Correlation between inflection of heart rate/work performance curve and myocardial function in exhausting cycle...

Area of Science:

• Exercise Physiology
• Cardiovascular Physiology
• Sports Science

Background:

• The heart rate/work performance (fc/W) curve typically exhibits an S-shape.
• A flattening at the apex of the fc/W curve is not consistently observed.
• Understanding factors influencing fc/W curve morphology is crucial for assessing exercise capacity.

Purpose of the Study:

• To investigate the relationship between heart rate/work performance (fc/W) curve characteristics and left ventricular ejection fraction (LVEF) during exercise.
• To determine if changes in LVEF correlate with the presence or absence of inflection in the fc/W curve.
• To explore the association between stress-dependent myocardial function and fc/W curve morphology.

Main Methods:

• Utilized radionuclide ventricular scintigraphy to assess LVEF in 15 sports students.
• Performed cycle ergometry with incrementally increasing exercise intensities.
• Analyzed the fc/W curve and LVEF performance curve (LVEFPC) using polynomial fitting to calculate inflections and slopes.

Main Results:

• Left ventricular ejection fraction (LVEF) initially increased with exercise, then plateaued or decreased at higher intensities.
• The inflection of the fc/W curve became less pronounced or absent when LVEF decreased more significantly towards the end of exercise.
• A significant negative correlation (P < 0.01, r = 0.673) was found between fc/W curve inflection and stress-dependent myocardial function (LVEFPC inflection).

Conclusions:

• The absence of an inflection in the fc/W curve appears linked to diminished stress-dependent myocardial function.
• LVEF behavior during exercise provides insights into the fc/W curve's morphology.
• This study highlights the importance of considering myocardial function when interpreting exercise performance data.