Muscle Oxygen Saturation Responses During Maximal and Submaximal Exercise According to SLC16A1 (MCT1) Gene...

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 %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.