Yes, it is called VDrop. When you set your CPU at 1.4V in BIOS and CPU-Z is reporting 1.37V while your PC is idle is VDrop. When you give the CPU full load, CPU-Z should report the voltage even lower, to around 1.33V, this is called VDroop (yes, that's an extra 'o').
If you don't see this VDroop, then probably you have VDroop control enabled in BIOS. It is called Load Line Calibration in BIOS for ASUS mobos, different on other boards. All of these things are normal, no need to be alarmed.