Author(s): MORISHIMA, T., FUJIE, S., KOJIMA, C., ITO, R., NAKAO, K., IEMITSU, M., Institution: CHUKYO UNIVERSITY, Country: JAPAN, Abstract-ID: 1169

INTRODUCTION:
Acute high-intensity resistance exercise transiently reduces endothelial function in untrained individuals, whereas this impairment is not observed in those who habitually perform resistance training. However, the underlying physiological mechanisms remain unclear. Therefore, this study examined differences in central and peripheral circulatory responses to acute high-intensity resistance exercise between resistance-trained and untrained individuals, focusing on hemodynamic factors related to endothelial shear stimulus.
METHODS:
Twelve young untrained men were assigned to a control group (CON) and twelve resistance-trained men with >2 years of training to a resistance-trained group (RT). During visit one, one-repetition maximum (1RM) for the leg extension was determined. During visit two, body composition was assessed, followed by seated baseline measurements. Measurements included blood pressure, left ventricular outflow tract diameter, left ventricular inflow and ejection velocities, and brachial artery diameter and blood velocity. Participants performed five sets of ten repetitions at 70% 1RM with 60-s rest intervals. Measurements were repeated during and after exercise. A two-way repeated-measures ANOVA (time × group) was used, and P < 0.05 was considered significant.
RESULTS:
Leg extension 1 RM and muscle thickness of rectus femoris and hamstrings were significantly greater in RT than CON (P < 0.05). Hemodynamic variables changed significantly with exercise in both groups (time effect, P < 0.05). Stroke volume and cardiac output during exercise and immediately after exercise were significantly greater in RT than CON (P < 0.05). Changes (Δ) in left ventricular ejection velocity and heart rate in response to exercise were significantly greater in RT than in CON (P < 0.05). Although systolic blood pressure was significantly higher in RT (P < 0.05), diastolic blood pressure did not differ between groups. There were no differences in vascular conductance or resistance between groups. Brachial artery shear rate during and after exercise was significantly higher in RT than CON (P < 0.05).
CONCLUSION:
RT showed central–peripheral hemodynamic coupling. Increases in stroke volume and cardiac output were accompanied by parallel increases in brachial artery shear rate during and after exercise. The larger rise in cardiac output in RT might be associated with greater response in left ventricular ejection velocity and heart rate. This indicates effective transmission of central output to the peripheral vasculature and preservation of endothelial shear stimulus despite elevated arterial pressure. In conclusion, enhanced central–peripheral coupling in resistance-trained individuals may help maintain endothelial shear stimulus during and after acute high-intensity resistance exercise and could contribute to the preservation of vascular endothelial function.