To show how seriously the Corinthians must take their salvation, Paul refers to the Isthmian games, a well-known athletic event held in Corinth every two years.
Everyone who competes in the games trains with strict discipline: Athletes must have strict self-discipline to compete for a prize. In Paul's time, athletes trained rigorously for months before competing. Similarly, strict self-discipline (see Galatians 5:22–23) is needed to achieve the eternal prize of salvation. Christians must follow the daily discipline of obeying Christ.
for a crown that is perishable: Athletic prizes were often wreaths made of laurel leaves (see 2 Timothy 4:8; James 1:12; 1 Peter 5:4; Revelation 2:10).