Author Name: Ruth Taylor; BSc (Hons) Equestrian Sports Science
The aim of this literature review was to answer the question ‘should there be a weight restriction for horse riders?’ To do so four research databases were utilised, these were: Bristol UWE library, Google Scholar, Hartpury library, and Science Direct. The main search terms of ‘rider weight’ and ‘horse riding’ were combined with terms such as: ‘body weight ratio’, ‘endurance’, ‘fitness’, ‘jockey’, ‘restriction’ and ‘skill’ to find and evaluate relevant peer reviewed articles. The main research findings were: horses experience significantly increased soreness and tightness when carrying 30% of their body weight and significantly higher heart rates when carrying 25 and 30% of their body weight; added weight loads of 15% for jumping cause significant kinematic alterations to the horse; horses with increased loin width and cannon bone circumference become less sore carrying heavier weight loads; and rider skill is a contributor to force distribution upon the horse. In conclusion a weight limit of 20% of the horse’s body weight was deemed reasonable. Alongside this, riders should be encouraged to exercise off the horse and educated with regards to horse welfare. Further research is recommended assessing the effects of familiarisation periods on horses jumping with extra weight.
An early study by Springings and Leach (1986) explained that a horse’s centre of gravity (COG) should not be shifted by the rider because the rider sits directly above it (just behind the withers). However, the horse carries approximately 60% of its body weight (BW) on its front legs and 40% on its hind legs (Powell et al., 2008), therefore, the rider should aim to shift weight backwards to increase ‘lightness of the forehand and engagement of the hindquarters’ (FEI, 2015). This is backed up by recent studies which have found that rider posture and weight distribution does affect the horses COG (Münz et al., 2014; deCocq et al., 2009) making the original theories by Springings and Leach (1986) invalid.
The optimum weight a horse can carry in a safe manner depends on a variety of physical traits including: the horse’s size, conformation, body condition and age (Powell et al., 2008; Garlinghouse et al., 1999) as well as duration, frequency and intensity of work to be done (Greve and Dyson, 2013). Forces applied to the horse increase as rider weight increases (Greve and Dyson, 2013) which has the potential to disturb the horses kinematics and COG, decreasing performance rates and even causing injury (Garlinghouse et al., 1999; Clayton, 1997). Despite a rise in obesity, rider body weight tends to be an ignored topic (Halliday and Randle, 2013). Consequently, the purpose of this review is to establish if there should be a weight restriction for horse riders.
2.0 Literature Review
2.1 Weight limit suggestions within equestrianism
Recent studies have begun to investigate the optimal rider to horse BW ratio. Halliday and Randle (2013) suggested that the optimum rider BW is 10% of the horse’s BW. The authors detailed that all 50 riders studied were of a healthy BMI with the average BW percentage at 14.2 and 16.6% of the horse’s weight, making 10% an unrealistic goal. Moreover, BMI has been deemed an inaccurate measurement of body fat (Shah and Braverman, 2012; Freedman and Sherry, 2009). With the increase in overweight riders being one of the author’s primary concerns, a more accurate measurement of body fat would have increased the studies reliability and validity.
Ernst et al. (2015) and Powell et al. (2008) also investigated rider to horse BW ratios. Similarities between these studies were the use of the same rider to horse BW ratios, a sub-maximal exercise protocol and measurement of the horse’s heart rate values. Ernst et al. (2015) found that as rider weight increases the horse’s stress levels increase, but these findings were not significant. Powell et al. (2008) found that heart rate remained significantly higher with horses carrying 25 and 30% of their BW and horses experienced significantly increased soreness and tightness when carrying 30% of their BW. Soreness and tightness was determined using a subjective scoring system which was supported by taking heart rate and venous values – increasing reliability and validity. Creatine Kinase (CK) is used as an indicator of muscle damage and is associated with post-exercise muscle soreness (Garcia-Lopez, 2006) and plasma lactate is used as an indicator of work load (Faud et al., 2009); these levels were highest at 30%. Furthermore, Powell et al. (2008) revealed that loin width and cannon bone circumference negatively correlated to changes in muscle soreness and tightness, concluding that horses with wider loin and thicker cannon bone circumference became less sore when carrying heavier weight loads.
Ernst et al. (2015) and Powell et al. (2008) both failed to mention fitness levels. Fitness influences work rates (Gendron, 2015), which could mean that Ernst et al. (2015) used fitter horses than Powell et al. (2008) and this is why their results were not significant. Additionally, Powell et al. (2008) used a small sample size of eight horses compared to other studies (Halliday and Randle (2013) used 50 horses and Garlinghouse and Burril (1999) used three hundred and sixty horses). As well as this, the breed of horse was not stated. With a small sample size and a potential variety of equine breeds used, the reliability and validity of this study is questionable. Ernst et al. (2015) has only released an abstract so far which did not mention the type of horse or sample size used. Despite the weaknesses of these studies, they both found that horses were negatively affected by increased weight loads. In addition, optimal rider to horse BW ratio is a fairly new concept so these preliminary studies are bound to require further research.
