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This Article Full Text Full Text (PDF) All Versions of this Article: 559/1/315    most recent jphysiol.2003.057729v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Haouzi, P. Articles by Chalon, B. Search for Related Content PubMed PubMed Citation Articles by Haouzi, P. Articles by Chalon, B.

Laboratoire de Physiologie, EA 3450, Faculté de Médecine de Nancy, France

This study was designed to test the hypothesis that the frequency response of the systems controlling the motor activity of breathing and walking in quadrupeds is compatible with the idea that supra-spinal locomotor centres could proportionally drive locomotion and ventilation. The locomotor and the breath-by-breath ventilatory and gas exchange (CO₂ output (_CO2) and O₂ uptake (_O2)) responses were studied in five sheep spontaneously walking on a treadmill. The speed of the treadmill was changed in a sinusoidal pattern of various periods (from 10 to 1 minute) and in a step-like manner. The frequency and amplitude of the limb movements, oscillating at the same period as the treadmill speed changes, had a constant gain with no phase lag (determined by Fourier analysis) regardless the periods of oscillations. In marked contrast, when the periods of speed oscillations decreased, the amplitude (peak-to-mean) of minute ventilation (_E) oscillations decreased sharply and significantly (from 6.1 ± 0.4 l min^–1 to 1.9 ± 0.2 l min^–1) and the phase lag between ventilation and treadmill speed oscillations increased (to 105 ± 25 ° during the 1 min oscillation periods). _E response followed _CO2 very closely. The drop in _E amplitude ratio was proportional to that in _CO2 (from 149 ± 48 ml min^–1 to 38 ± 5 ml min^–1) with a slightly longer phase lag for ventilation than for _CO2. These results show that beyond the onset period of a locomotor activity, the amplitude and phase lag of the _E response depends on the period of the walking speed oscillations, tracking the gas exchange rate, regardless of the amplitude of the motor act of walking. Locomotion thus appears unlikely to cause a simple parallel and proportional increase in ventilation in walking sheep.

(Received 24 March 2004; accepted after revision 25 June 2004; first published online 2 July 2004)
Corresponding author P. Haouzi: Laboratoire de Physiologie, EA 3450, Faculté de Médecine de Nancy, France. Email: p.haouzi{at}chu-nancy.fr

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