uddy came to Dee as a 6-year-old who had been used for pulling logs in Ireland. Dee had a good position, but Buddy is a big horse and at that stage he had a limited understanding of the aids and was used to pulling himself forward on his forehand.
We began by working on basic circles, ignoring Buddy’s head position on the vertical, and focusing on having correct bend through circles and corners. Dee learnt to feel when Buddy was out of balance by the weight in his shoulders and how to correct this by adjusting his bend. This took a few weeks to become established, but it was important that Dee knew how to feel the issue and how to correct it, so that Buddy became better balanced, and started to develop suppleness in order to bring him out of his shoulders.
This work was done in walk so that both Dee and Buddy had time to learn what was needed before introducing a few steps of trot. Initially we kept to a jog trot, Buddy had a big unbalanced trot movement and the jog trot allowed them to develop the work done in walk through to the trot.
We also introduced shallow quarters out of the circle in walk to further supple him and began a programme of lunging and in-hand work to supplement the ridden work and help Buddy learn some of the techniques he would need for shoulder-in.
When Buddy was confident doing shoulder-in, in hand, we introduced it as a ridden exercise. He found the shoulder-in to the left much easier than to the right and to help correct this Dee rode some counter flexions on the left rein to bring Buddy off his right shoulder more. Linking exercises together helped to supple and strengthen Buddy, and we gradually increased the impulsion in trot.
For example: -
This type of exercise consolidated Buddy’s existing work, improved his mobility and suppleness, and set things up to start half pass. Using in-hand and ridden exercises we developed shoulder-in on small circles, travers, half pass and renvers, building Buddy’s ability to collect.
Rein back was started through the in-hand work and then ridden. Over several weeks it was developed further so Buddy could do rein back to trot transitions, as we continually worked on improving Buddy’s suppleness, strength and understanding.
We started in-hand trot work and then developed that on to trot shoulder-in from the ground, creating more suspension in the steps. Dee had to carefully balance her aids - asking for too much collection and Buddy would walk, not enough and he would flatten out - but when Dee’s aids were perfectly balanced, Buddy engaged his haunches more and lightened his forehand in self-carriage.
Extended trot steps were developed from the collected trot work to create some ridden lengthened steps, throughout which Buddy maintained his balance, not tipping on to the fore hand.
I focused on Buddy’s trot work because that would follow through into his canter. If we cantered too soon, Buddy would not have been able to keep his balance and the result would have been a very uncomfortable experience for both Buddy and Dee. Developing Buddy’s collection in trot allowed Dee to find the best possible moment to ask Buddy to canter, which is light, balanced and collected.
Buddy continue to improve and with Dee’s dedication and consistent approach we are now developing piaffe in-hand with him.
Throughout this steady, regular work Dee’s riding improved, Buddy would not let her be anything less than subtle and precise!
In last month’s blog I wrote about the benefits of in hand work with your horse and how to start and stop when working in-hand. This month covers the next stage, circles.
Once your horse is walking on and halting with confidence, you can start to go around circles. Begin by walking on a straight line and then start to bring yourself round the circle and your horse should follow you.
If your horse continues down the side of the school, don’t try to pull him round the circle as this could make him push his outside shoulder out and fall more away from you. Instead, gently indicate to him that you want him to follow you with a soft give-take on the lunge line to bring his head round.
The hardest part is for you to make a correct circle shape, usually riders step to the inside, so move slightly towards your outside shoulder to avoid this.
It is important that your horse starts to curve round the shape of the circle, so initially don’t make the circle too small, give both of you a chance to understand what you are doing.
Keep your space: if he crowds you by falling in through his inside shoulder, use your hand against his shoulder or the whip gently on his side to invite him to move away.
If he drifts away from you, make sure the whip is quiet and gently give-take on the lunge line to bring him round. Keep walking backwards to draw him round the circle.
Stay in front and to the side of him.
After you have completed the circle go on to a straight line making sure you give your horse enough space between you and the fence, and halt. You can then build up to more circles and, as your horse becomes more supple and balanced, you can make the circles a little smaller.
In-hand work is a very useful method for helping horses develop the strength, suppleness and understanding of movements without the added weight of a rider. I also use this technique to help riders with difficulties in certain movements.
At the Quinta all our young horses were started using this in-hand method and by developing the basic work in hand before the rider was in the saddle. The whole process of starting the horse was calmer and simplified. They had the strength and balance to carry the rider more easily, and understood the basics; walking and halting, circles, stepping sideways, shoulder-in and rein back. Further on in their training, in-hand work was used to introduce the first steps of piaffe and passage.
