ABSTRACT
Whereas in engineering, the term ‘fl exibility’ refers to deformation characteristics of (bio)materials resulting from external load - ing, in kinanthropometry, ‘fl exibility’ basically refers to the ability of being supple, and generally focuses on the range of motion of a particular joint or joint unit. However, reaching a particular range of motion is dependent not only on the degrees of freedom provided by synovial joints, but also the mechanical properties of a number of involved tissues. Spinal motion is determined not only by the architecture of the facet joints and the
directly involved capsuloligamentous system, but also by the properties of the adjacent intervertebral discs, representing cartilaginous joints of the symphysis type, and by the long ligaments, representing fi brous junctions of the syndesmosis type between the vertebrae. In the spine, synovial joints, symphyses and syndesmoses are arranged in parallel within one single motion segment while acting in a serial arrangement throughout the entire spinal region. In this way, muscular action continuously trims the complex osteofi brous tunnels of the central spinal canal and the intervertebral foramina, allowing for movement and deformation of the spine, without loss of the main confi guration of these neurovascular tunnels (Van Roy et al. 2000). Thus, range of motion is often provided by the interaction of several joints or junctions. On the other hand, the limits of motion in a particular joint or joint unit are determined by the mechanical properties of a number of surrounding tissues.
