Abstract:
Analyses of human patterns of movement have shown that a large number of
daily activities require movement of the head and trunk as a basic component. The
control of postvertebral muscles is obviously of importance in these movements as
well as in the maintenance of posture, particularly that of the head.
Electromyographic evidence in subjects studied by Zuk (1962), Hoogmartens &
Basmajian (1973), Monticelli, Ascani, Salsano & Salsano (1975) and Hoogmartens
& Stuyck (1977) shows that asymmetry of stretch reflexes in spinal muscles may
play a part in the causation and progression of many cases of idiopathic scoliosis.
Spencer & Eccles (1976), Spencer & Zorab (1976) and Spencer (1977) have produced
morphological and histochemical evidence to show that there are relatively more
tonic (Type I) fibres on the convex side of the scoliotic curve than on the concave
side, although it is not clear from their report whether this asymmetry in the distribution
of muscle fibre types is a predisposing factor or a result of idiopathic scoliosis.
Nevertheless, earlier work by Cooper (1960, 1966) showed that long, complex
spindles were particularly numerous in tonic muscles.
