CAN HOOF SHAPE INFLUENCE SADDLE SLIP?

Studies have previously demonstrated that saddle slip can be related to hind limb lameness (1) and movement asymmetry (2). However, are there other factors which can influence saddle slip as well as the aforementioned? It is often thought that the rider is responsible for inducing saddle slip however, this is not currently supported by any experimental data, in contrast studies have found that the rider is not, in most cases a contributing factor (2, 3) .
 
An area we are currently investigating is front hoof shape and its relationship with saddle slip. In horses with uneven feet, the side with the flatter foot has been shown to have an increase in vertical ground reaction force (GRF) and a larger vertical fetlock displacement whereas the more upright foot was linearly correlated with an earlier braking-propulsion transition (4). Therefore, in horses who have uneven feet, different ground reaction forces (left-right) are present. GRFs provide gravitational support to the body and the vertical GRFs are higher in the front limbs compared to the hind limbs.
 
Where are these forces transmitted to? Vertebral morphology with respect to shape, size and orientation of the facet joints, largely determines movement along with soft tissues. The vertebrae of the cranial thoracic spine up to the anticlinal vertebra (~T16) modulates the forces from the forelimb, head and neck.
In respect of the saddle and rider; the saddle is positioned in the thoracic region. The lowest part of the saddle would be approximately in the region of ~T13, corresponding with the lowest part of the back. Therefore, the area of the back that the saddle and rider are positioned, is an area which is responsible for modulating forces from the forelimbs, head and neck. In cases where the front feet are asymmetric, this leads to asymmetric GRFs which will lead to asymmetric forces being applied to the body influenceing function and posture. Could this have an effect on the kinematics of the back and consequently saddle position….? This is a question we are currently investigating – from preliminary data (5) we collected from a group of horses, it appears that there is a relationship between hoof shape and saddle movement however, more studies are scheduled to investiagte this further.
 
Although we don’t have all the answers yet, the purpose of this blog was to further highlight the complexities of saddle fit and highlight the need for a team approach when managing horses who have saddle slip. It would be great to have a simple model of just “correcting” the rider to eliminate saddle slip or "replacing the saddle", however as said previously, this is not supported by any experimental evidence. Instead, working collectively with your qualified saddle fitter and equine/human team will help evaluate, support and manage the horse which will help to reduce / eliminate the saddle slip. As previously said, saddle fitting is complex and in the case of horses who have saddle slip the complexities are increased further.
 
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Dr. Russell MacKechnie-Guire
Centaur Biomechanics
 
1. Greve L, Dyson SJ. An investigation of the relationship between hindlimb lameness and saddle slip. Equine Vet J. 2013;45(5):570-7.
2. Mackechnie-Guire R, Mackechnie-Guire, E., Fisher, M., Mathie, H., Bush, R., Pfau, T., Weller, R. Relationship between saddle and rider kinematics, horse locomotion and thoracolumbar pressures in sound horses. JEVS. 2018;69:43.52.
3. Greve L, Dyson SJ. The interrelationship of lameness, saddle slip and back shape in the general sports horse population. Equine Vet J. 2014;46(6):687-94.
4. Wiggers N, Ambrósio CE, Nauwelaerts SLP, Hobbs SJ, Bool S, Wolschrijn CF, et al. Functional Locomotor Consequences of Uneven Forefeet for Trot Symmetry in Individual Riding Horses. Plos One. 2015;10(2):e0114836.
5. MacKechnie-Guire R et al., Hoof Shape and its Relationship with Saddle Slip, Pilot Study, 2018

 

ARE WE SITTING EQUALLY - RIDER PERCEPTION?

 

The rider needs to be able to withstand the propulsive forces generated by the horse during locomotion and adjust to the temporal and spatial movement patterns of the horse’s trunk. The coupled system of the horse and rider produces coordinated patterns which can be used to determine gait and riding styles. It is widely accepted that the rider’s position is influential for enhancing equine locomotion and performance. Riders attempt to be positioned on the horse symmetrically; however, this is sometimes challenging due to the rider’s skill level, functional asymmetries, perception, and pre-existing or historic injuries which the rider may have.

 

Understanding the interaction between the horse and rider (and saddle) has becoming better understood. Previously in an “off horse” study we have quantified rider perception (1). Thirty experienced riders, who were all right-handed, were asked to sit on a pressure mat which was positioned on a horizontal platform. Whilst sitting, the riders were asked to say when they “felt” evenly weighted on their seat bones, at which point five seconds worth of data was recorded which was then repeated three times resulting in fifteen seconds worth of data being used for analysis (1).

 

Despite riders saying they were “sitting equally”, from the pressure mat data, they had increased weight distributed beneath their left seat bone in comparison to the right (1) (image). Therefore, based on this study (and others), in this case riders’ perception of weight distribution appears to differ from objective measures. The next question is how does this translate to horse? – although riders may feel “straight” when riding, is there is a discrepancy between what is being perceived and what is objectively apparent? It is appreciated that in the current study riders were assessed using a static model; however, work is well underway quantifying seat pressures in a dynamic model (2021/2). It is speculated that the asymmetries seen in the “on horse” study will be similar to the findings from the “off-horse” study (1). Previous blogs have highlighted the effect that tack, and equipment have on quine locomotion. In the case of the rider, who is sitting on one seat bone more than the other, what effect will this have on the horse (and saddle)? As previously discussed, horses will develop a locomotor strategy to compensate to alleviate any discomfort and/or imbalance, in this case caused by the asymmetric rider.

