Rider Biomechanics and Saddle Fit: Seat Bones, Pelvis Shape, and Rider Posture Explained

Following on from my last blog about why the seat bones are for sitting, I had lots of comments about pelvic position when sitting compared to standing, and the differences between men’s and women’s pelvises. I was also tagged into several videos from saddle fitters discussing the importance of saddle fit for riders.

What stood out to me is that many of these conversations make sweeping generalisations but don’t provide evidence to support them. And that brings us back to the same issue I raised in my last blog: a lot of what gets talked about in riding is based on opinion rather than science.

As an equine physio, my first priority is always that the saddle fits the horse. Only after that does it then needs to fit the rider. The length of the femur and the size of the seat are usually the most practical starting points.

But as a rider physio, I also believe riders should take more responsibility for their own pelvic position in the saddle. Several saddlers have highlighted how important rider fit is - and I agree. But when riders are told, “this saddle will put you in neutral” or “this saddle is wrong for you,” it can shift responsibility entirely onto the tack. That risks reducing a rider’s internal locus of control.

👉 What does that mean? An internal locus of control is the belief that you are in charge of your own actions and outcomes - rather than everything depending on external factors like the saddle. For riders, this matters: the more you understand your own posture, the more you can adjust and adapt - no matter what tack you’re in.

Of course, there are cases where a saddle genuinely won’t work for a rider because of their individual anatomy. But to borrow a line from the film He’s Just Not That Into You - that’s the exception, not the rule (and will be covered later in this post)

There are also saddle companies gathering data on pelvic shapes and designing saddles to fit them. That’s an interesting direction, but most of this data isn’t publicly available or peer-reviewed. Without knowing the methods - things like reliability of their measurements, how subjects were included or excluded, or whether the same results would be found by different testers - it’s hard to evaluate. Right now, it’s more like internal company data than independent research.

A common theme I’ve noticed in these discussions is that the difference between male and female pelvises is presented as the main reason women struggle in the saddle. So here’s my take - looking at the published research, rather than relying on generalisations. Yes, there are differences . But a) are they really as large as we think when we consider factors like size and sitting vs standing posture? and b) isn’t there often more variation between individuals than between sexes?

I don’t have a bias either way; I’m not selling saddles. My role is to help riders improve physically through exercises and understanding - which applies regardless of the brand of saddle you sit in.

The differences between female and male pelvises widely accepted in scientific literature.

When I talk about riding posture, I always emphasise that I want riders to think of a sitting posture rather than a standingone. When you’re in the saddle, your seat bones should be the part of you that takes your weight, not your feet as if you were standing upright. If you stand too tall in the saddle, you risk tipping your pelvis out of neutral, losing balance, and putting excess weight down into your stirrups instead of allowing your seat to connect with the horse. A true sitting posture creates stability, lets your pelvis move with the horse, and gives a more secure and effective position.

Rider Posture in Standing: Men vs Women

Before we start looking at what happens in the saddle, let’s begin with the differences we see in standing posture. Men and women don’t start from the same baseline.

• Lumbar lordosis (low back curve): Women have a deeper lower back curve than men (Bailey et al., 2016; Rajabi et al., 2024). This adaptation helps women stay balanced during pregnancy (Whitcome et al., 2007; Hay et al., 2015). Women’s spines are also more flexible, showing bigger changes when they move into sitting (Mizukoshi et al., 2024).

  
  

  👉 In simple terms: women usually stand with more of an “arched” lower back, while men stand flatter.

• Pelvic orientation (tilt): Women stand with a pelvis tilted more forward (16–20°) compared to men (12–15°) (Chen et al., 2021; Borgeaud et al., 2022). They also show bigger shifts when they sit down (Mizukoshi et al., 2024).

👉 Put simply: women naturally stand with their pelvis tipped more forward, while men stand more upright.

• Sacrum shape: The female sacrum is shorter, wider, and more curved, while the male sacrum is longer and straighter (Imai et al., 2019). This contributes to women’s greater forward tilt and deeper lower back curve (Lazennec et al., 2013).

👉 For riders, this means women’s pelvic bones are shaped to naturally roll forward

more than men’s.

• Spinal curve distribution: Women’s lumbar curve is concentrated in the lower vertebrae (L3–L5), making the curve sharper, while men’s is spread more evenly through the spine (Hay et al., 2015).

👉 That’s why women often look more “arched” in their lower back, while men look straighter through the whole spine.

Rider Pelvis Biomechanics in Sitting vs Standing

When we move from standing to sitting, the pelvis naturally posteriorly tilts - it tucks under, the sacral slope decreases, and the lumbar curve flattens. This happens because body weight shifts onto the ischial tuberosities (seat bones), whereas in standing the weight is supported through the feet.

👉 This is a key difference for riders: many coaches and saddle fitters talk about wanting a “standing posture” (shoulder–hip–heel line) in the saddle, but sitting posture is not the same as standing posture. The pelvis changes shape under load, so what looks neutral in standing won’t look the same in sitting.

