Kinetics of pulmonary oxygen uptake and muscle phosphates during
moderate intensity calf exercise.
McCreary, C. R., P. D. Chilibeck, G. D. Marsh, D. H. Paterson, D. A.
Cunningham, R. T. Thompson.
Department of Nuclear Medicine and the Centre for Activity and
Ageing, Lawson Research Institute, St. Joseph's Health Centre;
Faculty of Kinesiology and Departments of Medical Biophysics and
Physiology, The University of Western Ontario. London, Ontario,
Canada. N6A 4V2
APStracts 3:0199A, 1996.
The purpose of this study was to directly compare the dynamic
responses of phosphocreatine (PCr) and inorganic phosphate (Pi) to
those of oxygen uptake (INVALID_FIELD: Object) measured at the lung,
during transitions to and from moderate intensity exercise. Changes
in PCr and Pi were measured by phosphorus-31 nuclear magnetic
resonance (31P-NMR) spectroscopy and changes in INVALID_FIELD: Object
were measured breath-by-breath by mass spectroscopy during
transitions to and from moderate intensity square wave ankle plantar
flexion exercise in 11 subjects (7 males and 4 females; mean age 27
y). Three repeated transitions were averaged for improvement in
signal to noise ratio of phosphate data, and 12 transitions were
averaged for INVALID_FIELD: Object measures. Averaged transitions
were fit with a monoexponential curve for determination of the time
constant (t) of the responses. Mean t's for on-transients of PCr, Pi,
and phase 2 INVALID_FIELD: Object were 47.0, 57.7, and 44.5 s,
respectively, while mean t's for off-transients were 44.8, 42.1 and
33.4 s. There were no significant differences between t's for
phosphate and INVALID_FIELD: Object measured transients, or on- and
off-transients. The similarity of on- and off-kinetics supports
linear, first-order respiratory control models. Measurement of phase
2 pulmonary INVALID_FIELD: Object kinetics to and from moderate
intensity, small muscle mass exercise reflect muscle phosphate
kinetics (and muscle oxygen consumption).
Received 12 December 1995; accepted in final form 3 April 1996.
APS Manuscript Number A1300-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 23 April 96