The shape of the spine in young males with and without back complaints.

Twenty-one young male subjects without back complaints (group I) and 21 young males with back complaints (group II) were investigated in the easy standing position with the inclinometric method(1). By means of EMG recordings from the trunk muscles each of the two groups were divided into two subgroups: one (the largest) which maintained standing posture by activity in the back muscles, and another which did it by activity in the abdominal muscles. It was found that: 1) subjects with active abdominal muscles in group I had a more pronounced thoracic kyphosis and lumbar lordosis than the other three subgroups, 2) subjects with active abdominal muscles in group II had a smaller pelvic inclination than the other three subgroups, 3) the forward inclination of the trunk was greatest in subgroups with active back muscles. It is concluded that compared to the subgroups without back complaints and active back muscles, subjects without back complaints and active abdominal muscles maintain the static equilibrium of the spine in easy standing by adjustment of the inclinations of the spine segments above the maximal lordosis, while in the corresponding subgroup with back complaints the adjustments are mainly made by a change of the pelvic inclination.