The Barefoot study

Background and previous studies

In trotting, barefoot driving has been practiced for many years, mainly because it gives the horses the opportunity to run faster. Although there are no scientific studies that directly show this effect, it is a straightforward and simple physical calculation to show the increased effect and thus extra energy required to quickly accelerate an extra weight at the end of a lever back and forth, i.e. a shoe at the end of a horse's leg.

The opposite, increasing the weight on the shoe or other ways to weigh down the hoof/leg is practiced in other disciplines, for example in competitions with Icelandic horses. In this case, you change the movement pattern so that, among other things, you get a higher lift of the front leg. There is good scientific documentation about this. There are several other examples of how weight on the lower part of the leg is used and can affect movement patterns in equestrian sports.

When it comes to the biological/health effects of barefoot work, people often talk about the hoof mechanism, which, simply put, is an expansion/contraction across the heels and which is supposed to be important for the hoof's shock-absorbing ability and contributes to good circulation in the lower part of the leg. The latter is assumed to be of significant importance for long-term orthopedic health status. There are studies that show in different ways how the horse has a great ability to adapt its hooves to different surfaces and how circulation in the hooves changes with and without shoes. An experimental lab study, for example, clearly shows how a normal shoe limits the movement of the hoof capsule compared to no shoe.

In recent years, Peder Fredricson has tried training and competing his competition horses in international show jumping without shoes. He’s and likewise a number of other riders at an international high level who trained and competed without shoes have very positive experiences both from a health and performance perspective. This is anecdotal information that it would be very interesting to investigate more deeply with natural scientific methods to better understand possible mechanisms of action.

Purpose and goals of the study

The purpose of the project is to use scientific quantitative methods to investigate how movement patterns can change when a horse moves with or without shoes, with particular focus on the lower part of the limb and hoof. We also want to try using methods that have been developed to calculate forces in tendons, ligaments and joints based on pure movement measurements.

Forces are very important both in terms of performance and the risk of injury and are therefore in many cases the best indicator by far if you want to test the effect of, for example, methods or equipment. More specifically, if we can quantify load in e.g. the hoof joint or deep flexor tendon when the horse is working with or without shoes, we can get very important information that can be used to explain the positive or negative effect of shoeing on various specific anatomical structures. This, in turn, is the necessary basis for being able to give recommendations about whether, when and how it may be appropriate to work the horse shod or unshod.

Main findings and conclusions

1. The internal movement of the hoof changes in several ways when comparing the same horse moving with and without shoes. When barefoot compared to shod, you see:

1.1. Expansion across the quarters

1.1.1. An increased widening and thus a greater range of motion

1.1.2. An increased contraction is seen during the rollover

1.1.3. Just before impact, an increased contraction is seen.

1.2. The inner and outer quarters have greater mobility in the vertical direction in relation to each other

Mechanisms of action

The increased mobility is simply believed to be due to a rigid, nailed iron shoe preventing the mobility seen in barefoot locomotion.

A normal iron shoe is relatively stiff in terms of movement up and down between the branches.

The deep flexor tendon attaches to the lower side of the coffin bone and stretching it as it runs along the palmar/plantar side of the distal limb is a likely mechanism of action for the tracts to contract (approach each other) more during certain phases of the stride compared to how it looks out during the majority of the swing phase, i.e. when the hoof is unloaded. When the front edge of the hoof is in contact with the ground and the quarters have begun to lift, i.e. during the rollover, this is a highly logical explanation. A very interesting finding is that there can be a contraction of the quarters also just before impact. Here, one can speculate whether it is due to the horse preparing the hoof for landing and weight bearing by starting to tense the deep flexor tendon at the same time as the hoof is slowed up in both rotation and position and thus creates inertial forces which mean that the tension in the deep tendon, so to speak, receives a counterweight similar to what you see during rollover.

Discussion

There are no good scientific studies that show how a changed internal mobility in the hoof affects the health or performance of the horse.

A widespread theory, for which there is some evidence, claims that you get an increased blood circulation in the hoof when the hoof is loaded/unloaded, i.e. while the horse moves. If this theory is correct one can speculate further that increased mobility would improve this circulation even more.

In general, blood circulation is important for supplying nutrients and oxygen to tissues and for removing waste products. This whole chain, which is important to point out, lacks direct evidence in several cases, but what one likes to believe is that this is a mechanism of action for better health that can affect more than the hooves themselves.

