Introduction: With respect to cardiopulmonary performance testing in athletes, invasive (lactate) and labor-intensive (spirometry) are the current gold standard. Wearable near-infrared spectroscopy (NIRS) devices, easily superficially attached to the vastus lateralis, have been successfully applied to gold standard testing to assess endurance performance. Therefore, our goal was to determine whether NIRS derived muscle oxygen saturation (SmO₂) break points from a segmented regression analysis are valid alternatives to an automatically calculated Fatmax and MLSS as well as ‚conventional’ first ventilatory threshold (VT1). Methods: Two break points of SmO₂ in the vastus lateralis were determined by a segmented regression analysis. PRE-test (n = 8) and POST-test (n = 7) were conducted in healthy, moderately and continuously trained male cyclists (V̇O_2max 58.4 ± 6.7 mL×min^-1 ×kg^-1). Between both measurements an unspecific self-guided 8-week cycling intervention was performed. Cycling exercise tests consisted of a 15s all-out sprint and an incremental test with a subsequent ramp test to voluntary exhaustion. Time effect was examined on the remained subjects (n = 7), whereas comparison of first and second break point versus Fatmax/VT1, and MLSS, respectively, was applied on the full data set (n = 15; ANOVA). Results: VT1 was significantly higher than first break point (p = .005, d = -.994) and Fatmax (p = .032, d = - .758). However, Fatmax and first break point of SmO₂ were 177 ± 23 W and 173 ± 20 W, correlated strongly (r (13) = .74, p = .002) and showed acceptable agreement with a mean difference (-3.7 ± 16 W; Bland Altman Analysis).  MLSS and second break point were 268 ± 27 W and 258 ± 14 W, correlated only moderately but significantly (r (13) = .65, p = .009) and showed acceptable agreement with a mean difference (9.9 ± 21 W). Conclusion: At all exercise trials, Fatmax and first break point as well as MLSS and second break point coincided significantly. Accordingly, the current results suggest that NIRS-based SmO2 measurements could provide a mobile, time and cost saving, and non-invasive tool for testing training intensities in cardio-pulmonal endurance performance.