Unstable Bridge ~ Sasuke Ninja Warrior

The Unstable Bridge (アンステーブルブリッジ) is a Second Stage obstacle that was added to SASUKE 23 course replacing the Swing Ladder as the fourth obstacle. It became the third obstacle in SASUKE 24 with the Stick Slider's removal. The obstacle featured two wooden planks to swing from. Both planks measure 60cm wide and 1.8m long. The first one would hang by four metal chains, held by one in each corner. The second plank would hang from only 2 metal chains, each down the center of the plank, one at each end. This would force the plank to easily lop-side to either the left or right side if the contestant either did not transfer from the first plank correctly, or if they lost their balance while maneuvering across to the other end. Similar to the Delta Bridge, a competitor must hold onto to both sides while crossing. While crossing the first plank, competitors must use momentum to reach the second plank. On the second plank, competitors must reach the other side while keeping both ends even.

This obstacle proved to be much harder than the Swing Ladder. Although the obstacle can be beaten by those who take their time on it, like many other Second Stage obstacles, the timer forces people to rush through, causing many failures. In its first tournament, it eliminated American qualifiers Richard King (who failed the transition to the second plank) and Brian Orosco (who failed trying to reach for the ending platform) and SASUKE 22 finalist Urushihara Yuuji (who lost his balance when reaching the other side).

From SASUKE 24 forward it was placed as the third obstacle, replacing the Stick Slider and immediately following the Salmon Ladder. The obstacle's previous position as the fourth obstacle was taken by the Balance Tank.

The obstacle was also used in American Ninja Warrior 3 as the eighth obstacle immediately following the Salmon Ladder.

For SASUKE RISING, the obstacle was placed after the new Swap Salmon Ladder, but the second board was taken out. Only the four-chained board remained. This version proved to be much easier as no competitors failed or even showed signs of struggling.