 

Riders are athletes and all attempts should be made by the rider to optimise their position and physical fitness. Off-horse exercise, working with a human sports science team (physio, Pilates, therapist, biomechanist etc.) can be hugely beneficial. Improving rider’s dynamic stability “off-horse” will translate to dynamic stability and awareness “on-horse”, which will help optimise the interaction between the horse and rider.
 
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Dr. Russell MacKechnie-Guire
Centaur Biomechanics

 

 

1. Guire R, Mathie H, Fisher M, Fisher D. Riders’ perception of symmetrical pressure on their ischial tuberosities and rein contact tension whilst sitting on a static object. Comparative Exercise Physiology. 2017;13(1):7-12.

 

 

RIDER AYSMMETRY - DOES IT MATTER TO THE HORSE?

Riders attempt to be positioned on the horse symmetrically; however, this is sometimes challenging due to the rider’s skill level, functional asymmetries, perception, and pre-existing or historic injuries which the rider may have. Previous blogs have highlighted the effect that tack, and equipment have on quine locomotion. In the case of the rider what effect does rider asymmetry have on equine locomotion? As previously discussed, horses will develop a locomotor strategy to compensate to alleviate any discomfort and/or imbalance, in this case caused by the asymmetric rider.
 
Previously we have demonstrated the immediate effect that rider asymmetry has on the equine locomotor system when in trot. This was achieved by shortening one stirrup by 5cm which induced a measurable about of rider asymmetry (1). Using motion capture and inertial measuring units, the horse’s limb and back movement was quantified. Horses will develop a locomotor strategy to compensate and alleviate any discomfort. As a result of the asymmetric rider, this compensation strategy was evident with changes in back movement and limb loading (1). With the asymmetric rider the horses back movement altered with an increased range of motion which could be an indication of instability as opposed to dynamic stability. In addition to the changes in back movement, limb loading (derived from fetlock extension) front and hind was increased (overloaded) – interestingly, only the limbs on the opposite side to the shortened stirrup were affected therefore, one side of the horse has increased limb loading compared to the other (1).
 
Rider asymmetry not only affects equine locomotion but also saddle pressure distribution (2). In sitting trot, riders who collapse through one hip have been shown to increase saddle pressures beneath the saddle on the opposite side to the collapse (i.e. collapse of the right hip = increased saddle pressures beneath the left side of the saddle) (2) and riders who lean too one side with their trunk, result in an increase in saddle pressures on the same side as the rider is leaning too (2). Riders who lean forward, as maybe expected will increase saddle pressures in the front region of the saddle (3).
 
Rider asymmetry influences equine locomotion (1) and saddle pressures (2) which may lead to locomotor compensation strategies. It is accepted that humans (and horses) have some degree of asymmetry, laterality and handedness however, attempts should be made to help optimise rider biomechanics / symmetry in order to optimise the horse-saddle-rider interaction. It is appreciated that some riders are asymmetric as a result of skill level, functional asymmetries, perception, and pre-existing or historic injuries, in these cases, it is essential that the horse+rider are managed as a team in order to monitor and manage any locomotor compensation strategies which if left could manifest into long term compensations strategies.
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Dr. Russell MacKechnie-Guire
Centaur Biomechanics
1. MacKechnie-Guire R, MacKechnie-Guire E, Fairfax V, Fisher M, Hargreaves S, Pfau T. The Effect That Induced Rider Asymmetry Has on Equine Locomotion and the Range of Motion of the Thoracolumbar Spine When Ridden in Rising Trot. Journal of Equine Veterinary Science. 2020;88:102946.
2. Gunst S, Dittmann MT, Arpagaus S, Roepstorff C, Latif SN, Klaassen B, et al. Influence of Functional Rider and Horse Asymmetries on Saddle Force Distribution During Stance and in Sitting Trot. Journal of Equine Veterinary Science. 2019;78:20-8.
3. Unpublished data from Mackechnie-Guire et al., 2021

 

 

SHOULD WE RIDE WITH ODD STIRRUPS?

The answer to this may seem obvious however, sometimes riders are unaware that one stirrup is longer than the other and furthermore, riders (and trainers) may deliberately alter one stirrup as a possible solution to help “improve” the riders’ position or manage rider limb length differences.
 
In some cases, when rider’s ride on one rein they may feel more symmetrical than when riding on the other rein. On the rein where they feel less symmetrical, the rider would usually feedback that their seat/hips are consistently slipping out to one side. From a visual observation, when the rider is riding towards you, it may appear that the stirrups look equal and when riding towards you on the opposite rein, the outside stirrup may appear longer. This observation will generally coincide with the rider’s feedback that their seat/hips are displacing to the outside. At first glance, it may seem that the rider is putting increased weight in the outside stirrup due to it being “longer” which is causing the riders seat/hips to displace towards the side with the longer stirrup. Therefore, based on this visual observation, riders (and trainers) shorten the stirrup to make them appear visually “symmetrical”.
 
The key word used here is “appear”. What needs to be considered here is the position of the saddle. We (1) and others (2, 3) have demonstrated that saddle slip generally occurs on one rein as a result of the horse’s locomotor system. As saddle slip generally occurs on one rein, this will have a significant effect on the rider’s position. In the above scenario, with the saddle slipping to the outside, this will change the position of the stirrup bar (relative to the horse) which will give the appearance that the stirrup is longer on the side that the saddle has slipped towards, and the rider will follow the saddle causing them to displace their seat/hips (Image: Left rein). When on the other rein, as the saddle is “straight” the position will be improved (Image: Right rein).
 
