Given a category and a set of five words, find the word from the set that does not belong (i.e. is the least relevant) with the other words in the category. Words are separated by commas.

Category: physical activity 
Words: sprint, cow, duck, jog, squat
cow

Category: boxing terminology 
Words: ring, lifeline, jab, deck, knockout
lifeline

Category: food 
Words: frank, wienerwurst, pork, sausage, courage

courage