There are two methods of working a horse in hand, and I use both in my teaching. The first is to work the horse from the ground by using the cavesson and the second is to work them using the reins. I start horses and riders using the cavesson because it is easier for both the horse and rider and is less harsh for the horse if the rider makes a mistake.
The model for the pictures is a young pony who is learning in hand work as part of being backed.
Use the lunge cavesson and whip with the long end wound up round the whip handle. Stand in front of, and to the side of your horse, so that you can see all of him and he can see past you.
The lunge line should be safely looped up and held close to the cavesson. Have your elbow near your side so you can control your horse on the cavesson.
Hold the whip in your other hand. Have the handle in the palm of your hand so you can rotate your wrist, and hold it pointing it down towards the floor when you are not using it, and raise it gently when you use it.
Keep yourself on the inside; don’t step across your horse or allow him to step across you.
When you are walking, you need to step backwards and at the same speed as he does– but he should not rush past you. Use a light flick on the lunge line against the cavesson to slow him down. Keep your shoulders soft and your elbows bent, a lot of riders let the horse go past them and then they lose control of the horse, or hold their hand close to themselves which draws the horse’s head inwards, pushing the horse towards the outside shoulder.
Some horses are very wary of the whip, so you can use a schooling whip or just your hand if they are more settled like that.
Walking and Halting
The first thing to teach your horse is to stop. This is done by gently placing the whip on his quarters but first you need to acclimatise him to this. He already understands the lunging instructions and so start by using these voice directions.
Gently encourage him to walk forwards, stepping back at the same time and speed that he does (some horses can be confused when you stand in this position, but gently encourage them to walk and they will move forward.)
Then, using your voice only, ask him to halt. If he does not stop you can use a small jiggle on the cavesson to help. Try to keep the tension out of your body and just hold the whip softly, pointing down. It’s very important that this work is done calmly and quietly. Your horse will take triggers from your voice, body position and the whip (as well as any noises from outside!)
When he has taken a few steps, ask him to halt, again using your voice. You need to stop walking backwards when your horse stops. If you stop before he does he will walk straight past you!
When he stops, give him a pat. Repeat this a few times until you are both comfortable with walking and stopping.
Now you can introduce the idea that the whip is asking for halt. We do this through 3 steps. Firstly, ask your horse to walk and then ask your horse to halt by the wall or fence.
When your horse is quietly standing, very gently raise the whip up and rest it on his quarters. Some horses move away from the whip because they understand that this is what the whip indicates. Quietly lower the whip and ask them to stand again using your voice and repeat the raising of the whip to the quarters.
Once your horse is standing quietly from your voice command and doesn’t move when you raise the whip to his quarters, you can start to lift the whip while he is walking.
Ask your horse to walk on and then, using your voice ask him to halt and at the same time, raise the whip to his quarters. Repeat this several times until he is quietly halting as you use both your voice and the whip together. You can support this with a light feel on the cavesson, but don’t rely on this aid.
If he becomes anxious at any time, go back to the previous step.
Once he is stopping confidently from both your voice and the whip, start to bring the whip up before you use the voice command. You are looking for him to stop from the whip movement and your voice becomes a supplement to confirm the action. Look for the moment when your horse stops as you bring the whip up, before it touches his quarters!
Some horses pick this up very quickly, whereas others take a few sessions. It’s important that you don’t rush things. This work it takes as long as it takes, especially if both you and your horse are learning together.
Again, if at any point your horse becomes anxious, go back to the level he was comfortable with and repeat that step until he is calm again.
Common problems that riders find with this technique are:
Sometimes it is because the aid you are giving is too big or the whip is not still.
To start the new year I'm looking at definitions for some of the French terms associated with higher levels of classical dressage; Descente de Mains, Ramner and Rassembler. Please see my previous blogs for discussions on other dressage terms; Cadence and Collection and Rhythm, Impulsion and Engagement.
Descente de mains
This is a French term and the literal translation is “descent of hands”. For classical dressage purposes, descente de mains is a lowering or giving of the rider’s hands to softly release the contact and have the horse remain in the movement without altering the frame, rhythm or cadence, and is most telling in piaffe.
