Performance Context
“Flattened out” describes a situation where a horse looks like it’s going to emerge as the winner, driving right up alongside the leaders, but just doesn’t have enough to go by. The horse appears to be making a winning move but then fails to sustain the effort and cannot complete the pass.
When a horse “flattens out,” it slows considerably while dropping its head on a straight line with its body. This physical posture indicates the horse is very tired and struggling to maintain its racing effort. The horse’s natural head carriage becomes lowered as fatigue sets in during the late stages of a race.
This term is more severe than “weakened” but less drastic than “stopped” in racing commentary. It indicates that while the horse made an effort, it lacked the stamina or energy reserves needed to finish strongly. Some horses naturally run with their heads lowered as a running style, so context is important when interpreting this term in race charts and past performances.