If you're looking for synonyms for the phrase "second wind," there are a variety of alternatives you can use depending on the context. For instance, you could use "renewed vigor" to describe the feeling of getting a burst of energy when you might have otherwise felt tired or worn out. "Resurgence" also works well when describing a moment of renewed strength or momentum. "Renewed energy" is another option that conveys a sense of fresh motivation or enthusiasm. Other phrases like "sustained effort" or "continued push" can also capture the idea of finding renewed energy to keep going.