Three-dimensional kinematic and kinetic analysis of quadrupedal walking in the common marmoset (Callithrix jacchus).

The common marmoset has recently gained a great deal of attention as an experimental primate model for biological science and medical research. To use the common marmoset for development of novel treatments and rehabilitation for locomotor disorders, it is crucial to understand fundamental baseline characteristics of locomotion in this species. Therefore, in the present study we performed kinematic and kinetic analyses of quadrupedal locomotion in this animal. A total of 14 common marmosets walking quadrupedally along a walkway were analyzed using synchronized high-speed cameras, with two force platforms set in the walkway. Our results demonstrated that the marmoset uses a lateral sequence walking pattern, in contrast to the macaque and other primates, which usually adopt a diagonal sequence pattern. Furthermore, peak vertical ground reaction force on the forelimb was larger than that on the hindlimb. The rate of energy recovery for quadrupedal walking in the common marmoset was much smaller than that in the macaque, indicating that the marmoset generally utilizes bouncing mechanics in locomotion, even though the duty factor is >0.5. This description of locomotor characteristics of intact marmosets may serve as a basis for comparative analyses of changes in gait due to rehabilitation and regenerative treatments.

Muscle architectural properties in the common marmoset (Callithrix jacchus).

The common marmoset, Callithrix jacchus, is a small New World monkey that has recently gained attention as an important experimental animal model in the field of neuroscience as well in rehabilitative and regenerative medicine. This attention reflects the closer phylogenetic relationship between humans and common marmosets compared to that between humans and other experimental animals. When studying the neuronal mechanism behind various types of neurological motor disorders using the common marmoset, possible differences in muscle parameters (e.g., the force-generating capacity of each of the muscles) between the common marmoset and other animals must be taken into account to permit accurate interpretation of observed motor behavior. Differences in the muscle architectural properties are expected to affect biomechanics, and hence to affect neuronal control of body movements. Therefore, we dissected the forelimbs and hind limbs of two common marmosets, including systematic analysis of the muscle mass, fascicle length, and physiological cross-sectional area (PCSA). Comparisons of the mass fractions and PCSA fractions of the forelimb and hind limb musculature among the common marmoset, human, Japanese macaque, and domestic cat demonstrated that the overall muscle architectural properties of the forelimbs and hind limbs in the common marmoset are very similar to those of the Japanese macaque, a typical quadrupedal primate. However, muscle architectural properties of the common marmoset differ from those of the domestic cat, which has relatively larger hamstrings and pedal digital flexor muscles. Compared to humans, the common marmoset exhibits relatively smaller shoulder protractor, retractor, and abductor muscles and larger elbow extensor and rotator-cuff muscles in the forelimb, and smaller plantarflexor muscles in the hind limb. These differences in the muscle architectural properties must be taken into account when interpreting motor behaviors such as locomotion and arm-reaching movements in the common marmoset.