Torque patterns of the limbs of small therian mammals during locomotion on flat ground.

This research article investigates the forces and torques at work in the limbs of three small therian mammal species during locomotion. The researchers used inverse dynamic analysis to determine these mechanical properties at various joints in the forelimbs and hindlimbs.

Methodology

• The researchers studied three species of small therian mammals: Tupaia glis, a scandentia; Galea musteloides, a rodent; and Ochotona rufescens, a lagomorph.
• They analyzed four kinematically relevant joints in the forelimbs and hindlimbs: the scapular pivot, shoulder joint, elbow joint, wrist joint in the forelimbs, and the hip joint, knee joint, ankle joint, intratarsal joint in the hindlimbs.
• The forces and torques acting on these joints during the stance phase of locomotion were studied using inverse dynamic analysis.
• Their movements were captured via cineradiography at 150 frames per second. Simultaneously, the ground reaction forces were measured using forceplates.
• The morphology of the limbs was studied using a scanning method that utilized structured illumination.

Findings

• The joint force vector is largely accounted for by the vector sum of the ground reaction forces and the mammals’ weight.
• Inertial effects on net joint forces are minimal, with errors amounting to at most 10%.
• The researchers found similar joint torque patterns across all three species in all the forelimb joints and the ankle joint.
• Differences appeared in the intratarsal joint torques between mammals with tails and those without.
• The torque patterns in the knee and hip joints were found to be unique to each species.
• This is the first study that provides a comprehensive description of torque patterns in the forelimbs, giving special attention to the role of the scapula as the dominant propulsive segment.
• The study’s findings are compared with the sparse existing torque data for various joints in cats, dogs, goats, and horses.

Significance

• This comprehensive study provides valuable insights into the biomechanics of small mammal locomotion, offering a detailed understanding of the torques and forces at work in their limb joints.
• The findings could be useful in the field of biomechanics, providing a basis for understanding the dynamics of movement in animals and potentially inspiring designs in robotics and prosthetics.