In the above scenario (saddle slip right, right stirrup appears longer and riders seat displaced to the right), if the right stirrup is shortened this will compound the issue further as an element of rider asymmetry will be induced into the horse-rider system as a function of different stirrup lengths (4). When assessing stirrup length dynamically, it is important to assess the position of the saddle relative to the horse. This observation must be made from a rear viewpoint, with the horse/rider going away and must be performed on both the left and right rein and in all gaits (if appropriate). If the stirrups “appear” to be different because of saddle position, then initially this must be addressed with the qualified saddle fitter (and others). In the above case, riders and trainers should avoid the temptation to shorten one stirrup to resolve the issue as this is not addressing the fundamental reasoning i.e. why is the saddle slipping?
 
In addition to this, riders often report that they have one leg longer and then self-prescribe a plan to alter one stirrup. This will be addressed in a future blog, but caution should be taken over this, along with clarification from a specialist, confirming if the rider has an actual or functional limb length difference. In either case, it is imperative that riders seek clarification on this before altering stirrups, as for reasons outlined in previous blogs, riding with asymmetric stirrups will cause the horse to seek a locomotor compensation strategy to compensate.
 
So to answer the initial question, it is important that the length of the stirrup is equal and not asymmetrically altered to “correct’ saddle or rider position.
Check your stirrup leathers regularly to ensure that they are symmetrical and get someone to watch you ride away from a left and right rein approach.
 
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Dr. Russell MacKechnie-Guire
Centaur Biomechanics
1. Mackechnie-Guire R, Mackechnie-Guire, E., Fisher, M., Mathie, H., Bush, R., Pfau, T., Weller, R. Relationship between saddle and rider kinematics, horse locomotion and thoracolumbar pressures in sound horses. JEVS. 2018;69:43.52.
2. Greve L, Dyson SJ. An investigation of the relationship between hindlimb lameness and saddle slip. Equine Vet J. 2013;45(5):570-7.
3. Greve L, Dyson SJ. The interrelationship of lameness, saddle slip and back shape in the general sports horse population. Equine Vet J. 2014;46(6):687-94.
4. MacKechnie-Guire R, MacKechnie-Guire E, Fairfax V, Fisher M, Hargreaves S, Pfau T. The Effect That Induced Rider Asymmetry Has on Equine Locomotion and the Range of Motion of the Thoracolumbar Spine When Ridden in Rising Trot. Journal of Equine Veterinary Science. 2020;88:102946

 

SADDLE FITTING: A COMPLEX PROCESS

Saddle fitting is complex: individuals are required to fit a fairly rigid structure to a dynamic platform which has to conform to the shape of both the horse and rider whilst distributing forces. The complexities are further compounded with alterations in body shape (horse) occurring as a result of seasonal changes, exercise, body weight, travelling etc. To highlight this further, we have shown changes in back shape throughout an eight-hour period (1) and others have shown changes after 30-minutes of exercise when ridden in a correctly fitted saddle (2).
 
We and others have extensively investigated the effect that saddle fit and design can have on saddle pressures, equine locomotion, back health and function. In respect of saddle fit, a horse which is ridden in a saddle which is “out of balance” can create areas of high pressure causing the horse to adopt a locomotor strategy to compensate. This compensation strategy can result in asymmetries, and asymmetries can lead to asymmetric forces and sadly this can result in over/under load of structures. The importance of saddle fit should not be underestimated for all horses, in all sports and riding activities. The horse can feel a fly…in the case of incorrect saddle fit, the horse develops a locomotor strategy to alleviate any discomfort caused.
(Images A: Correct fit - uniformed pressure; B= saddle which is too narrow - 4 points of pressure; C= saddle which is too wide - localised pressures at the front)
 
Given the complexities and factors which affect saddle fit and the direct link with saddle fit, back health and locomotion, it seems logical and crucial that a qualified individual should be responsible for saddle fit. With advances in research and methods, saddle fitting has evolved for the good of the horse. In 2016 we ran a poll and just over half of the responses were aware if their saddle fitter was qualified and just over half thought that it was important that their saddle fitter was qualified. Comparing the poll to the one we ran recently (2021) there appears to be a shift with the majority of responders recognising that their saddle fitter is qualified and majority recognising the importance of using a qualified saddle fitter.
 
This is hugely positive. Like all sectors within the industry there are qualifications which can be achieved in a fairly short time (i.e. weekend courses) to qualifications which follow an in-depth process (i.e. Society of Master Saddlers (SMS) +3 years). Whilst the differences are clear, as a due diligence mechanism it is important for individuals to be aware of differences in qualifications and the training process/duration etc. Another consideration is the continual development of the qualification, as highlighted at the beginning of this blog, through evidence we are understanding the complexities and challenges of saddle fit therefore, it seems essential that practising saddle fitters are up to date with advances in research and methods in order to optimise saddle fit for the good of the horse.
 
I hope the above is of interest and helpful as mentioned previously, we must not underestimate the effect that the saddle and saddle fit can have on equine health and performance.
 
Long gone are the days where saddles arrive through the post in a box or saddles which are fitted without any ridden observations – or at least I hope!
Please SHARE to raise awareness on the complexities of saddle fit.
 
Kind Regards
Dr. Russell MacKechnie-Guire
 
1) R. MacKechnie-Guire, M. Fisher, D. Fisher, T. Pfau, V. Fairfax,, 2020. Variations in epaxial musculature dimensions and horse height over a period of eight hours. BEVA 2020 Congress. https://doi.org/10.1111/evj.08_13365,https://beva.onlinelibrary.wiley.com/.../10.../evj.08_13365
 
2) Greve L, Murray R, Dyson S. Subjective analysis of exercise-induced changes in back dimensions of the horse: The influence of saddle-fit, rider skill and work quality. Vet J. 2015;206(1):39-46.

 

TRAINING ROLLER PRESSURES – ARE THEY OF CONCERN?

