Regulation of Mitochondrial Oxygen Consumption at Exercise Onset: O 2 delivery or O 2 utilization?. F.W. Kolkhorst Kasch Exercise Physiology Lab San Diego State University, San Diego, CA. Why study VO 2 kinetics?. Grassi et al., JAP , 1996.
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Regulation of Mitochondrial Oxygen Consumption at Exercise Onset:O2 delivery or O2 utilization?
Kasch Exercise Physiology Lab
San Diego State University, San Diego, CA
Grassi et al., JAP, 1996
Kolkhorst et al., MSSE, 2004
Peripheral O2 diffusion (capillary-to-mitochondria) as a limiting factor?
VO2 response to electrical stimulation in isolated canine muscleThere were no differences in the time constant between the three conditions. (RSR13 is a drug that shifts O2-Hb dissociation curve to the right) (Grassi et al., JAP 1998)
O2 deficit during electrical stimulation in isolated canine muscleBlood flow enhanced with administration of adenosine was compared to control. O2D was ~25% less during enhanced blood flow at high-intensity stimulation (Grassi et al., 1998, 2000).
Effect of Cr supplementation on VO2 kinetics during heavy exercise
Shedden et al., unpublished observations
Effect of Cr supplementation on repeated bouts of supramaximal cycling
Kolkhorst et al., unpublished observations
Can O2 supply during entire adaptation phase precisely anticipate/exceed O2 demand? (Hughson et al., ESSR, 2001)
Light warmup exercise
Heavy warmup exercise (Bohnert et al., Exp Physiol, 1998; Gerbino et al., JAP, 1996)
Top: VO2 responses to repeated bouts of supra-LT exercise.
Bottom: VO2 responses to repeated bouts of sub-LT exercise.
Gerbino et al., JAP, 1996
Bicarbonate ingestion would:
slow rapid component
decrease magnitude of slow component
To investigate effects of bicarbonate ingestion on VO2 kinetics
Initiation of exercise
VO2(t) = VO2base + A1 • (1-e-(t-TD1)/1)
+ A2• (1-e-(t-TD2/2)
+ A3• (1-e-(t-TD3)/3)
* P < 0.001
* P < 0.05
Kolkhorst et al., MSSE, 2004
Why did bicarbonate affect rapid component?
alkalosis decreased vasodilation and caused leftward shift of O2-Hb dissociation curve
effects of prior heavy exercise on rapid component are equivocal
2 and MRT (MacDonald et al., 1997; Rossiter et al., 2001; Tordi et al., 2003)
n/c in 2, but A'2 and A'3(Burnley et al., 2001; Fukuba et al., 2002)
Why did bicarbonate affect slow component?
bicarbonate attenuates decreases in muscle pH (Nielsen et al., 2002; Stephens et al., 2002)
Does pH cause fatigue?
Westerblad et al. (2002) suggested Pi accumulation primary cause
bicarbonate ingestion performance
VO2 kinetics appears to be more sensitive than VO2max or LT to perturbations such as exercise training