When describing someone who puts in extra effort or spends additional time to complete a task, "works overtime" is a common phrase used. However, there are numerous synonyms that can be used to express the same idea in different ways. Some words to consider include "exerts oneself," "redoubles one's efforts,' "goes the extra mile," "puts in extra shifts," "burns the midnight oil," or "puts in extra hours." Each phrase suggests that someone is working hard, dedicating themselves to achieving a goal, and putting in additional effort that is not typically required. By using these synonyms, you can add a bit of variation and nuance to your language and express your message in a more compelling manner.