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

Introduction: The oxygen uptake (V<SUP>center dot</SUP>O<INF>2</INF>) vs power output relationship from ramp incremental exercise is used to prescribe aerobic exercise. As power output increases, there is a delay in V<SUP>center dot</SUP>O<INF>2</INF> that contributes to a misalignment of V<SUP>center dot</SUP>O<INF>2</INF> from power output; the mean response time (MRT). If the MRT is not considered in exercise prescription, ramp incremental-identified power outputs will elicit V<SUP>center dot</SUP>O<INF>2</INF> values that are higher than intended. We compared three methods of determining MRT (exponential modeling (MRT<INF>EXP</INF>), linear modeling (MRT<INF>LIN</INF>), and the steady-state method (MRT<INF>SS</INF>)) and evaluated their accuracy at predicting the V<SUP>center dot</SUP>O<INF>2</INF> associated with power outputs approximating 75% and 85% of gas exchange threshold and 15% of the difference between gas exchange threshold and maximal V<SUP>center dot</SUP>O<INF>2</INF> (Delta 15). Methods: Ten males performed a 30-W center dot 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 triangle 15. At each intensity, the measured steady-state V<SUP>center dot</SUP>O<INF>2</INF> during each 30-min test was compared to the V<SUP>center dot</SUP>O<INF>2</INF> predicted after adjustment by each of the three MRTs. Results: For all three MRT methods, predicted V<SUP>center dot</SUP>O<INF>2</INF> was not different (p = 1.000) from the measured V<SUP>center dot</SUP>O<INF>2</INF> at 75%GET (MRT<INF>EXP</INF>, 31 mL, MRT<INF>LIN</INF>, -35 mL, MRT<INF>SS</INF> 11 mL), 85%gas exchange threshold (MRT<INF>EXP</INF> -14 mL, MRT<INF>LIN</INF> -80 mL, MRT<INF>SS</INF> -32 mL). At Delta 15, predicted V<SUP>center dot</SUP>O<INF>2</INF> based on MRT<INF>EXP</INF> was not different (p = .767) from the measured V<SUP>center dot</SUP>O<INF>2</INF>, but was different for MRT<INF>LIN</INF> (p < .001) and MRT<INF>SS</INF> (p = .03). Conclusion: Given that the intensity is below gas exchange threshold, all model predictions implemented from the current study matched the exercise prescription.