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Why do cheetahs and greyhounds have a no-contact phase during fast running?

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Least tern, Sternula antillarum, flying with wings raised and its yellow-tipped black bill pointed forward. — Locomotion These birds largely reside in coastal areas of North America, although some populations live in the continent's interior along large rivers.

The premise that cheetahs and greyhounds have a no-contact phase following hind foot contact is a specific characteristic of their high-speed gallop.

In terrestrial locomotion, the fastest runners utilize asymmetrical gaits to achieve maximum velocity. During a gallop, an animal is supported by no more than two legs at any given time, and there are moments when the animal is supported by none at all. For specialized cursorial mammals like cheetahs and greyhounds, this no-contact phase—often referred to as a suspension phase—occurs as part of the stride cycle to maximize stride length and efficiency at high speeds.1

By spending time in the air, these animals effectively extend their reach beyond what would be possible if they maintained constant ground contact, allowing for the rapid, powerful movements required for their hunting and racing capabilities.21