11.2 Postural discomfort

In ergonomic practice, standards and methods such as ISO 11226, EN 1005-4, RULA, and REBA43F¹ provide criteria for assessing the acceptability of particular postures and prioritizing preventive intervention. They classify angular deviations into intervals and, depending on the method, combine them with factors such as posture duration, muscle use, applied force or load, and coupling quality. The result is usually expressed through discrete risk categories or scores. These procedures are not designed to provide a continuous assessment for every degree of angular variation, nor do they consider every possible joint degree of freedom.

By contrast, postural discomfort refers to the subjective (perceptual) sensation of discomfort associated with a joint posture, especially when it is maintained under static conditions. It is interpreted as a psychophysical outcome: when joint configurations move away from the neutral or preferred zone, people tend to report less comfort even if the instantaneous mechanical demand (e.g., joint moment) is low.