Caffeine Improves Simulated 800-m Run Performance without Affecting Severe Exercise-Induced Arterial Hypoxemia.

Although caffeine is known to possess ergogenic effects, previous studies demonstrated no effect of caffeine on 800-m run performance outdoors which might be due to several uncontrolled factors including pacing strategies. We hypothesized that caffeine ingestion improves a pace-controlled simulated 800-m run performance. We also hypothesized that exercise-induced arterial hypoxemia (EIAH) occurs during the simulated 800-m run, and this response is mitigated by caffeine-induced increases in exercise ventilation. In a randomized, double-blind, placebo-controlled and crossover design, sixteen (3 females) college middle-distance runners who have 800-m seasonal best of 119.97 ± 7.64 s ingested either 1) placebo (6 mg of glucose/kg of body weight) or caffeine (6 mg of caffeine/kg of body weight). Then they performed an 800-m run consisting of 30-s running at 103% of their 800-m seasonal best, followed by running at 98% of seasonal best until exhaustion, which mimics actual 800-m run pacing pattern. Running time to exhaustion was extended by 7.3 ± 6.2% in the caffeine-ingested relative to placebo trial (123 ± 12 vs. 114 ± 9 s, P = 0.04). Arterial oxygen saturation markedly decreased during the simulating running, but this response was similar (76.6 ± 5.7 vs. 81.1 ± 5.2%, at 113 s) between the caffeine vs. placebo trials (P ≥ 0.23 for time×supplement interaction and main effect of supplement). Minute ventilation, oxygen uptake (all P ≥ 0.36 for time×supplement interaction and main effect of supplement) and rate of perceived exertion (all P ≥ 0.11) did not differ between the trials throughout the simulating running. HR was higher in the caffeine-ingested trial throughout the simulated running (P < 0.01 for main effect of supplement). Postexercise blood lactate concentration was higher in the caffeine trial (P = 0.02). Caffeine ingestion improves simulated 800-m run performance without affecting exercise ventilation and severe EIAH.

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Conflict of Interest and Funding Source: This study was not supported by any grants. The authors report no conflicts of interest. The results of this study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The results of this study do not constitute endorsement by the American College of Sports Medicine.