What do we really know about what shockwave machines are used for?

A shockwave machine delivers sound waves to the problem area, while the ‘dose’ concerns the number and intensity of the of pulses. Photo: horsevet.co.uk

As the industry presses on with what can often feel like the Sisyphean task of comprehensive medication reform, a group of drugs and medical treatments continues to prove especially slippery to lasso — those that are difficult, or currently impossible, to test for.

These are the ones around which backstretch rumors swirl — stories of illicit midnight visits into stalls, of illegal race-day practices, and horses producing knockout performances seemingly out of nowhere.

Nothing epitomizes this corner of the debate more than extracorporeal shockwave therapy — a common-place treatment for horses in training, one that’s extremely useful in tackling some of the routine aches, stresses and strains that all equine athletes are subject to.

The main sticking point concerns its analgesic properties, which the science currently points to as lasting for up to three days. That, and there’s currently no conclusive way to test whether a horse has been administered shockwave therapy.

Veterinary staple

What happens, therefore, if a horse is administered shockwave treatment immediately before a race to dull pain and mask injury?

This is the sort of question that has been asked about shockwave machines ever since they began to become a veterinary staple at the turn of the century. But, where does the issue lie now? What do we know about the science behind shockwave machines? And what have regulators done to investigate and govern their use?

“There’s still not a test for it,” said Mary Scollay, Kentucky equine medical director, and someone who has long been outspoken of her concerns about the instrument.

“While it’s possible to achieve reasonable regulation of the use of the instrument at the racetrack and under a regulated environment, it’s use at private farms, training centers, locations outside the track is virtually unregulated regardless of what the rules actually say,” she added.

How do they work?

A shockwave machine delivers sound (acoustic) waves to the problem area, while the ‘dose’ concerns the number of pulses applied within a given period of time, and the intensity of these pulses.  

Each pulse produces an unmistakable loud click, and it’s the noise they make that typically bothers horses more than the dull thud each pulse emits. Horses usually undergo a series of treatments over a period of weeks.

These pressure waves promote and hasten the healing process a number of ways: by triggering an anti-inflammatory response within the body, for example, and by promoting the growth of new blood vessels, among other ways.

Even so, there still remain question marks concerning how and why shockwave therapy is effective, and therefore, for exactly what shockwave therapy can and should be used.

“When you have a hammer, everything looks like a nail,” said Jeff Blea, a veterinary practitioner based in Southern California, about how his use of shockwave therapy has evolved over the years. “We’re using it now more as a therapy, rather than as a means to get to a race,” he added.

Early last year, Blea co-authored a report for the California Horse Racing Board (CHRB), summarizing the issue as the state reviewed its shockwave regulations.

And he said that shockwave therapy is most beneficial when used to treat the sorts of concussive injuries — suspensory problems, for example, tendonitis, osteoarthritis and sacroiliac issues — typical among horses in training. Still, the jury’s still out as to its full orthopedic effects.

Ryan Carpenter, a practicing veterinarian and co-author of last year’s report for the CHRB, uses it, like many veterinarians do, to treat sore shins, which are caused by tiny-micro-fractures in the cannon bone.

“There’s not a lot of science as to its use this way,” he said. Rather, there’s plenty of anecdotal evidence of its success, especially when used in conjunction with changes to the horse’s training program. “When it comes to sore shins, it’s a multi-factorial problem.”

‘That’s the frustrating part, not just for the regulators but the jocks, too’

The widest concerns surround the analgesic properties of shockwave therapy. The best current science has the painkilling effect lasting between two to three days. Some experts also point towards a 2004 study that found some sort of sensory analgesia could last up to 35 days post-treatment.

Carpenter questions the clinical significance of the study as it relates to the way shockwave machines are commonly used on racehorses. And he believes that California’s shockwave regulations, which weren’t altered as part of last year’s review, protect, when adhered to, against abuses.

“We’re not masking anything,” said Carpenter. “How we use it, it’s another form of treatment to help allow the horse to maintain training or to help maintain alternate programs so they can achieve their potential.”

Major sticking points also surround how, when shockwave machines don’t leave any visible mark, there are currently no methods to test for its use.

There have been in the past few years attempts to identify certain biomarkers — a measurable biological response to things like medical treatments — that would indicate when a shockwave machine has been administered. But these studies haven’t come up with anything “from a regulatory standpoint”, said Jeff Blea.

And the complexities of identifying biomarkers specific to shockwave use make it unlikely that a test will arrive any time soon, he said. “That’s the frustrating part, not just for the regulators but the jocks, too.”


As expected, there’s a patchwork of different regulations from state to state. The vast majority adhere, if not in full, at least in part to the Association of Racing Commissioners International (ARCI) model rule, the fundamentals of which look like this:

  • That machines are registered with the racing commission and used only by licensed veterinarians
  • That they’re used only in designated locations
  • That horses cannot race or breeze for at least ten days after treatment
  • That horses are placed on a vet’s list for ten days after treatment, and that jockeys, their agents, and other regulatory jurisdictions have access to this list

Idaho, for example, has no shockwave regulations in place. In Arizona, shockwave therapy is banned entirely. It’s the same in Colorado. In Michigan, horses can’t race for seven days post-treatment.

