What does it mean when a dog sleeps on its back with all four legs up?

Usually, a dog's sleeping position is determined by comfort. If a dog sleeps on its back with all four legs up, it means that the dog trusts its owner very much and enjoys being with them, showing a sense of security. If the dog is uncomfortable, its sleeping position may be curled up or lying on its side, with accelerated and rapid breathing, severe body tremors during abdominal pain, refusing to let the owner touch it, which is exactly the opposite of sleeping on its back.

There are several reasons why a dog is willing to sleep on its back:

Firstly, when a dog has no defense or suspicion towards its owner, it will sleep on its back. Pet dogs that live in their own homes do so because they have been with their owners since they were young, and they are completely relaxed in the familiar environment. Therefore, they drop their guard and are willing to expose their most vulnerable belly.
Secondly, dogs are afraid of heat in summer. They usually lie down on the floor or sleep on their backs with their tongues hanging out, taking big breaths. Since dogs don't have sweat glands, they can only sweat through their tongues to lower their body temperature. Sleeping on their backs also helps them to cool off, which is a way for dogs to survive summer.
When the owner comes home, the dog suddenly rushes towards them, rubs its body against their legs, and then lies on its back, twisting and turning. This shows the dog's intimacy and enthusiasm for its owner, wanting to be stroked on its belly to please them.

Careful owners will find that if the dog is uncomfortable, its sleeping position is likely to be curled up or lying on its side, with accelerated and rapid breathing, severe body tremors during abdominal pain, refusing to let the owner touch it, and often making whining sounds. The dog will be restless, uneasy, and keep changing its sleeping position. At this time, observers should look for any other symptoms in the dog besides its sleeping position. If there are other symptoms, it is recommended to take the dog to a pet hospital for inspection as soon as possible.