The antonyms for the phrase "lays back" can vary depending on the context. However, some of the common antonyms include "sits up," "stands straight," "stays alert," "remains focused," and "acts promptly." These antonyms suggest an active and alert state, as opposed to the laid-back and relaxed state implied by the original phrase. Depending on the situation, it may be more appropriate to use one of these antonyms to communicate a sense of urgency or attentiveness. Antonyms are a useful tool in language to help convey a different meaning than that portrayed by the original word or phrase.