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In the spring of 2013, research out of Duchy College in the United Kingdom suggested that many riders were heavy enough to cause welfare concerns for their horses. The study was based on the assertion that a rider should ideally weigh 10 percent of her horse’s weight. As word of the research spread around equestrian circles, riders did some quick mental math—and panicked.

If an average riding horse weighs 1,000 pounds, then the ideal rider would weigh 100 pounds—not exactly an attainable goal for most adults. But before writing off horseback riding as an activity only for kids and jockeys or trading in your light horse for a Clydesdale, take a closer look at the research.

The Duchy College study was a collection of data from riders and horses in the United Kingdom designed to be a starting point for further research. The researchers looked at riders with what is considered a healthy body mass index (BMI), the measure of a person’s weight in relation to their height. The survey revealed that these riders were between 14.2 and 16.6 percent of their horse’s weight.

So where did that 10 percent figure come from? The researchers used numbers provided by “an industry practitioner” as the basis for their scale. According to that source, a 10 percent rider-to-horse bodyweight ratio is optimal and 15 percent is satisfactory. Once a rider’s weight hits 20 percent, it would be considered a welfare issue.

Mainstream news outlets picked up the 10 percent statistic and published it in somewhat sensationalized headlines, even though the study allowed for a more attainable 15 percent. Still, the stories brought an important issue to light. As obesity rates climb, are we jeopardizing our horses’ welfare?

How Heavy is Too Heavy?

One of the most frequently cited recommendations on matching horses and riders comes from the U.S. Cavalry Manual of Horse Management. It recommends that the rider and gear weigh no more than 20 percent of the horse’s weight.

The mention of gear is important. A western saddle can add another 30 pounds or more to a horse’s back, easily pushing the total burden past that 20-percent point. These standards were based on the educated opinions of military horsemen at the time, and scientific studies in more recent decades have backed them up.

Research from Ohio State University (OSU) published in 2008 measured stress and soreness indicators in horses before, during and after exercise while carrying 15, 20, 25 or 30 percent of their body weight. The horses were put through a 45-minute workout designed to replicate an average riding lesson. Lead weights were added to both sides of the saddle to reach the necessary total weight.

The researchers found that the horses started to exhibit a change in muscle soreness and tightness once their burden reached the 25-percent point, and those measurements increased significantly at 30 percent. Horses carrying 25 or 30 percent of their body weight also had an elevated heart rate, respiration and temperature compared to those that carried 15 or 20 percent. These findings appear to verify the old cavalry guideline.

Karen Wimbush, Ph.D., is an associate professor in the Agricultural Technologies Division at OSU and was one of the researchers who conducted the 2008 study.

“The horse that carries more weight is doing more work,” says Wimbush. “That is simple physics.”

The riders in the OSU study were experienced equestrians instructed to ride as quietly as possible. The horses still showed increased stress and soreness indicators when carrying 25 and 30 percent of their weight. However, Wimbush believes that the skill and balance of the rider are more influential than weight when it comes to the horse’s comfort and soundness.

“Without a doubt, a quiet, balanced rider causes less stress to a horse than a ‘busy’ or unbalanced rider,” says Wimbush. “Rider weight is a factor as well, as the study proved. But a balanced rider centered over the horse’s center of gravity is less stressful than an unbalanced rider of the same weight. Even a heavier rider that is balanced probably isn’t as hard on a horse as a lighter-weight rider that isn’t as balanced.”

Wimbush also points out that, in her experience, lameness issues pop up more in horses subjected to frequent improper or novice riding than in those that carry more weight but are consistently ridden correctly.

Not All Body Weight is Created Equal

When we talk about a horse’s body weight in relation to how much weight he can carry, it may seem too simplistic. Should a fine-boned Thoroughbred be expected to carry the same amount of weight as a stocky Quarter Horse of equal body weight?

The OSU study examined this question by looking not just at the equine subjects’ body weight, but also at their amount of bone. This is done by measuring the circumference around the middle of the cannon bone. The researchers also measured the width of each horse’s loin. They found that the results correlated inversely with muscle soreness. In other words, horses with more bone and a wider loins seemed better able to carry weight without negative effects.

Fitness Matters

Type and size aren’t the only considerations. A young or green horse with little under-saddle mileage is akin to a sedentary person hitting the gym for the first time. Even a small amount of exercise will leave them sore for a few days. Similarly, a senior horse or one with a history of injuries won’t be able to bear the same amount of weight that he could when he was younger and sounder. But adult horses with a high level of conditioning are able to push the boundaries of athletic achievement.

A pair of studies performed in 1996 and 1999 examined horses that competed in the Tevis Cup, a challenging 100-mile endurance race that takes place each year in California. The researchers looked at the body weight and condition of all horses that started the race in 1995, 1996 and 1999, as well as the amount of weight they carried. Over the course of both studies, the horses’ body condition proved to be the strongest indicator of whether or not they would successfully complete the course-—more so than the amount of weight they carried.

Using the Henneke Body Condition scoring system, which rates horses from a 1.0 (emaciated) to 9.0 (extremely fat), the researchers found that horses were more likely to complete the race if they had a higher body condition score. It’s important to note that these subjects were highly conditioned endurance athletes, and none scored higher than a 5.5. The correlation would not necessarily continue for overweight or obese horses—those scoring 6.0 or above.

