The phrase "upright posture" means sitting or standing in a straight and balanced position, with your spine and body aligned vertically. Full definition
If you find yourself leaning forward and pushing the stroller with straight arms, eyes down, take a brief rest and resume pushing with upright posture and a strong core. (momstown.ca)
They are crucial for maintaining proper upright posture, and provide support in activities such as walking, jumping and running. (fitnessandpower.com)
But this new upright posture posed a problem for pregnant women. (sciencemag.org)