Ground schooling activities including lunging, are routinely performed in the training and rehabilitation of horses. Training rollers (from here on: roller) are commonly used to provide attachment for training aids however, little attention is given to the fit and design of the roller, and the effect it has on the horse.
It may be thought, that as there is no rider (or saddle) during lunging, the pressures beneath the roller may not be of any significance. Previously we have demonstrated (1) in trot and canter, when lunging, using a roller fitted with a wool pad and dressage square, designed with two foam pads providing a semi sort of gullet, that roller pressures were located directly on the midline of the back (spine) (Image A ). Despite no rider or saddle, the roller pressures were greater than those thought to cause back discomfort and of a similar magnitude to those seen during ridden exercise suggesting that the pressures observed are influenced by locomotor forces and roller design (1).
 
We should not underestimate the effect that rollers have on the locomotor apparatus of the horse, especially in horse’s who are undergoing rehabilitation for back related conditions. Pressures of this magnitude, directly on the spine are not ideal. Like saddle and bridle pressures (see previous blogs), the pressures were influenced by locomotion. In trot, two peak pressures occurred, coinciding with the stance phase of the forelimbs and in canter, one peak pressure occurred coinciding with the stance phase of the inside forelimb.
 
The location and magnitude of pressures beneath the roller was influenced by the training aid being used. When using side reins high pressures beneath the roller were located towards the front edge of the roller, likely due to the connection of the side rein with the roller/bit, pulling the roller forwards and down. When using a Pessoa training aid, areas of high pressures were located towards the back edge of the roller (Image B ) again, when considering the attachment of the Pessoa, attaching to a ring positioned on the back (centre) of the roller, during locomotion, the roller is tilted backwards (1).
 
Training aids are used for multiple reasons however, in the context of this blog, if using a training aid with a roller which is creating high pressures directly on the midline of the back, then it seems reasonable to suggest that any benefits of lunge exercise and or the training aid, are likely to be diluted. As I have said many times, horses will develop a locomotor strategy to alleviate any discomfort caused, in this case, by the roller. This is amplified when considering the already existing locomotor adaptions as a result of circling versus moving in a straight line. If we apply this to our lunge session: lunging horses on a ~20m circle, for ~15-20 minutes, in trot/canter, during each stance phase of the forelimb, a peak pressure directly on the midline of the horses back occurs, of a magnitude similar to pressures seen during ridden exercise.
 
Like everything else, considering roller fit and design is essential – some take home messages:
 
🟢Users should ensure that the roller is well padded providing clearance of the midline (spine).
🟢When using training aids, ensure that during locomotion, the training aid is not causing the roller to tilt or draw down on the horses back.
🟢Consider girth fit and design (see previous blog) when lunging.
🟢Use of a correctly fitted saddle (providing there is no clinical reasoning) and positioning the roller over the top maybe advantageous.
 
Hope this is of interest. Please SHARE to raise awareness of the importance of training roller fit/design.
 
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Kind Regards
 
Dr. Russell MacKechnie-Guire
 
 
1. Mackechnie-Guire R, Mackechnie-Guire E, Bush R, Fisher D, Fisher M, Weller R. Local Back Pressure Caused by a Training Roller During Lunging With and Without a Pessoa Training Aid. Journal of Equine Veterinary Science. 2018;67:112-7.

 

SHOULD WE FIT SADDLES WIDER THAN INDUSTRY GUIDELINES*?

This is a question which has been raised multiple times. Some of the thoughts which underpin the idea that fitting a saddle “wider” than industry guidelines are; “allows the horse to work over the back better”, “allows the horse to lift up”, “allows muscle activation” and “won’t restrict scapula mechanics” just to list a few. Although at first glance this may seem logical, fitting a saddle wider, allowing the region of the back beneath to have more room, there is no experimental evidence to support this approach.
 
In the static horse, a wide saddle will have the appearance that the front of the saddle is down when compared to the back of the saddle (image B.). When applying pressure with your hand to the front of the saddle, the back will lift up. In the dynamic horse, the position and orientation of the saddle remains the same (down at the front), plus we add the mass of the rider. Previously we have demonstrated the effect that a “wide” saddle has on back movement, muscle dimensions, locomotion and rider position when compared to a “correctly” fitted saddle (1, 3, 4). During trot and canter when ridden in a wide saddle, the back showed altered range of motion, which is likely as a result of the saddle instability (down at the front, up at the back). As a function of the front of the saddle being down during locomotion, this resulted in areas of high pressures in the front region of the saddle (left and right, image B. ), the magnitude of pressure and locations were consistent across all horses with peak pressures being directly influenced by limb movement. To emphasise the effect that tree width has on the locomotor apparatus of the horse, after twenty minutes of exercise in a wide saddle, compressions (concavities) in the epaxial musculature in the region of T13 were recorded (1, 3, 4). These compressions are as a result of the high pressures which occurred as a function of saddle width (down at the front). Horses develop compensatory strategies to alleviate any discomfort caused, in this case by the saddle width. In a wide saddle, every motion cycle, the horse will experience high pressures in the front region of the saddle, and of course will alter its locomotion to compensate.
 
The idea that fitting a saddle wider than industry guidelines is a fallacy. In contrast to the anecdotal beliefs, it could have deleterious effect on the horse’s locomotor apparatus. It is assumed that if the horse has more room, it will be able to utilise that space by altering its biomechanics. However, the dynamic forces from the rider must be considered, in the case of the wide saddle which is down at the front when the horse is stood square (no rider), then adding the mass of the rider, combined with the locomotor forces, the saddle will remain and increase its pitch in a forward / downward direction – comprising the horses locomotor function. The wide saddle will also affect the rider biomechanics which will be addressed in part 2.
 
