Block Run is the third obstacle in the Atlanta Qualifying. Competitors would have to run across 5 tilted cubes on a horizontal pole that roll and slide under the competitors feet that was narrowly touching the water so those who slipped too much would have their feet hit the water. The casualty rate was decent but nothing major.
In Atlanta Finals, the middle block was removed. While it didn't take out any competitors, many ninjas did stumble and for some, it affected their performance later on
This obstacle was brought back as the fourth obstacle on the Los Angeles course. The numbers of blocks have increased by 1 making a total of 6, and each block has a different size. This obstacle took out 13 competitors in the qualifiers, including veterans Brian Kretsch and Ben Melick.