Relation between Exercise Training-Induced Changes in Oxygen Uptake Kinetics and the Power-Duration Relation.

Abstract

This study aimed to determine the relation between training-induced changes in the variable values of the power-duration relation (critical power [CP] and ) and those of pulmonary oxygen uptake ( ) kinetics (the fundamental phase time constant; , and the slow component amplitude; ). Eleven healthy untrained males underwent 2 wk of severe-intensity exercise training. Before and after training, was assessed via an incremental exercise test on a cycle ergometer, CP and were assessed via constant power determination trials, and kinetics were assessed during exercise at a power output 10% above CP (posttraining at the same absolute and relative intensity as pretraining). A previously described and validated computer model of the human skeletal muscle bioenergetic system was used to provide further insight into training-induced changes. CP and were strongly inversely correlated before and after training, and their training-induced changes were also correlated. Computer simulations suggested that increased oxidative phosphorylation activity (k OX ) was the main factor determining the training-induced changes in CP and . Exercise training increased and reduced the amplitude of the , however, the training-induced changes in and were not correlated. Model simulations suggested that variations in k OX , the accessible phosphate (+creatine) pool (P acc ), and the peak inorganic phosphate (P i ) concentrations attained before task failure (Pi peak ) could explain the observed training-induced alterations in and . The present study suggests that the bioenergetic mechanisms underpinning CP and are similar, whereas the relation between and appears somewhat more complex.