The Forward-Lean

Psoas major is the headline player in this pattern. It runs from the bodies and discs of your lower spine (T12 to L5) and inserts onto the inside of your femur. That gives it three jobs at once: flex the hip, tilt the pelvis forward, and pull on the lumbar spine.

When your deep core isn't doing its job, psoas takes over postural duty by default. A psoas that has become tonically short and overactive will hold your femur in slight flexion (hello, forward lean), drag your lumbar vertebrae forward into extension because its top attachment is on the front of the spine (hello, hollow back), and tip your pelvis forward (hello, anterior tilt). One muscle, three problems.

There's also a fascial connection between psoas and the diaphragm at L1/L2. A short psoas drags the diaphragm into a less efficient dome shape, which is why this pattern almost always shows up alongside dysfunctional breathing. Loss of zone of apposition and a stuck-in-tilt pelvis are the same problem viewed from two ends.

Your deep core is four muscles working as a single system: the diaphragm on top, the pelvic floor on the bottom, transversus abdominis (TrA) wrapping the front and sides, and multifidus down the back. Together they form a pressurised canister whose structural job is to hold your ribs over your pelvis and resist forces that want to collapse, twist, or fold the trunk.

When the canister fails as a structural unit, three things go wrong at once. There's nothing to resist the anterior pull of psoas, so the pelvis tips forward. There's nothing locking your ribs down over your pelvis, so they flare upwards as the lower back hollows. And there's no anti-rotation control, so when limbs move underneath you, the trunk wobbles instead of staying still.

Rib flare and forward lean are canister problems first. Trying to "tuck the ribs" or "sit back" without rebuilding the system that should hold those positions automatically just creates a different compensation.

Glute max is the primary posterior pelvic tilter. It's the direct antagonist to the hip flexors at the pelvis, which means the question of "is your pelvis tipping forward" is largely a question of "what's louder right now: psoas or glute max?"

Reciprocal inhibition makes this worse. When psoas is overactive, the nervous system dampens glute recruitment as a matter of basic neurological housekeeping. Two muscles that pull in opposite directions can't both be loud at once, so the body picks one. In riders stuck in forward lean, psoas wins by default, and the glute goes quiet.

This is why riders who train their glutes heavily can still ride in anterior tilt. The muscle exists. It even tests strong on a bridge or a squat. But it doesn't switch on at the right moment when you're riding, because the neurological pattern hasn't been corrected.

Your hamstrings have two roles people usually forget. They flex the knee, which everyone knows. But they also attach to the back of your seat bones, which means they pull the seat bones down and back when they shorten. That makes them posterior pelvic tilters, just like the glutes.

In a rider stuck in anterior tilt, the hamstrings have usually become long and weak. The pelvis has tipped forward over time, dragging the seat bones with it, and the hamstrings have given up trying to pull them back. They've adapted to the lengthened position they're held in all day, sitting at desks and slumping in cars, and they no longer generate force at the proximal end where it matters for the pelvis.

This is the partner muscle group to the glutes in pulling the pelvis back to neutral. Even if your glutes work, you need the hamstrings to complete the posterior chain.

Your thoracic spine is the upper back. Twelve vertebrae built for rotation and extension. The lumbar spine below is built for stability, not extension, and only allows a small amount of it without strain. When the t-spine is stiff, the lumbar spine borrows the extension it needs to keep you upright, because something has to.

That borrowed extension is most of where the hollow back actually comes from. You're not really arching from the lower back by choice. The lower back is taking up the slack for an upper back that won't extend.

The same is true for rotation. Following the horse's movement requires t-spine rotation in canter, in lateral work, in turns. If the t-spine is locked, the lumbar spine takes the rotation too, which it really isn't built for. This is where lower back pain after riding usually starts.

Tibialis anterior runs down the front of the shin and pulls the toes up towards the shin. The anatomical name is dorsiflexion. It's the muscle that should be active to pull the toes up and anchor the foot when riding, creating the drape from heel through to the ball of the foot.

Most riders never train tib anterior directly. It's neglected even in conventional gym programmes because nothing in everyday life loads it heavily. But for riders it matters more than for almost anyone else, because the foot needs to be active in the stirrup, not passive.

Heels lift not just because of a tight calf, but because nothing is pulling the toes up to anchor the foot. Even if your calf complex is mobile enough to allow heel drop, without tib anterior pulling the foot up against the stirrup, there's no force creating the drape. The foot collapses through the stirrup rather than pressing into it.

The calf complex is two muscles, not one. Gastrocnemius is the visible one that crosses the back of the knee. Soleus sits underneath it and only crosses the ankle. When the knee is straight, gastroc dominates. When the knee is bent, gastroc goes slack and soleus takes the load.

Soleus is the muscle that loads when the heel is dropped down with the knee bent, which is exactly the position of the riding leg. A stiff, weak soleus prevents the heel from dropping, and prevents tendon stiffness from developing in the achilles. Tendon stiffness is what allows the heel to spring-load into the stirrup rather than collapse through it.

The word "stiffness" sounds negative for tendons, but it's the goal. A stiff tendon stores and returns energy. A compliant tendon lets the heel pancake into the stirrup and gives nothing back. You want stiff tendons. You want a strong, mobile soleus that can lengthen under load and return.