The other potentially important effect of increased mobility could be that you get a better shock absorbing mechanism in the lower part of the limb which could reduce maximum loads in joints, tendons and ligaments. The latter we have so far not been able to quantify in this trial, but there is still some analyses that can be done.

 2. The rotation of the hoof around the transverse axis, i.e. seen from the side of the horse is affected in the following way when it comes to the unshod hoof compared to the shod

2.1.   The total range of motion decreases

2.2.   The rotational acceleration increases

Mechanisms of action

With less weight on the hoof, the horse does not have to lift the leg as high during the hovering phase. This in turn is due to the moment of inertia created by a weight far out on a moment arm.

Discussion

Faster accelerations allow the horse to switch more quickly between support phase and swing phase, which in turn is a prerequisite for point 3 below. Figuratively speaking, we can say that it becomes more light-footed, which in turn could be an explanation for the fact that the horses could be faster both over and between obstacles. This can also be measured by the hoof not being lifted as high off the ground when walking barefoot as described above and in the introduction.

3. The movement pattern in terms of how long the hoof is on the ground versus in the air changes in this way when walking barefoot

3.1.   Increased so-called duty factor, which is how high a percentage of the entire stride the hoof is on the ground/ in stance.

3.2.   Increased stride frequency at given speed

Mechanisms of action

With a less high leg lift and a faster change between support and hover phase, the horse can keep the hoof on the ground relatively longer during each stride cycle

Discussion

In human athletes, it is generally known that increased duty factor is important both from an energy and efficiency point of view, i.e. running with reduced energy consumption and faster. It is not unreasonable that it would have the same effect in horses. Another simple way to describe it is that all the work of movement whether it is straight forward movement, acceleration or deceleration, quick turns or jumps is done during the time that the hoof is in contact with the ground. The more time, relatively speaking, during each stride, muscles get to work, the more efficiently the work can be done.

Increased step frequency simply means taking more steps per second. The effect of this is that for a given distance between two fences, let's say 4 canter strides (approx. 17.5-18m), you can ride faster!

4. The slide phase of the hoof in connection with impact is affected when barefoot in relation to being shod in the following way

4.1.   The hoof slides slightly further

Mechanisms of action

How much the hoof cuts into the surface depends on the edge of the hoof/shoe and in this case you can imagine that a sharper edge of the shoe could build up more material in front of the hoof so that it does not slide as far as without a shoe. This must be seen as specific to the footing on which the survey was carried out in this case.

Discussion

A slightly longer sliding phase will give more time to distribute the total horizontal force that occurs when the hoof and limb must be decelerated from forward motion to stationary in relation to the ground. This in turn means that the maximum horizontal peak force is reduced. An important principle that one must understand when it comes to forces in general is the difference between what we call maximum force and impulse. The latter is the work that must be done to slow down the hoof and it is controlled entirely by mass and weight. In other words, it cannot be changed by the shoe or no shoe

5. The results of the interviews can be summarized as follows

There are many specific answers from individual interviewees that are interesting, but in this compilation the aim has been to summarize the things on which there was the greatest agreement.

5.1.  General requirement for individual assessment before training and competition without shoes

The interviewees were consistently careful to point out that training and competition without shoes must be preceded by careful individual assessment. Shoes are needed for mainly three reasons. 1) Grip, 2) Wear protection, 3) Protection against point pressure. If the horse does not have the prerequisites to meet the requirements according to these three points in the activity that is intended to be carried out, it must be shod!

5.2.  The riders at the 5* level who today train and compete without shoes firstly speak about the positive health effects

The riders who were interviewed and who regularly train and compete their horses without shoes were all clear that not all horses could 100% be trained and competed without shoes, compare the previous point. For some horses it may not work at all, some would need more or less protection in certain situations such as riding outside prepared arenas or better grip on, for example, a grass track. An important and interesting observation was that everyone primarily talked about and wanted to emphasize health benefits. All felt that they had fewer orthopedic injuries that required veterinary treatment. In second place came performance benefits such as the horses becoming more "light-footed" and nimble in their movement pattern.

5.3.  Relatively few have experience of training and competing without shoes in equestrian sports

There seem to be low amount of experience with training and competing without shoes at high level show jumping unless you ask those who specifically do this. What is a more common experience is that it could be positive when used in rehabilitation. This applies to equestrian sports. In trotting, it is common today to compete without shoes and it is considered to be motivated by performance gains. With less weight at the end of a long lever arm, less force is needed to rapidly swing the leg forward and backward with each step. It is important to point out that trotting horses are often competed without shoes, but it is few or none that are trained 100% without shoes.

