The idea our bodies operate as a whole i.e. head, intestines and limbs, dates back to Antiquity. In the fables of Aesop, he reminds people, "limbs" must be co-operated with the head (or Senate). Romans believed the head contained the soul which in turn directed the body. The innards which processed food and nourished the whole body were regarded as the seat of passions with the liver given the same emphasis as the heart is today. The body metaphor was eagerly adopted by Christians and the Church became the body, with believers as "multiple limbs" of which Christ was the head. The "mystic body of Christ" was also central to followers and remains so today in Holy Communion.
As the Christian empire evolved the importance of the pope and king became more prominent as heads and the heart became the seat of vital forces. St. Bernard's 12th century Sacred Heart of Jesus developed into a major theme by the 17th century. The innards, especially the liver, lost its importance and became the "seat of lewdness". Political Body metaphors were frequent in texts that debated the status of clergy and nobility. One that favours the clergy in 11th century called it the eyes, and secular power the limbs. John of Salisbury (12th century) makes the prince the head, and his officials the eyes etc., with peasants as the feet, indispensable but requiring support from above. Wealth-producing activities had an ambiguous place in the intestines.
From the 13th century violent conflict, usually involving religious wars were viewed by both sides in terms of “heart and hand” fighting for mortal head of their Church i.e. King or Pope. Later what mattered was not the physiological unity of the body but separation of the spiritual from the temporal.
Fashionable men of the 14th Century wore poulaines, long toed shoes often 24 inches longer than the feet themselves, and adopted a high stepping, stomping gait similar to the staccato movement of a puppet. This was considered as style and copied slavishly. There is no evidence to support our forefathers were aware of deliberate muscular activity and its balancing function nor was the knowledge of anatomical analysis of movement and posture possible at a time when dissection was considered taboo.
From the Middle Ages to the 16th century, "failures of physical uprightness" were attributed to deformity or bad deportment. Good posture meant esteem and in the 16th century a new class of courtiers, paid greater attention to deportment. Physical appearance became synonymous with moral attitudes and bad body attitudes, was thought to cause physical deformities. Clothing became more rigid as a result and imposed a standard form. Contemporary text on deportment characterised the best as natural and stressed "grace," which was defined as the opposite of affectation. Aristocrats were thought to emulate grace and in the Judo-Christian belief, regarded as godlike, i.e. ‘made in the image of the maker.’ The elite of society spent long periods of preparation learning gracefulness with noble exercises like fencing, riding, and dancing.
Apart from the practicalities of defence, the movements of fencing, which were circular, was a "Pythagorean" concept of geometry with no regard for bone or muscle structure. Movement was not a way to correct posture and the body was regarded merely as the outline of a surface.
The origins of corsetry, as support for deportment, date from the 16th century. Adult corsets appeared with whalebone stays for aesthetics or metal stays for therapeutics. In 17th century a new morality based on civility and propriety demanded that one "cut a fine figure," with the public as judge, and emphasis on posture grew. Acceptance the body could be manipulated became a specific focus and the orthopaedic approach (straightening) a distinct discipline especially in children. Acceptance children were not small adults, but developing skeletons, lent physicians to develop manipulation. Even well-formed children were manipulated by hand or with swaddling clothes as a preventative measure to deformity.
Manners become theatrical and the aim of exercise (dance, etc.) was to control movement, but not benefit from it. Since the body was no longer a microcosm, it no longer had to follow ideal proportions. Now the motive (often disguised with religious rationales) was to avoid ridicule.
In Jesuit schools, bulwarked against secular education, public speaking became important to teach the code of performance. Jesuits in 17th century schools encouraged plays to teach control and memory, elegance (with ballet) and decorum.
Muscular Christianity and physical culture of the last four centuries have ensured the same curriculum has been maintained throughout and still forms part of our modern education in Western Society.