Is it okay to say ”arm wrestling” instead? Is ”arm wrestle” a more common expression?
Both the word "arm wrestle" and "arm wrestling" are correct. "Arm wrestle" is the simple present verb for the term, as well as being the acceptable noun. "Arm wrestled" would be the acceptable past tense, unless used in a question form with "did". "Arm wrestling", however is present participle verb and gerund to show the ongoing act. Therefore changing this statement to "arm wrestling" would sound a little bit strange. Ex: Why are they arm wrestling? Ex: Why did they arm wrestle? Ex: They arm wrestled? Ex: I will arm wrestle you and win.