When faced with the final lap, the runner had to dig down deep to find the strength to finish.
Когда настал заключительный круг, бегуну пришлось найти в себе силы, чтобы добежать до финиша.
Definitions
To make a great effort to find inner strength, determination, or resources, especially in a difficult situation; to search within oneself for extra motivation or resilience.