Background/Objectives: Monocarboxylate transporters (MCTs) comprise 14 known isoforms, with MCT1 being particularly important for lactate transport. Variations in lactate metabolism capacity and aerobic performance are associated with the T1470A polymorphism in MCT1. We aimed to investigate the frequency of the T1470A polymorphism and compare relevant physiological parameters among long-distance runners, wherein these parameters are fundamental to athletic performance. Methods: We included 158 Japanese long-distance runners (LD) and 649 individuals from the general Japanese population (CON). The frequency of the T1470A polymorphism was compared between these groups and across athletic levels using the chi-square test. Additionally, physiological data were collected from 57 long-distance runners, and respiratory gas measurements were obtained using the mixing-chamber method during a graded incremental exercise test. Results: We observed a significant difference between the LD and CON groups in the dominant model and between the sub-28 min group and 28 min or above group in the recessive model. As the competitive level increased, the frequency of the AA genotype also increased. When comparing physiological parameters between the AA genotype and T allele, subjects with the AA genotype showed significantly higher values for oxygen uptake at lactate threshold (p = 0.001), oxygen uptake at onset of blood lactate accumulation (p = 0.01), maximal oxygen uptake (p = 0.005), and maximal blood lactate concentration (p = 0.038). Conclusions: These results suggest that the AA genotype of the T1470A polymorphism of MCT1 is an effective genotype associated with athletic status and aerobic capacity in Japanese long-distance runners.

Background: Blood lactate concentration and muscle oxygen saturation (SmO₂) are widely used indicators of endurance performance, reflecting the balance between oxygen delivery and utilization during exercise. To date, no studies have examined how the rs1049434 polymorphism of the SLC16A1 gene (the polymorphism) influences SmO₂ referenced to blood lactate thresholds in long-distance (LD) runners. This pilot study aimed to investigate the association between SmO₂ referenced to blood lactate concentration during maximal and submaximal exercise and the polymorphism in male collegiate LD runners. Methods: Overall, 15 Japanese male collegiate LD runners participated. Physiological parameters, including respiratory gas data, were measured during a graded incremental exercise test using the breath-by-breath method. SmO₂ was recorded from the right vastus lateralis muscle. Participants were genotyped for rs1049434, and comparisons were made between the AA genotype and T-allele carriers (AT + TT genotype). Results: Runners with the AA genotype exhibited significantly higher %$\stackrel{·}{\mathrm{V}}$O_2max at the lactate threshold (p = 0.044) and at the onset of blood lactate accumulation (OBLA) than T-allele carriers (p = 0.023). For SmO₂ measurements, those with the AA genotype displayed shorter t1/2_{reoxygenation} (p = 0.043) and higher SmO_2max (p = 0.045). Furthermore, SmO₂-OBLA was significantly higher in the AA genotype than in T-allele carriers (p = 0.029). Conclusions: These findings suggest that runners with the AA genotype may have greater oxygen utilization efficiency and potentially improved muscle oxygen delivery during high-intensity exercise. However, these are preliminary results, and further studies with larger and more diverse cohorts are needed to confirm these observations.

The effects of contrast water therapy (CWT) on dehydration at moderate altitudes during training camps remain unknown. We hypothesized that CWT reduces dehydration resulting from training at moderate altitudes and improves performance, akin to conditions at sea level. A 13-day endurance training camp was held at a moderate altitude of 1100 m and included 22 university athletes, who were divided into two groups (CWT group, n = 12; control (CON) group, n = 10). The sample size was calculated based on an α level of 0.05, power (1 β) of 0.8, and effect size of 0.25 based on two-way ANOVA. Longitudinal changes over 13 days were compared using a two-group comparison model. Additionally, 16 athletes participated in an additional performance verification analysis. Subjective fatigue, body mass, and water content (total body water (TBW), extracellular water (ECW), and intracellular water) were measured using bioimpedance analysis every morning, and the titin N-terminal fragment in urine (UTF) was measured as an index of muscle damage. For performance verification, 10 consecutive jump performances (with the reactive strength index (RSI) as an indicator) were evaluated as neuromuscular function indices. The results indicated that the UTF did not significantly differ between the two groups. Moreover, the ECW/TBW values, indicative of dehydration, on days 4 and 5 in the CWT group were significantly lower than those in the CON group. However, there was no significant difference in RSI between the two groups. Therefore, although CWT reduces dehydration in the early stages of the training camp, it may not affect performance.