Why a Circle Is Really a Thousand Squares - and What That Means for Rider Alignment

This week online I have been focusing heavily on the rider’s position when riding a circle, particularly the instruction I frequently use: rotate your pelvis in the direction of travel. This single phrase creates more discussion, debate and resistance on social media than almost anything else I talk about (except maybe heels down!) because it challenges conventional thinking about rider alignment. Many riders misunderstand it to mean overly twist into the circle, drop the inside seat bone, lean inward, or collapse through the ribcage. Others assume it contradicts traditional instructions on lateral work such as shoulder-in or travers as the riders pelvis isn’t on the same direction as the horses.

Rotating the pelvis in the direction of travel does not mean facing the centre of the circle, how much you rotate in will depend on the size of the circle. It does not mean tipping in or out. It does not mean loading one seat bone. It means following the horse’s constantly changing line of movement along the arc, so that the rider stays aligned with what the horse is actually doing beneath them.

Many riders have asked how this applies to movements like shoulder-in or travers, which require a different body organisation. There are so many ways to achieve the same end result in horse training, but most explanations focus on the aids rather than on what is truly happening beneath the rider in terms of physics, biomechanics, and how horses actually learn. When we strip everything back to these fundamentals, the reasoning behind rotating in the direction of travel becomes very clear.

A Circle Is Not One Bend: Understanding the Physics of Directional Change for Rider Alignment

Most riders picture a circle as one smooth, continuous curve. In school geometry, this seems accurate. But in physics and mathematics, a circle is not one single curved direction at all. It is formed by an infinite series of tiny straight lines, each pointing in a slightly different direction. Each of these micro straight lines has a tangent, and the tangent is the instantaneous direction of travel at that exact moment. This means that as the horse travels around the circle, the direction changes continuously, step by step, degree by degree.

Consider the arrow as the direction of the horses pelvis, whereas the straight line between the arrows is the direction of travel which the rider needs to follow (the outline/circumference of the circle)

Newton’s First Law states that an object in motion will continue in a straight line unless acted on by another force. This describes the rider’s body perfectly. When the horse turns, the horse generates centripetal force to maintain the curve. The rider, however, experiences what feels like being pushed outward. This is the effect of inertia resisting the turn. This is the origin of what the centrifugal force is, even though in physics it is not a true external force but the sensation of resisting inward pull.

If the rider keeps their pelvis facing straight, their pelvis is not following the arc; it remains aligned with the tangent that the horse is momentarily leaving behind. The rider therefore begins to drift outward. The outside seat bone becomes heavier, the pelvis rotates slightly outward relative to the saddle, and the horse responds to the changed balance by drifting outward to keep both bodies’ centres of mass aligned. It is a predictable mechanical reaction.

Understanding the relationship between centripetal force, inertia, the rider’s mass, and the horse’s curved path explains why riders who keep their pelvis fixed quickly find themselves being pulled outward physically and destabilised biomechanically and want to /are told to load the inside seat bone. But this is a correction to a problem.

Why We Align with the Horse’s Shoulders Rather Than the Hindquarters

Biomechanically, the horse initiates turns with the shoulders, not the hindquarters.

Locomotion studies consistently show that the shoulders define the line of travel while the hindquarters provide propulsion. If the rider attempts to align their pelvis with the horse’s hindquarters, they inadvertently align themselves with the direction the hind end would push if it were travelling straight ahead. This is why riders who try to “match pelvis to pelvis” on a circle often feel like they are falling out of the turn. They are aligning with the direction of push instead of the direction of travel. We don't sit over the pelvis so this doesn't make sense from that perspective either.

This is also why some traditional schools attempted to compensate by instructing riders to sit heavier on the inside seat bone. This increased frictional contact reduced outward slipping, but it did not address the underlying issue: the pelvis was not following the path of travel. Maintaining equal weight in the seat bones becomes entirely possible when the pelvis itself moves with the arc rather than resisting it.

When a rider matches pelvis to pelvis then weight shifts to outside and the rider will often then lean inwards or be told to put more weight into inside seat bone

Rotating the pelvis in the direction of travel therefore means staying aligned with the shoulders and the curved track, rather than the straight-line vector of the hindquarters.

What Pelvic Rotation Actually Does in the Rider’s Body

When the pelvis rotates, the hip joints respond. The inside hip undergoes internal rotation; the outside hip undergoes external rotation. What is crucial is that this happens without shifting the rider’s weight. The thighs do not grip or push; they simply adjust their angle of contact. The rider’s weight remains centred and evenly distributed across both seat bones when done correctly.

