ECG test or electrocardiogram test has nothing to do with
hair. Its testing heartbeat to check if you got heart problem.
Possible types of testing include using the suction cups and
threadmill but I don't recall that as a requirement for NS callup.
Maybe things have changed.
I haven't heard of anyone sent back due to inappropriate
attire/looks yet (but my experience is limited to medical centre)
esp if pre-NS.
If not sure, call up NS hotline: 1800-3676767.