Are there differences in running economy at different velocities for well-trained distance runners?

The present study investigated whether there are differences in running economy at different velocities for well-trained distance runners, and to what extent a commonly used incremental protocol for measuring oxygen uptake (VO₂) at different velocities affects the reliability of these measurements. Fifteen well-trained distance runners (9 male and 6 female) participated in this study. Gross oxygen cost of running (C _R), heart rate (HR) and [La⁻]_b during 5-min runs at velocities ranging from 8.0 to 17 km h⁻¹, representing intensities ranging from 60 to 90% of maximal oxygen consumption (VO_2max) was measured on two different days in random order. The athletes were also tested for lactate threshold, VO_2max and time to exhaustion at MAS (_tMAS). No significant differences in C _R between the different relative velocities or the different set velocities were found up to 90% of VO_2max. The incremental protocol for measuring VO₂ at different velocities was found not to affect the reliability of these measurements. All athletes reached their VO_2max whilst running to exhaustion at MAS. The females showed significantly lower VO_2max, but significantly better C _R than the males. At velocities representing intensities between 60 and 90% of VO_2max, no differences in C _R were found. The commonly used incremental protocol for measuring oxygen uptake (VO₂) at different velocities was found not to affect the reliability of these measurements. This means that C _R measured at sub-maximal velocities are representative for C _R at race velocity for distances above 10,000 m for most runners.