This is where confusion often arises around aids such as the outside leg for canter. Someone recently asked how rotating the pelvis inward could be compatible with the canter aid, which traditionally involves bringing the outside leg slightly back. The answer lies in joint independence. The pelvis can rotate inward while the outside hip simultaneously extends and externally rotates to apply the leg aid. These movements are separate. An independent seat means the pelvis, hips, legs, and torso can move individually without interfering with one another.

Pelvic rotation is not a leg aid and you shouldn't need your pelvis in a certain position for a leg aid.

What Research Has Found About Pelvic Rotation in Riders

Biomechanics researchers including Peham, Münz, González Álvarez, Clayton, Hobbs and others have extensively studied the horse–rider system using force plates, pressure mats, kinematic motion capture, rein-tension sensors and saddle-pressure measurement devices. Several important findings relate directly to pelvic rotation.

When riders deliberately rotated their pelvis outward on a circle, the outside seat bone became heavier, the inside of the saddle unloaded, the rider drifted outward due to inertia, and the horse drifted outward to stay underneath the rider’s centre of mass. This was consistent across multiple studies. Increased lateral forces were recorded when the rider’s pelvis was not aligned with the direction of travel.

A side flexion of the upper body often happens on a circle when weight isn't equal in seat bones or pelvis facing direction of travel and rider compensating to try and stay balanced.

When riders rotated their pelvis moderately inward to follow the horse’s changing direction, pressure under the seat bones became more equal. The rider experienced less outward drift. Rein tension became more symmetrical. The horse’s stride pattern remained more regular. The system as a whole became more stable.

When riders rotated too far inward, torsion occurred through the lumbar spine, causing ribcage collapse, uneven seat-bone pressure, and disruptions in horse symmetry. Excessive rotation created instability similar to insufficient rotation.

One of the most useful findings across studies was that pelvic rotation had beneficial effects only in riders who possessed independent hip mobility. Riders who lacked hip independence gripped with the thighs when rotating the pelvis, destabilising themselves and confusing the horse. Riders with good hip independence maintained equal seat-bone pressure, consistent rein tension, and a centred upper body while rotating the pelvis.

These findings support exactly why I teach rotational following on circles: it aligns the rider with the direction of travel when done moderately and correctly, but causes problems when done excessively or without sufficient joint independence.

Why Twisting the Pelvis and Shoulders in Different Directions Does Not Work (for a circle)

Some traditional instruction tells riders to match shoulders to shoulders and pelvis to pelvis. In lateral work, this makes sense because the horse is simultaneously stepping sideways and forward, and the rider’s pelvis can remain forward-facing (same as horses pelvis and direction of travel). However, applying this rule to circles creates biomechanical conflict. The rider ends up attempting to face two directions at once on a circle, which the human spine cannot support without torsion.

The lumbar spine has very limited rotational capacity. If the pelvis turns one way and the shoulders another, the rider is actively teh movement and on a circle resisting mirroring the horses movements. This blocks the rider’s ability to absorb movement, affects seat-bone pressure, and destabilises rein tension. Most riders who attempt to separate shoulders and pelvis on a circle become crooked or braced, not because of poor riding but because the movement contradicts spinal mechanics.

The forces on a circle are different to that of a straight line so you can’t apply the same principles of lateral work with a circle.

Not rotating pelvis but rotating head and shoulders (Again at different angles)-‘ look into centre of circle’ is often used to help riders turn their bodies in direction of travel but often ends up causing more problems unless the movement starts at the pelvis

Pure axial rotation of the torso or head doesn’t significantly move the rider’s centre of mass, because the mass simply rotates around a vertical axis without shifting sideways or forward–backward. In practice, though, many riders unintentionally combine rotation with leaning or collapsing through flexion, side-flexion, or lateral shifting, and it is these compensations, not the rotation itself, that shift the centre of mass and alter the horse’s balance.

How Upper-Body Rotation Affects Rein Tension and the Horse’s Balance

Even slight rotation of the upper body affects the reins. When the torso rotates inward, the inside elbow moves back, increasing tension on the inside rein without the rider intending it. Simultaneously, the outside hand moves forward and reduces tension. This creates a mechanical signal to the horse that the inside rein should create more bend while the outside rein opens the door for the shoulders to drift outward. It is why outside rein is talked about so much for balance of the horse and to prevent overbending or falling out. The horse is following what the riders change in position is causing to the change in tension on the reins and therefore the bit.