5.4.  There is a lot of experience-based knowledge about barefoot gait, but there is a lack of good scientific studies.

Anatomically, the hoof is well described scientifically, and to a large extent this also applies to function. When you look more specifically at the effect of shoeing, there is a lot of solid experience-based knowledge in the farrier and veterinary professions. There is also a lot of scientific documentation about how trimming and special shoes (bars, wedges etc) can affect the movement pattern, but there is very little scientifically based knowledge based on comparing a horse that works with or without shoes and description of mechanisms for such possible changes.

Future studies

Based on the results of this study, it would above all be interesting to proceed with studies that focus on better understanding and mapping of possible positive health effects and, above all, being able to describe mechanisms of action.

There are several possible ways forward. Epidemiological studies with a focus on hoof and orthopaedic health in relation to working barefoot and shod would be interesting, but also a challenge as there are many factors that can influence, which are difficult to control in a study.

An exciting area to dive deeper into is to see how the shock absorption is affected by working barefoot vs shod. One would then want to look at load patterns in both joints (joint moment or axial load), tendons and the ligament apparatus in the distal limb.

Material and methods Horses

8 horses participated in the trial, 1 mare and 7 geldings, 5 to 8 years old. All warm-blooded, selected and trained for jumping. The horses were ridden by 4 different experienced riders who also rode and trained the horses regularly on a daily basis

Experimental design

A measuring volume for motion analysis, 20m long, 10m wide and 3m high, was created in the middle of a riding hall that was 24m wide and 70m long. The surface was a representative fibre sand surface that was prepared with watering, harrowing and rolling so that it corresponded to what can be seen at higher level jumping competitions. The middle track where most of the riding was done were maintained between every other horse.

All horses were allowed to trot and gallop in both right and left canter on a straight and a circle (approx. 10m diameter) on both right and left hand in the measurement volume. Then a normal jump warm up exercise was made. This involved jumping while approaching alternating right and left hand first on an up right and then an oxer. First jump was made on a small cross, then you started at 70cm and successively raised 10-15cm at a time to the horse's training level, which varied up to 130cm. In order to get as standardized a ride as possible, there was a small additional fence at a distance of 3 canter strides in front of the  fence that the measurement were made on. The additional fence was then outside and in front of the measuring volume.

All horses had to do this exercise barefoot or shod with an 8 mm iron shoe. During the measurement, every other horse had to start barefoot and then be shod and vice versa. Before the experiment began, the horses were trimmed so that no further trimming needed to take place during the switch between shod/unshod. Work and shoeing took place with the help of two very experienced farriers who also checked each other's work so that it took place according to an established protocol (see appendix). This gave a total of between 40 and 50 measurements per horse.

Motion analysis

The movement of the horses was measured using a so-called motion analysis system (Qualisys) which consisted of 30 high-speed cameras mounted on a camera rig shaped like a rectangle (10 by 20m) and suspended from the roof of the stable at a height of 4.5 m. This left the riding house completely free of cables and cameras so that you could ride everywhere except for a small area where a control table was set up.

Markers were attached to the horses as follows:

3 on each hoof, one on the dorsal hoof wall and one at each quarter over the coronary band. One marker on the lateral collateral ligament of the fetlock at the height of the joint space, 3 markers on the canon bone, one on the dorsal side midways, on one proximal and distal respectively on the lateral side, one over the lateral collateral ligament of the elbow joint at the level of the joint space, one over the shoulder joint in the middle between the tuberculum minus and majus, one over the tuber spina scapulae, one over the lateral collateral ligament of the knee joint at the height of the joint space, one over the tuber coxae on each limb and one on top of the tuber sacral and one in the middle of the neck. All markers 19 and 24mm in diameter were attached to a rubber plate, which were first attached in the right place with double-sided tape and then further fixed with elastic gauge and tissue tape on the hooves and with elastic tape over the cannon bones. On the upper joints and body, only the double-sided tape was used.

The cameras recorded the 3-dimensional position of each marker within the measurement volume with a precision of less than 1 mm and at 400 frames per second.

