New research is looking at how the pattern of muscle activity changes to produce the altered gait seen in lame horses.
Lameness is a common reason for veterinary examination. Current diagnostic methods rely heavily on subjective assessment, including observing how the horse shifts weight between legs at rest and when moving. More subtle changes in gait can be detected using kinematic gait analysis.
To date, interest has concentrated on the changes in gait that occur in lameness, but little is known about the changes in patterns of muscle contractions that lead to the gait alterations.
Research, led by Dr Lindsay St George, Research Fellow at the University of Central Lancashire (UCLan), aims to look at how a horse’s muscles and limb movements adjust to accommodate lameness.
“We know that horses alter their movement pattern when they’re lame, but we don’t know much about the functional changes in muscles that facilitate these changes in movement,” she said. “We want to define muscle activity in clinically sound, non-lame horses, and then use this knowledge to quantify adaptive changes in muscle activity that occur when a horse is lame.”
St. George’s team uses surface electromyography (sEMG) to quantify muscle function and 3D motion capture technology to quantify movement in horses.
sEMG is a non-invasive technology that measures muscle activation by recording the electrical activity produced by skeletal muscles when they contract. This study uses Delsys Trigno sEMG sensors, which are small, wireless sensors attached to the horse’s skin over-lying superficial muscles of interest.
This study builds on previous work by St. George and her colleagues at Utrecht University*. They placed sEMG electrodes over selected muscles and reflective kinematic markers on each horse’s forelimbs, hindlimbs and back. Each horse was then trotted down a hard surface runway. The data collected from these trials were used to establish a baseline for each horse’s movement and muscle activity patterns when they were clinically sound.
Then, veterinarians induced mild, temporary lameness by applying pressure to the sole, using a modified horseshoe technique. This is a common method used in research to standardise lameness. Left or right forelimb lameness was randomly induced, and horses were trotted to collect data. After a minimum of 24 hours and ensuring the horses did not show residual lameness, sEMG and kinematic data were collected again from baseline and hindlimb lameness conditions.
Now the team is analysing the data, looking for differences in the activation timings and amplitude of the sEMG and kinematic signals between the conditions. Analysing both sEMG and 3D kinematic data will allow the researchers to accurately measure the relationships between changes in muscle function and movement during lameness.
“Although gait analysis technologies have been embraced by veterinarians in both practice and research to quantify movement asymmetries that occur during lameness, the clinical application of surface electromyography for evaluating equine locomotion is in its infancy,” said St George.
“There have been huge advances in the use of 3D motion capture and IMU technologies for aiding veterinary lameness evaluation, but these technologies do not reveal anything about adaptive muscle activity, and this is a missing link to understanding potential causes and/or clinical signs of equine lameness. The incorporation of both kinematic and muscle activation data is essential to gain a more comprehensive understanding of the factors at play during equine lameness.”
The study, is funded by the Morris Animal Foundation, and is run in collaboration with colleagues at Utrecht University, and Delys Inc.
“Lameness is one of the most common problems we see in horses, but we still have a lot to learn about diagnosis and treatment,” said Dr. Janet Patterson-Kane, Morris Animal Foundation Chief Scientific Officer. “If this technique will help us objectively measure the true condition of all of an animal’s musculoskeletal tissues, it will assist in optimizing treatment on an individual basis.”
If her study is successful, St. George would like to conduct a similar survey, but collect data from a larger group of horses on different muscle groups and clinical lameness cases.
For more details, see:
https://www.morrisanimalfoundation.org/article/better-assess-lameness-in-horses
*https://beva.onlinelibrary.wiley.com/doi/10.1111/evj.48_13152
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