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Updated: Mar 27, 2026

Determining the Contribution of the Energy Systems During Exercise
Published on: March 20, 2012
Relation between Exercise Training-Induced Changes in Oxygen Uptake Kinetics and the Power-Duration Relation
Tze-Huan Lei1, Luuk Vos2, I-Lin Wang1
1College of Physical Education, Hubei Normal University, Huangshi, CHINA.
Purpose:
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; ).
Methods:
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.
Results:
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 .
Conclusions:
The present study suggests that the bioenergetic mechanisms underpinning CP and are similar, whereas the relation between and appears somewhat more complex.
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