Why the study?
Does exercise muscle ischemia compared to post-exercise muscle ischemia alter the mechanism of cardiac output increase in healthy volunteers?
Does exercise muscle ischemia compared to post-exercise muscle ischemia alter the mechanism of cardiac output increase in healthy volunteers?
The mechanism of metaboreflex-induced cardiac output increase differs depending on whether ischemia occurs during or after exercise, driven by differences in heart rate and diastolic filling time.
Distinguishes cardiac output mechanisms by ischemia timing in healthy volunteers; leaves open clinical relevance or need for patient studies.
We hypothesized that the role of stroke volume (SV) in the metaboreflex-induced cardiac output (CO) increase was blunted when the metaboreflex was stimulated by exercise muscle ischemia (EMI) compared with post-exercise muscle ischemia (PEMI), because during EMI heart rate (HR) increases and limits diastolic filling. Twelve healthy volunteers were recruited and their hemodynamic responses to the metaboreflex evoked by EMI, PEMI, and by a control dynamic exercise were assessed. The main finding was that the blood pressure increment was very similar in the EMI and PEMI settings. In both conditions the main mechanism used to raise blood pressure was a CO elevation. However, during the EMI test CO was increased as a result of HR elevation whereas during the PEMI test CO was increased as a result of an increase in SV. These results were explainable on the basis of the different HR behavior between the two settings, which in turn led to different diastolic time and myocardial performance.
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Crisafulli et al. (2011) studied this question.
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