The purpose of this study was to determine the effects of a running-specific, periodized strength training program (performed over the specific period [8 weeks] of a 16-week macrocycle) on endurance-trained runners' capacity to maintain stride length during running bouts at competitive speeds. Eighteen well-trained middle-distance runners completed the study (personal bests for 1500 and 5000 m of 3 minutes 57 seconds +/- 12 seconds and 15 minutes 24 seconds +/- 36 seconds). They were randomly assigned to each of the following groups (6 per group): periodized strength group, performing a periodized strength training program over the 8-week specific (intervention) period (2 sessions per week); nonperiodized strength group, performing the same strength training exercises as the periodized group over the specific period but with no week-to-week variations; and a control group, performing no strength training at all during the specific period. The percentage of loss in the stride length (cm)/speed (m.s) (SLS) ratio was measured by comparing the mean SLS during the first and third (last) group of the total repetitions, respectively, included in each of the interval training sessions performed at race speeds during the competition period that followed the specific period. Significant differences (p < 0.05) were found in mean percentage of SLS loss between the 3 study groups, with the periodized strength group showing no significant SLS change (0.36 +/- 0.95%) and the 2 other groups showing a moderate or high SLS loss (-1.22 +/- 1.5% and -3.05 +/- 1.2% for the nonperiodized strength and control groups, respectively). In conclusion, periodized, running-specific strength training minimizes the loss of stride length that typically occurs in endurance runners during fatiguing running bouts.