How Rider Biomechanics Affect Rein Tension & Horse Welfare

pegasusphysiotherapy
Jun 7
7 min read

❤️ I love helping riders learn and understand how what they do with their hands and upper body affects the horse- it's why behind rider biomechanics is so important.

When I share videos online showing this work on the simulator, there are always some comments like: "I rode the simulator and the pressure shown was much higher than I use on my horse." " You're teaching people to have too heavy pressure on the reins".

But they miss the point that it is about helping the rider understand what they currently does and how that translates into bit pressure. How their body and hand position has such an effect on what happens down the reins. That every horse will be different but this is showing a default setting for the rider for them to be able to adapt on a real horse. It's not about chasing a magic number on the screen but about learning manage whatever pressure is appropriate for that horse - consistently and with elasticity.

Look at the difference in the line from the elbow to the bit - on the left a nice consistent contact with the bit, on the right as wrist out of alignment then will be inconsistent or wrist will seek to give the consistency with tension.

Having measured the pressure on the Racewood Eventer simulator again this week, I can confirm that its higher head carriage position is approx. 1 kg rein tension using one rein (ie would be 50% on each rein) which matches what research considers a light contact during dynamic riding. Although it can't be directly compared to a live horse due to the difference in mechanics of head/neck and the elastic reins used.

So I thought it would be useful to explain how I use the simulator to help riders improve their rein control but also what you can think about off horse too. And why this matters for both horse welfare and rider performance.

🐴 Contact Comes From Behind - But the Rider Must Manage It

One of the most common comments I hear when we work on rein exercises off the horse is: "But the horse should work into the contact - you shouldn’t pull them into it."

✅ Absolutely correct. You do not create correct contact by pulling the horse into the reins. The horse develops correct contact through:

Engagement of the hindquarters
Lifting and rounding through the back
Reaching forward into an elastic, stable connection

👉 But knowing this does not teach riders how to manage their side of the contact.

👉 And it does not explain to riders how correct contact should feel in their own body.

In fact, many riders:

❌ Hold the reins too tightly or too far into the palm

❌ Brace through the wrist or shoulder

❌ Collapse their torso or lean back when moving their arms

❌ Overuse grip strength instead of fine finger control

👉 These errors create an inconsistent, unstable feel - which horses experience as discomfort or even pain.

From the side see how a change in hand position effects the line from elbow to bit

⚠️ Horse Welfare - Why It Matters

Rein tension and contact quality matter greatly for horse welfare.

📚 Peham et al. (2010, 2011)

Average rein tensions of 1-2 kg, with peaks of 4-6 kg during transitions and corrections.
Higher rein tensions linked to discomfort and mouth injury risk.

📚 Murray et al. (2015)

Even light rein tensions (~1 kg) caused more conflict behaviours when contact was inconsistent or braced.

📚 Cook (2003)

The bars and tongue are richly innervated and covered by thin mucosa - even light, jerky or fixed tension can cause bruising or pain.

📚 Egenvall et al. (2015)

Top-level dressage horses showed more signs of discomfort when contact was inconsistent - even when tensions were light.

👉 Inconsistent contact is a welfare issue - not just a performance problem.

🧬 Why Every Horse Experiences Contact Differently

👉 Every horse will feel rein pressure differently:

Mouth anatomy varies greatly between horses
Prior injury or trauma can create sensitivity
Bit choice affects pressure distribution
Each horse’s stage of training changes how it responds to contact

👉 There is no single "correct" rein tension.

👉 What matters is that the rider can deliver stable, elastic, following contact that the horse can trust and confidently work into.

👉 Saying “contact comes from the hind end” is true - but it does not teach riders how to manage their side of the contact when the horse starts to offer it.

🎓 Why We Train Rein Contact Off the Horse

This is not a riding lesson - it is rider physio work:

To improve the rider biomechanics
To remove barriers to better contact
To protect horse welfare

We use the bit/rein sensors to give riders objective feedback - showing how posture and movement change rein tension.

