biomechanics 101

Biomechanics 101

The goal of a Mobility Dog partnership is moving together – synchronized and balanced. A dog’s center of gravity is totally different from a human’s, and it shifts forward when in motion.

To perform mobility assistance efficiently, the center of mass for both the dog and the person need to coordinate. Here’s a brief overview of the physics of biomechanics and how the dog’s relative position changes depending on the task being performed. An appropriately designed harness is required to properly distribute the forces required for balance and pulling support. Learn more about harnesses here.

Center of Mass (COM)

aka center of gravity

The closer a load is to the center of mass (COM), the less work is required to perform a task

The green star in the following diagrams represents the approximate center of mass (COM). A human’s center is at the pelvis, a dog’s is in the middle of their torso.

Heel

In a formal heel position while standing or in motion, the person’s hip is aligned to the dog’s neck
Note that the dog’s COM is behind the human’s
Mobility assistance cannot be performed in this position
MDRG does not recommend training a “formal heeling position,” or an “automatic sit” because a dog cannot offer support in these positions

General position for standing or walking together

Person’s hip is aligned to: Dog’s girth line
COM are aligned vertically
Dog can maintain light contact or offer counterbalance the person via the harness handle
Pulling up on the harness handle provides support by balancing opposing forces

Momentum Pulling

Person’s hip is aligned to: Dog’s flank
COM are connected with light tension on the harness handle
Dog pulls into the harness to offer support, leading the person forward to maintain momentum and stabilize the gait
When biomechanically aligned, the dog’s mass does most of the work and the team moves together as a unit

Guide

Person’s hip is aligned to: Dog’s pelvis
Dog provides directional assistance via tha harness handle
Needs to be further ahead to allow for reaction time
Dog can manuver, turn, and halt without tripping their person

Diagrams shown with permission of Bold Lead Designs

biomechanics 101