Many riders believe their horse is falling out of the circle because of the horses imbalance or training but the imbalance often begins in the rider’s torso and pelvic position. This is why it's important for shoulders to stay over hips in a neutral spine with no leaning back or to the side (check out the last blog post talking about this in more detail)

Weight as the Most Powerful Aid in Riding

Horses organise themselves under the rider’s centre of mass. This is a fundamental principle of balance, not training. If the rider drifts outward, the horse follows to remain upright. If the rider collapses inward, the horse falls inward. These are not trained responses; they are natural reactions driven by physics.

Horses also move away from pressure reflexively. When you press a horse’s barrel with your hand, it moves away from pressure because skin receptors detect a stimulus and trigger a response. Inside leg aids rely on the same sensory mechanism. However, the horse cannot detect the difference between a leg placed one centimetre forward or back. The meaning and precision of the aid comes from operant conditioning, not anatomical precision.

How Horses Learn: Operant Conditioning and Why Different Aid Systems Exist

Every aid in every riding discipline fits into one of the four categories of operant conditioning. In traditional riding, negative reinforcement predominates: pressure is applied, the horse responds, and the pressure is released. Positive reinforcement adds rewards such as scratches or food. Positive punishment adds an aversive like a whip tap, and negative punishment removes something the horse wants.

Different riding systems use these quadrants differently. Horses do not learn aids because they are innately meaningful. They learn because pressure is applied and removed in patterns. This is why different schools (classical, modern, Western, Portuguese, German) use slightly different aids for shoulder-in or travers. Horses learn the version they are taught, just as a dog learns “sit” whether the cue is English, German or a hand signal.

Coaches talk about taking an outside leg to act like a wall and stop hindlimbs falling outwards or an inside one around the girth for it to bend around, but the horse only knows to do that from training. The association with a neutral leg position is to move forward or away from the pressure, it can’t differientiate which moves where when you move your leg 2cm back. It is a learnt response.

The fine tuning of legs aids is training, however, underneath all conditioning, the horse still responds to balance and weight first and stimulus with some of our aids. The biomechanics of the rider determine whether the horse can interpret the aid clearly. We need to be clear if what we are asking if because how the horse responds to us or its training.

How This Relates to Lateral Work

In movements like leg yield, the horse steps sideways and forward in alternating sequence. The pelvis remains facing forward because the horse’s pelvis does too. Rider weight shifts slightly toward the outside, which the horse then responds to. Whereas some schools of thought teach that you push the inside seat bone to 'push' the horse to the outside. In my opinion that is more of a trained response than the horse reacting naturally to what the rider is doing, but happy to hear thoughts differently.

Most errors in lateral work come from the rider’s inability to organise their own body: they cannot keep the pelvis stable while applying an independent leg aid, or separate lateral pelvic tilting from torso rotation, and these unintended compensations change the horse’s balance before the horse even has a chance to respond.

In shoulder-in, the horse’s pelvis tracks straight while the shoulders move inward. Here, aligning the rider’s shoulders with the horse’s shoulders while keeping the pelvis forward can make sense, because the horse is doing two directions at once. The pelvis is not following a curved line; it remains aligned with the original path. For shoulder in we want a bend, which we previously talked about which happens when torso rotates but the horse moving forward (due to change in rein tension when body rotates) so pelvis and shoulders matching the horses makes sense, when not on a circle.

And although I have said that the pelvis and torso (shoulders) doing different things causes tension and problems, that was because it was due to the forces of a circle which don't apply in a straight line. And that is why shoulder-in rules cannot be applied to circles. The biomechanics and physics of the movement are entirely different.

Understanding Torque in the Rider’s Body During Lateral Work

Rotating the upper body independently from the pelvis is a crucial part of effective lateral work. The rider needs to separate these movements - turning through the ribcage while keeping the pelvis stable and the weight equal through both seat bones unless a subtle lateral tilt is required.

Equally important is the ability to laterally tilt the pelvis to load one seat bone while maintaining a neutral spine and keeping the shoulders aligned over the hips.

Lateral work becomes a coordinated combination of these skills:

• controlled thoracic (upper body) rotation,

• pelvic stability or subtle lateral tilt,

• independent leg aids that don’t disturb either of those positions.

This is where torque enters the picture.

When the shoulders rotate in one direction and the pelvis stays neutral or moves differently, the rider’s body experiences a gentle twisting force. Torque simply means that one part of the body is turning while another part is stabilising.

This torque is not a mistake - it’s a necessary part of good lateral work.

It allows the rider to:

• guide the shoulders,

• organise the pelvis,

• maintain clear weight distribution,

• apply leg aids without collapsing or gripping.

