If your child is prone to have tight muscles (they may have been diagnosed with hypertonia - high tone, or a condition that includes high tone), W sitting is that much more stressful and detrimental to your child's joints. (day2dayparenting.com)
Neurologically, the primary features seen most often and most evidently in infants were alterations in motor activity, reflected in body tone, posture and motility or movement; severe hypertonia (abnormal muscle tension and contraction); abnormal neurobehaviors, such as poor or delayed response to visual stimuli, and excitability. (sciencedaily.com)
It may be possible to elicit mild hypertonia and hyperreflexia in the limbs on one side. (lowchensaustralia.com)