The results outlined here are in accordance with researchers in Europe (2) where a group of horses were ridden on a treadmill with saddles of varying widths. It is appreciated that the saddle width can be corrected with a half pad/front riser. This strategy may be of benefit however, we must consider the half pad/front riser being used, in respect that the pad must be able to manage the dynamic forces and not deform under load, as the saddle which is “in balance” with a half pad/front riser , which then deforms during locomotion will become “out of balance” wide. From preliminary data, saddles which were wide but rebalanced to correct width with the use of a front riser, after twenty minutes of exercise, the concavities at T13 were still apparent (sadly, COVID has prevented pressure data collection). Therefore, although the saddle is “in balance” we must be cautious that it doesn’t become out of balance during locomotion. There are situations where a half pad/front riser can used to help rebalance saddles, in these cases it is essential that horse owners work closely with their qualified saddle fitter with regular checks in order to monitor any changes and rebalance saddles accordingly.
 
*NB: correct width defined as: The shape of the head of the tree and the angle of the tree points corresponding to the shape and angle of the horse 5cm behind the scapulae.
Please like / follow our page for more blogs and please share to raise awareness.
 
Dr. Russell MacKechnie-Guire
 
Centaur Biomechanics
 
1. MacKechnie-Guire R, MacKechnie-Guire E, Fairfax V, Fisher D, Fisher M, Pfau T. The Effect of Tree Width on Thoracolumbar and Limb Kinematics, Saddle Pressure Distribution, and Thoracolumbar Dimensions in Sports Horses in Trot and Canter. Animals (Basel). 2019;9(10).
2. Meschan EM, Peham C, Schobesberger H, Licka TF. The influence of the width of the saddle tree on the forces and the pressure distribution under the saddle. Vet J. 2007;173(3):578-84.
3. R. MacKechnie-Guire, E. MacKechnie-Guire, V. Fairfax, D. Fisher, M. Fisher and T. Pfau. (2019), Kinematics of the thoracolumbar spine whilst cantering in horses fitted with a saddle of three different widths, BEVA Congress, EVJ Supplement, https://onlinelibrary.wiley.com/.../10.1111/evj.13_13152...
4. R. MacKechnie-Guire, E. MacKechnie-Guire, V. Fairfax, D. Fisher, M. Fisher and T. Pfau. (2019), Can saddle tree width affect saddle pressure distribution whilst cantering?, BEVA Congress, EVJ Supplement, https://onlinelibrary.wiley.com/.../10.1111/evj.16_13152..

 

KNEE BLOCK DESIGN AND ITS EFFECT ON RIDER BIOMECHANICS AND EQUINE LOCOMOTION

Previously the complexities of saddle fit, and the importance of correct saddle fit in relation to equine health and performance have been discussed (see previous blogs). To add to the complexities, we must not neglect the effect that the rider has on the horse (and saddle) but also the effect that the saddle has on the rider. In respect of the saddle, there are multiple factors which can have an influence on rider biomechanics, seat size/shape, waist/twist, panel content, stirrup bar positioning just to name a few.
 
Knee blocks come in all shapes and sizes and their function, to provide support to the rider and aid positioning. Over the last decade, knee blocks have increased in size and design, largely driven by the rider, in an attempt to provide greater support and security. Although this mechanism could be interpreted as a benefit, the effect that knee block design/size can have on rider biomechanics and consequently the effect this has on the horse’s locomotion should not be underestimated.
 
During locomotion, whilst maintaining dynamic stability, the rider has to manage and absorb propulsive forces being generated by the horse. In gaits where there is a suspension phase (trot and canter) the riders’ segments (pelvis, trunk, limbs etc) respond differently during each component of the stride. In the context of the knee block, following the suspension phase, during stance, the rider’s knee/thigh moves forward and can be pressed up (restricted) against the knee block. Depending on the size and shape of the knee block and anatomy of the rider, if restrictive, the rider’s pelvis can restricted. In a rider model, the segments are stacked on top of the pelvis, if the pelvis is restricted as a result of the knee being restricted by the knee block, then the segments above will have to compensate.
 
Recently we have demonstrated the effect that knee block design can have on the rider’s biomechanics and equine locomotion. With knee block modifications, allowing the knee to move forward (i.e. not being restricted by the edge of the knee block) the riders pelvic function was improved with a more neutral position being achieved throughout the motion cycle. The riders were more synchronised with the movement of the horse. This makes logical sense, if the pelvis is neutral (not restrcited) then force absorption and transmission can be better achieved. It would seem logical, like other parts of the saddle, that knee block design would influence rider biomechanics, however, we should not underestimate the effect that knee block design can have one equine locomotion, as a function of altered (restricted) rider biomechanics. With knee block modifications, allowing the rider’s knee to be less restricted, allowing the pelvis to be in a more neutral position resulted in alterations in the horse’s back movement and limb kinematics in trot and canter.
As previously said, horses will develop a locomotor compensatory strategy to alleviate any discomfort caused. In the case of a knee block, where the rider’s knee is restricted by the knee block, resulting in the pelvis being restricted, may have an effect on the horses back and limb movement.
 
Following on from the previous blog(s), I hope this helps and further highlights the complexities with saddle fit for both horse and rider and the importance of working with a qualified saddle fitter who understands these complexities from both a horse and rider view point.
 
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Dr. Russell MacKechnie-Guire
 
Centaur Biomechanics
 

 

WE ALL USE A MOUNTING BLOCK, BUT IS IT THE CORRECT HEIGHT?

