Sagittal spine movements of small therian mammals during asymmetrical gaits

Abstract

SUMMARY Mammalian locomotion is characterized by the use of asymmetrical gaits associated with extensive flexions and extensions of the body axis. Although the impact of sagittal spine movements on locomotion is well known, little information is available on the kinematics of spinal motion. Intervertebral joint movements were studied in two metatherian and three eutherian species during the gallop and halfbound using high-speed cineradiography. Fast-Fourier transformation was used to filter out high frequency digitizing errors and keep the lower frequency sinusoid oscillations that characterize the intervertebral angular movements. Independent of their regional classification as thoracic or lumbar vertebrae, 7±1 presacral intervertebral joints were involved in sagittal bending movements. In only one species, no more than five intervertebral joints contributed to the resulting `pelvic movement'. In general, the trunk region involved in sagittal bending during locomotion did not correspond to the traditional subdivisions of the vertebral column (e.g. as thoracic and lumbar or pre- and postdiaphragmatic region). Therefore, these classifications do not predict the regions involved in spinal oscillations during locomotion. Independent of the gait, maximum flexion of the spine was observed in the interval between the last third of the swing phase and touch-down. This results in a retraction of the pelvis and hindlimbs before touch-down and, we hypothesize, enhances the stability of the system. Maximum extension occurred during the first third of the swing phase (i.e. after lift-off) in all species. In general, the observed timing of dorsoventral oscillations of the spine are in accordance with that observed in other mammals and with activity data of respiratory and epaxial back muscles. Although no strict craniocaudal pattern was observable, the more cranial intervertebral joints tend to flex and extend earlier than the more caudal ones. This is in accordance with the organization and the activation of the paravertebral musculature in mammals. The amplitude of intervertebral joint movements increased caudally, reaching its highest values in the presacral joint. The more intense sagittal bending movements in the caudal intervertebral joints are reflected by the muscle fiber type composition of the back muscles involved. Despite the highly similar amplitude of `pelvic motion', touch-down and lift-off positions of the pelvis were clearly different between the species with a long, external tail and those with no external tail.

New insights on equid locomotor evolution from the lumbar region of fossil horses

“…The use of sagittal bending of the spine during fast running gaits is a distinctive mammalian feature [4,5]. However, several groups of large-bodied ungulates have secondarily lost this sagittal mobility in favour of a stiff-backed (dorsostable) running gait, of which horses are the best-known example [3,19].…”

Distribution Pattern of Muscle Fiber Types in the Perivertebral Musculature of Two Different Sized Species of Mice

“…This region of the trunk was chosen because the posterior thoracic and the lumbar part were shown to play a significant role during fast locomotion in small mammals (Schilling and Hackert, 2006). The region comprises the subvertebral muscles completely, with the most cranial slips of the m. quadratus lumborum inserting onto T12 and T12/13, respectively.…”

“…Thus, the musculature of the pika becomes increasingly more Type IIB dominated toward the pelvis. This was interpreted with respect to the preferred use of asymmetrical gaits in this lagomorph and the caudad increasing importance of sagittal bending in body propulsion (Schilling, 2005;Schilling and Hackert, 2006). In contrast, the laboratory mouse prefers symmetrical gaits such as walk and trot and the harvest mouse climbs along stalks primarily using its limbs in an alternating sequence (Frank, 1957;Nowak, 1999;Clarke and Still, 1999;Herbin et al, 2004).…”

“…In contrast, the laboratory mouse prefers symmetrical gaits such as walk and trot and the harvest mouse climbs along stalks primarily using its limbs in an alternating sequence (Frank, 1957;Nowak, 1999;Clarke and Still, 1999;Herbin et al, 2004). In contrast to the intense dorso-ventral motions of the spine during asymmetrical gaits (Hildebrand, 1959(Hildebrand, , 1974Gambaryan, 1974;Schilling and Hackert, 2006), vertebral column movements are much less pronounced during symmetrical gaits and concern the horizontal and the transversal body planes only (Jenkins and Camazine, 1977;Schilling and Fischer, 1999). The preference for symmetrical gaits may thus be reflected by the smaller glycolytic fraction in the cross section of the perivertebral muscles of both mice, particularly in the more caudal parts of the trunk leaving an overall higher oxidative potential of the perivertebral musculature.…”

Empirical validation of a spined sagittal-plane quadrupedal model

“…The biological literature on core actuation offers several careful studies regarding its low-level mechanics [3], [4], [5] and its proposed role as a mechanical energy storage in gaits [6]. To the best of the authors' knowledge, however, there is a lack of work concerning biological templates [7] of core actuation.…”