It is a simple and very tactful movement for the rider, but comes as the result of precise training; a horse in balance, with the correct level of impulsion and rhythm. Descente de mains is not riding with loose reins or when the horse has his neck stretched down with his nose near the floor!
Nuno Oiveira and Arthur Kottas Heldenberg both give clear precise descriptions of descente de mains.
Arthur Kottas Heldenburg from Kottas on Dressage (glossary) describes descente de mains as
A term from French equitation; basically, a yielding of the rein contact, either as a reward or to check the horse’s self-balance. In respect of the hands, ‘descente’ can mean either a physical lowering, or ‘reduction’ (lessening) of the contact – commonly both.
Nuno Oliveira, Reflections on Equestrian Art
Descente de main: the rider relaxes his fingers and the horse meanwhile maintains the same pace, the same attitude and the same cadence.
A good definition of Ramner can be found in Dom Diogo de Bragança’s book Dressage in the French Tradition (page 18)
Ramner, the neck is raised and self-supporting, verticality of the head (or a position of the head close to the vertical, and in front of it), the poll at the highest point of the neck.
It is possible to position the horse’s head by raising your hands, but this will not create ramner, which is a position that the horse chooses for himself based on other factors. The horse must be supple, balanced and able to control the impulsion generated from the haunches. As these qualities develop, the horse becomes more engaged, and the forehand will become lighter, the neck will lengthen from the withers and the poll will appear to advance with the nose near vertical. It is important to understand that this starts from the withers, not the head.
The translation of rassembler is given as
To bring together.
To assemble, to gather together.
To gather together, to collect.
In classical dressage terms it defines a horse who is in perfect balance, haunches engaged with the weight displaced back to the haunches as much as the horse’s conformation will allow, creating lightness in the forehand and a very maneuverable horse. Again, it is a position that the horse acquires for himself through careful and precise training and is one of the ultimate goals of classical dressage.
In Dressage in the French Tradition by Dom Diogo de Bragança, he describes rassembler as
..balance or equilibrium on a short (collected) base of support (the horse's feet placed close together).
…which is the harmonization of the means necessary for the execution of natural gaits, or those that are derived from them, on a short base of support.
Rassembler is indispensable for classical high school training. It is different to collection because it is a quality that is more tied to lightness and ramner than collection alone implies. Whilst ramner refers to the position of the horse’s head, rassembler refers to the whole horse.
This is the second of my blogs looking at the interpretations of dressage terms. Last month I looked at Rhythm, Impulsion and Engagement and in this blog I’m looking at two often misunderstood terms, Cadence and Collection.
Cadence is the most important quality of a pace. It requires balance, impulsion and rhythm all at the level appropriate to the individual horse at that time. The dictionary definition refers specifically to voice or music, but we can draw a meaningful conclusion if we combine the dictionary meaning with the description in the FEI guidelines.
A modulation or inflection of the voice.
A sequence of notes or chords comprising the close of a musical phrase.
From the FEI dressage hand book guidelines for Judging
The marked accentuation of the rhythm and (musical) beat that is the result of a steady and suitable tempo harmonising with a springy impulsion.
However, these two definitions alone don’t convey the precise meaning of cadence when applied to dressage. Arthur Kottas Heldenburg and Nuno Oliveira expand the definition further in their books
Kottas on Dressage, page 100
Even assuming the basic rhythm is good…..the hard part is to find the correct cadence. To do this first find the best possible posture of the horse: more or less on the bit, neck more or less elevated, degree of bend controlled in the circles..
It is for you to feel and choose what balance to give your hose. Start with minimal forward thrust (impulsion), go with the essential relaxation of the trot. When the horse is on the bit and relaxed, progressively ask for more impulsion.
…When your horse feels good and does not alter anything in his balance, his impulsion or posture on the circles and changes of bend….you have found the cadence that suits your horse. You can validate this by reducing the effects of your hands and your legs. The horse should be able to carry himself in the trot without your rein aids.
Nuno Oliveira from the Truth in the Teaching of Nuno Oliveira page 77.
Cadence is rhythm and energy combined, resulting in more suspension in the horse’s movements.
It is precisely in the maintenance of the appropriate cadence in each movement that one maintains the lightness, the weight on the haunches and one achieves collection.
And from the Wisdom of Master Nuno Oliveira, page 67
The cadence is something very important, more important than people think.
The cadence is rhythm [tempo] with energy.