The Racewood simulator itself helps illustrate this beautifully as it has two head positions:
- A lower head carriage, which often means the horse is not on contact and the bit is unloaded
- A higher head carriage, which holds ~1 kg of rein tension - considered a light contact in many riding disciplines

👉 This gives riders a clear opportunity to learn:

✅ What light contact should feel like in their arms and hands

✅ How their body changes rein tension

✅ How to maintain a stable, elastic feel - without bracing or gripping

✅ How finger control (and wrist position) plays such an important part for riders

The Racewood Eventer simulator provides brilliant real-time feedback during Rider Physio sessions - helping you learn exactly how your body affects rein contact, before you take that feel back to your horse. Many riders are amazed when they see how small postural errors or wrist tension cause big changes in rein tension - even when they think they are being soft.

📖 What the Research and Top Biomechanics Experts Say

Studies from Centaur Biomechanics have repeatedly shown that:

✅ Consistency of rein tension is more important than simply aiming for "light" contact

✅ Horses display more conflict behaviours when rein tension is variable, even if average tension is low

✅ Elite riders demonstrate much more stable, elastic rein contact

✅ Poor rein tension patterns are often caused by instability or stiffness in the rider’s arm or upper body

Lots of people talk about rider biomechanics but don't really explain the reasons why- understanding is key to improving.

🔍 Key Exercises We Use

1️⃣ Arm Movement Without Losing Body Position

Many riders cannot move their arms independently of their torso.

✅ We teach riders to:

👉 Move the arms forward while keeping core and shoulder stability

👉 Bring elbows back into correct position without tipping or bracing

When instructors say “bend your elbows”, they often mean “bring your elbows back” - which restores a more neutral shoulder position and allows the elbow to bend naturally.

This is something you can practice with a band for resistance or a weight- can you maintain an upright and neutral sitting posture when you move your arms forward or up?

2️⃣ Hand Position & Fine Finger Control

We focus heavily on hand anatomy and rein mechanics, because these are rarely taught well.

✅ The ring finger should align with the bit - creating a straight line from elbow → wrist → finger → bit.

Too many riders:

❌ Hold their hands too close together or too low

❌ Break the line from elbow to bit

❌ Alter wrist mechanics, making fine control impossible

Once the correct line is established:

✅ The reins should sit loosely towards the ends of the fingers - not gripped in the palm

✅ The hand should be relaxed, not braced

✅ We train isolated ring finger flexion to adjust rein pressure precisely - without moving the whole hand or arm

This allows the rider to give the exact level of pressure their horse needs - with subtlety and control.

🏇 Practising in Motion

Once these skills are developed, we practise them through simulated gait movement, it is no good having perfect contact while stationary if you can’t maintain it in trot or canter.

This week a rider struggled to maintain canter on the simulator - repeatedly breaking to trot, as her horse does. The cause? Her rein tension became inconsistent at canter, creating an unstable feel that led to the rhythm breakdown - on both the simulator and her horse. After correcting her posture and rein control, she was able to maintain consistent tension - and her horse improved as well.

❤️ Horse Welfare First

As a Rider Physio, I care deeply about horse welfare:

⚠️ Oral lesions in competition horses are common (Uldahl & Clayton, 2019).

⚠️ Conflict behaviours linked to inconsistent rein tension are well documented.

⚠️ Many of these problems start with uneducated rider mechanics, not intentional rough riding.

Teaching riders how their body and hands affect the bit is one of the most powerful ways to improve both rider performance and horse comfort.

📝 Coming Next: Hand Anatomy & Rein Contact

👉 Next week’s blog will cover hand anatomy and rein contact:

✅ How your fingers should hold the reins

✅ Why wrist bracing is so damaging

✅ How your hand anatomy should create subtle, effective communication

I’m always amazed at how many riders have been told how to hold the reins, but never shown why - or how it connects to their body and their horse’s welfare.

If you’d like to learn how your rein contact affects your horse - and how to improve it - you can: Book a Rider Physio session and experience this work on the simulator, or explore the Rein Control Exercises in the Video Subscription.