Lactate and Acid–Base Responses in Sprint Kayaking: Effects of Race Format and Sex

Human locomotor performance requires continuous physiological adaptation to task-specific mechanical and metabolic demands. In sprint kayaking, it remains insufficiently understood how race or performance format and sex influence metabolic responses, particularly in elite athletes. This exploratory study compared blood lactate concentration and acid–base status after 500 m K1 and K4 races and a 30 s kayak-ergometer Wingate test in 22 elite Czech sprint kayakers (12 men, 10 women). Capillary blood was analysed for lactate, pH, pCO2, base excess (BE), and bicarbonate (HCO3−). Whole-blood buffering index (β) was calculated as Δ[lactate]/ΔpH. In paired K1–K4 comparisons (n = 18; 11 men, 7 women), lactate was higher after K1 than K4 (12.87 ± 2.96 vs. 9.10 ± 1.80 mmol·L−1; p < 0.001). In paired K1–Wingate comparisons (n = 13; 10 men, 3 women), neither statistically significant difference nor statistical equivalence were demonstrated in pH, BE, or HCO3−, despite significantly higher lactate concentrations after K1 (p = 0.016). During the Wingate test (n = 12 men, n = 10 women), men showed greater HCO3− and BE decrements and lower post-exercise pH than women, whereas no significant differences were detected for β. To characterize the relationship between mechanical performance and buffering capacity, a novel index, the acid–base cost of performance (ABCP), was proposed and defined as the absolute change in bicarbonate concentration (|ΔHCO3−|) normalized to relative mean power (W·kg−1). No statistically significant sex differences in ABCP were observed during the Wingate test. These findings highlight task-specific metabolic responses across different sprint kayaking formats and introduce ABCP as an exploratory index relating bicarbonate depletion to mechanical performance during high-intensity human locomotion, although its physiological validity and test–retest reliability require further investigation.