Vladimir Janda identified upper and lower cross syndromes, where specific musculature becomes tight (overactive) and other musculature becomes weak (underactive).

“professor yonda he had a keen sense of observation and he formulated um concepts and principles that tied into postural postural habituation specifically the tendency for specific musculature to tend towards tightness and other musculature to tend towards weakness and he he termed this upper cross and lower cross syndrome”