The Influence Of Blood Removal On Pacing During A 4-Minute Cycling Time Trial

Purpose: To examine the influence of manipulating aerobic contribution after whole-blood removal on pacing patterns, performance, and energy contribution during self-paced middle-distance cycling. Methods: Seven male cyclists (33 +/- 8 y) completed an incremental cycling test followed 20 min later by a 4-min self-paced cycling time trial (4MMP) on 6 separate occasions over 42 d. The initial 2 sessions acted as familiarization and baseline testing, after which 470 mL of blood was removed, with the remaining sessions performed 24 h, 7 d, 21 d, and 42 d after blood removal. During all 4MMP trials, power output, oxygen uptake, and aerobic and anaerobic contribution to power were determined. Results: 4MMP average power output significantly decreased by 7% +/- 6%, 6% +/- 8%, and 4% +/- 6% at 24 h, 7 d, and 21 d after blood removal, respectively. Compared with baseline, aerobic contribution during the 4MMP was significantly reduced by 5% +/- 4%, 4% +/- 5%, and 4% +/- 10% at 24 h, 7 d, and 21 d, respectively. The rate of decline in power output on commencement of the 4MMP was significantly attenuated and was 76% coproduct 20%, 72% +/- 24%, and 75% +/- 35% lower than baseline at 24 h, 21 d, and 42 d, respectively. Conclusion: Removal of 470 mL of blood reduces aerobic energy contribution, alters pacing patterns, and decreases performance during self-paced cycling. These findings indicate the importance of aerobic energy distribution during self-paced middle-distance events.