Incomplete bowel emptying: How chronically tight pelvic sling muscles block the rectal angle

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The short answer

If you feel like you can never fully empty your bowels, or if you have to strain even when your stool is soft, the issue may not be your digestion. It often comes down to a muscle called the puborectalis, which forms a U-shaped sling around the lower rectum.

Normally, this muscle relaxes and lengthens during a bowel movement to straighten the passage for stool. If it is chronically tight or fails to relax on the toilet (a condition known as dyssynergic defecation or pelvic floor non-relaxation), the bend in the rectum remains sharp, acting like a kinked garden hose.

What is happening?

To keep you continent throughout the day, the puborectalis muscle stays in a state of light, continuous contraction. This pulls the rectum forward, creating a sharp bend known as the anorectal angle.

RESTING STATE (Puborectalis contracted)
Rectum ──┐  (Sharp kink keeps stool in)
         └── Anus

BOWEL MOVEMENT (Puborectalis relaxed + Knees elevated)
Rectum ──│  (Straightened passage allows easy passage)
         └── Anus

When you sit down to have a bowel movement, two things must happen:

  1. The puborectalis muscle must fully relax, widening the anorectal angle.
  2. The anal sphincters must open smoothly while you gently increase pressure in your abdomen.

If the puborectalis remains tight or paradoxically squeezes tighter when you bear down, the rectal angle stays sharp. Stool gets trapped behind this muscle “shelf,” leading to straining, incomplete evacuation, or needing to return to the bathroom shortly after.

Why this can happen

An overactive or uncoordinated puborectalis muscle rarely develops in a vacuum. Common triggers include:

  • Chronic straining or constipation: Pushing hard against a closed pelvic floor trains the muscles to contract protectively during bowel movements.
  • Pelvic pain or inflammation: Conditions such as endometriosis, painful intercourse, painful bladder syndrome, or anal fissures cause nearby muscles to guard and tighten.
  • History of holding it in: Frequently suppressing the urge to pass stool due to a busy schedule or public toilet anxiety forces the pelvic sling to stay braced.
  • Postpartum tissue changes or birth trauma: Tear recovery, scar tissue, or altered nerve signaling after delivery can disrupt muscle relaxation timing.
  • Stress and central nervous system bracing: The pelvic floor reflexively holds emotional stress and physical tension.
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Weakness vs. Tightness: Why Kegels make this worse

When people hear “pelvic floor problem,” they often assume they need to do Kegels (pelvic floor squeezes).

If your issue is incomplete emptying caused by a tight puborectalis, doing Kegels will likely make your symptoms worse.

Kegels train the pelvic floor to shorten and lift—the exact opposite of what needs to happen on the toilet. Incomplete emptying from muscle tightness requires pelvic lengthening, relaxation, and coordination, not extra strength.

What you can do

1. Change your toileting posture

Sitting at a standard 90-degree angle maintains a partial kink in the rectum.

  • Use a toilet footstool (or block of books) to elevate your knees above your hips.
  • Lean forward slightly with your elbows resting on your knees.
  • This position naturally unwinds the puborectalis sling and straightens the rectal angle without extra effort.

2. Master “Mooing” instead of straining

Holding your breath and blowing out your cheeks (the Valsalva maneuver) drives downward pressure onto a braced pelvic floor.

  • The technique: Lean forward on the stool, take a deep breath into your lower abdomen and ribs, and make a low “Moo” or “Sss” sound as you gently widen your waistline.
  • What you should feel: Your belly expands outward while your pelvic floor drops down and opens.
  • What you should NOT feel: Red-faced straining, chest tightness, or pushing down from your throat.

3. Keep stool soft and formed

Hard, dry stool requires more mechanical force to pass, which triggers protective muscle guarding. Ensure adequate daily fluid intake and soluble fiber, or discuss gentle stool softeners with your healthcare provider if needed.

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What to avoid

  • Do not strain or push forcefully: Straining reinforces the reflex that tells the puborectalis to tighten. If nothing happens after 3 to 5 minutes, get up, walk around, and try again when you feel a natural urge.
  • Do not hover over the toilet: Hovering forces your pelvic floor and thigh muscles to work intensely to stabilize you, preventing the puborectalis from relaxing.
  • Avoid unnecessary pelvic floor strengthening exercises: Pause Kegels until a professional evaluates whether your muscles are hypertonic (overly tight).

Beyond muscle tightness: Other possible causes

While a tight puborectalis is a frequent culprit, incomplete emptying can also involve structural or nerve factors. These may include:

  • Rectocele: A bulging of the front wall of the rectum into the back wall of the vagina, where stool can get temporarily caught during a bowel movement.
  • Pelvic organ prolapse: Lowered support for the uterus or bladder that alters pelvic mechanics.
  • Neurological or motility disorders: Slow transit constipation, nerve changes from diabetes, or spinal issues affecting bowel signaling.

Because symptoms overlap, an individual evaluation is necessary to confirm the root cause.

When to get assessed

Self-care tools like posture changes and breathing can significantly improve mild symptoms. However, you should seek evaluation from a doctor or specialized pelvic health physical therapist if:

  • Incomplete emptying is chronic and significantly impacts your daily quality of life.
  • You routinely rely on laxatives, enemas, or manual support (digitation) to pass stool.
  • You experience rectal pain, severe abdominal cramping, or persistent pelvic heaviness.
  • Warning signs are present: Unexplained weight loss, blood in your stool, sudden changes in bowel habits, or severe pain require prompt medical attention.
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A pelvic health physical therapist can assess muscle tone, test whether your pelvic floor relaxes or contracts when you push, and use biofeedback to help retrain the puborectalis to open smoothly.

Bottom line

Incomplete bowel emptying is frequently a mechanical and coordination issue, not a digestive failure. When the puborectalis muscle stays tight, it keeps the rectal angle kinked. Elevating your knees, avoiding straining, and learning to drop the pelvic floor can help unkink the hose and restore normal, comfortable bowel movements.

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