Purpose: Highly trained endurance athletes train and race at relatively high intensities and are often confronted with challenges throughout a running event. The purpose of this study was to examine the effects of the anticipation of a proposed challenge on effort sense, heart rate (HR), ventilation ([dotVE), and ventilatory equivalent VE/VO2), a measure of ventilatory efficiency.

Methods: Highly trained endurance athletes (VO2max = 68.46 +/- 1.47 mL x kg(-1) x min(-1) ran two sessions at approximately 75% of VO2max for 35 min in a control condition and a proposed challenge condition. During the control condition, the subjects ran on a treadmill while simultaneously viewing a video depicting a runner exercising at 75% of VO2max and were told the run would continue at a speed that elicited 75% of VO2max. During the proposed challenge condition, subjects completed the same exercise protocol but viewed a video of a struggling runner and were told that the treadmill speed would be increased to "an extremely difficult" 95% of VO2max matching the intensity of the runner on the video. However, after data assessment at 17 min, subjects were told that the treadmill was malfunctioning and the treadmill speed could not be altered. The same intensity was maintained in both conditions. RPE, HR, VE, and VE/VO2 were assessed during the treadmill runs at 10, 17, 25, and 35 min.

Results: The effects of the manipulation were represented by a significant increase in state anxiety immediately following the video proposing the 95% challenge. RPE, HR, and VE increased similarly under both conditions, while VE/VO2 did not change.

Conclusion: These findings suggest that for highly trained endurance athletes, anticipation of proposed challenge during running does not influence cardiorespiratory responses; thus these athletes demonstrate a "physiologically toughened" response.