Traditionally, large muscle dynamic movement (DM) and acute static stretching (SS) prior to performance based activities have been used as a warm-up activity and are reported to enhance performance. Recent research has focused on performance variables associated with anaerobic based activities. Researchers have determined that anaerobic performances may decrease following acute SS because of losses in stored elastic energy from passive connective tissue. Few studies have examined aerobic activity and the impact of acute SS on running economy (RE). The purpose of this study was to investigate the effectiveness of DM-SS and DM-no stretch (NS) activities on RE. The subjects consisted of eight highly trained college endurance athletes. All participants were orientated to the treadmill and the submaximal protocol used to evaluate their RE. Participants were randomly assigned to the two trials of DM-SS and DM-NS with each separated by a week. The DM protocol consisted of 10 min of submaximal treadmill running with 5 min at 6.0 mph and 5 min at 6.5 mph. The SS protocol consisted of six bilateral lower extremity static stretches that spanned the ankle, knee, and hip. The stretches were consistent with sagittal plane movement associated with running. Each stretch was performed four times for 30s at a self-selected intensity, which was controlled with the descriptor “stretch to the point of mild discomfort without pain”. The DM-NS consisted of only DM warm-up. Each condition was followed by a 5 min rest period. Following the rest period, each subject ran at an 8.0 mph pace with RE determined by the average relative oxygen consumption between the 5th and 6th minute. In addition, continuous heart rate data were collected and analyzed during the 5th and 6th minute. There were no significant differences between relative oxygen consumption and heart rate of the DM-SS and DM-NS conditions. Based on previous research, it was expected that RE would decrease following SS. Previous investigations have demonstrated that during the stretch-shortening cycle, active stiffness present in the eccentric phase of muscle contraction should improve RE. This should occur because there is a need for less active energy in both the braking and propulsion phase of running. Based on this research, it appears that SS does not improve RE. Additional research is needed to clarify this position. Physical Educators, coaches, and athletes can use this information when determining the best type of warm-up activity for optimal performance.Keyword(s): coaching, exercise/fitness/physical activity, research