A breakfall is a movement preformed to prevent one from injuring themselves when landing. The most commonly used breakfall in parkour is the roll. A roll is very useful in that it dissipates energy but allows the traceur to quickly get back up on their feet; however, rolls require forward momentum, making them useless when falling straight down. If a roll cannot be used, the best way to land is to make use of the martial arts "slap" (commonly seen in Judo, Aikido and Hapkido) to absorb the impact.