Perhaps not surprisingly, of the horses that scored below a 3.0, none completed the race in any of the three years surveyed. A score of 3.0 is considered “thin.”

Most of us won’t ever ask our horses to cover 100 miles of rugged terrain in a single day, but the findings of this study are still relevant to the average horse owner. Consider your horse’s body condition when determining who can ride him. A horse that is underweight may not be able to safely carry as heavy a rider as he could at his ideal weight.

But My Horse is Fine

These studies provide interesting fodder for academic purposes, but when it comes to applying the findings to the real world, it’s not so simple. It may seem like your horse is doing fine even if he’s being asked to carry more than 20 percent of his weight regularly, so why worry about it?

Horses are often stoic. They will work through discomfort because they’re bred and trained to do so. Even when they do show slight soreness or lameness, it’s virtually impossible to conclusively trace these problems back to a rider’s weight. Many horses that are not asked to carry excessive weight come up mysteriously lame. Others that do have a heavy rider might appear sound for years before problems arise.

It’s up to riders to be honest with themselves about what they’re asking their horses to do. Just because a horse appears to be OK doesn’t mean he’s not overburdened.

A Weighty Issue

Rider weight is a sensitive topic. On one side, there is legitimate concern that our 21st-century sedentary lifestyles are leading us to unhealthy weights. Statistics back this up. According to the Centers for Disease Control, the percentage of overweight or obese Americans sharply increased around 1980 and has continued on an upward trend in the three decades since. Riders aren’t exempt from this trend, and as our weights increase, so does the burden we place on our horses.

On the other hand, it’s hard to separate legitimate concerns about rider weight from the superficial obsession with being skinny. The horse world in America has a large population of girls and young women who enjoy the barn as a place for respite from the outside world. Scrutinizing rider weight just adds to the pressures that cause self-esteem problems and eating disorders. Even for adults, studies have shown that discrimination against overweight people is a real issue in the U.S. No one wants to bring those ugly problems into the barn.

But for equestrians, this subject has to be viewed through the lens of equine welfare above all else. This doesn’t mean overweight adults can’t ride. It does mean that they need to be realistic and ride horses of a size and build appropriate for their weight, or take steps to lose weight in order to keep riding the horse they already have. That’s easier said than done, but few horse owners would say that their horse’s well-being isn’t worth the effort.

For riders in the market for a horse, the problem has an easier solution. Grit your teeth and hop on the scale. Take into account the weight of your saddle and any other gear you might ask your future horse to carry. Then only look at horses that are sized appropriately for the job that you need them to do. It’ll make for a happier, healthier horse-and-rider relationship in the long run.

Setting Weight Limits

The issue of rider weight becomes more complex for riding instructors, trail guides and other professionals who provide horses to the public. It’s not easy to turn away paying customers, especially when the reason for doing so could offend them on a personal level. Some public riding facilities are proactive by stating a weight limit so that would-be riders know ahead of time whether or not they will be able to sit on a horse.

The Traditional Equitation School (TES) in Burbank, Calif., has had a strict 195-pound weight limit for students in effect since it opened its doors 30 years ago.

“We cater to a large number of adult beginner riders,” says Andrea Call, office manager of TES. “Beginners are harder on their horses until they learn to balance themselves and control their bodies while mounted.”

Restricting the pool of potential clients might seem like a business risk, but Call says the benefits outweigh any negatives.

“We have had to turn away some clients, though not many,” says Call. “Having happy, healthy horses is the foundation of our business, and the most important thing to us. We gain more by taking good care of our wonderful horses than we stand to lose by turning away a few potential clients.

“We have relatively few back problems [in our school horses],” she adds. “We attribute that to both the weight limit and proper saddle fit. Our horses tend to have great longevity. We have quite a few horses working in our school that are in their mid- to late 20s. We credit this to good care and maintenance along with a workload that is tailored to each horse’s needs. Our weight limit is a part of that equation.”

New students at TES have an initial evaluation lesson, during which the weight limit is made clear. “Part of booking that lesson is asking the client their height and weight, along with their riding experience and other details,” says Call. “I think most clients tend to be truthful when asked their weights. If they’re over the limit, I apologize and briefly explain the purpose [of the limit].”

And what if an aspiring student is dishonest about her weight?

“I do have a scale in the front office,” says Call. “I could ask a rider that appears to be over the limit to step on the scale, though it’s never come to that.”

Resources:

1. The horse and rider bodyweight relationship within the UK horse riding population. E. Halliday. H. Randle. Journal of Veterinary Behavior: Clinical Applications and Research. Volume 8, Issue 2, Pages e8–e9, March–April, 2013   http://dx.doi.org/10.1016/j.jveb.2012.12.020
2. Evaluation of indicators of weight-carrying ability of light riding horses. DM Powell, K Bennett-Wimbush, A Peeples, M Duthie. Journal of Equine Veterinary Science (2008), 28-33. DOI: http://dx.doi.org/10.1016/j.jevs.2007.11.008
3. Relationship of body condition score to completion rate during 160-Km endurance races. S.E. Garlinghouse, M.J. Burrill. Department of Animal and Veterinary Sciences. California State Polytechnic University, 1999.

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This article originally appeared in the February 2014 issue of Horse Illustrated. Click here to subscribe!