Meeting Abstract
Walking in animals and birds is commonly modeled as an inverted pendulum, while running is often modeled as a spring loaded inverted pendulum. The dynamics of both systems are dependent on the length of the pendulum, which corresponds to the hip height of the animal, and the gravitational acceleration experienced by the centre of mass. Manipulation of an animal’s gravitational environment therefore enables investigation of the fundamental principles behind walking and running, as well as informing related topics such as scaling. We have used a centrifuge to expose five female FVB mice to varying levels of hypergravity, and measured a number of biomechanical parameters, including preferred speed, running intermittency and stance and stride times.
The centrifuge has an overall diameter of 4m and has four arms, each of which carries a gondola. Inside each gondola is a standard mouse cage outfitted with an instrumented exercise wheel, and a Basler acA2000-165umNIR infra-red high speed camera capable of filming both in light and dark conditions, along with instruments to continuously monitor welfare and environmental conditions. Hall sensors are used to measure the deflection of pads on the exercise wheel, allowing vertical ground reaction forces (GRF) to be determined. Recordings of GRF and speed, as well as high speed video at 200Hz are triggered automatically when mice run on the wheel; this allows us to study how mice adapt their posture, gait and behavior in response to the increase in gravity, and hence provides empirical data for testing the predictions made by pendulum models of legged locomotion.
