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A Learned Component of the Ventilatory Response to Exercise in Man
Author(s) -
Wood Helen E.,
Fatemian Marzieh,
Robbins Peter A.
Publication year - 2003
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2003.047597
Subject(s) - chemoreceptor , ventilation (architecture) , repeated measures design , airway , medicine , hypoxic ventilatory response , steady state (chemistry) , respiratory minute volume , analysis of variance , pco2 , physical therapy , physical exercise , anesthesia , respiratory system , physical medicine and rehabilitation , chemistry , mathematics , statistics , mechanical engineering , receptor , engineering
The ventilatory response to mild‐to‐moderate exercise in humans is isocapnic, or ‘error‐free’. It has been suggested that this response is learned over many repetitions of exercise through the process of minimising any deviations from normal in the blood gas tensions, as sensed by the chemoreceptors. However, relatively limited training programmes have failed to produce any convincing evidence in humans that forcibly altering the blood gas tensions during repeated periods of exercise alters the subsequent steady‐state ventilatory response to exercise. In this study, eight healthy young subjects were exposed, over a 7 day training period, to a total of 70 repeated bouts of exercise paired with a simultaneous airway CO 2 load to stimulate the chemoreceptors (protocol EX + CO 2 ). The ventilatory response to exercise was measured before and after training to determine whether it had been modified. Two further training protocols were undertaken as controls. One employed repeated exercise without an airway CO 2 load, and the other employed repeated airway CO 2 loading without exercise. On the 1st and 2nd days following training with protocol EX + CO 2 , end‐tidal P CO2 was regulated at a lower level during steady‐state exercise than following training with the control protocols and than before training (mean ± s.e.m. reduction in end‐tidal P CO2 = 1.32 ± 0.36 Torr, ANOVA, P < 0.05 ). In contrast to previous studies, this finding demonstrates that the steady‐state ventilatory response to exercise can be modified by a prior period of altered chemoreception during exercise. This suggests that ventilation is matched to metabolic rate during exercise by a mechanism that involves learning and memory.