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 versus 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 increases RM and decreases reflected wave transit time (RWTT). Applanation tonometry was used to record radial artery pressure waveforms in 30 adults (25 ± 4 yr) at baseline and during dynamic and isometric HG exercise. Wave separation analysis was performed offline using a physiological flow wave to derive Pf, Pb, RM, and RWTT. We found that RM increased during dynamic and isometric HG exercise compared with 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 with 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 that wave reflection timing (RWTT) and magnitude (RM) are important factors that contribute to increased central blood pressure during HG exercise.NEW & NOTEWORTHY This study demonstrated that wave reflection magnitude is increased while reflected wave transit time is decreased during handgrip exercise in healthy young adults. The larger backward pressure waves and earlier return of these pressure waves were not different between dynamic and isometric handgrip exercise. These acute changes in wave reflection during handgrip exercise transiently augment pulsatile load.

Keywords: handgrip exercise; wave reflection; wave separation analysis.

Fig. 1.

Measures of wave reflection. A: surrogate measures of wave reflection were derived from central pressure wave morphology alone. Tr, time to inflection point; AP, augmented pressure; cPP, central pulse pressure; AI, augmentation index. B: wave separation analysis measures of wave reflection were calculated using central pressure-flow relations. Pf, forward pressure wave amplitude; Pb, backward pressure wave amplitude; RM, reflection magnitude; RWTT, reflected wave transit time.

Fig. 2.

Measures of wave reflection during handgrip exercise derived from the central pressure waveform. A: augmentation index increased during dynamic and isometric handgrip exercise compared with baseline. B: time to inflection point decreased during dynamic and handgrip exercise compared with baseline. n = 30 Subjects. *P < 0.05 versus baseline.

Fig. 3.

Measures of wave reflection during handgrip exercise derived from wave separation analysis. A: forward pressure wave amplitude did not change during handgrip exercise. B and C: backward pressure wave amplitude (B) and reflection magnitude (C) increased during dynamic and isometric handgrip compared with baseline. D: reflected wave transit time decreased during dynamic and isometric handgrip exercise compared with baseline. n = 30 Subjects. *P < 0.05 versus baseline.