A "Step-Ramp-Step" Protocol to Identify the Maximal Metabolic Steady State

Danilo Iannetta, Erin Calaine Inglis, Silvia Pogliaghi, Juan M Murias, Daniel A Keir
Medicine and Science in Sports and Exercise 2020 March 20

The oxygen uptake (V[Combining Dot Above]O2) at the respiratory compensation point (RCP) closely identifies with the maximal metabolic steady-state. However, the power output (PO) at RCP cannot be determined from contemporary ramp-incremental exercise protocols.

PURPOSE: To test the efficacy of a "step-ramp-step" (SRS) cycling protocol for estimating the PO at RCP and the validity of RCP as a maximal metabolic steady-state surrogate.

METHODS: 10 heathy volunteers (5 women; age: 30±7 yr; V[Combining Dot Above]O2max: 54±6 mL·kg·min) performed in series a: moderate step-transition to 100 W (MOD); ramp (30 W·min); and, after 30 min of recovery, step-transition at ~50% peak PO (HVY). Ventilatory and gas exchange data from the ramp were used to identify the V[Combining Dot Above]O2 at lactate threshold (LT) and RCP. The PO at LT was determined by linear regression of the V[Combining Dot Above]O2 versus PO relationship after adjusting ramp data by the difference between the ramp-PO at the steady-state V[Combining Dot Above]O2 from MOD and 100 W. Linear regression between the V[Combining Dot Above]O2-PO values associated with LT and HVY provided, by extrapolation, the PO at RCP. Participants then performed 30 min constant-power tests at the SRS-estimated RCP and 5% above this PO.

RESULTS: All participants completed 30 min of constant-power exercise at the SRS-estimated RCP achieving steady-state in V[Combining Dot Above]O2 of 3176±595 mL·min that was not different (p=0.80) from the ramp-identified RCP (3095±570 mL·min) and highly consistent within-participants (bias=-26 mL·min; r=0.97; CV=2.3±2.8%). At 5% above the SRS-estimated RCP, four participants could not complete 30 min and all but two exhibited non-steady-state responses in blood lactate and V[Combining Dot Above]O2.

CONCLUSIONS: In healthy individuals cycling at their preferred cadence, the SRS protocol and RCP are capable of accurately predicting the PO associated with maximal metabolic steady-state.

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