OBJECTIVE: To determine the temporal pattern of the repeated bout effect of eccentric exercise on perceived pain and muscular tenderness associated with delayed-onset muscle soreness (DOMS). DESIGN AND SETTING: Subjects completed 2 identical eccentric exercise bouts separated by 6, 7, 8, or 9 weeks. The experiment was conducted in a biokinetics research laboratory. SUBJECTS: Sixteen male and 15 female untrained subjects (age = 24.59 +/- 4.42 years, height = 171.71 +/- 7.81 cm, weight = 73.00 +/- 11.20 kg). MEASUREMENTS: Two physiologic characteristics of DOMS were measured immediately before and 0, 24, 48, and 72 hours after each eccentric exercise bout. Perceived pain was measured using a visual analog scale (VAS), and muscular tenderness was measured using a punctate tenderness gauge (PTG). RESULTS: Two 4 x 2 x 5 (group x bout x time) analyses of variance with repeated measures on the bout and time factors were performed on the VAS and PTG data. Significant (P <.05) main effects were found for group, bout, and time for the VAS and the PTG data. No significant interactions were detected. Post hoc analysis revealed significantly less perceived pain for the 9-week group than the 8-week group. The 7-week group had significantly less and the 8-week group had significantly more muscular tenderness than any other group. Perceived pain and muscular tenderness were significantly less after exercise bout 2 than after exercise bout 1. All subjects had significantly less perceived pain and muscular tenderness pre-exercise than 0 and 24 hours after the eccentric exercise bouts. CONCLUSIONS: An effective prophylaxis for perceived pain and muscular tenderness associated with DOMS is the performance of an eccentric exercise bout 6 to 9 weeks before a similar exercise bout.