Anna Pisz

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.

Objectives: This study investigated bilateral strength asymmetry, the bilateral asymmetry index, and the bilateral deficit ratio during one-repetition maximum leg press testing performed under bilateral, unilateral, and split-load conditions and examined their associations with isokinetic knee and hip strength asymmetries. Methods: 31 resistance-trained males completed 1RM leg press tests in all loading modes, followed by isokinetic knee flexion/extension and hip extension assessments at 60°·s⁻¹. Results: The repeated measure ANOVA showed that split-load leg press had a significantly greater bilateral deficit ratio (14.29 ± 7.71%) compared to the bilateral condition (5.16 ± 9.60%, p < 0.001). Isokinetic testing showed significant inter-limb differences for knee flexion and extension but not hip extension. The bilateral strength asymmetry varied across tasks (5.17 ± 4.44% in leg press to 17.84 ± 12.40% in eccentric hip extension), while bilateral asymmetry index remained consistently lower. Bilateral strength asymmetry differed significantly across leg press conditions, whereas the bilateral asymmetry index did not. Knee flexion bilateral asymmetry index correlated with dominant and non-dominant hamstring to quadriceps ratios (respectively, r = 0.61; r = 0.37) and cross-limb flexor–extensor ratios (r = 0.42). No significant relationships were found for hip extension asymmetry. Conclusions: Split-load leg press might be used to test lower limb bilateral deficit, because it provides easily detectable deficit values. Unilateral leg press might be used to detect lateral strength differences, since it provides relation to isokinetic strength of knee flexors and extensors.