2.1.1 Weight restrictions within equestrianism
188.8.131.52 Weight restrictions within racing
Horse racing has strict weight restrictions in comparison to other equestrian disciplines, for example, flat racing requires the rider and saddle to weigh between 52.7–64 kg (Cullen et al., 2015; Caulfield and Karageorhis, 2008). As a consequence, jockeys have been found to adopt extreme weight loss methods which over time compromises their psychological and physical well-being (Wilson et al., 2014; Caulfield and Karageorhis, 2008). A study by Torres-McGehee et al. (2011) estimated that eating disorders affect 42% of female equestrian collegiate athletes because English and Western riding is appearance based, which could pressurise an athlete to become thin. From this, if weight limits were imposed throughout the equestrian population, a level of deterioration similar to jockeys could be predicted. However, Torres-McGehee et al. (2011) used a screening tool (EAT-26) rather than a diagnostic tool so could not conclude with certainty that the participants ‘at risk’ actually had an eating disorder. Moreover, those concerned about their diet or those that generally respond positively to surveys may have inflated the results. The authors stated that ‘professionals working with this population should avoid making negative comments about their physical size and appearance’. It could be argued on the contrary, that riders should be made aware if they are too big or heavy for their horse to protect the horse’s welfare (Halliday and Randle, 2015; Ernst et al., 2013).
Apart from racing, anthropometrics of horse riders appears to be a neglected area of research. Reasons for this neglect could be due to the variety of disciplines, junior riders, senior riders, males and females competing against each other and the fact that the horse must also be accounted for (Douglas et al., 2012). Boxers and jockeys are both examples of weight category athletes (Wilson et al., 2014; Caulfield and Karageorhis, 2008; Khana and Manna, 2006), yet Dolan et al (2011) found boxers to have a higher bone mass. They thought that this was due to the decreased energy availability in jockeys because of their weight loss methods. Moreover, they indicated that boxers have a higher bone mass due to their high intensity, high impact training, which acts as an osteogenic stimulus. This backs up a seminal study by Alfredson et al. (1998), which found that riders had high muscular strength of the thigh but not bone mass due to the type of loading. Both studies used dual energy X-ray absorptiometry (DXA) scanning to measure bone mass. Using quantitative computer tomography would provide a cross sectional and more comprehensive and complete view of the bone architecture and strength of mass (Leonard et al., 2004) improving the validity of these studies.
184.108.40.206 Weight restrictions within endurance racing
Endurance is another equestrian discipline with rider weight rules. For example, at all senior CEI4* championships the minimum riding weight for athletes must be 75kg to include all riding equipment (FEI Endurance Rules, 2014). When considering the aforementioned studies regarding rider weight and that endurance horses are typically light Arabian types (Bergeroa et al., 2005), the minimal weight load of 75kg would seem quite high. However, a seminal study by Garlinghouse and Burril (1999) found that rider weight (20-30% of the horse’s BW) had no effect on completion rate of a 160km endurance race, and that the condition score of the horse was of more significant importance when considering success rate. A weakness of this study was that they did not check CK levels post-race; if they had, as with Powell et al. (2008), they may have found that horses carrying heavier weights had higher levels of muscle damage.
A study by Schott et al. (2006) also measured the difference between finishers and non-finishers competing in a 160km endurance race. They did measure CK levels post-race and did not find any significant differences between finishers and non-finishers, backing up Garlinghouse and Burril’s (1999) findings, which explained that rider weight within reasonable limits may not have a deleterious effect on physiology due to the relatively low intensity of long-term endurance exercise.
220.127.116.11 Weight restrictions for jumping
Jumping is a discipline requiring higher intensity bursts of efforts compared to endurance racing (Murray, 2006). A seminal study by Clayton (1997) found that the addition of 18kg weight during jumping caused significant kinematic alterations to the horse during the landing phase. The leading forelimb landed closer to the fence because the horses struggled to increase impulsion and balance sufficiently at take-off. It is interesting to note that the added weight condition in this study represented 15% of the horse’s body weight. Halliday and Randle (2013) identified that for optimum performance 15% was satisfactory and Powell et al. (2008) identified that 15% of the horses body weight did not significantly influence work rate, heart rate, and lactate concentrations. Clayton’s (1997) study would have had a greater effect than the other studies because of the significant rise in ground reaction force through the forelimb when landing from a jump, which increases even further with extra weight and higher intensity (Murray et al, 2006).
Unlike the other studies in this area, Clayton (1997) identified injury risk – explaining that the increase in rider weight and exaggerated hyperextension of the carpus in the leading forelimb could predispose the horse to strain of the suspensory ligament. A weakness of this study was that horses had not been familiarised to working with extra weights (decreasing the study’s reliability and validity) and two of the horses had made serious jumping errors over 1 metre fences in the added weight condition. When considering this, a weight limit of less than 15% of the horse’s BW for jumping should be implemented if further research finds that the horse is still at greater risk when jumping after a familiarisation period. Also, it would have been useful for Clayton (1997) to measure heart rates and venous values to understand how hard the horses were working and to make results more comparable to the other studies.