These definitions give clear indications of how important it is to have the correct cadence for you horse, and how to achieve it. It is specific to each horse and if the horse loses their balance they lose the cadence. Often today, horses are ridden too fast at trot, and this results in a stiff unbalanced horse without cadence. Good cadence is when the horse remains in the same balance, with the same impulsion and rhythm and with minimum aids from the rider - who must have perfect balance too!
The dictionary definition of Collection does not directly relate to the dressage interpretation, and this can lead to an incorrect understanding of collection in dressage terms.
The action or process of collecting someone or something.
A group of things or people.
The description given for collect is a more relevant definition for dressage
Bring or gather together (a number of things)
Regain control of oneself, (typically after a shock.)
Both the idea of bringing a number of things together and to have a level of control over oneself can be used to infer that the rider needs to bring the horse together from the haunches with impulsion (link) whilst both horse and rider maintain their self-control.
The definition of collection from the FEI Dressage Hand Book Guidelines for Judging gives a good description of the physical characteristics that the judges should see from a collected horse:-
Collection is the increased engagement and activity of the hind legs, with joints bent and supple, stepping forward under the horse's belly.
However, collection is more than simply increasing the activity of the hind legs. It requires strength and suppleness which is built up through correct gymnastic exercises, whilst keeping the horse light in his mouth and appropriately flexed at the poll. The degree of collection will depend on level of training, the horse’s conformation, strength and suppleness.
Arthur Kottas Heldenburg gives a good description of collection in his book Kottas on Dressage (page 202)
Collection describes the state in which the horse, having developed the strength in the hind quarters through correct, progressive training, uses the strength in this area to carry a greater proportion of his and the rider’s weight, thus improving his balance and poise. The altered balancer and lowered hindquarters increased the ratio of lift to thrust in the hind quarters producing characteristically elevated, animated steps. There is a lightening of the forehand, with the poll at the highest point, and the horse flexes readily at eh poll and jaw. .. attempts to force a partly trained horse into a ‘collected’ outline are counterproductive and may actually cause damage. The development of collection is a long-term process.
Developing a truly collected horse has been an issue for as long as dressage has existed. As you can imagine the classical masters have a great deal to say about collection, from describing the method of collection;
The basic principle of that work is that of gradually increasing the action of the hocks to engage just a little further under the body; it implies the shortening of the base whereon the horse moves just a little; the horse brings his rump and quarters a little nearer to his head; to do so, the horse must of necessity lower his quarters a fraction, resulting in a relatively higher position of the head.
…It must be clearly understood that in all the work undertaken to reach … ‘collected movement’ we must pursue, and can not do other than pursue, two aims simultaneously: that of increasing the energy of the horse’s action on a shorter base and that of creating a happy mouth; the two are inseparable. Henry Wynmalen “Dressage A Further Study of the Finer Points of Riding”
To counselling about obtaining collection incorrectly;
Proper collection is the result of a long process of education through various stages that allows not tricks, no short cuts. Alfred Knopfhart “Fundamentals of Dressage”
… The rider cannot hasten the improvement of the neck carriage by shortening the reins, but must adapt the length of the reins to the horse’s improvement. The difference between following and initiating the shortening process is considerable. It is bad practice not to follow this natural improvement, but it is even worse when the rider tries to enforce it arbitrarily by shortening the reins. From such an attempt originates the greatest fault in riding, namely the forced compression of the horse. Lt Col. A.L.d’Endrödy from “Give Your Horse a Chance”
Talking with many people about dressage I have found that there are a lot of different interpretations of the terms used to describe the qualities we are trying to develop in our horses.
I have looked at the Oxford Dictionary, the FEI Judging guidelines, and descriptions from the works of classical riders to try to find a common thread between them. In this and the next two blogs, I have attempted to draw together some of the differing concepts for commonly used terms.
The interpretation that generally comes to mind when talking about rhythm is
“A strong, regular repeated pattern of movement or sound. A regularly recurring sequence of events or processes.” -oxfordenglishdictionaries.com
For dressage, this dictionary definition is appropriate, however the FEI Dressage Hand Book Guidelines for Judging give a more precise definition relating to dressage:
“The characteristic sequence of footfalls and phases of a given pace. “
In dressage terms, rhythm is the regularity of the foot falls the horse makes; it is not the speed of the footfalls, that’s the tempo.
The following quote by Arthur Kottas Heldenburg from his book Kottas on Dressage, (page 100), expands on the definition and starts to define more of the qualities that are needed for a horse to have a good rhythm.