Research shows that in sitting, pelvic tilt increases by ~16.7°, sacral slope reduces by ~15°, and lumbar lordosis decreases by ~21° (Tan et al., 2024). The pelvis rotates back ~20° and the lumbar curve flattens significantly (Lazennec et al., 2013). These reductions are also confirmed in healthy adults (Endo et al., 2012), with the lower lumbar segments (L4–S1) flattening most (Borgeaud et al., 2022). Women start with more tilt in standing, and they show larger changes than men when they sit (Mizukoshi et al., 2024). People with higher pelvic incidence show bigger posture changes overall (Yang et al., 2024).

👉 In rider-friendly terms: sitting always makes your pelvis tuck under and your back flatten (it's the degree in which it changes is individual). Women often start with more forward tilt, so they change more when they sit. Men start flatter, they have less distance to move from but tend to want to tilt back more.

Either way, sitting posture is different from standing posture - which is why a “standing neutral” can’t just be copied in the saddle. And sitting in the saddle is no different - in fact, it’s even more important, because unlike in a chair, there’s less load going through the back of your thighs. That means the pelvis is carrying more of your weight directly on the seat bones, so how you manage that position really affects your balance and movement with the horse. You can still achieve shoulder–hip–heel alignment, but it will look different to how it looks when you hover over a saddle with your weight on the floor.

Rider Posture: How Men Sit in the Saddle

Men already start with a flatter lumbar spine and less anterior tilt in standing. When they sit, they often collapse further - posterior tilt increases and lumbar lordosis reduces even more. Their lumbar curves are distributed more evenly across the spine, so when the pelvis tucks under, the whole lumbar region tends to flatten (Hay et al., 2015). This can roll the pelvis heavily back onto the sacrum. In saddles, men are also more likely to feel pressure at the pubic area, which may cause them to adjust their posture to avoid discomfort.

Much of what is still talked about in terms of posture in the saddle comes from military training in the early 1900s. Men are more likely to posteriorly tilt, so to achieve the upright military-style posture they were taught, they would actually have needed to anteriorly tilt slightly. This - not anatomical differences - is the key factor in why men and women sit differently in the saddle when we talk about the 'ideal' posture- they need to do different movements to achieve it.

👉 For riders: men are more likely to tilt their pelvis back in the saddle, because they already do this more than women in standing - and comfort at the front of the saddle often dictates how much they allow that tilt.

Rider Posture: How Women Sit in the Saddle

Women begin with more anterior pelvic tilt and lumbar lordosis in standing, and even in sitting they often maintain this anterior bias. Although women posteriorly tilt when they sit (like men), they still tend to sit with more tilt forward overall (Mizukoshi et al., 2024). This can mean some women risk over-arching their lower back if they try too hard to “sit tall” without controlling the pelvis- sound familiar riders?

👉 For riders: women are more likely to stay tipped forward through the pelvis, which can make them look arched in the saddle. The adjustment many need is a slight posterior tilt to find neutral balance. If the pelvis tips too far forward and the rider’s weight doesn’t sit on the seat bones, the hip angle closes, making it harder to access the range of movement needed for riding. Their weight also shifts forward, which means they have to recruit muscles to stop falling forward (e.g. the lower back extensors) or falling off (e.g. the adductors). That’s the opposite of the relaxed, neutral position we want for effective riding.

What the Research Says About Seat Bone Width

Researchers have used different methods to measure the distance between the ischial tuberosities (ITs) - the “seat bones” we sit on. The results vary depending on how they were measured:

• Using a foam impression method in an upright seated posture, women’s IT width was ≈ 134.9 mm and men’s ≈ 116.5 mm - women wider by ~18 mm. They also measured hip joint centre-to-centre width and found no significant sex differences (Sauer et al., 2007).

• With impression vs pressure methods, women looked wider on impressions (~135 mm vs 120 mm), but under pressure mapping men and women were almost the same (~134 mm vs 133 mm) (Chen & Yang, 2016).

• Testing 90 people across four postures, women averaged ~12–14 mm wider, but posture changed effective width: more upright sitting = wider, forward lean = narrower (Chen et al., 2021).

• In a large cycling dataset (n = 49,785), men were on average wider in forward-lean cycling posture: most common = 121 mm (men) vs 111 mm (women) (SQLab, 2020).

  
  

👉 The big takeaway:

• Impression pads capture bony imprint → women appear wider.

• Pressure mapping captures effective width under load → posture-dependent, men often appear wider.

• Population size changes the picture - small lab studies show neat sex differences, large studies show huge overlap.

  
  

Rider Biomechanics Beyond Seat Bones: The Role of Q Angle

When people talk about “women having wider hips”, it’s easy to assume that means wider seat bones. But the research doesn’t really back that up. The hip joint centres (femoral heads) are not significantly further apart in women (Sauer et al., 2007; Wang et al., 2004; Atkinson et al., 2010). What is different is the Q angle.

Q angle differences

• The Q-angle is the angle between the hip, knee, and shin.

