More Turnout, Fewer Injuries?

Giving your horse more turnout time might lower the risk of soft-tissue injuries, a study suggests.

Researchers from Centenary University in Hackettstown, New Jersey, retrospectively examined six years of data from horses used in the school’s riding program and found those animals turned out 12 hours a day had a 25 per cent lower occurrence of soft-tissue injuries.

According to past studies, soft-tissue injuries to any tendon or ligament account for 13 to 18 per cent of horses requiring rest and time off and are responsible for 33 per cent of training losses and wastage in sport horses of all disciplines, Centenary undergraduate Abigail Reilly told delegates at last spring’s 2021 Equine Science Society Virtual Symposium.

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She was presenting “Incidence of soft-tissue injury and hours of daily paddock turnout in non-elite performance horses,” a study Reilly co-authored with Dr. Jesslyn Bryk-Lucy, assistant professor of equine studies.

Two contributing factors to soft-tissue injury are increase in acute workload and fitness level, she added.

“Restructuring of tendons is an exercise-driven process, which occurs when tendons functionally adapt to changes in the biomechanical environment.” In other words, “The tendons restructure in response to equine movement.”

The process occurs more rapidly under natural conditions, such as pasture turnout – which multiple studies suggest maintains fitness – and promotes development of thin collagen fibres, which give the tendon elasticity, added Reilly.

“Exercised and pastured horses have more thin fibers meaning their tendons are more equipped to adapt to their movements.” They also, she noted, are fitter overall, than their stalled counterparts.

In both humans and horses, she explained, a common way to define fitness and analyze injury occurrence is the acute-to-chronic workload ratio – the difference between baseline workload and intense training days. When the ratio is low, there’s less chance of injury, but when there are big differences between the acute and chronic workload, the likelihood of injury is much higher.

Baseline Fitness

“I was curious if this principle applied to non-elite horses with varying amounts of turnout. If a horse has a low chronic workload, like a stalled horse, they will have a lower baseline fitness. When these horses are asked to perform, there will be a large spike in the acute to chronic workload ratio no matter the intensity of work,” said Reilly.

“If horses are out on pasture their maintaining a higher chronic workload because they’re walking around grazing and being a horse, when they’re asked to perform and have a spike in the acute-to-chronic workload ratio, they already have this baseline fitness and the difference between the acute and chronic workload is less.”

She hypothesized that horses with more than 12 hours of turnout would have significantly less incidents of soft-tissue injury than horses turned out for less than 12 hours due to their increased baseline fitness.

Her data source was the intake medical records of 146 horses (median age 17 years) donated to the Centenary University Equestrian Center lesson program from 2014 to 2020. The records were examined to identify the time of initial soft-tissue injury, if any, by the resident veterinarian, whether by ultrasound, magnetic resonance imaging or process of elimination.

A comparison was made between the incidence of soft-tissue injury in two groups: one that consistently received more than 12 consecutive hours of turnout per 24-hour period and another that had less than 12 hours per 24 hours. Injuries were only included after a horse had adjusted to a new turnout schedule or group for 30 days.

The duration of 12 hours was chosen, as it is a “sufficient amount of time to cause a physiological change in response to exercise as noted by previous studies,” said Reilly. It also suited Centenary’s turnout schedule. The barn manager chose the turnout groups, all horses were under similar stable management, had consistent workloads appropriate to their riding levels and were ridden on the same arena surfaces.

After analyzing the data, Reilly found 25 per cent of the horses (14 of 57 animals) turned out for more than 12 hours sustained a soft-tissue injury compared to 51 per cent of horses (45 of 89 animals) in the less-than-12-hour group. The results suggest an “inverse relationship between the length of paddock turnout and risk of soft tissue injuries in non-elite horses,” said Reilly. The results also support the idea that turnout maintains a baseline fitness level, allowing horses to better manage workload spikes with a reduced risk of injury.

Of the horses turned out for more than 12 hours, 25 per cent sustained an initial soft-tissue injury compared to 51 per cent turnout out for less than 12 hours.

Other research opportunities using this data could include investigating whether there was a significant difference in severity of soft tissue injuries and amount of turnout among the injured horses, said Reilly. Additional areas to pursue, she suggested, include whether the size, terrain or surface of the turnout area affect incidence of soft tissue injury if turnout is a viable treatment option.