Short sprints are just the tonic for healthy bones, researchers find

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Remarkably little exercise is needed by calves to build healthier and stronger bones, according to researchers, who say their findings deliver an important message for the development of young horses.

The recently reported Michigan State University study used calves as a model for juvenile horses.

Alyssa Logan and her colleagues, reporting in the Journal of Animal Science, found that calves needed only one short sprint a week to experience increased bone strength in their lower legs.

Their work showed that calves sprinted for 71 meters either once, three times, or five times a week derived this improvement.

Calves sprinted just 1 day a week exhibited a 26% increase in fracture force compared to calves confined without sprinting, they reported.

Over the six-week study, calves assigned to sprinting once a week had only sprinted 426 meters by the end of the experiment.

“This demonstrates the very few strides at speed needed to increase bone health, and that lack of dynamic loading for just 6 weeks leads to deleterious effects on skeletal strength.”

Sprint-exercising young animals once a week while young involves little time or expense, they say. The payoff is increasing the physical welfare of the young animal and potentially reducing the risk of a musculoskeletal injury during training and racing.

“Sprint exercise also influences bone formation,” they wrote, “evidenced by the fact that calves sprinted 5 days a week had greater osteocalcin concentration.” Osteocalcin is a calcium-binding protein.

“This study demonstrates the remarkably few strides at speed needed to enhance bone strength and emphasizes the danger to skeletal strength if sprinting opportunities are not afforded.”

The study involved 24 Holstein bull calves, who entered the study at an average age of 9 weeks who were housed throughout the six weeks of the study. They were divided into groups, with one group confined but not sprinted at all. The other groups were confined but sprinted 1, 3 or 5 days a week.

Previous research has already determined that maintaining young animals in stalls is detrimental to their bone health, while the addition of 50 to 82-meter sprints 5 days a week aids in counteracting the reduction of bone strength from confinement.

The Michigan State University researchers wanted to determine if sprinting 1 day a week, or 3 days a week, afforded the same benefits as sprinting 5 days a week, compared to animals confined with no sprinting.

Discussing their findings, the study team says confinement has been known for years to harm bone strength. “In the absence of loading, the skeleton reverts to its genetic minimum, a reduced bone mass that can support basic function without failure.”

They noted that the calves subjected to stall confinement for six weeks in their study did not experience alterations to bone mass density, but fracture force was found to have reduced when compared with the animals that undertook the sprints.

“It is common practice in the horse industry that young horses are removed from pasture and kept in stalls during race training,” the authors noted.

“While young horses are in the initial stages of race training, they undergo walking, trotting, and cantering before any speed is added to their exercise regimen.

“This schedule of slow exercise, coupled with the loss of free-exercise from pasture, leads to decreased bone mineral content, and presumably strength.

“The addition of dynamic loads to confinement is crucial in counteracting the loss of bone strength.

Sprinting young horses short distances 1, 3, or 5 days a week, as done with the calves, should lead to a subsequent increase in bone strength, they said, potentially reducing the risk of catastrophic injury during their racing career.

The authors say further research is needed to determine if sprinting animals at least one day a week at a young age can maintain heightened bone strength into maturity.

The study team comprised Logan, Brian Nielsen, Cara Robison, Jane Manfredi, Daniel Buskirk and Harold Schott, all with Michigan State University; and Kristina Hiney, with Oklahoma State University.

Alyssa A Logan, Brian D Nielsen, Cara I Robison, Jane M Manfredi, Daniel D Buskirk, Harold C Schott, Kristina M Hiney, Calves, as a model for juvenile horses, need only one sprint per week to experience increased bone strength, Journal of Animal Science, Volume 97, Issue 8, August 2019, Pages 3300–3312, https://doi.org/10.1093/jas/skz202

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

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