Introduction Middle-distance running requires a balance of aerobic and anaerobic energy systems, necessitating efficient physiological profiling for optimized training. Performance biomarkers, such as the Speed Reserve Ratio (SRR), have been used to improve training and performance but may not always be practical for routine assessment. Other biomarkers, such as skeletal muscle oxygenation (SmO 2 ) and blood lactate concentration (Labmax), may be more cost-effective and easier to integrate into training programs than the SRR. This study investigates the relationship between SmO 2 and Labmax with SRR in NCAA Division I middle-distance runners to determine whether these physiological markers could serve as viable alternatives for athlete profiling. Methods Male NCAA Division I athletes (n = 11) completed a series of sprint trials and incremental treadmill tests to assess SmO 2 and blood lactate responses. Results The change in skeletal muscle oxygenation (ΔSmO 2 ) exhibited a significant positive correlation with SRR (r = 0.656, p = 0.028), while Reoxygenation Hemoglobin Slope (ROHS) displayed a negative correlation (r = -0.644, p = 0.033), suggesting that oxygen utilization and recovery kinetics differentiate athletes with higher anaerobic or aerobic capacities. Discussion These findings highlight the potential of SmO 2 -derived metrics as accessible, noninvasive alternatives for profiling aerobic–anaerobic balance in middle-distance runners, particularly in situations where SRR measurement is impractical or unavailable. Future research should explore how these markers integrate into training models, their predictive validity across different competition levels, and their application in optimizing individualized athlete development programs. Conclusion Integrating noninvasive SmO 2 monitoring can be a beneficial addition to training programs for enhancing performance outcomes in middle-distance runners.
Kraft et al. (Mon,) studied this question.