WordNet records no synonym and no antonym for second wind. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
renewed energy or strength to continue an undertaking
“She had dinner and got a second wind to finish painting”
the return of relatively easy breathing after initial exhaustion during continuous exertion
Synonyms, antonyms and the broader and narrower relations for second wind come from Princeton University’s WordNet. Full sources and licences.