The purposes of this investigation were to document the changes in stride length of college-age male novice runners (n = 13) who were allowed of freely choose their stride length throughout a 7-week training period (FCSL), and to compare subsequent changes in running economy to those observed in a similar group of runners (n = 13) that ran for 7 weeks with constant stride lengths equivalent to their initially chosen stride lengths (CSL). Subjects trained 3 days per week for approximately 7 weeks (22 training bouts). Each training bout consisted of a minute warmup (60% VO2max) and a 15-minute run at a speed equivalent to 80% of the subjects' initial VO2max. Absolute stride length (ASL), heart rate (HR), and ratings of perceived exertion (RPE) were measured during the 12th and 20th minute of exercise. Relative and absolute submaximal VO2 were measured during the 4th and 22nd training bout. No significant differences in percent change in ASL were found between the groups or across the weeks of training at the 12th or 20th minute of exercise; however, there was a significant difference (p less than or equal to .05) between the groups during the 4th week of training. No significant differences were found between the groups in relative or absolute submaximal VO2. Relative submaximal VO2 at the 12th minute of exercise decreased significantly following the training period in both the FCSL (-3.38%) and CSL (-4.32%) groups. Absolute submaximal VO2 did not change significantly following the training period.(ABSTRACT TRUNCATED AT 250 WORDS)