Researchers explore hoof stresses in horses trained in circles

Scientists find that slower gaits are safest in terms of reducing injury risk from the imbalances that arise.
File image by Myriams

Handlers looking to train their horses in a circle might want to do so at slower gaits in order to prolong equine careers, according to researchers.

Circular exercise is used frequently to exercise, train, and evaluate horses both under saddle and with lunging. However, little is known about how this type of repetitive exercise affects the front limbs.

Researchers in the Michigan State University study noted that some riding disciplines, such as dressage, reining, and barrel racing, use circular exercise during training and competition throughout a horse’s career.

The circles performed in these disciplines often have a small radius, with high speeds used frequently in training sessions. Thoroughbred racehorses also experience circular forces as they lean into bends at high speeds.

Lunging, with and without lunging aids, and the use of mechanical horse walkers is also found in many rehabilitation protocols.

Alyssa Logan and her fellow researchers fitted hoof sensors to nine healthy horses to determine the effects of circular work. In particular, they looked at whether changing the circle size and gait affected the hoof readings.

The horse’s feet were trimmed for balance by a qualified farrier a week before. Sensors, incorporated in glue-on shoes, were fitted on the day of the experiment.

Sensor information was collected while horses travelled in a straight line at the walk and trot, and in small (10 meter) and large (15 meter) counterclockwise circles at the walk, trot, and canter.

The study team, writing in the journal Animals, found that gait was a driving factor for differences in outputs, with the average loaded area of the hoof, average vertical force, and average pressure being greater at the walk in a straight line, and the loaded area being greater at the canter when circling.

When traveling in a counterclockwise circle, the average loaded area of the outside front leg was highest at the canter.

“This study shows gait is an important factor when evaluating exercise in a circle or straight line,” they said. “Horse owners may choose to perform circular exercise at slower gaits or minimize unnecessary circular exercise to decrease differences between limbs and potentially reduce injury.”

They found that gait and exercise type (circular or straight) had the biggest effects on the loaded hoof area, but the leading leg did not.

Circular exercise is used frequently to exercise, train, and evaluate horses both under saddle and with lunging. However, little is known about how this type of repetitive exercise affects the front limbs.
Circular exercise is used frequently to exercise, train, and evaluate horses both under saddle and with lunging. However, little is known about how this type of repetitive exercise affects the front limbs.

The walk had a greater average loaded hoof area than the trot by 12%. Gait and exercise type constituted a significant interaction, but “gait and leg” as well as “exercise type and leg” were non-significant interactions. “Gait, exercise type, and leg” was not a significant interaction, either.

At the walk and trot, there were no significant between-leg (left versus right) differences in the average hoof load area.

At the walk, the loaded area was different between exercise types, but not at the trot. While trotting in a straight line, the average hoof load area was lower than at the walk. Within the small and large circles, gait was not different in terms of the loaded hoof area.

In terms of vertical force, the effects of gait and exercise type were both significant. The walk resulted in a greater average vertical force than the trot by 14%. Again, there were no significant between-leg differences in the average vertical force.

Gait was found to be the significant main effect for hoof pressure, while exercise type and leg were not significant. The walk had a greater average pressure than the trot by 23%.

For both the right and left limbs, the walk was found to have a greater average pressure than other gaits. In both the large and small circles, the walk was found to have a larger averaged pressure than other gaits. Within each gait, there were no differences between the large and small circle sizes.

“When evaluating gait differences, the walk typically had greater mean area and vertical force in this study,” they said. “But when canter was included, the canter had the greatest mean area loaded.”

The continued: “The lower outputs seen at the trot in this study may be due to the fact that horses are able to utilize both forelimbs and hindlimbs within a trot stride in a more even manner than the walk and canter. The trot and canter also have moments of suspension, where the walk does not.”

They noted that, at the trot, the average hoof area loaded was similar regardless of exercise type, once again suggesting the trot to be the more stable gait.

Vertical force was greatest on a straight line for both the walk and trot, while pressure was not found to be different between exercise types at the walk or trot. However, while the walk had greater vertical force in this study, other forces, such as lateral force, may be greater in the trot and canter, especially during circular exercise, they said.

Discussing their findings, the authors noted that a review of risk factors for lameness in dressage horses found lunging to be protective against lameness.

“When lunging is utilized in dressage, often the use of a surcingle and bridle could encourage the horse to track in an upright and balanced manner, very similar to the way that a horse is ‘on the bit’ while under saddle in dressage.

“In disciplines outside of dressage, lunging is typically performed with only the lunge line attached to a halter. This gives the handler less control of the horse, often resulting in lunging sessions where the horse is leaning into the circle and does not consistently engage the hindquarters and topline musculature to travel in an upright manner, making lunging in this manner less likely to be a protective factor against lameness.”

In conclusion, they said that gait (walk, trot or canter) drove changes to outputs more than exercise type (straight or circular). “The trot frequently had lower mean outputs than other gaits, suggesting that it is a more dynamically stable gait that could potentially allow horses to adapt to circular exercise easier than other gaits.”

Even so, handlers might consider minimizing the use of circular exercise or employing slower gaits when doing so, because differences in outside limb output were noted at the canter.

They say further studies will be required to determine if a round-pen allows the horse to adapt to changes in gait and diameter better than when exercised on a lunge line or under saddle.

“Lateral forces may be greater during circular exercise and should be evaluated and compared with the findings of vertical forces provided in this research.”

The study team comprised Logan, Brian Nielsen, Cara Robison, Jane Manfredi, Daniel Buskirk and John Popovich Jr, all with Michigan State University; David Hallock, with 3R Forge and Farriery; and Kristina Hiney, with Oklahoma State University.

Logan, A.A.; Nielsen, B.D.; Robison, C.I.; Hallock, D.B.; Manfredi, J.M.; Hiney, K.M.; Buskirk, D.D.; Popovich, J.M., Jr. Impact of Gait and Diameter during Circular Exercise on Front Hoof Area, Vertical Force, and Pressure in Mature Horses. Animals 2021, 11, 3581.

The study, published under a Creative Commons License, can be read here

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