From Diaphragm to Pelvic Floor: The Pressurized Core Explained

The human core is a pressure system, and like any pressurized system, it must be carefully managed to maintain function and prevent breakdown. One of my favorite ways to understand this system is through the pop can analogy. Imagine your core as a closed pop can: the diaphragm forms the top, the pelvic floor forms the bottom, and the abdominal wall and deep back muscles form the sides. When all these structures are working in harmony—coordinated and strong—the pop can holds its shape under pressure. But when any part of the pop can becomes weak, poorly coordinated, or injured, it collapses or bulges, leading to problems throughout the core and pelvis. 

Let’s explore how pressure imbalances in this system can contribute to symptoms like low back pain, constipation, urinary or fecal leakage, pelvic pain, and pain with intercourse, and how pelvic floor physical therapy can help restore balance and function. 

In a healthy, well-functioning core, pressure is efficiently generated and regulated. The diaphragm moves down during inhalation, increasing pressure in the abdominal cavity. A responsive pelvic floor and abdominal wall accommodate this change and distribute the pressure evenly. During exhalation, the diaphragm rises and the abdominal and pelvic floor muscles gently contract, helping maintain spinal stability and supporting internal organs. 

This natural rhythm is essential for: 

• Supporting posture and spinal alignment 

• Controlling intra-abdominal pressure during exertion (lifting, coughing, exercise) 

• Maintaining continence 

• Facilitating bowel and bladder function 

• Supporting sexual health 

Problems arise when the coordination or strength of these structures is compromised. Let’s look at two primary scenarios where pressure management fails. 

Imagine shaking a sealed pop can and then opening quickly.  A similar thing can happen when intra-abdominal pressure increases without proper control—especially when there is poor coordination between the diaphragm, abdominal wall, and pelvic floor. 

When the diaphragm pushes down, but the pelvic floor doesn’t respond by eccentrically lengthening, or if the abdominal wall is held too rigidly due to muscle tightness or scar tissue, pressure becomes trapped and unevenly distributed.  

Symptoms of excessive intra-abdominal pressure with poor coordination include: 

• Low back pain due to excessive spinal compression and instability 

• Constipation because excess pressure impairs bowel motility and can lead to straining 

• Urinary or fecal leakage as pressure overcomes weak pelvic floor muscles 

• Pelvic organ prolapse when internal organs press downward over time 

• Pelvic pain or pain with sex caused by tight or overactive pelvic floor muscles bracing against pressure 

Many people unknowingly contribute to this pattern by breath-holding during exertion (a Valsalva maneuver), clenching their abdominal muscles constantly (“sucking in”), or having shallow or chest breathing patterns that disconnect the diaphragm from the pelvic floor. 

Now imagine an empty pop can that’s already been opened. It’s flimsy, unstable, and can’t hold shape. This scenario illustrates a low-pressure core system, where decreased strength or integrity in the diaphragm, abdominal wall, or pelvic floor results in collapse and poor function. 

This is common in individuals with: 

• Diastasis rectus abdominis, a separation of abdominal muscles, often postpartum 

• Pelvic floor weakness 

• Changes in tissues due to hormone changes with pregnancy, postpartum or menopause 

• Poor breathing mechanics or chronic chest breathing 

• General deconditioning or lack of core engagement 

In this scenario, the core cannot generate or regulate pressure adequately. Symptoms may include: 

• Urinary or bowel leakage especially with coughing, sneezing, movement 

• Urinary or bowel urgency 

• Constipation due to lack of support or coordination for effective pooping 

• Pelvic instability leading to feelings of heaviness or “falling out” 

• Low back pain as the spine lacks proper support 

• Pelvic pain due to decreased stability 

Ultimately, the core’s ability to handle pressure comes down to coordination—the timely, responsive action of the diaphragm, abdominal wall, and pelvic floor working together. These muscles must not only be strong but adaptable to demands like movement, breathing, posture, and internal pressure changes. 

You might have great pelvic floor strength, but if you’re breath-holding during exercise or clenching your abs too tightly, pressure will build and cause issues. Conversely, you may be breathing well, but if your abdominal wall is separated or your pelvic floor doesn’t engage appropriately, your system will lack the tension needed for support. 

This dynamic, reflexive coordination is what pelvic floor physical therapists are trained to assess and restore. 

Pelvic floor physical therapists are uniquely qualified to assess all components of the pressure system, not just the pelvic floor. They evaluate: 

• Breathing mechanics of diaphragmatic versus chest breathing 

• Abdominal wall function including diastasis recti, scars, or trigger points 

• Pelvic floor tone and strength both at rest and during activity 

• Core coordination with different activities and loads 

Treatment may include: 

• Breathing retraining to reconnect diaphragm-pelvic floor coordination 

• Core activation exercises emphasizing timing, not just strength 

• Pelvic floor muscle training for coordination, strengthening and down-training 

• Manual therapy for soft tissue mobility and pain relief 

• Education and strategies for pressure management during daily tasks like lifting, toileting, or exercise 

Through individualized assessment and treatment, pelvic floor physical therapy helps restore balance in the core system—strengthening where needed, improving timing and control, and re-establishing the body’s ability to handle pressure appropriately.  

The pop can analogy is a powerful visual for understanding how the diaphragm, abdominal wall, and pelvic floor work together to regulate pressure in the body. When pressure is too high or too low, dysfunction results—ranging from pain to leaking to instability. 

Pelvic floor physical therapy plays a vital role in retraining this system. By focusing on coordination, strength, and breathing, therapy helps you rebuild your pop can so it’s strong, responsive, and stable under pressure. 

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Disclaimer: This blog is here for your help. It is the opinion of a Licensed Physical Therapist. If you experience the symptoms addressed you should seek the help of a medical professional who can diagnose and develop a treatment plan that is individualized for you.