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O2 kinetics and the
O2 deficit in heavy exercise
Department of Nutrition, Food, and Exercise Science, The Florida State University, Tallahassee, Florida 32306
The purpose
of this study was to examine a new method for calculating the
O2 deficit that considered the O2 uptake
(
O2) kinetics during
exercise as two separate phases in light of previous research in which
it was shown that the traditional O2 deficit calculation
overestimated the recovery O2 consumption (ROC). Eight subjects completed exercise transitions between unloaded cycling and
25% (heavy, H) or 50% (very heavy, VH) of the difference between the
lactic acid threshold (LAT) and peak
O2 for 8 min. The
O2 deficit, calculated in the traditional manner, was
significantly greater than the measured ROC for both above-LAT
exercises: 4.03 ± 1.01 vs. 2.63 ± 0.80 (SD) liters for VH
and 2.36 ± 0.91 vs. 1.74 ± 0.63 liters for H for the O2
deficit vs. ROC (P < 0.05). When the kinetics were viewed as
two separate components with independent onsets, the calculated
O2 deficit (2.89 ± 0.79 and 1.71 ± 0.70 liters for VH and H, respectively) was not different from the measured
ROC (P < 0.05). Subjects also performed the same work rate
for only 3 min. These data, from bouts terminated before the slow
component could contribute appreciably to the overall
O2 response, show that the
O2 requirement during the transition is less than the final
steady state for the work rate, as evidenced by symmetry between the
O2 deficit and ROC. This new method of calculating the
O2 deficit more closely reflects the expected
O2 deficit-ROC relationship (i.e., ROC 
O2
deficit). Therefore, estimation of the O2 deficit during
heavy exercise transitions should consider the slow component of
O2 as an additional deficit
component with delayed onset.
recovery oxygen consumption; lactic acid threshold; square wave; steady state
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