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Left ventricular mechanical limitations to stroke volume in healthy humans during incremental exercise
Eric J Stöhr1, José González-Alonso, Rob Shave
1Centre for Sports Medicine and Human Performance, Brunel University, Uxbridge, United Kingdom.
Summary
Stroke volume (SV) plateaus during exercise due to limitations in left ventricular (LV) twist mechanics. This study found LV twist mechanics also plateau, suggesting a mechanical limit to cardiac output during intense exercise.
Area of Science:
- Cardiovascular Physiology
- Exercise Physiology
- Cardiac Mechanics
Background:
- Stroke volume (SV) plateaus at submaximal exercise intensities in healthy individuals.
- Left ventricular (LV) twist mechanics contribute to SV at rest, but their role in exercise-induced SV plateau is unclear.
Purpose of the Study:
- To investigate if the SV plateau during incremental exercise is linked to blunted LV twist mechanics.
- To examine the relationship between LV twist mechanics and hemodynamic variables during exercise.
Main Methods:
- Nine healthy males performed continuous and discontinuous incremental cycling exercise.
- Two-dimensional speckle tracking assessed LV twist and untwisting velocity.
- Measurements included LV volumes (EDV, ESV), SV, and heart rate.
Main Results:
- SV, EDV, and ESV plateaued at submaximal intensities, while heart rate increased continuously.
- LV twist and untwisting velocity increased with exercise intensity and then plateaued.
- LV twist mechanics correlated with ESV, SV, heart rate, and cardiac output.
Conclusions:
- The plateau in LV twist mechanics suggests a mechanical limitation on LV output during high exercise intensities.
- Diastolic filling limitations, indicated by EDV plateauing before LV twist mechanics, also contribute to limiting cardiac output.
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