I suppose you know you can turn into superwoman or superman in an emergency. Mrs Pam Weldon reported that her baby nearly slipped under the wheels of a car. Mrs Weldon weighs only 50 kilos, but she said she lifted the car to save her baby. Dr Murray Watson, a zoologist, wrote that he jumped nearly three metres into the air to grab the lowest branch of a tree when hyenas chased him in Kenya. Perhaps you wonder if you can perform such feats. The chances are that you can. Doctors say that we can find great reserves of strength when we are afraid. It's well-known that adrenalin can turn us into superwomen or supermen!
Source: Longman English grammar practice, L. G. Alexander, Page 11
I looked up both superman and superwoman in many dictionaries and they all know them as countable nouns. Shouldn't there be an a before superwoman in the first line:
I suppose you know you can turn into a superwoman or superman in an emergency.