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

Abstract

Early return and increased magnitude of wave reflection augments pulsatile load, wastes left ventricular effort, and is associated with cardiovascular events. Acute handgrip (HG) exercise increases surrogate measures of wave reflection such as augmentation index. However, augmentation index does not allow distinguishing between timing vs. magnitude of wave reflection, and is affected by factors other than wave reflection per se. Wave separation analysis decomposes central pressure into relative contributions of forward (Pf) and backward (Pb) pressure wave amplitudes to calculate reflection magnitude (RM=Pb/Pf) and determine the timing of apparent wave reflection return. We tested the hypothesis that acute dynamic and isometric HG exercise increase RM and decrease reflected wave transit time (RWTT). Applanation tonometry was used to record radial artery pressure waveforms in 30 adults (25±4 years) at baseline and during dynamic and isometric HG exercise. Wave separation analysis was performed offline using a physiologic flow wave to derive Pf, Pb, RM, and RWTT. We found that RM increased during dynamic and isometric HG exercise compared to baseline (p=0.04 and p<0.01, respectively; baseline 40±5, dynamic 43±6, isometric 43±7%). Meanwhile, RWTT decreased during dynamic and isometric HG exercise compared to baseline (p=0.03 and p<0.001, respectively; baseline 164±23, dynamic 155±23, isometric 148±20 ms). Moreover, the changes in RM and RWTT were not different between dynamic and isometric HG exercise. The present data suggest wave reflection timing (RWTT) and magnitude (RM) are important factors that contribute to increased central blood pressure during HG exercise.

Lower‐body dynamic exercise reduces wave reflection in healthy young adults

“…We recently found that central blood pressure also increased during handgrip exercise, but wave separation analysis parameters responded differently. For example, in the present study Pf increased while Pb and RM decreased, but during handgrip exercise Pf did not change while Pb and RM increased (Stock et al, 2020). The RWTT decreased in both studies, suggesting that the exercise modality does not influence reflected wave timing, whereas pressure wave amplitudes are affected differentially.…”

“…The vasoactive response during LBD appears to limit the impact of wave reflection on the left ventricle, whereas we have shown that handgrip exercise transiently increases the work imposed on the left ventricle as a result of wave reflection (Stock et al, 2020).…”

“…The RWTT decreased in both studies, suggesting that the exercise modality does not influence reflected wave timing, whereas pressure wave amplitudes are affected differentially. Central blood pressure was influenced by wave reflections during handgrip exercise (Stock et al, 2020), but wave…”

“…Previously, we demonstrated that wave separation based on a subject-specific physiological flow waveform showed greater equivalency to measured aortic flow via echocardiography compared with triangulation of flow (Shenouda et al, 2021). Furthermore, we have used these same methods to investigate the effect of handgrip exercise on wave reflections (Stock et al, 2020).…”

“…Nevertheless, a 'normal' forward and backward pressure wave response in a young, healthy population is yet to be established. Additionally, it is unclear whether the increase in central blood pressure is influenced by backward pressure amplitude and timing, as seen during handgrip exercise (Stock et al, 2020), or if the increase in central blood pressure during LBD exercise is determined by forward pressure alone, as suggested by Schultz et al…”