Assembling more O2 uptake responses: Is it possible to merely stack the repeated transitions?

• Unwieldy data treatments are applied to assemble more VO2 responses at exercise onset.
• Results of the mere “stacking” of simulated repeated responses were investigated.
• Mere stacking gave average estimated parameters close to the correct ones.
• Mere stacking gave asymptotic confidence intervals very close to the correct ones.
• Due to its simplicity, stacking is endorsed to assemble more O2 uptake responses.

Kinetic parameters for pulmonary O2 uptake at exercise onset are estimated by non-linear regression on repeated responses assembled together. The native data contain the information, thus the “stacking” of the responses should provide correct values and uncertainties. Kinetic parameters and corresponding uncertainties (computed from the asymptotic standard errors; ASE) were estimated on 104 simulated noisy responses (with time constant τ = 25 s), repeated 10 times and assembled over an increasing number of repetitions (Nr) by “stacking” or ensemble averaging the responses processed to obtain 1 s bins (“1-s-bins”). Independent of the assembling method, the average estimated τ amounted to ∼25.05 s. Independent of Nr, the “1-s-bins” and the “stacking” yielded an ASE/SD ratio for τ amounting to ∼0.52 and ∼0.98, respectively, resulting in a probability of including τ = 25 s within the estimated uncertainty from an individual kinetics amounting to ∼70% and >94% for the “1-s-bins” and the “stacking”, respectively. In conclusion, the “stacking” allowed obtaining, also for individual kinetics, coherent estimated parameters and associated uncertainties.