Sleep in a chair, or support your body with pillows.
If you have an adjustable bed you can use that function also.
upright position
Kidneys in cats are usually lower than in humans because humans are taller and walk upright.
The tendons in the human rectus abdominis act as focal points for muscle contraction, providing stability and support to the torso during upright posture. They help maintain proper spinal alignment and distribute forces evenly throughout the core muscles to prevent excessive strain on the spine. Their presence contributes to the overall strength and functionality of the abdominal muscles in supporting the body's upright position.
human muscles are meant to maintain posture in upright position walking on 2 feet; cat muscles function to walk on 4 paws
When the human body is in the standard anatomical position it is upright, erect on two legs, facing frontward, with the arms at the sides each rotated so that the palms of the hands turn forward.
Homo erectus
The position of the forearm magnum on the skull of Australopithecus africanus indicated to Raymond Dart that the spinal cord entered the skull from below, similar to humans, suggesting they walked upright. This helped provide evidence for the theory that Australopithecus was a bipedal hominin.
An alternate term for Homo erectus is "upright man" or "upright human."
Homo erectus
The only non-human primates without a tail are the great apes and regular apes such as gibbons . Of them the only one that walks upright all of the time is a Human. So the answer to your question is a Human. The other great apes can walk upright, but they do so only for short periods of time when needed.
Homo erectus
The anatomic position is a standardized way of describing the human body, standing upright with arms at the sides, palms facing forward. This position serves as a reference point for describing the location of body parts and helps avoid confusion in medical and scientific fields where precise terminology is crucial.