Background: No study has demonstrated the effects of sodium bicarbonate plus caffeine (NaHCO3 + CAF) on power output (PO) distribution (e.g., pacing), physiological parameters and energy system contribution during a 4-km cycling time trial (TT). Thus, we aimed to investigate the effects of NaHCO3 + CAF on pacing, physiological parameters, and energy system contribution during a 4-km cycling TT. Methods: Using a double-blind and counterbalanced design, 10 cyclists performed three ingestion protocols (NaHCO3 + CAF, NaHCO3 and placebo) followed by a 4-km cycling TT. Results: 100 min after substance ingestion, the magnitude of change in blood pH and bicarbonate concentration [HCO3-] for NaHCO3 + CAF (+0.04 ± 0.03 and +5.9 ± 1.6 mmol·L-1, respectively, P < .05) and NaHCO3 (+0.02 ± 0.03 and +4.1 ± 2.0 mmol·L-1, respectively, P < .05) was more pronounced than in placebo (-0.01 ± 0.02 and 0.4 ± 0.9 mmol·L-1, respectively). The increase in plasma lactate concentration was more pronounced in NaHCO3 + CAF than in NaHCO3 and placebo (P < .05). Mean ventilation and carbon dioxide production were higher in NaHCO3 + CAF compared to NaHCO3 and placebo (P < .05). The PO and anaerobic power output were increased at the beginning of the 4-km TT (P < .05) in NaHCO3 + CAF compared to the other two conditions, resulting in an improved overall performance (P < .05). Conclusion: NaHCO3 + CAF results in a higher PO and increased anaerobic contribution and respiratory parameters during a 4-km cycling TT.
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