But this also explains why many riders struggle. Maintaining that separation - upper body rotating one way, pelvis staying level or tilting slightly - requires strength, control, and mobility. If those aren’t developed yet, the body compensates. That’s when we see:

• collapsing through the ribcage,

• losing neutral pelvis,

• over-rotating the shoulders,

• gripping with the thigh,

• unintentionally shifting weight off the correct seat bone.

And then comes the real challenge:

keeping that torque organised once the horse starts moving.

It’s one thing to create the correct organisation while standing still. It’s another to maintain it while the horse lifts, swings, and bends underneath you. The pelvis is being moved by the horse’s back, the ribcage is being rotated rhythmically, and yet the rider still needs to:

• keep the upper body softly rotated,

• keep the pelvis either neutral or subtly tilted,

• follow the horse’s movement without losing alignment,

• apply leg aids that don’t disrupt any of this.

The rider isn’t just producing torque - they’re controlling it dynamically, moment by moment. The horse’s movement constantly tries to pull the rider out of position, and this is where stability, body awareness, and good biomechanics really matter.

The good news?

This ability can be trained. With targeted rider physio, thoracic rotation work, pelvic stability training, and exercises that teach dissociation between upper and lower body, riders can develop the control they need to maintain torque while still moving fluidly with the horse.

When the rider can stabilise what needs to be stable, move what needs to move, and maintain clarity through the whole body, lateral work becomes smoother, clearer, and far less effortful for both horse and rider.

Why Having the Pelvis Face in the Direction of Travel Works

In the end, having the pelvis face the direction of travel simplifies everything about rider biomechanics. It gives riders a clear, practical reference point that works on straight lines, circles, and lateral work. It aligns the rider with the horse’s arc or line, keeps weight centred, reduces gripping and collapse, and prevents unnecessary torsion between pelvis and torso.

I find a big part of improving rider understanding is learning the difference between aids and physics. Aids are the things we train the horse to respond to – like a specific leg position for canter, or a half-halt that has been conditioned over time. These responses exist because the horse has learned them.

Physics, however, is not trained. It happens automatically. A lateral weight shift, the direction the rider’s pelvis faces, or the rotation through the torso will always create a physical response in the horse’s body because of how force travels through the rider into the horse. Horses don’t learn to respond to these – they physically just respond. Understanding this difference matters.

If a rider mixes up trained aids with biomechanical effects when they are taught different methods of riding, they end up giving unclear signals, or unintentionally overriding their own aids with conflicting body mechanics. But when a rider knows which parts of their position influence the horse through physics and which cues rely on training, they can organise their body more deliberately, communicate more cleanly, and get far more consistent results.

Want help with your circles or lateral work? Book in for a Rider Physio session and consider buying a SymmFit Core training top for you to start to clearly see what you body is doing v what you think it is doing!

References

Byström, A., Clayton, H.M., et al. (2010). Rein tension differences between novice and experienced riders. The Veterinary Journal.

Clayton, H.M. (1994). Comparison of the stride kinematics of the collected, working, medium and extended trot in horses. Equine Veterinary Journal.

Clayton, H.M. (1997). Sagittal plane kinematics of the equine hind limb at walk and trot. Equine Veterinary Journal.

Clayton, H.M. & Hobbs, S.J. (2017). The role of biomechanical analysis in equitation science. Applied Animal Behaviour Science.

Gómez Álvarez, C.B., et al. (2007). The effect of rider asymmetry on rein tension in the ridden horse. The Veterinary Journal.

Hobbs, S.J., Licka, T., & Clayton, H.M. (2014). Pelvic and thoracolumbar kinematics in horses ridden in different positions. The Veterinary Journal.

Hobbs, S.J. & Clayton, H.M. (2013). A method of evaluating rider-induced movement in the horse. Comparative Exercise Physiology.

Lagarde, J., Peham, C., Licka, T., & Kelso, J.A.S. (2005). Coordination dynamics of the horse–rider system. Journal of Motor Behavior.

McGreevy, P. & McLean, A. (2010). Equitation Science. Wiley-Blackwell.

Münz, A., Eckardt, F., & Witte, K. (2014). Rider–horse postural coordination during walk and trot. Human Movement Science.

Peham, C., et al. (2004–2010). Studies on rider stability, saddle pressure and horse–rider interaction. Equine Veterinary Journal; Journal of Biomechanics.

Sankey, C., et al. (2010). Positive reinforcement learning in horses: Effects on behaviour and welfare. Applied Animal Behaviour Science.

Terada, K. (2000). Comparison of trunk/hip movement between advanced and novice riders. Journal of Equine Science.