Purpose: A critical assumption in modeling optimal pacing strategy is that the amount of anaerobic energy that can be produced during a time trial is a constant value, independent of pacing strategy. To test this assumption, the effect of manipulations of pacing strategy on anaerobic work produced during a 1500-m cycling time trial was studied. Additionally, the effect of pacing strategy on aerobic and total work was studied. Methods: Nine well-trained cyclists performed three 1500-m cycle ergometer time trials with different strategies (conservative (SUB), even paced (EVEN), and aggressive (SUPRA)). Anaerobic work, aerobic work, and total work were calculated on the basis of VO2, RER, gross efficiency, and external power output. Results: ANOVA showed that total anaerobic work did not differ per strategy (EVEN: 27,604 +/- 1103 J, SUB: 26,495 +/- 1958 J, and SUPRA: 26,949 +/- 2062 J). No differences in aerobic work (EVEN: 28,266 +/- 1623 J,SUB: 27,950 +/- 1418 J, SUPRA: 27,844 +/- 1965 J) were evident, either. Subjects were able to accomplish significantly (P < 0.05) more total work during EVEN (55,870 +/- 2245 J) than during SUB and SUPRA (54,444 +/- 2306 and 54,794 +/- 2402 J, respectively). Conclusion: No difference in anaerobic and aerobic work was found per pacing strategy. Though relevant for sports performance, the differences in total work were relatively small (~2%), considering the broad range of imposed strategies. The assumption that anaerobic work is a constant value, independent of pacing strategy, seems valid in the range of different strategies that are currently simulated in the energy flow models.
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