• On average, women have a larger Q-angle (~15–23°) than men (~10–15°) [Sharma et al., 2023; Choudhary et al., 2017].

• This is usually attributed to women having broader pelvises at the iliac crests with shorter femurs, while hip joint centres stay similar → the femurs angle more inward toward the knees [Çankaya et al., 2014; Shantanu et al., 2023].

• Height matters: when men and women are matched for height, the difference in Q-angle is much smaller [Choudhary et al., 2017; Shantanu et al., 2023].

• Since women are on average shorter than men, this effect is more pronounced in women [Çankaya et al., 2014].

  
  

• 👉 So, “wide hips” doesn’t necessarily mean a wider seat in the saddle — it often means the legs simply start from a different alignment.

  
  

Why Q Angle Matters in the Saddle

• Thigh position: A higher Q angle means the knees tend to fall inward, changing how the thigh lies on the saddle flap.

• Seat bone loading: Even with the same IT width, a high Q angle can change pressure distribution on the saddle.

• Wide horses: High-Q-angle riders often struggle more on wide horses - the hips are forced into extra abduction (legs spread), which can feel like “doing the splits” and overload hips, knees, or back.

• Saddle design: Narrower twists, adjusted flap/block shapes, and stirrup bar position can help match the rider’s natural alignment.

Why Saddle Fit Can’t Be Based on Sex or Height Alone

• Height: Pelvic size loosely correlates with stature, but not in a proportional way. Two riders the same height can have completely different pelvic shapes, Q angles, and seat bone widths. So using height charts to predict saddle fit is unreliable.

• Sex: On averages, women often show slightly wider sit bones in impression studies - but pressure studies and large samples reveal huge overlap between the sexes. Some women measure narrower than many men, and vice versa.

• Measurement: Different methods give different results.

  
  

👉 Yes, when looking at the pelvis alone we all accept there are differences - but it’s how the pelvis interacts with the saddle and all the other parts (seat size, femur length, Q angle, pelvic tilt, soft tissue) that becomes important.

👉 Takeaway: Saddle fit must be individualised. It’s about how the rider’s pelvis interacts with the saddle in sitting and in motion, not just their sex, height, or standing diagrams.

Saddles Can Help - But They’re Not the Whole Answer

That’s not to say some saddles won’t make life easier or harder for certain riders:

• A deep-seated saddle with big thigh blocks won’t help a rider who naturally wants to sit in an anterior tilt.

• A very flat saddle won’t help a rider who naturally wants to sit in a posterior tilt.

  
  

Does that mean those riders can’t sit in neutral? No. But it may take more effort to find and maintain neutral while moving, and they may need to work on their physical ability to do it. Would I recommend those saddles as their main saddle? No.

Here this rider naturally sits in an anterior tilt in the photo on the left. She can sit in neutral with weight into seat bones but is unable to do that with the hip extension needed to have her thighs parallel to the blocks in the deep seat.

👉 A well-chosen saddle should support the rider’s natural tendencies - but riders still need to help themselves. If you can’t find neutral at all, it’s more likely down to stiffness, weakness, lack of control, or reduced body awareness - things you can improve with the right exercises and feedback.

Final Thoughts: Rider Biomechanics + Rider Physio in Practice

When it comes to saddle fit, the message is simple: there’s no one-size-fits-all based on sex or height.

• Standing vs sitting: The pelvis changes shape when you sit - it tilts back, the spine flattens, and neutral looks different. So a “standing diagram” doesn’t tell us what happens in the saddle.

• Seat bones: How wide your sit bones measure depends on the method and posture. Impression pads, pressure maps, and real saddles all give different answers.

• Q angle: “Wide hips” doesn’t always mean wider seat bones. The way your legs angle down from your pelvis (Q angle) makes just as much difference to how you sit and how your thighs drape on the horse.

• Individual variation: The overlap between men and women is so large that sex and height alone don’t predict how a saddle will feel. Two riders of the same size can sit completely differently.

👉 The saddle’s job: Fit the horse first, then the rider - giving enough space and balance for the pelvis and legs to work.

👉 The rider’s job: Use rider physio, rider biomechanics training, pilates, posture awareness etc to find and hold neutral in motion, whatever saddle you’re in.

So yes, saddle fit matters - but so does rider biomechanics. The best outcome is when both are considered together.

Quick Rider Checklist

• Sit on a chair with feet on the floor.

• Take a photo or video of yourself from the side.

• Can you tilt your pelvis forward and back? Does one direction feel easier than the other?

• Can you find the middle, where your weight rests evenly on your seat bones?

Anterior tilt v neutral sitting on a stool.

If you can’t do this on a chair with feet supported and thighs in contact - how can you expect to do it in a saddle?

Want help with your position? Book in for a Rider Physio session or sign up for the Video Subscription.

References

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Borgeaud, C., Roussouly, P., Le Huec, J. C., & Obeid, I. (2022). Influence of sitting and standing postures on spinopelvic parameters: A systematic review. European Spine Journal, 31(9), 2361–2371.

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