2.2 Physical fitness for horse riders
High levels of body fat (thus increased body mass) are indicative of low levels of physical fitness (Khana and Manna, 2006). There are only several studies regarding physical fitness for horse riders. Roberts et al. (2009) reported that high body fat percentages among equestrian athletes reflects a lack of physical conditioning when compared to other groups of athletes. They emphasised that horse riding requires physical fitness for the maintenance of rider balance and general effectiveness. Meyers (2006) established that horse riding alone is not enough to improve health and fitness and Symes and Ellis (2009) suggested that cross training could build core stability, flexibility and reduce asymmetry. As previously mentioned horse riders have been found to lack bone mass (Alfredson et al., 1998), so it could be suggested that horse riders would benefit from participation in other sports such as netball to assist bone mineral development and structural skeletal adaptations (Karlsson and Rosengren, 2012). Interestingly, 96% of horse riders participate for leisure (Beta, 2015), as this is a large portion of the equestrian population it would be useful for researchers to study leisure riders rather than competitive riders to enhance future applications. Another reason for this is that more emphasis has already been placed on fitness for elite riders such as those on the ‘Equestrian World class Programme’ (BEF, 2014).
2.3 Horse and rider interaction
Many studies have investigated the force and weight distribution of the saddle on the horse (Bellock et al., 2012; Zimmerman 2011a; 2011b; Kotschwar 2010a; 2010b; Von Peinen et al., 2010; Meschan et al., 2007; deCocq et al., 2006). Bellock et al. (2012) compared how a treeless saddle and a conventional saddle distribute the rider’s weight. Although they only used one lightweight rider (weighing just 57kg), the authors explained that heavier riders would be expected to exert proportionally higher total forces on the horse and that a heavy rider using a treeless saddle would be of concern (due to harmful pressure peaks beneath the rider’s seat bones (Peham et al., 2010)). Von Pienen et al. (2010) found that horses showing clinical signs of back trauma had significantly higher pressures between the saddle and back during walk, trot and canter, yet the only reference to rider weight throughout the study was regarding the fact that ponies had not been presented to their services with saddle problems. They thought that this was due to ponies being ridden by lightweight riders so they were not exposed to high pressure strains. Despite these important links between rider weight and pressures on the horses back, both studies paid little attention to the weight of the riders used in their study and the effects on the horse.
A possible reason why these studies have not used a variety of rider weight is because rider skill is an influencing factor to forces applied to the horse (Greve and Dyson, 2013; Peham et al., 2010; 2004; 2001; Symes and Ellis, 2009; Legarde et al., 2005). Zimmerman et al. (2011b) specified that poor riding could influence functional thoracolumbar biomechanics negatively, causing hollowness of the back and loss of core strength which could result in thoracolumbar regional pain. Beginner riders have been found to be tense against the horse’s movements causing them to lean forwards to maintain balance, disturbing the horses regularity of pace and COG (Münz et al., 2014; Legarde et al., 2005). An advanced rider, on the other hand, has been found to synchronise with the horse, maintaining an upright posture which has an overall positive effect on the horse (Münz et al., 2014; Legarde et al., 2005). Greve and Dyson (2013) stated that a heavier rider who is synchronised with the horse could be less detrimental to the horse than a lighter rider who is not able to synchronise with the horse. However, no study has actually investigated the effect of a heavy experienced and heavy novice rider on the horse. Thus it would be useful for studies into horse and rider interaction (Münz et al., 2014; Peham et al., 2010; 2004; 2001; Legarde et al., 2005) to use a larger sample size (rather than one novice and one experienced rider) to determine the effect of different weights (within reasonable limits) and skill levels upon the horse. From the aforementioned research, it can be predicted that a heavier rider would still have a more deleterious effect on the horse than a lighter rider.
From the findings of this literature review it can be proposed that there should be a weight limit of 20% of the horse’s BW and horses with wider loins and thicker cannon bone circumference would be more suited to riders in the upper range of this weight limit. Instead of causing riders to feel pressurised into losing weight, these weight limits should educate and encourage riders to exercise off the horse, not only to enhance the horse’s welfare but also to benefit the health and performance of the partnership. Moreover, because the majority of horse riders participate for leisure purposes, improved performance may encourage them to compete. Additionally, with increased levels of physical fitness and reduced overweight riders, research into the ideal body composition for top performance could become possible. Overall this may make training programmes easier to formulate so that success rates can increase over time. Further research is required to assess the effect of a familiarisation period on horses jumping with 15% extra weight to conclude if this weight limit should be imposed. As well as this, research to distinguish the effect of different rider weights and experience levels on the horse is required to establish whether riders with different experience levels should have different weight limits.
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