Limb mechanics as a function of speed and gait: a study of functional strains in the radius and tibia of horse and dog.

The study investigates the strain on bones in horses and dogs as they move at different speeds and gaits, suggesting that the skeleton is designed to withstand peak strain without reaching the point of failure.

Research Methodology

• The study involved attaching rosette strain gauges to the midshaft of the radius (forelimb bone) and tibia (hind limb bone) of two horses and two dogs.
• The animals were made to run on a treadmill at varying speeds and gaits, allowing the researchers to measure the strain on the bones throughout the entire speed range.
• A force transducer, a device that converts force into a measurable electrical output, was also attached to the shoes of one horse to record changes in ground load.

Research Findings

• The variations in principal strain (the maximum and minimum strain experienced by an object) on opposite cortices (outer layers) of each bone remained steady during the stance phase of the stride, with an orientation variation of just 14 degrees across all speed ranges.
• The maximum strain rate (the change in strain over time) increased in linear correlation with speed.
• The peak strain (the maximum strain experienced by the bone) was also found to be dependent on the gait used. It increased up to 59% at the transition from walk to trot and decreased by 42% when transitioning from a trot to a canter.
• The changes in peak strain were similar to the changes in ground load recorded by the force transducer on the horse’s shoes.

Implications of the Findings

• The study found that peak strains during vigorous activity are uniformly high across a wide range of animals.
• This implies that the skeleton is built to offer constant safety margins, providing a buffer between peak functional strains and yield strains where structural failure is likely to occur.
• The findings can be beneficial to sports medicine and physiotherapy for both animal and human subjects, providing new insights into anatomical strains during various activities.