Time course of cardiovascular responses to acute sustained handgrip exercise in young physically active men

Abstract

We aimed to assess currently unexplained effects of isometric exercise on central hemodynamic, arterial, and cardiac cycle parameters. Twenty-three young physically active males performed 5-min forearm sustained exercise at 20% of maximum voluntary contraction. The pulse wave analysis (SphygmoCor) was conducted at baseline (BL) and at 1, 5, 10, 15, and 20 min of post-load recovery. The General Linear Model repeated measures analysis with post hoc test was used to compare the BL values, 1-min, and 15-min recovery states. Exercise immediately elevated central and peripheral systolic blood pressure (BP), augmentation index, left ventricular contractility, and its relative relaxation time. These prompt reactions were followed by a hypotensive response and positive lusitropic effect with shortening relaxation in 15 min after the contraction ceased. The diastolic BP decrement was inversely correlated with the amount of body lean mass and body muscle but not fat mass measured by the bioelectrical impedance method. It is hypothesized that (1) the body lean mass-dependent BP-lowering effect of exercise is due to the arterial distending influence of metabolites accumulated in the muscle during exercise-induced occlusion and then washed out into general circulation, and (2) muscle arteries are more sensitive to these effects than vessels of fat tissue.

Keywords: Sphygmocor; arterial stiffness; body composition; hand grip; inotropy; lusitropy.

FIGURE 1

Study protocol. IHG, isometric hand grip exercise; MVC, maximum voluntary contraction; R1–R20, recovery at 1 min to 20 min. Arrows indicate applanation tonometry (AT) measurements.

FIGURE 2

Aortic and LV pressure profiles and timing of the cardiac cycle in healthy young individuals (withdrawn from Wiggers' diagram, modified). SBP, DBP, systolic and diastolic blood pressure; EoE, end of ejection; P1, pressure at T1; P2, pressure at T2; SoE, start of ejection, the zero‐point for aortic cycle; T1, time to first peak; T2, time to second peak; Tf, end of cycle; Tr, time to the beginning of reflection. The x‐axis is distended for better visualizing time points. The bold curve corresponds to period of early (asynchronic) LV relaxation. T1 point represents the first peak of pulse wave that corresponds to maximum pressure of antegrade (forward) wave generated by LV and represents the duration of LV late contraction. The second systolic peak P2 (and T2) represents the maximum of reflection (backward) wave, coming to the aortic root at Tr, from the periphery. The P2 value is equal to the sum of the amplitudes of primary and reflected waves. The time difference between the opening and closing of aortic valve is ejection duration (ED = DoE–SoE). The difference between the cycle duration Tf and the end of ejection EoE corresponds to the duration of diastole (DD). The augmentation pressure (AugP, mmHg) is the difference between the amplitudes of the second and first systolic peaks. The augmentation index (AugI, %), adjusted to HR = 75, is calculated according to the formula (P2–P1)/(SBP–DBP) × 100 and corresponds to the proportion of AugP in pulse pressure. The Buckberg's Subendocardial Viability Ratio (SEVR) is the diastolic‐to‐systolic integral ratio and characterizes the myocardial perfusion, that is, oxygen supply/demand balance.

FIGURE 3

The time course of aortic systolic mean pressure (aSMP) and diastolic mean pressure (aDMP) before and after a 5‐min IHG single exercise bout at 20% of MVC. R, recovery, min. p value versus baseline (GLM repeated measures analysis with Bonferroni correction).