Key result
Following 1-min isometric dorsiflexion contractions, perfusion increased ~2.5-fold, with oxygen consumption and perfusion showing varied recovery rates across 20% and 40% MVC intensities.
Why the study?
How do different submaximal contraction intensities affect the kinetics of oxygen delivery, extraction, and consumption in healthy subjects?
How do different submaximal contraction intensities affect the kinetics of oxygen delivery, extraction, and consumption in healthy subjects?
The study demonstrates varied recovery rates of perfusion and oxygen consumption, but similar rates of deoxyhemoglobin recovery, across different submaximal exercise intensities in healthy humans.
Studying the magnitude and kinetics of blood flow, oxygen extraction, and oxygen consumption at exercise onset and during the recovery from exercise can lead to insights into both the normal control of metabolism and blood flow and the disturbances to these processes in metabolic and cardiovascular diseases. The purpose of this study was to examine the on- and off-kinetics for oxygen delivery, extraction, and consumption as functions of submaximal contraction intensity. Eight healthy subjects performed four 1-min isometric dorsiflexion contractions, with two at 20% MVC and two at 40% MVC. During one contraction at each intensity, relative perfusion changes were measured by using arterial spin labeling, and the deoxyhemoglobin percentage (%HHb) was estimated using the spin- and gradient-echo sequence and a previously published empirical calibration. For the whole group, the mean perfusion did not increase during contraction. The %HHb increased from ∼28 to 38% during contractions of each intensity, with kinetics well described by an exponential function and mean response times (MRTs) of 22.7 and 21.6 s for 20 and 40% MVC, respectively. Following contraction, perfusion increased ∼2.5-fold. The %HHb, oxygen consumption, and perfusion returned to precontraction levels with MRTs of 27.5, 46.4, and 50.0 s, respectively (20% MVC), and 29.2, 75.3, and 86.0 s, respectively (40% MVC). These data demonstrate in human subjects the varied recovery rates of perfusion and oxygen consumption, along with the similar rates of %HHb recovery, across these exercise intensities.
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Buck et al. (2015) studied Healthy (n=8). 1-min isometric dorsiflexion contractions at 20% and 40% MVC vs. Precontraction levels was evaluated on On- and off-kinetics for oxygen delivery, extraction, and consumption. Following 1-min isometric dorsiflexion contractions, perfusion increased ~2.5-fold, with oxygen consumption and perfusion showing varied recovery rates across 20% and 40% MVC intensities.
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