Every athlete exercises self-control in all things. They do it to receive a perishable wreath, but we an imperishable. So I do not run aimlessly; I do not box as one beating the air. But I discipline my body and keep it under control, lest after preaching to others I myself should be disqualified. – 1 Corinthians 9:25-27
Paul changes the metaphor from the runner to the boxer. Old verb (only here in N.T.) from πυκτης (pugilist) and that from πυγμη (fist). See on Mr 7:3). As not beating the air (ως ουκ αερα δερων). A boxer did this when practising without an adversary (cf. doing "the daily dozen") and this was called "shadow-fighting" (σκιαμαχια). He smote something more solid than air. Probably ου negatives αερα, though it still occurs with the participle as a strong and positive negative.