“The rhythm is correct when the horse moves with ease, in a stable and balanced posture, active and relaxed at the same time. The horse feels good and works with pleasure; the rider is relaxed stable and can work without tiring.”
The emphasis here is that the horse has learnt to balance himself through correct suppling exercises and has the strength to maintain the regular rhythm.
Points to consider
The definition on Impulsion from oxforddictionaries.com gives the impression of force or pressure being used, which is not quite in line with the dressage meaning:
“the act of impelling or the state of being impelled
motion produced by an impulse: propulsion
a driving force; compulsion."
The FEI Dressage Hand Book Guidelines for Judging gives a slightly different description:
“Impulsion is the transmission of controlled, propulsive energy generated from the hindquarters in to the athletic movement of the eager horse. Its ultimate expression can be shown only through the horse’s soft and swinging back and is guided by a gentle contact with the rider’s hand.”
Arthur Kottas Heldenburg From Kottas on Dressage page 203
“The propulsive energy generated by the horse’s hind quarters and controlled by the rider’s leg, seat and reins.”
Nuno Oliveira’s description takes things a little further, showing that impulsion is more than just power or energy:
“Impulsion can be defined as the ability by the horse to stay in the same cadence, the same position [attitude], with the same level of energy without the constant help of the rider.”
Nuno Oliveira from “The Wisdom of Nuno Oliveira” by Antoine de Coux (page 74), and on page 67
“Impulsion has nothing to do with speed. Impulsion begins by the mind of the horse, not his legs.”
By this he means that the horse must be willing to go forward when the rider lightly touches with the leg.
The FEI definition only focuses on the physical side of impulsion i.e. the energy and where it is directed, and emphasizes a gentle contact through the reins. Classical dressage combines this with the attitude of the horse in terms of its self-carriage, enable through controlled strength and balance.
For this term, the oxforddictionaries.com description is far from the meaning that dressage implies by the word. It defines engagement as :
“The action of engaging or being engaged”
However, the definition of Engage gives a more meaningful description in dressage terms
“Engage, (with reference to a part of a machine or engine) move into position so as to come into operation.”
If we take this explanation and relate it to the action of the horse’s haunches, it becomes more meaningful. The FEI Dressage Hand Book Guidelines for Judging shows it is more than simply bringing something into position, such as the horses haunches.
“Hind legs stepping well under the horse’s body. Increased flexion of the joints of the hind quarters during its weight-bearing phase. This causes a relative lowering of the hind quarters/ raising of the forehand, thus shifting more of the task of load bearing to the hind quarters. A prerequisite for upward thrust/impulsion.”
This explanation has a good description of the mechanics of engagement, but a horse cannot engage without impulsion, so you have a circle of requirement: increase the impulsion and you can increase the engagement.
Arthur Kottas Heldenburg (from Kottas on Dressage page 203) describes engagement as
“The hind limbs are said to be engaged when, during the forward (stance) phase of the movement, they are placed sufficiently forward under the horse’s mass to enhance balance and provide a good level of forward propulsion/lift.”
Whilst these definitions give good descriptions of engagement, they don’t convey the whole picture. Engagement is part of a process that enables to horse to carry their weight towards the haunches and lighten the forehand. It is one element combined with balance, suppleness, rhythm and impulsion which brings the horse to its point of collection and lightness.
The leg sequence in canter creates an uneven, twisting movement, unlike trot where the diagonal pairing of legs gives a more even step. In canter, it is harder to straighten the horse who is often bent more towards the soft side and travels with quarters to that side, quarters in on one side and falling to the shoulder on the other side, and the rider can be pushed to one side by action of the horse's back.
Some common problems in canter are that the horse;
And among the most common cause are;
It is always worth giving your horse a general check, - particularly the back, saddle, bit and teeth - to ensure that there are no physical problems causing the reaction to canter.
Clarity of aids very important, start your correction here, checking that you are not tipping your upper body and causing a loss of balance and that your aids are correct. There is a lot of discussion over which aids are best, some people favour lateral inside aids, others prefer diagonal aids and still other use outside lateral aids. It doesn’t matter which you choose, but you must be 100% consistent with them.
If your horse is crooked in trot, holding weight in one shoulder, the canter transition will be difficult, and these horses often only canter on one lead. In this instance, go back to suppling work using circles and shoulder-in, half pass travers and renvers to rebalance your horse, and then ask for the canter again. Working correctly in a well-balanced trot will improve your horse’s canter.
