0153 Bright light exposition potentiates the vasodilation promoted by dynamic handgrip exercise

Abstract

Abstract Introduction Bright light (~5000 lux) directed at human skin increases plasma nitric oxide concentration promoting vasodilation, with increased skeletal muscle blood flow (BF) and decreased blood pressure (BP). The same stimulus directed at the eyes increases sympathetic activity, promoting vasoconstriction and increased BP. If bright light potentiates or mitigates the vasodilation promoted during exercise is unknown. Therefore, this study aimed to compare the effect of different intensities of lights on vasodilation of the active skeletal muscle during dynamic handgrip exercise. Methods Eleven healthy and physically inactive adult men (29±6 years) participated of the current study. All experiments were conducted between June and July 2021, beginning at 5 PM and under constant environmental conditions. Subjects performed dynamic handgrip exercise using the dominant arm at a 90º angle in the supine position with 2 s cycles of contraction and relaxation for 6 min at 40% of maximal voluntary contraction during the three experimental condition in a randomized order: (BL) 5000 lux, Control light (CL) 500 lux, and Dim light (DL) ≤8 lux. In each condition, (BL, CL or DL), subjects remained in a rested state for 20 min before 1 min of baseline assessment followed by exercise. Conditions were always separated by 20 min of washout (under CL). Assessments comprised BF, vascular conductance (VC), and diameter of brachial artery of exercising arm (Ultrasound); BP measured in the rest arm (Photoplethysmography) and heart rate (ECG). Two-way ANOVA for repeated measures, p≤0.05. Results Baseline were not different (p>0.05). During exercise, BF and VC increased in the three conditions, however it was potentiated by BL (p < 0.0001 and p < 0.0001, respectively) compared with CL (+19% and +15%, respectively) and with DL (+12% and +11%, respectively). Arterial diameter increased similarly in the three conditions. Mean BP increased in the three conditions, however it was attenuated in the BL compared with DL (-23%) and similar to CL (<0.0001). Conclusion Bright light can potentiate skeletal muscle vasodilation during a small-mass muscle exercise attenuating the increase of BP. Support (If Any) The São Paulo Research Foundation - FAPESP 2020/11588-2.