Data analysis

From the marker data, a number of different positions over time were calculated for the markers themselves and for combinations of markers. For example, the three markers on the hooves were used to look at how the distance between the inner and outer tracts changed between tracts laterally and vertically. The three markers were also used to create a so-called rigid body of the hoof so that rotations of the hoof around different axes and the center of the hoof could be determined with respect to position, speed and acceleration in 3 dimensions/axes. Correspondingly, combinations of markers have been used to represent other anatomical structures such as bones and joints.

This work has been done with own scripts in Matlab and then statistic processing has been made with Matlab or Minitab.

Interviews

Selection of people for interviews was made through a strategic and goal-directed process. In practice, this means that from a strategic perspective we were looking for people who could be expected to have solid knowledge and experience in the field. We therefore chose professional veterinarians, farriers and show jumpers with experience from 5* competition level. Goal-oriented, we chose people both with and without specific experience of training and competition without shoes.

The interview questions that were used can be found in the appendix.

Appendix, interview questions

We are performing a survey on the practice of training and competing show jumping horses without shoes.

We would like to make an interview with you on this subject. The following questions will be asked so you can prepare by reading them in advance.

We are keen to collect both positive and negative experience from people in the horse industry with varying competences as veterinarians, farriers and riders.

The answers will be used for planning and performing locomotion analysis of horses in different gaits and jumping with and without shoes. It will also be compiled and presented in a digital booklet.

• Health

o   Which advantages can you see by training and competing with unshod horses?

o   Which disadvantages or risks can you see by training and competing with unshod horses?

o   Which mechanism/explanations do you think could be behind answers to the previous two questions?

• Performance

o   Which advantages can you see by training and competing with unshod horses?

o   Which disadvantages or risks can you see by training and competing with unshod horses?

o   Which mechanism/explanations do you think could be behind answers to the previous two questions?

• Limitations

o   Do you see any circumstances where you shouldn’t train or compete bare footed?

o   Why?

o   How can it be ensured that horses will not be exposed injuries or suffering when trained or competed without shoes?

• Other

o   Do you see any economic consequences?

o   Do you see any environmental consequences?

o   Other comments or views on the subject?

Appendix, shoe protocol

Shoeing protocol

The goal with trimming and shoeing is to obtain medial/lateral and anterior/posterior symmetry in static evaluation and straight flight pattern and even landing in dynamic evaluation.

All horses are assessed statically and in walk and trot before and after trimming and shoeing.

Trimming

Sole and frog.

• Remove loose horn, not more than to live sole horn creating an even sole.

• Creating equal sole thickness and symmetry.

• Medial lateral and central sulcus's opened removing loose horn and root,

Bars.

• Loose horns removed keeping bars strong and straight.

• Making sure there is no pressure on the seat of corn

Distal hoof wall solar aspect is to be trimmed with the goal to:

• leave HWL above live sole to let HW to be weight bearing on firm (concrete) surface.

• have the heels in line with the highest and widest part of the frog.

• keep the ground (solar) surface of the foot to be parallel to the live frog.

• have heels of equal length

• hoof/pastern axes to be straight lateral medial and anterior posterior

• ground (solar) surface perpendicular to the long axes of the distal leg when of the ground.

• solar shape to be symmetrical from the midline of frog and following the shape of withe line/perimeter edge of sole

Hoof wall is to be dressed not more than ½ thickness and ½ of HWL and only when needed with the goal to:

• remove flares and create equal medial and lateral HW angels

• obtain equal thickness and HW parallel to dorsal P3

Shoeing

Size and dimension

• All horses are shod with Mustad Libero 22x8 (7.6)mm

• Length of the shoes to the widest part of the frog/frog-heel connection

Fit

• The shoe is fitted perimeter and to the shape of white line from the widest part to the widest part of the foot.

• From the widest part the shoe is fitted to obtain a medial lateral symmetry with the goal to gradually give width and fit heel in middle of bar stock or wider if needed to obtain medial lateral symmetry

• Fronts and hinds are fitted with no clips.

• Shoes are set back no more than ½ of HW thickness

• Shoes are in full contact with wall and not sole with minimum of 1.5 mm sole relief.

Nailing and clenching

• Shoes are nailed on with 6 appropriate size Mustad EXL nails with the goal to be 1/3 up on HW and not behind the widest part of the foot.

• Clenches to be in the wall

• No artificial substances are applied.

• Dressing and sanding are to be on the distal ½ of HW

Axle Vibe AWCF

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