The 'backyard ultras' are a relatively recent competition, originating in 2011, that tests participants' endurance capacity. It involves completing a 6.7-kilometer loop every hour, non-stop, until only one runner remains active. This event, which can extend for over 100 hours, demands extraordinary physical and mental preparation.

The complexity of this format lies in the impossibility of training for the exact race conditions, as it involves running without rest and managing aspects such as nutrition, hydration, and equipment in real-time. Oriol Antolí, one of the few athletes capable of facing this challenge, shares his experience and the motivations that lead him to participate in these ultra-endurance events.

In addition to the history of 'backyard ultras', the episode also explores the origins of the 24-hour ultra-endurance event in Barcelona and how this competition modality began to gain popularity in the United States.