Jamieson, Fausset and Brown on 1 Corinthians 9:25

25. striveth--in wrestling: a still more severe contest than the foot race.

is temperate--So Paul exercised self-denial, abstaining from claiming sustenance for the sake of the "reward," namely, to "gain the more" (1Co 9:18, 19).

corruptible--soon withering, as being only of fir leaves taken from the fir groves which surrounded the Isthmian race course or stadium.

incorruptible--(1Pe 1:4; 5:4; Re 2:10). "Crown" here is not that of a king (which is expressed by a different Greek word, namely, "diadem"), but a wreath or garland.