asymmetry | Horse Racing Free Tips

Obese Horses More Likely To Move Unevenly

In an effort to determine how added weight affects equine fitness and performance, Dr. Anna Jansson and a research team from the Swedish University of Agricultural Sciences and Hólar University published a study in Physiological Reports in which horses were fed controlled diets to add or restrict weight gain. The scientists used nine Icelandic horses that they split into two groups. Changes in body weight and fat were induced in the group being fed a high-energy diet for 36 days.

During the last seven days of the study period, researchers recorded body condition score and weight, and percentage of body fat was estimated with an ultrasound. Each horse was then given an exercise test on a treadmill and a field test that mimicked a competition, which was scored by judges. Blood samples were taken, as well as heart rate, temperature and respiratory rate.

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On the treadmill test, the horses that had gained weight had a higher heart rate and temperature, and heavier respiration. Blood tests showed that heavier horses had lower physiological fitness.

The team also found that overweight horses showed a marked gait asymmetry compared with leaner horses, as was shown both by sensors placed on the horses while they moved. The heavier horses moved most asymmetrically on the day after their field test.

Judges overseeing the field test also scored heavier horses lower than their leaner counterparts, suggesting that weight affects performance.

The authors conclude that higher body fat and body weight lowers equine performance, made horses move more unevenly, and delayed their recovery from exercise.

Read the full study here.

Study: Majority of Horses Considered ‘Lefties’

Wither measurements of 490 horses taken with a flexible tracing tool have shown that the majority of horses have larger measurements on the left side of their withers as compared to their right, suggesting they are “lefties.” Dr. Katrina Merkies, with the University of Guelph, and a team of undergraduate students digitized and compared years of measurement data to come to this conclusion.

The study included a variety of breeds, including finer-boned breeds like Thoroughbreds and Arabians to heavier breeds like Warmbloods and draft horses. Overall, 60 percent of study horses had larger muscles on the left sides of their withers.

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Merkies and her team considered laterality as a possibility for why horses have a tendency to build muscle on the left. Laterality refers to a horse's preference for using one side of his body. The right side of the brain controls the left side of the body and this is where fearful stimuli are processed, the team reported. Merkies noted that horses will often look at an object they are afraid of out of their left eye or step off trailers with their left front leg first, both of which reinforce the notion that these horses are “lefties.”

While examining differences in body sizes and shapes, the scientists also found that horses of medium height were more likely to have more-curved backs than their brethren of other sizes. The team hypothesize that this is because medium-sized horses are often ridden by adults, whose saddle might not properly fit, being too long in the seat and applying pressure to the lumbar region.

Pressure from an ill-fitting saddle can cause pain and affect performance, as well as prevent the muscles from building in a symmetrical way. Merkies stated that proper and twice-yearly saddle fittings are imperative for equine comfort and the development of balanced muscles.

Noticing Asymmetry Under Saddle? The Solution Could Come From A Single Bell Boot

Though all horses have some degree of asymmetry, a rider can make a slight asymmetry better by placing something loose around the fetlock of the weaker leg, according to a report from the archives of The Horse. The horse will feel it and work harder to engage his limb, said Dr. Adrian P. Harrison, who works with Copenhagen University in Denmark.

The fix could be as simple as occasionally using a bell boot on the weaker leg; the boot uses proprioception to remind the horse that the weaker leg is still there. Proprioception is the awareness of body parts, and knowing and remembering where they are and what they are doing. The bell boot helps a horse “remember” his leg is there.

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This correction could resolve issues relating to an old injury or dominant limb. Old injuries can sometimes cause horses to be unwilling to fully engage a limb for fear of pain; the bell boot trick helps them realize they are pain free.

Harrison created a study using eight sound dressage horses that had slightly weaker left hind limbs when measured using acoustic myography (AMG). AMG measures how muscle and ligament fibers move, and how much power the central nervous system must exert to get a muscle to contract.

Riders of the horses placed a cob-sized bell boot on the horse's weaker limb when the horse was ridden for 60 minutes every three days for six weeks. At the end of the study, AMG shows that the asymmetries had resolved.

Asymmetrical Movement Common In Young Standardbreds

Scientists from the Norwegian University of Life Sciences and the Swedish University of Agricultural Sciences found asymmetrical movement in most of the Standardbred horses used in a study.

The group recruited the help of 12 Standardbred trainers across Norway and Sweden. They used wireless inertial sensors to detect uneven movement at the trot on 103 horses. All the horses had been broke to harness and were beginning race training; each was considered fit to train by their trainers.

Drs. Anne Kallerud, Cathrine Fjordbakk, Eli Hendrickson, Emma Persson‐Sjodin, Marie Hammarberg, Marie Rhodin and Elin Hernlund chose to study this group, which had an average age of 18 months, to reduce the chances of the presence of training-related injuries. All horses received a physical exam before the study; measurements were taken to see if any associations could be found with the uneven movement that could be detected.

Of the 103 horses, 77 were seen in-hand and on the track; 24 were assessed in-hand only and two were assessed only on the track. The scientists used thresholds established for other breeds to determine asymmetry. They determined that 94 of horses (93 percent) showed front and/or hind limb asymmetry in the in-hand reviews. In the track trials, 74 horses (94 percent) showed asymmetry. Though most of the asymmetry was mild, one in five horses switched the asymmetrical side for one or more parameters between in-hand and on-track trials.

The study team explored the prevalence of asymmetry, but not its underlying causes. It is unclear if the asymmetrical movement increases, decreases or stabilizes with age and training. They suggest that future studies look at the changes in asymmetry over time, and explore any associations between the asymmetrical movement and the development of clinical lameness.

Read the study here.