Dr. Russell MacKechnie-Guire

January 2021

 

Mounting the horse seems like a routine task performed ~daily. However, mounting technique and the height of the mounting block should be considered. Previously we have demonstrated that mounting a horse from the ground can put as much pressure on the horses back as a horse landing over a 1.30m fence. When mounting, the rider’s weight is supported by the stirrup and the rider then lifts their centre of mass up. During this process, the saddle is pulled over to the left, which causes the back of the saddle to cross the midline (spine). As a function of the saddle being pulled towards the rider, along with the rider’s weight, an area of high pressure (> than a horse landing over 1.30m) on the right side of the horses back is created. As a strategy to withstand the forces from the mounting rider, the horse will alter its posture and limb loading. As has been said in previous blogs and publications, horses develop a compensation strategy to alleviate any discomfort caused, in this case from mounting.
 
Rider height affected saddle pressures when mounting; a smaller rider had higher pressures than a taller rider. It is thought that this is due to the length of the rider’s levers (legs) and the need for the smaller rider to pull the saddle (and horse) towards them as opposed to a taller rider, who could direct their centre of mass up and over, thus reducing the pressures when mounting.
 
Rider fitness can also have an effect; athletic riders were able to bounce and generate greater force when pushing off from the ground, raising their centre of mass vertically, versus the less athletic riders who had less force on push off, as a result, used a pulling mechanism to mount (i.e. pulling the horse towards them).
Another area to consider is how the rider descends on the saddle - riders who land “heavy”, create areas of high pressures towards the back of the saddle.
It is appreciated that the majority of riders do not mount from the ground. Instead, riders tend to use an easy to move, portable stool or step. Although this is positive, mounting block height should also be considered relative to horse height. It was demonstrated that a small mounting block of 22.5” did not help reduce saddle pressures when mounting. In contrast when using a tall mounting block, defined as a mounting block where the rider can put their foot in the stirrup and then mount as if stepping onto the horse. As the “mounting” (from foot off to seated) process time was shortened this was associated with reduced saddle pressures when mounting.
 
Therefore, the higher the mounting block, the better, to help reduce pressures beneath the saddle. Having someone hold the opposite stirrup is advantageous and recommended even when using a high mounting block.
 
"Leg ups" can be useful at reducing pressures beneath the saddle when mounting, although it must be stressed that leg up technique is also a factor for consideration. Riders who get propelled into the air by an over enthusiastic helper are likely to cause high pressures on the horses back as the rider lands in the saddle.
 
Some take home messages:
 
🟢Mounting from the ground creates high pressures on the horses back, particularly on the right side of withers.
🟢Where possible, use a high mounting block that allows you to place your foot in the stirrup and then mount as if you were stepping on.
🟢Ask someone to hold the opposite stirrup when mounting, even if using a high mounting block.
🟢When giving a leg up – be cautious on “leg up” technique, so that the rider does not land heavy on the horses back.
🟢Consider rider fitness in relation to mounting technique.
🟢Consider how the rider lands on the saddle once mounted.
 
Although mounting seems a routine task which occurs ~once a day, we should not underestimate the effect that mounting can have on the horses back, posture and limb loading. Attention also for those horses who are mounted several times a day, such as trekking centres, riding schools etc. Although knowing how to mount a horse is important, it is also important to understand the effects this has on the horse and where possible using a high mounting block would be advantageous.
 
Hope the above blog is interesting.
 
Please SHARE to raise awareness on mounting technique.
 
Regards
Dr. Russell MacKechnie-Guire
 

 

GIRTH PRESSURES AND ITS EFFECT ON EQUINE LOCOMOTION

Dr. Russell MacKechnie-Guire

January 2021

Previously it has been assumed that the highest pressures beneath the girth are localised to the sternum. From a study we did before the London 2012 Olympics, using an electronic pressure mat positioned beneath the girth combined with motion capture, we quantified the effect that girth fit and design has on grith pressures and locomotion (1). In that study we demonstrated that, contrary to popular belief, areas of high pressures were localised behind the elbow and not on the sternum.
We observed areas of high pressure beneath girths in dressage, jumping and event horses, across all gaits (walk, trot & canter) (1) and more recently we have demonstrated the areas of high pressures in racehorses galloping occurs in the same region as previously described, behind the elbows. When girth pressures were reduced with girth modifications, the horses gait altered across all disciplines, highlighting the effect that girth pressures can have on locomotion.
We must not underestimate the effect that girth fit and design can have on locomotion. A girth that causes high pressures will cause the horse to seek a compensatory strategy to alleviate the discomfort caused, in this case by the girth. It should be noted that the areas of high pressure occurred every stride, therefore in a schooling session, in a girth which is poorly designed and or doesn’t fit, the horse is experiencing areas of high pressure behind the elbows every stride.
 
Some of the take home messages:
 
🟢Ensure the girth buckles are up as high as possible - away from the sensitive areas behind the elbows
🟢If using a martingale or training aid, which goes around the girth, caution should be taken as you will create a ridge of pressure on the sternum. Consider using a girth which has the girth attachment on the outside of the girth.
🟢Anatomically shaped girths with medical grade closed cell foam are preferred as they do not deform and help to reduce girth pressures
🟢Make sure the inside of the grith does not have cracks
🟢Ensure that girth buckles (left and right) are equal +- one hole
🟢Make sure that the girth is fitted in relation to the horse’s anatomy
 
Since this study, there are a lot of girths on the market which claim to be pressure relieving and or allow “freedom”. Whilst I am supportive of new designs for the good of the horse, users must be cautious over such claims which are not supported by evidence and particularly look at the fit and design of the girth, as from this study, girth fit and design must not be underestimated.
Please share to raise awareness of girth fit.
Hope the above is of interest.
 
