Caffeine intake is associated with increased blood pressure and decreased forearm blood flow during dynamic exercise.
This study investigated how caffeine affects the cardiovascular system during dynamic exercise. Researchers studied 10 professional, caffeine-naïve cyclists who were assigned into either a caffeine group or a placebo group. After intervention with caffeine or fructose (placebo), the subjects were made to rest for 100 minutes or rest for 45minutes followed by 55minutes of bicycle ergometry. The mean arterial pressure (MAP), systolic and diastolic blood pressures, skin temperature, rectal temperature, heart rate, forearm blood flow (FBF), plasma angiotensin II and forearm vascular conductance (FVC) were assessed in all the subjects during dynamic exercise and at rest.
Researchers observed increased systolic, diastolic, and mean arterial pressures in the caffeine group during the resting and exercise stages. However, reduced FBF and FVC and elevated serum concentrations of angiotensin II were found in the group given caffeine during the exercise phase. Caffeine had no effect on FVC and FBC in the resting phase and on heart rate, rectal temperature, and skin temperate in both phases. The results of this study reveal that caffeine reduces forearm blood flow and increases blood pressures during dynamic exercise.