Thermodynamics of Animal Locomotion.

The study explains how horses manage and optimize their energy consumption during different phases of movement, using a thermodynamic model that considers the muscles as an assembly of energy-converters working in sync.

Research Objective

• The researchers aimed to understand the thermodynamic principle of how living organisms, specifically horses, optimize their energy cost during different gaits. They considered muscles as parallel-connected actuators that convert chemical energy to mechanical energy.

Methods

• The study employed Hill’s classic empirical model, which perceives muscles as separate biomechanical entities. This approach, however, was augmented with considerations for physiological and environmental constraints that a living organism encounters.
• The energy cost of effort was introduced, which speaks to the generalization of the known oxygen cost of transport. The horse’s oxygen consumption was measured during a transaction experiment to provide data regarding energy cost management.

Results

• The researchers found that horses adapt to a particular gait by a nearly constant number of muscle units, which minimizes waste production per unit distance covered. On changing their gait, this number changes significantly.
• The study establishes that the mechanical function of an animal is determined by its own thermodynamic characteristics and by the metabolic operating point of the locomotor system. This means that the horse’s locomotion efficiency depends on both its internal physiological mechanisms and the energy requirements of the specific gait.

Significance

• This research is significant because it provides an overarching thermodynamic principle about how living organisms manage their energy cost. This understanding could be useful in various fields, like sports science and veterinary medicine, where optimized energy expenditure is vital.
• The findings may also have implications for designing bio-inspired machines or robots, helping to improve their efficiency by mimicking the energy optimization methods used by living organisms.