Exercise elevates shear stress (SS) in the supplying conduit artery. Although this is the most relevant physiological stimulus for flow mediated dilation (FMD), the fluctuating pattern of shear that occurs may influence the shear stress-FMD stimulus-response relationship. This study tested the hypothesis that the brachial artery FMD response to a step increase in shear is influenced by the fluctuating characteristics of the stimulus as evoked by forearm exercise. In 16 healthy subjects we examined FMD responses to step increases in shear rate in 3 conditions: FH_Stable - stable shear upstream of heat-induced forearm vasodilation; FH_Fluctuating - fluctuating shear upstream of heat-induced forearm vasodilation and rhythmic forearm cuff inflation/deflation; FE_StepIncrease - fluctuating shear upstream of exercise-induced forearm vasodilation. The mean increase in shear rate (±SD) was the same in all trials (FH_Fluctuating : 51.69 ±15.70 s^-1; FH_Stable : 52.16 ±14.10 s^-1; FE_StepIncrease : 50.14 ±13.03 s^-1 P=0.131). However the FH_Fluctuating and FE_StepIncrease trials resulted in a fluctuating SS stimulus with rhythmic high and low shear periods that were 96.18± 24.54 s^-1 and 11.80 ±7.30 s^-1 respectively. The initial phase of FMD (phase I) was followed by a second, delayed onset FMD and was not different between conditions (phase I: FH_Fluctuating : 5.63 ±2.15%; FH_Stable : 5.33 ±1.85%; FE_StepIncrease : 5.30 ±2.03%; End-trial: FH_Fluctuating : 7.76 ±3.40%; FH_Stable : 7.00 ±3.03%; FE_StepIncrease : 6.68± 3.04% P=0.196). Phase I speed also did not differ (P=0.685). In conclusion the endothelium transduced the mean shear when exposed to shear fluctuations created by a typical handgrip protocol. Muscle activation did not alter the FMD response. Forearm exercise may provide a viable technique to investigate brachial artery FMD in humans.