Dynamic and isometric handgrip exercise increases wave reflection in healthy young adults

Area of Science:

• Cardiovascular Physiology
• Hemodynamics
• Exercise Physiology

Background:

• Early return and increased magnitude of wave reflection augment pulsatile load, wasting left ventricular effort and increasing cardiovascular event risk.
• Augmentation index, a surrogate measure, is affected by factors other than wave reflection and doesn't distinguish between timing and magnitude.
• Wave separation analysis offers a more precise method to assess wave reflection magnitude and timing.

Purpose of the Study:

• To test the hypothesis that acute dynamic and isometric handgrip exercise increase reflection magnitude (RM) and decrease reflected wave transit time (RWTT).

Main Methods:

• Applanation tonometry recorded radial artery pressure waveforms in 30 adults at baseline and during dynamic and isometric handgrip exercise.
• Wave separation analysis was performed offline using a physiological flow wave to derive forward (Pf) and backward (Pb) pressure wave amplitudes.
• Reflection magnitude (RM = Pb/Pf) and reflected wave transit time (RWTT) were calculated.

Main Results:

• Reflection magnitude (RM) increased during both dynamic and isometric handgrip exercise compared to baseline (P=0.04 and P<0.01, respectively).
• Reflected wave transit time (RWTT) decreased during both dynamic and isometric handgrip exercise compared to baseline (P=0.03 and P<0.001, respectively).
• Changes in RM and RWTT did not differ significantly between dynamic and isometric handgrip exercise.

Conclusions:

• Acute dynamic and isometric handgrip exercise increase wave reflection magnitude and decrease reflected wave transit time in healthy young adults.
• These alterations in wave reflection contribute to increased central blood pressure during handgrip exercise.
• The findings highlight the importance of wave reflection timing and magnitude in modulating pulsatile load during acute exercise.