On Exercise—Don’t Overdo It!

This long-form article was originally written for the Margaux Farm website, and was featured in the February 2014 newsletter.  It covers an article written on The Blood-Horse’s website, as well as some highlights from a recent issue of the Thoroughbred Daily News.  While I don’t normally re-post articles I write for the farm, there are enough similarities shared in human and animal exercise to make it a worthwhile read.  Further, for those unfamiliar with how horses are trained, the linked articles may help to answer more raised questions.

As anyone who has followed Thoroughbred racing over the last couple of decades knows, the statistics have changed dramatically.  Possibly not as clear when looking at the change from year to year, but when comparing recent years with statistics from the early 80’s, the differences start to show.  Consider the Triple Crown – the fact that there hasn’t been a horse to win every leg of the championship in over thirty years is blatant proof that the breed has changed significantly.  Further, a cursory glance through the 2014 Stallion Register will find a significant portion of sires with a race record that rarely – if ever – climbs into double digits.  Both of these factors – the difficulty today’s Thoroughbreds have racing further than a mile and a quarter, and the brevity of their careers – can be attributed to their breeding and training.

Pedigree analysis, conformation evaluation, all the planning that goes into breeding – everything comes down to the breeder’s goal for the hypothetical foal.  The race course is not the only end goal some breeders may consider – a significant number, possibly THE significant number of foals, are bred with the sales ring in mind.  The fact that the buyer will then go on (or hopes) to race the hypothetical foal may not be considered — either in the breeding considerations or in the training of the young horse.  While training is, to most, what happens at the track, the truth of the matter is that a horse is ‘trained’ from the first human contact.

The animal body (horses, the same as humans) responds to cues from nature – just as we exercise to stay healthy and build muscle, equine athletes require the same to continue proper growth and development.  When horses are raised with the express purpose of going through either weanling or yearling sales, however, they are often not allowed the exercise required.  As noted in Ryan Goldberg’s article in the January 28th edition of the TDN, “at some Lexington farms yearlings come in months before the sales.”  Given that horses will often cover twenty (or more) miles per day when turned out in the field, one can only imagine how detrimental this lockdown is to the young horse’s physical (and mental) development.  Goldberg’s lengthy study of the German breeding industry was centered around an interview with Andreas Jacobs, who oversees Gestüt Fährhof (among other farms).  Jacobs, who continues to breed for soundness, stated:

We try to keep them as natural as they are.  For the weanlings and yearlings, we like to keep them in groups of six, seven, sometimes eight, where they can play and have competitive group behavior.  With larger groups it’s more competitive, so they can run more and exercise a lot, to strengthen the bones and optimize their lung and heart capacity. 

Nature is the best way to get a racehorse – not always the best way to get a sales horse.

Thoroughbred Daily News

The above style of management affords young horses every opportunity to develop a healthy mind, as well as the level of physical fitness necessary for a healthy racing career.  Until recently, however, common belief was that the skeletal system was thought to be static, defined entirely by genetics (rather than dynamic, as the cardiovascular system is known to be).

In humans, studies have shown that martial arts experts have greater bone density in their knuckles (the result of years of the body responding to increased stress) than the larger percentage of the population.  In an article by Nancy S. Loving, DVM, posted by The Blood-Horse, it is suggested that the skeletal system is dynamic, not static, as was once believed.  In the article, Larry Bramlage, DVM, MS, Dipl. ACVS states, “Selective breeding dictates the initial skeleton, but adaptive training in response to exercise modifies it further.”  He goes on to explain that “bone is the only tissue capable of entirely reconstituting itself.”  Considering that the bones will respond to exercise (or the lack thereof), it can be inferred that adequate turnout is a critical component of the development of a racehorse, given the amount of ground covered during a day in the field.

Of particular import is that bone becomes stiffer over time – according to Bramlage, “this can become a problem when bone formation stops for a time and then is reinitiated due to changing stimuli.”  Loving goes on to add that “as bone loses its homogeneous structure, a distinct interface forms between new and old bone that can promote failure, similar to the interface of two types of pavement in a patched pothole.”  If a horse’s bones are as at risk as a filled pothole, it’s no wonder that so many careers end after just a handful of races.

It’s no coincidence that most Thoroughbreds begin formal training in their 2-year old year – the bones are still growing at that point, and as Bramlage states: “by converting growing bone into exercising bone before it stops growing, there isn’t the interruption in the bone formation, and therefore, quality.”  For training not to be detrimental to the skeletal system, care must be taken to allow the body to rest and repair itself (Bramlage refers to this need for repair as “exercise debt”).  A critical point, according to Bramlage is that:

Bone trains in a stair-step fashion with adaptations being work-specific.  Overloading results in microfractures that stimulate bone to strengthen… but if there is inadequate repair in the face of exercise, damage accumulates.  Rest… enables overlying new bone to become as stiff as the underlying, older bone, to repair any damage, and to add more bone to better stand the level of exercise seen.  After a number of cycles necessary to stimulate bone strength, further repetitive work becomes traumatic. 
We gallop too much and don’t vary gaits enough.

Larry Bramlage, DVM, MS, Dipl. ACVS, The Blood-Horse

Anyone who frequents a gym understands that to train consistently, they have to create a schedule that allows for their muscles to heal after the stress of exercise – otherwise they are at risk of suffering an injury and interrupting their training regimen.  The same goes for horses.  As Bramlage goes on to note, high speed exercise is the greatest contributor to the damage that must be repaired.  As he states, “a horse running 35 high-speed furlongs in a two-month period is four times more likely to experience fatal skeletal injury than a horse running 25 high-speed furlongs over the same time.”  The fact that just 10 additional high-speed workouts causes the risk factor to go up by 400% is incredible.  If there was ever an argument for a varied workout schedule focused on several days rest (gallops) between breezes, it’s this.

What is the take-home message here?  In an earlier article, I examined a study which found that horses turned out 24 hours per day in large fields traveled more distance than stalled, exercised horses – even on days that the stalled horses were exercised.  Not only did the turned out horses maintain a similar level of fitness to the stalled horses – they also had greater bone mineral content than those which were exercised and stalled.  Paddock turnout is obviously a key factor in producing and maintaining a sound horse.  As I speculated in that earlier article (linked above), it would have been interesting to have a fourth group in the study – horses that were exercised in a farm setting, rather than a track setting.  Given the benefits of paddock turnout, it is only logical that horses should spend a minimum amount of time at the racetrack: to receive their race training, and to race.  The more time spent in the stall, the more lost fitness.


 – Dayn


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