Field biomechanics: linking muscle energetics to performance and environment

Alan Wilson

Royal Veterinary College, UK

A three axis accelerometer (a type of Inertial Measurement Unit, IMU) enables quantification of movement in frequency and magnitude and from that a summary or classification of movement type and intensity. Adding gyroscopes (and magnetometers) to the IMU enable processing to quantify dynamic changes in IMU orientation and changes or fluctuations in the velocity and displacement of the sensor.  Such an IMU can also be used to infer movement of a point distant from the sensor – for instance the centre of mass of an animal or collar.

GNSS provides location and velocity but GNSS is degraded by acceleration and jerk so fusion of data (and ideally hardware) with an IMU delivers performance benefits especially in environments without clear sky view. Data from tags suitable in size and cost for mounting on animals can be processed to deliver position accuracies of a few centimetres.

I will discuss some of the opportunities and pitfalls with these approaches in the context of our work on the biomechanics of predator and prey interaction in southern Africa. We have used accelerometers and gyroscopes in isolation to describe activity and movement, trigger data logging and also in combination with GNSS to allow high data rate and accurate motion tracking. We have used a variety of data based approaches to estimate athletic performance and  energy consumption and relate them to ecology and muscle physiology.