nm. The posterior probabilities were 0.45, 0.28, 0.19, and 0.06 for H1, H2, H3, and the unconstrained model, respectively. H1 was 1.5 and 2.2 times more likely than H2 and H3, respectively. CONCLUSIONS: The current evidence indicates that if a PAP effect exists, it is small and may be specific to the muscle being conditioned. There does not seem to be a substantial cross over effect in PAP.