A Simple Method to Quantify the V[Combining Dot Above]O2 Mean Response Time of Ramp-Incremental Exercise

During ramp-incremental exercise, the mean response time (MRT) of oxygen uptake (V[Combining Dot Above]O2) represents the time delay for changes in muscle V[Combining Dot Above]O2 to be reflected at the level of the mouth and is generally calculated by linear (MRTLIN) and mono-exponential (τ[Combining Acute Accent] ) fitting of V[Combining Dot Above]O2 data. However, these methods yield MRT values that are highly variable from test-to-test. Purpose Therefore, we examined the validity and the reproducibility of a novel method to calculate the MRT. Methods On two occasions, twelve healthy men (age: 30±10 years; V[Combining Dot Above]O2max: 4.14±0.47 L[BULLET OPERATOR]min-1, 53.5±7.3 ml[BULLET OPERATOR]Kg-1[BULLET OPERATOR]min-1) performed a ramp-incremental cycling test (30 W[BULLET OPERATOR]min-1) that was preceded by a step-transition to 100 W. The ramp power output corresponding to the steady-state V[Combining Dot Above]O2 at 100 W was determined and the difference between that power output and 100 W was converted to time to quantify the MRT (MRTSS). Results The values of MRTLIN, τ[Combining Acute Accent], and MRTSS were 28±16 s, 27±12 s, and 26±11 s, respectively, which were not different (P>0.05) from each other. However, compared to the MRT parameters derived from the fitting-based methods, MRTSS had a higher correlation coefficient (R=0.87) and a smaller coefficient of variation (15±9%) from test-to-test. Conclusion In conclusion, the novel method proposed in the current study was found to be valid and highly reproducible in a test-retest design. Therefore, we advocate the use of this approach when a precise and accurate determination of the MRT is needed to properly align the V[Combining Dot Above]O2 data with power output during ramp-incremental exercise. Corresponding authors: Dr. Juan M Murias, Assistant Professor, Faculty of Kinesiology, University of Calgary, KNB 434, 2500 University Drive NW, Calgary, Alberta, Canada, T2N 1N4. +1 (403) 220-7955. jmmurias@ucalgary.ca Funding from the Faculty of Kinesiology of the University of Calgary supported this study. We would like to thank the participants of this study. CONFLICT OF INTEREST: None of the authors have any conflict of interest to declare. The results of the present study do not constitute endorsement by the American College of Sports Medicine. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for publication: 18 December 2018. © 2018 American College of Sports Medicine

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