A Comparison of Methods to Identify the Mean Response Time of Ramp-Incremental Exercise for Exercise Prescription

ABSTRACT

Introduction: The oxygen uptake ($\dot{\mathrm{V}}$O₂) vs power output relationship from ramp incremental exercise is used to prescribe aerobic exercise. As power output increases, there is a delay in $\dot{\mathrm{V}}$O₂ that contributes to a misalignment of $\dot{\mathrm{V}}$O₂ from power output; the mean response time (MRT). If the MRT is not considered in exercise prescription, ramp incremental-identified power outputs will elicit $\dot{\mathrm{V}}$O₂ values that are higher than intended. We compared three methods of determining MRT (exponential modeling (MRT_EXP), linear modeling (MRT_LIN), and the steady-state method (MRT_SS)) and evaluated their accuracy at predicting the $\dot{\mathrm{V}}$O₂ associated with power outputs approximating 75% and 85% of gas exchange threshold and 15% of the difference between gas exchange threshold and maximal $\dot{\mathrm{V}}$O₂ (Δ15). Methods: Ten males performed a 30-W∙min⁻¹ ramp incremental and three 30-min constant power output cycle ergometer trials with intensities at 75% gas exchange threshold, 85% gas exchange threshold, and ∆15. At each intensity, the measured steady-state $\dot{\mathrm{V}}$O₂ during each 30-min test was compared to the $\dot{\mathrm{V}}$O₂ predicted after adjustment by each of the three MRTs. Results: For all three MRT methods, predicted $\dot{\mathrm{V}}$O₂ was not different (p = 1.000) from the measured $\dot{\mathrm{V}}$O₂ at 75%GET (MRT_EXP, 31 mL, MRT_LIN, −35 mL, MRT_SS 11 mL), 85%gas exchange threshold (MRT_EXP −14 mL, MRT_LIN −80 mL, MRT_SS −32 mL). At Δ15, predicted $\dot{\mathrm{V}}$O₂ based on MRT_EXP was not different (p = .767) from the measured $\dot{\mathrm{V}}$O₂, but was different for MRT_LIN (p < .001) and MRT_SS (p = .03). Conclusion: Given that the intensity is below gas exchange threshold, all model predictions implemented from the current study matched the exercise prescription.

KEYWORDS:

• Constant power exercise
• correction methods
• exercise intensity domains
• time delay
• $\dot{\mathrm{V}}$O₂ kinetics

Acknowledgments

Thank you to Brad Matushewksi for his technical expertise. We declare that the results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contribution statement

NB, BH, JM, GB contributed to the study conception and design. Data collection was performed by NB and BH. Material preparation and analysis were performed by NB. The first draft of the manuscript was written by NB and BH, JM, DK commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Data availability statement

Data generated or analyzed during this study are available from the corresponding author upon reasonable request.

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.