Kind Regards
 
Dr Russell MacKechnie-Guire
 
 
1) Murray R, Guire R, Fisher M, Fairfax V. Girth pressure measurements reveal high peak pressures that can be avoided using an alternative girth design that also results in increased limb protraction and flexion in the swing phase. Vet J. 2013;198(1):92-7.
 

IS THE NOSEBAND THE ONLY CONCERN IN BRIDLE FIT?

Dr. Russell MacKechnie-Guire

January 2021

 
 
There is a growing awareness, both scientifically and on social media on the effect that noseband fit, and tightness can have on equine welfare. Whilst this is a positive step forward there is very little consideration for the effect that the rest of the bridle can have on equine welfare, comfort and performance.
The anatomy must be considered when fitting bridles, the bridle has to conform and sit over anatomical structures, various nerves etc. which can influence locomotion, swallowing mechanism, proprioception and function. The fit of the bridle (as a unit) can have a direct effect on equine welfare, comfort and performance. In the context of the headpiece, it is often thought that bridles cause “poll” pressure. Using a validated pressure mat (middle image) beneath the headpiece we have demonstrated (1) that there is pressure over the head but that this pressure is not excessively high. Instead areas of high pressures beneath the headpiece were localised at the base of the ears, in the region of the temporomandibular joint (TMJ) a sensitive area with complex nerve arrangements and articulation between the mandible and the skull.
 
Structurally, not all horses’ heads are the same shape so bridles should be fitted to individual horses. Headpiece width and design should be considered, a straight narrow headpiece can run forward putting pressure on the cartilage of the ears, likewise a headpiece which is too wide can put pressure on the wing of the atlas (L and R) empathising the need for bridle fit for each horse.
 
Headpiece design and noseband straps which are positioned underneath the headpiece can create a ridge of pressure over the head (Image A), by using a modified headpiece which is shaped, padded and where the noseband attaches either side, this ridge of pressure can be eliminated (Image B.) (1).
Buckles which are positioned over the head, or to one side of the midline, can result in focal pressures beneath the buckles. In respect of browbands, riders can express themselves with various colours or stones however, we must not neglect the fit. In some cases, the browband is fixed or can slide up and down the cheek/headpiece. In the case where the browband can slide up and down, at this junction, areas of high pressures may occur due to the ridge running under the headpiece. Likewise, a browband which is too small, can pull the headpiece forward, (into the back of the ears) creating areas of high pressure.
 
In trot peak pressures beneath the headpiece occur soon after midstance (75% of stance) for both diagonal support phases. The magnitude of pressure is directly influenced by the fit and design of the headpiece and attachment and fit of the browband. Meaning that every time the horse loads its limbs (every stride), wearing a headpiece and/or browband which is incorrectly fitted could cause areas of high pressure beneath the headpiece, every stride. The bridle should be considered as a unit and we must not underestimate the effect that the bridle (as a unit) can have on the horse. In respect of locomotion, when pressures were reduced beneath the bridle, an increase in carpal, tarsal flexion and limb protraction was reported (1). From unpublished data (3), back range of motion is also influenced by bridle fit and design this highlights the direct connection between bridle fit and whole horse biomechanics. In swimming, swimmers have been reported to suffer from supraorbital neuralgia (pain above the eye) headaches (2), this is thought to be due to the tightness of the goggles. Although we cannot confirm this is the case in horses, cautiously applying similar principles, we should not underestimate the effect that incorrect headpiece and browband fit can have on equine welfare, comfort, and performance similar to the effect that that noseband fit and tightness can have. What we have found is horses will develop a locomotor strategy to compensate and alleviate any discomfort, therefore correct bridle fit (and saddle fit) is essential.
Hope this blog is of interest.
 
Please share and like our page for more blogs
 
If you have any topics you want covered (horse, saddle and rider interaction) pls add a comment.
 
1. Murray R, Guire R, Fisher M, Fairfax V. A Bridle Designed to Avoid Peak Pressure Locations Under the Headpiece and Noseband Is Associated With More Uniform Pressure and Increased Carpal and Tarsal Flexion, Compared With the Horse's Usual Bridle. Journal of Equine Veterinary Science. 2015;35(11-12):947-55.
2. O'Brien J. C. J. Swimmer's headache, or supraorbital neuralgia. . Proceedings (Baylor University Medical Center). 2004;17(4: 418–9.
3. MacKechnie-Guire et al 2018 - unpublished

 

Pre and post images - useful or misleading? Don’t be fooled by the trickery….!

Dr. Russell MacKechnie-Guire

September 2020

In image A, the saddle is slipped to the right (orange arrow) and the rider is shortening through their left side with their seat displaced to the right. In image B, the saddle is straighter and the rider has an improved position as a result of the “intervention” – or is this a trick….? With reference to images C and D (same as the previous images, but now the limbs are visible) it can be seen that the horse is on different canter leads (image A and C = left lead and image B and D = right lead) - look at the orientation of the hoof. 

In the above scenario, riders may see these two images (A and B ) and believe the “intervention” has resolved the saddle slip and that their position is improved. The differences here, are as a function of the horse being on the opposite rein and the directional effects on locomotion and biomechanics. In addition, saddle slip generally only occurs on one rein. 

Riders could be under the impression that the “intervention” has 1) resolved the saddle slip; 2) that they are responsible for the saddle slip and 3) that the intervention has worked. Of course, if the intervention has worked and has been verified (correctly with no bias) then this is a positive.