Most states require shockwave therapy to be conducted only by licensed veterinarians with machines that are approved by and registered with the relevant racing commission. But fewer states require shockwave therapy to be performed at a pre-determined location within a licensed facility, as per the ARCI.

Where specified, most states make any violation of their shockwave regulations a Class A penalty, though Maine makes it a Class C violation.

This patchwork of different regulations extends internationally, too.

Earlier this year, the British Horseracing Authority instituted a mandatory five-day stand-down period from racing following its use. But in 2008, UK trainer Luca Cumani got into hot water for improperly shockwaving a horse in Australia within seven days of a race (the Melbourne Cup).

Cumani wasn’t aware it would be “an issue” as “it is only banned in England on race day,” the trainer argued at the time. After an investigation, the horse in question was allowed to keep its second place finish in the big race.

Interestingly, just last month, a leading Australian was charged with multiple counts of improperly using shockwave therapy within seven days of competition.

Returning to the U.S., there have been ten rulings for shockwave violations since 2007, according to information provided by the ARCI. This includes both Thoroughbred and harness racing. At least two of these rulings, however, were subsequently dismissed after appeal.

As expected, the rulings differ in terms of violators, fines, and specifics. Last year, after a year and a half of appeals, a practicing veterinarian in New Jersey was fined $4,000 and suspended 20 days for falsifying a shockwave therapy treatment slip to the racing commission.

Back in 2008, a trainer treated a horse in Minnesota with a shockwave machine, but the race fell within the ten-day post-treatment window. The horse was scratched before the race, and the trainer was fined $300 by the racing commission.


“It would not be considered a minor problem if somebody tried to cheat,” said Rick Arthur, equine medical director of the California Horse Racing Board, about how any violation of the state’s shockwave therapy rules would be treated. “I have no doubt that the veterinarian involved would be referred to the veterinarian medical board.”

Last year, the CHRB conducted a statistical analysis to see whether there was a correlation between shockwave use and a higher probability of catastrophic injury occurring.

This was done in response to a horse being fatally injured after coming off the ten-day vet’s list for shockwave therapy the day before it raced. That, and there have been trainers, said Arthur, who appear to shockwave horses as part of a routine program. “They were doing it just in time to come off the vet’s list,” he said. “That’s where the concern was.”

But according to Arthur, “we were unable to find any evidence of statistical risk of shockwave prior to fatality.” What’s more, as a consequence of the heightened scrutiny as a result of the investigation, Arthur doesn’t see the same level of shockwave usage as a pattern prior to racing.


California first adopted in 2006 shockwave regulations that the ARCI’s model rules would eventually mirror. So far in 2018 (up until May 25), there have been 394 reported separate uses of shockwave therapy in California (though a good number of horses have received multiple treatments).

“We hear rumors from time to time of shockwave machines being used improperly on the backside,” said Arthur. But he said that that these rumors are investigated, and invariably turn out to be a papimi machine — a device that sounds like a shockwave machine, but which emits electromagnetic pulses that are much less potent.

“I can’t tell you somebody can’t try to cheat, but I will tell you this, if anybody hears anything that sounds like a shockwave machine, we hear about it,” he said. “And we’ve never caught anybody improperly shockwaving a horse from those complaints.”

‘Everyone has a responsibility’

Among the experts I spoke with, their concerns fell into two primary camps — that horses are being shockwaved within the rules as part of a routine pre-race program, and that horses are being shockwaved improperly at unregulated facilities immediately prior to competition, then shipped to a racetrack to race.

Arthur, for example, doesn’t see any “therapeutic benefit” of its use prior to a race, even ten days out. “It’s the sort of treatment where you should treat a horse then turn it out, stop on it, or back off it,” he said. But many practicing veterinarians argue that shockwave therapy is extremely useful to treat typical aches and pains associated with the rigors of training.

Former jockey Chris McCarron has been outspoken about how growing awareness of the treatment hastened his retirement from the saddle in 2002. And, according to Terry Meyocks, national manager of the Jockeys' Guild, there remains skepticism among the nation’s jockey colony that the problem has been adequately reckoned with.

Which is why Meyocks would like to see the ARCI’s model rules instituted uniformly throughout the country, along with a more rigorous investigative process, to catch violators red-handed, a tough task. But still, “regulators need to get more involved,” Meyocks said, adding that the “majority of racetracks and the NTRA Safety and Integrity Alliance haven’t given riders the assurances” they’re looking for.

‘Honor system’

“One year I was up in Saratoga for a [ARCI] model rules meeting. A person came up to me and said a trainer told him he’d bought a [shockwave] machine and was asking a veterinarian how to use it.”

All of which leads back to the crux of this problem — the need for trainers and veterinarians to abide by the ‘honor system’ at the heart of any horse welfare issue.

“It all depends upon the way it’s used and how close to racing it’s used,” said Dionne Benson, the Racing Medication and Testing Consortium (RMTC) executive director. “Everyone has a responsibility to keep everyone honest in this regard.”

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