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Left ventricular volumes and hemodynamic responses to postexercise ischemia in healthy humans
B G Bastos1, J W Williamson, T Harrelson
1Department of Physiology, Instituto Biomédico, Universidade Federal Fluminense, Niterói, RJ, Brazil.
Insights
Postexercise circulatory occlusion activates muscle metaboreceptors, increasing blood pressure by raising total peripheral resistance. The Frank-Starling mechanism maintains cardiac output and stroke volume despite increased afterload.
Area of Science:
- Cardiovascular Physiology
- Exercise Physiology
Background:
- Understanding cardiovascular adjustments during and after exercise is crucial for assessing physiological responses.
- Postexercise circulatory occlusion (OCCL) is a model used to investigate sustained cardiovascular responses mediated by muscle metaboreceptors.
Purpose of the Study:
- To elucidate the cardiac mechanisms underlying cardiovascular adjustments during postexercise circulatory occlusion (OCCL).
Main Methods:
- Nine healthy volunteers underwent assessments of heart rate (HR), mean arterial pressure (MAP), cardiac volumes (EDV, ESV), stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR).
- Measurements were taken during rest, static exercise (30% MVC), and randomized OCCL or non-OCCL conditions.
Main Results:
- Exercise increased HR, CO, MAP, and TPR, while decreasing SV and EDV. These exercise responses were similar between OCCL and non-OCCL conditions.
- During OCCL, HR, SV, and CO returned to baseline, but MAP and TPR remained elevated.
- OCCL led to increased end-diastolic volume (EDV) and end-systolic volume (ESV) above resting levels.
Conclusions:
- Activation of muscle metaboreceptors during OCCL elevates MAP primarily through increased TPR.
- The Frank-Starling mechanism, evidenced by increased EDV, compensates for elevated afterload and increased ESV, maintaining CO and SV near resting levels.
Purpose:
The purpose of this study was to determine the cardiac mechanisms involved in cardiovascular adjustments during postexercise circulatory occlusion (OCCL).
Method:
Heart rate (HR), mean arterial pressure (MAP), left ventricular end-diastolic (EDV) and end-systolic volumes (ESV), stroke volume (SV), cardiac output (CO), and total peripheral vascular resistance (total peripheral resistance (TPR)) were assessed in nine healthy volunteers during rest and static exercise at 30% of maximum voluntary contraction followed by either OCCL for 3 min or non-OCCL in a randomized crossover protocol.
Results:
During handgrip, HR (+20%; P < 0.001), CO (+11%; P = 0.003), MAP (+18%; P = 0.001), and TPR (+6%; P = 0.004) increased, SV (-8%; P = 0.001) and EDV (-5%; P < 0.001) decreased, while ESV did not change (P > 0.05). These responses were similar between conditions (P > 0.05). During OCCL, HR, SV, and CO returned to baseline, whereas MAP (+19%; P < 0.001) and TPR (+9%; P = 0.004) remained elevated. EDV (+12%; P < 0.001) and ESV (+23%; P < 0.001) increased in parallel above resting values.
Conclusion:
Activation of muscle metaboreceptors during OCCL increased MAP by elevating TPR. Despite the higher afterload and increased ESV, CO and SV were kept similar to resting values because EDV also increased, implying the involvement of the Frank-Starling mechanism.