The greater concern is if riders believe an intervention has worked, and it hasn’t. In these cases, the rider is likely not to address the underlying mechanics as to why the saddle is slipping. Evidence from (Greve and Dyson), and our own (MacKechnie-Guire et al.) has shown that the horse is the contributory factor for inducing saddle slip with the rider following the movements of the saddle and horse. It is appreciated that there are a small number of riders who may induce saddle slip however, in the majority of cases it is initiated by the horse due to multiple reasons - lameness, functional asymmetry, laterality, seasonal effect, travelling etc. research is ongoing to understand further. 

The purpose of this blog is to raise awareness, I recently received a pre and post image from a rider. This rider was not advised nor did she think to explore the underlying mechanics as to why the saddle had initially slipped as the intervention had “fixed” the problem. A few months later, the rider was still crooked and the saddle slip was more evident– what long term effect did this have on the horse+rider….? 

Saddle slip is something that requires a detailed understanding of both equine biomechanics and the interaction between the horse, saddle and rider. Correcting saddle slip is something that requires a team approach (all or some) veterinarian, saddle fitter, farrier, coach, therapist, biomechanist, horse+rider physio etc. along with regular monitoring and saddle fitting checks. Importantly, saddle slip can be an early indicator of movement asymmetry hence it is essential that it is addressed in order to limit further asymmetries developing.

  • Things to look for when viewing pre and post images.
    Foot fall – you will see with image C and D the grounded limb (green arrow) and flexed hindlimb (red arrow) has been indicated – it can be seen that the grounded/flexed limb (s) differ when on either the left / right rein. This is easily identified when looking at the orientation of the hoof
  • Pelvic roll / height – look at the top of the horse’s pelvis and observe if it rolls (falls away) in the same direction
  • Gait – walk, trot and canter have different mechanics hence will have a different effect on the horse+rider+saddle

I hope the above post helps. I am a massive advocate of using technology to help support horse + rider performance but the interpretation of information / findings is crucial and if performed incorrectly can be misleading and in the scenario presented here, could have a detrimental effect on the horse+rider. 

For meaningful comparisons to be made, the horse+rider need to be on the same rein, same moment in the stride cycle and same gait.

Please share to raise awareness.

 

  

SADDLE SLIP – GOOD or BAD 

Dr Russell MacKechnie-Guire

Friday 24 July 2020

 

An evidence based discussion about saddle slip - recently, there has been a lot of activity on social media about saddle slip. We and others have studied this area extensively, therefore the purpose of this post is to provide an evidence based discussion around the topic.

Saddle slip, defined as a saddle which displaces to one side as can be seen in video (A). The third marker up from the top of the tail is the middle of the cantle, during locomotion, the saddle consistently slips to the right every stride. Saddle slip is generally only present on one rein therefore, a saddle which slips to the right will occur on the left rein and a saddle which slips to the left will occur on the right rein. If a saddle slips left and right, it is likely that the saddle is too wide therefore, saddle width should be checked by a saddle fitter. 

 

What effect does this have on the horse?

Video A - it can be seen that the left side of the saddle panel is brought up close to the midline of the horse (spine). This results in increased saddle pressures on the left side of the horse’s back, compressing the back muscles on the left. The horse’s limbs (front+hind) are loaded asymmetrically as a result of the asymmetric positioning of the saddle+rider.

 

What effect does this have on the rider?

Video A - the rider’s pelvis slips to the right (with the saddle), as a result, their upper body then shortens to the left, the rider’s left knee becomes tight and the right leg becomes straight. This is often easy to see, as the stirrup (on the side that the saddle has slipped too) “appears” to be longer however, this is a function of saddle slip not an asymmetry in the rider’s limbs or stirrup leathers. Lastly, rider’s may have an asymmetric rein tension, as a result of the rider trying to maintain stability.

As mentioned, saddle slip is generally only present on one rein, therefore all of the ridden work on that rein will be compromised – straight line, circling, half pass, jumping turns etc.

 

Correcting Saddle Slip

When saddle slip was corrected (video B – same horse/rider/saddle/day) you can see that the third marker is now aligned with the tail marker. When saddle slip was corrected, a more uniformed pressure distribution and symmetrical movement of the horse was found and a more symmetrical rider position along with an even rein tension.

 

Why does saddle slip occur?

There are multiple factors that influence saddle slip, there is evidence that saddle slip occurs as a result of lameness (Greve and Dyson, AHT/RVC). Saddle slip can also occur in non-lame horse’s (MacKechnie-Guire et al, . RVC). What is interesting, from our studies and others, saddle slip appears to be initiated by the horse and not the rider. Riders will follow the movement of the saddle but don’t necessarily cause the saddle to slip – more on that in another post. Research groups are investigating additional factors which could cause saddle slip – more on that in due course. 

 

Horses seek a locomotor pattern to alleviate any discomfort caused by a saddle. In this case, how can a saddle which is slipping to one side be of benefit to the horse? This locomotor pattern, can lead to increased asymmetry in the horse and rider, coupled with the asymmetric forces creates a vicious circle. 

I am a huge advocate of working as a team, therefore, in cases where saddle slip is present, it is essential that this is discussed with the acting saddle fitter in conjunction with the veterinarian, coach, equine/human physio, farrier, biomechanist, therapist etc. Saddle slip requires a team approach with regular saddle assessments to monitor progress etc. 

I hope the above notes are useful.

Please share to create awareness of the importance of addressing saddle slip AND help with saddle slip recognition, as in cases where the saddle is straight and then starts to slip could be used as an early indicator of movement asymmetry occurring!

Next post will be how to identify saddle slip and who is the primary cause – horse or rider!

Kind Regards  

 

Centaur Biomechanics

Dr. Russell MacKechnie-Guire

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