Cardiovascular Responses to Soft Drink Consumption during Mechano‐ and Metaboreceptor Stimulation

Abstract

IntroductionAcute consumption of a high‐fructose, caffeinated soft drink exacerbates the increase in blood pressure during exercise in the heat. The mechanoreflex and metaboreflex are important contributors to the blood pressure response during exercise. However, the effects of acute soft drink consumption on the mechanoreflex and metaboreflex, independent of heat stress, are currently unknown.ObjectiveWe tested the hypothesis that consumption of a high‐fructose, caffeinated soft drink would exacerbate cardiovascular responses to static handgrip (HG) exercise and post exercise muscle ischemia (PEMI) compared to water consumption.MethodsEight healthy adults (Age: 26±7 years, 3 females) consumed 500 mL of water (H2O) or soda (Soda, Mountain Dew®) in a randomized, double‐blind study design in a moderate thermal environment (24±1%, 21.7±6% relative humidity). After consuming the assigned beverage, subjects lied on their left side quietly for 20 min and then completed a 10 min baseline (BL) followed by 2 min of static HG at 30% of maximal voluntary contraction followed by 2 min of PEMI. Heart rate (HR, ECG) and mean arterial blood pressure (MAP, finger photoplethysmography) were recorded continuously. Stroke volume (SV) was estimated using Modelflow. Cardiac output (Q) was calculated as HR×SV. Total peripheral resistance (TPR) was calculated as MAP/Q. Data were analyzed as a change from baseline (Δ) to the last 30 s of HG and the last 30 s of PEMI. Data are reported as Δmean±SD.ResultsAt BL, there were no differences between Soda and H2O for HR (Soda: 67±9; H2O: 64±8 bpm, P=0.27), MAP (Soda: 79±10; H2O: 83±6 mmHg, P=0.16), or SV (Soda: 101±22; H2O: 95±11 mL, P=0.32). Q was higher with Soda (6.5±1.5 L/min) vs. H2O (5.9±0.8 L/min, P=0.04) and TPR was lower with Soda (12.3±2.5 mmHg/L/min) vs. H2O (14.6±2.1 mmHg/L/min; P=0.02) at BL. During HG, ΔHR (Soda: 15±12; H2O: 13±13bpm, P=0.57), ΔMAP (Soda: 12±13; H2O: 17±7mmHg, P=0.10), ΔSV (Soda: −4±13; H2O: −2±8 mL, P=0.71), ΔQ (Soda: 1.0±1.4; H2O: 1.1±0.9 L/min, P=0.93), and ΔTPR (Soda: −0.1±2.8; H2O: 0.5±2.0 mmHg/L/min, P=0.38) did not differ between drinks. Additionally, there were no differences between drinks during PEMI for ΔHR (Soda: 1±8; H2O: 2±9 bpm, P=0.67), ΔMAP (Soda: 12±13; H2O: 16±11 mmHg, P=0.22), ΔSV (Soda: −1±17; H2O: 4±8 mL, P=0.34), ΔQ (Soda: 0.0±1.1; H2O: 0.4±0.7 L/min, P=0.16), and ΔTPR (Soda: 1.6±2.4; H2O: 1.6±2.9 mmHg/L/min, P=0.98).ConclusionThese preliminary data indicate that acute consumption of a high‐fructose, caffeinated soft drink does not exacerbate cardiovascular responses to mechanoreflex and metaboreflex stimulation in moderate thermal conditions. Further investigation is warranted to determine if the mechanoreflex and/or the metaboreflex are altered following acute consumption of a high‐fructose, caffeinated soft drink during heat stress.