The Krayzie Midwinter Backyard Ultra is a last-person-standing ultramarathon held at Spencer Park in Christchurch. Participants run or walk one 6.706 km lap each hour. Anyone not finishing the lap within the hour is eliminated.
The format emphasizes pacing and recovery alongside speed. Completing a lap quickly provides more time for food, hydration, gear changes, or rest before the next start. This is a self-supported event, meaning participants provide their own food and fluids. The race concludes when a single runner completes one more lap than all other competitors.