The phrase "heels up" is a colloquial term that can have negative connotations, as it may refer to a sexual position or an image of a woman lying on her back with her legs in the air. To avoid using this phrase, one could use synonyms such as "legs in the air" or "feet elevated." Alternatively, one could use phrases like "upside down" or "inverted" to convey the same meaning without the potentially offensive connotations. In professional settings, it is best to use more formal language and avoid using slang or colloquial terms altogether.