Linear Modelling of the V̇O2/PO-Relationship during Constant Work Rate Exercise.

Abstract

Introduction: The linear and continuous increase in power output (PO) during ramp incremental (RI) exercise causes a distinct V̇O2/PO relationship compared to constant work rate (CWR) exercise. Current methods enabling a translation of ramp-derived PO to CWR PO assume a linear development of the CWR V̇O2/PO relationship in the heavy-intensity domain. This study aimed to model the RI versus CWR V̇O2/PO relationship to investigate whether the loss of mechanical efficiency above GET develops linearly. A second aim was to assess the reliability of ramp-derived parameters incorporated in translation strategies.

Methods: Fourteen healthy young participants (7 males; 7 females) performed a RI test and several CWR tests across the heavy- and severe-intensity domains in order to model the RI and CWR V̇O2/PO relationships. The CWR relationship was fitted using linear, polynomial and exponential models. Root mean square error (RMSE) and Akaike information criterion (AICC) were determined to evaluate the model's goodness-of-fit. For reliability purposes, target PO of CWR tests were achieved using a preceding RI portion, similar to the initial RI test.

Results: The linear fit of the CWR V̇O2/PO relationship was associated with the lowest RMSE and AICC. The associated R2 for the heavy-intensity domain was 0.94. Reliability measures were excellent for baseline V̇O2 and acceptable to good for s1-ramp and s2- ramp. For MRT, a high variability was observed.

Conclusions: This study confirmed that the CWR V̇O2/PO relationship in the heavy-intensity domain is linear. Based on these results, it is justified to apply correction strategies that mind the different dynamics of V̇O2 during RI versus CWR exercise.