Some people seem unable to stand completely upright for long. At a party, in a queue, at a metro station or while talking to someone, they quickly find a wall, pillar, table or railing and lean against it. Even while sitting, they may constantly shift position, slouch or look for something behind their back.
It can look like laziness or poor posture, but psychology and research on postural control suggest a more complicated explanation. Standing upright is not actually effortless. The body continuously makes tiny adjustments to keep the centre of mass within a stable base of support. When muscles become tired, maintaining that position can become more demanding. Studies have found that increasing muscular fatigue can increase postural sway during quiet standing.
