Comparisons of the Metabolic Intensities at Heart Rate, Gas Exchange, and Ventilatory Thresholds

International Journal of Exercise Science 13(2): 455-469, 2020. PURPOSE: This study compared the O2corresponding to the critical heart rate (CHRO2) and the physical working capacity at the heart rate fatigue threshold (PWChrtO2) to the gas exchange threshold (GET), ventilatory threshold (VT), and respiratory compensation point (RCP). METHODS: Nine runners (mean ±SD, age 23 ±3 years) completed an incremental test on a treadmill to determine O2peak, GET, VT, and RCP. The CHRO2and PWChrtO2were determined from 4 separate constant velocity treadmill runs to exhaustion and HR and time to exhaustion were recorded. Differences among the thresholds were examined with a one-way repeated measures ANOVA (p≤ 0.05). RESULTS: The GET (38.44 mL×kg-1×min-1, 78%O2peak), VT (37.36 mL×kg-1×min-1, 76%O2peak), and PWChrtO2 (38.26 mL×kg-1×min-1, 77%O2peak) were not different, but were lower than the RCP (44.70 mL×kg-1×min-1, 90%O2peak;p= 0.010, p< 0.001,p= 0.001, respectively). The CHRO2(40.09 mL×kg-1×min-1, 81%O2peak) was not different from the GET (p= 1.000), VT (p= 0.647), PWChrtO2(p =1.000), or RCP (p= 0.116). CONCLUSIONS: These results indicated that the initial metabolic intensities at CHR and PWChrtlie within the heavy and moderate intensity domains, respectively. Therefore, the PWChrtmay provide a relative intensity more appropriate for untrained populations, while the CHR may be more appropriate for more trained populations.