Hopefully he didn't mean an EKG, an electrocardiogram which measures the electrical activity of the heart<>.  When one gets off RA status and is joining the Reserves or entering a program of their choice or is selected, sometimes an EKG is required in the form of  a required physical or the member is due for an over-40 physical which includes persons who are 39.  The test would be needed to monitor the heart rate to determine if the member is physically cable of withstanding and enduring physical activities or has developed any heart complications.