Whilst young horses can benefit from cantering in straight lines outside, cantering in the school is difficult for them because of the frequency and tightness of the corners. The masters worked in trot, developing collected trot and sometimes even taking this as far as piaffe and passage before introducing canter in the school. A good collected trot will help all canter work, and any time spent developing the trot work and improving the collection and balance in trot will follow through to the canter and help to improve the balance and suppleness there.
Canter is improved by having well-balanced canter transitions from trot. Ensure that your horse is balanced and light before you ask for the canter. Then canter for a short time, once or twice round the school, as you will improve the canter by a good transition, not by cantering for a long time.
I recently read with interest in a Horse and Hound article that the German Dressage Federation has published an updated version of the well-known Training Scales. (http://www.horseandhound.co.uk/features/the-principles-of-riding-book-627462)
The origin of the training scale is unclear, but it has become widely adopted by the dressage community. The training scales identify some of the major elements required in training horses, and attempts to display the scale pictorially show how difficult it is to portray the complexity of dressage training as the qualities are very interconnected. Add to this the variety of alternative elements used by different authors as well as differing terms, it becomes confusing.
The diagrams tend towards a linear format that encourages the reader to follow a linear approach to their training, however, dressage training is not linear. Each element affects the others and progression is more circular than linear. Some authors have tried to portray a more interconnected version of the training scale, but these diagrams are, necessarily, very complex.
It’s easy to see how all this can be misinterpreted, however, the key is that each element is dependent on the others, and trainers should be conscious of this throughout their riding, e.g. ask for more impulsion and the cadence changes and needs to be readdressed.
The latest version in the “Principles of Riding: Basic Training for Horse and Rider” (above) shows that the elements are connected, but still implies a linear training system. The text that accompanies the diagram is much more informative. Each element has a relevant description and the main focus of the writing is that the steps influence each other and that the rider should understand and respect the natural abilities of each horse, never pushing them beyond what they can achieve at any given time. There is also more emphasis on the rider taking responsibility for the problems that occur, looking to themselves first before their horse. This is an improvement to previous versions, but despite efforts to clarify and refine the training scales, it remains a linear process; a good starting point but not necessarily the whole picture.
Half pass, travers and renvers and are all excellent exercises for developing suppleness, performed in different places in the school.
Introduce travers with care or your horse will not produce travers but a twisted contortion. Start at the beginning of the long side of the school and maintain a slight inside bend with your inside leg. Do not over bend the horse. Lightly touch with your outside leg back to bring your horse's quarters to the inside. As with half pass use intermittent touches with your leg, and only use the leg as necessary so you don't rush your horse in the movement. Don't over bend them to the inside or the outside shoulder will fall away.
The wall on the long side can prevent forward movement, to resolve this ensure your horse is carrying the movement from the inside hind leg not the inside shoulder.
Renvers is the reverse of travers, the quarters are to the wall and the shoulders are on an inner track with the horse bent in the direction of the movement. To position your horse for renvers, turn on to an inner track on the long side of the school. Change to bend towards the outside of the school. As with travers use your outside leg (outside to the bend, which will be on the inside of the school) to move the horse's haunches towards the wall.
Travers and renvers can be ridden on a circle and are both very beneficial to the development of a horse’s suppleness, engagement and collection. Care must be taken to ensure that the horse is correctly round the rider's inside leg and not just crooked.
The picture below shows the position of a horse in half pass, travers and renvers. The red line represents the wall and you can see how in each exercise the position of the horse is the same.
It is very common for a horse to confuse the canter and half-pass aids, particularly in early stages of learning half-pass. It is very important that you don't reprimand your horse for this as he will lose confidence in what you are asking and this can result in problems in both canter and half-pass.
The aids are similar but have small, very significant differences. In canter, the rider's outside leg comes back a little, the inside seat bone should lighten to allow horse's shoulder to lift, and the rider keeps their shoulders straight. These small movements in your upper body are significant aids to your horse.
In half-pass, your body position is different; your shoulders should turn towards the direction of the movement, your outside leg comes slightly further back than for the canter aid, and you should close your body towards the inside elbow on each stride. This will take your body weight towards the inside in the correct direction for the half-pass.
Consistent replication of the aids is paramount so you horse has clarity and you can help your horse more by asking for half-pass and canter in different places in the school.
Diane Followell Classical Dressage Trainer