Effect of moderate exercise-induced heat stress on carotid wave intensity. 
Exercise disrupts the interaction between the left ventricle and the vasculature, as measured by wave intensity (WI) analysis.  However, the effect of exercise-induced heat stress on WI amplitude is unknown.  WI measures are calibrated using brachial or carotid artery blood pressure, but the influence of calibration method on WI outcomes is unknown. ( 1) To compare WI analysis during low and moderate exercise-induced heat stress; (2) to examine differences in carotid WI analysis based on calibration method.  Eleven healthy, young men (22 ± 3 years) performed intermittent exercise in moderate- and low-heat stress conditions.  WI was assessed pre- and post-exercise on the right carotid artery, and calibrated with brachial and carotid blood pressures.  A main effect of time was found for W1 when calibrated by brachial, but not carotid pressure.  A time-by-condition interaction was observed for late systolic/early diastolic function (W2) in both brachial (p = 0.047) and carotid calibration methods (p = 0.042), where W2 increased following exercise-induced moderate-heat stress but decreased following low-heat stress.  The elastic modulus exhibited a significant time-by-condition interaction (brachial p = 0.039; carotid p = 0.044), increasing following moderate-heat stress but decreasing following low-heat stress.  Calibrations using carotid blood pressure significantly reduced WI amplitudes compared with brachial calibrations (p < 0.001).  Arterial-ventricular coupling is affected in different ways following moderate and low exercise-induced heat stress.  Wave amplitudes were lower (~13 %) following carotid calibration compared with brachial.