Strong from the Inside Out: Mastering the Deep Core for Lasting Stability

Lumbopelvic stability is the cornerstone of efficient, pain-free movement. At the heart of this stability lies a deep system of muscles often overlooked in conventional training or even in some rehabilitation programs: the multifidus, transverse abdominis (TrA), diaphragm, and pelvic floor. These muscles form what is commonly referred to as the “deep core unit” or “inner unit.” When functioning in harmony, they provide dynamic support to the spine and pelvis, allowing for efficient movement, load transfer, and postural control. However, dysfunction, weakness, or poor coordination among these muscles can set the stage for low back pain, sacroiliac (SI) joint pain, or pelvic pain. 

Let’s break down each muscle’s role in stabilizing the lumbopelvic region: 

1. Multifidus: 

 Located deep in the spine, the multifidus muscles span segmentally from one vertebra to another. Its primary role is to stabilize the vertebral column during movement. It acts as a local stabilizer, offering subtle, continuous support to prevent micro-instabilities that can lead to joint irritation or disc issues. 

2. Transverse Abdominis (TrA): 

 The TrA is the deepest abdominal muscle. When activated correctly, it wraps around the torso and increases intra-abdominal pressure, acting like a natural weightlifting belt that stabilizes the spine before limb movements occur. 

3. Diaphragm: 

 Best known for its role in breathing, the diaphragm is also integral to core stability. During inhalation, it contracts downward, increasing intra-abdominal pressure in coordination with the TrA and pelvic floor. Proper diaphragmatic breathing helps maintain this pressure and supports spinal alignment. 

4. Pelvic Floor Muscles (PFM): 

 These muscles form the base of the core and support pelvic organs, control continence, and contribute to core stabilization. They work synergistically with the diaphragm, TrA, and multifidus to create a pressurized cylinder that protects the spine and pelvis from strain. 

When these muscles don’t function in unison, the stability of the lumbopelvic region is compromised. This dysfunction can result from a variety of causes: pregnancy and childbirth, injury, increased or new stress on the system, prolonged sitting, surgery, or poor posture. 

Low Back Pain: 

Studies have shown that individuals with chronic low back pain often have delayed or poor activation of the TrA and multifidus. Without proper support, the larger superficial muscles (like the erector spinae or rectus abdominis) overcompensate, leading to fatigue, tightness, and eventual pain. 

Sacroiliac Joint Pain: 

 The SI joints depend on both form (bones) and force(muscles) closure. When the deep core is underactive or poorly coordinated, the muscles that provide force closure (like the pelvic floor and TrA) can’t effectively stabilize the joint, resulting in hypermobility, inflammation, and localized pain. 

Pelvic Pain or Dysfunction: 

 When pelvic floor muscles are weak, overactive, or uncoordinated, it can lead to symptoms such as incontinence, painful intercourse, or pelvic pressure. This not only affects function but also contributes to altered posture and faulty motor patterns, feeding into the cycle of pain. 

Motor control describes how well the nervous system recruits and coordinates the deep muscles to help with load transfer or limb movements. In many cases, the muscles themselves are not weak but are simply not being recruited in the right way at the right time. This motor planning dysfunction can persist even after the original injury or stressor is gone. 

For example, someone may have recovered from childbirth or a back injury, but if their deep core system hasn’t relearned how to coordinate properly, they remain vulnerable to recurring pain and instability. This is where pelvic floor physical therapy becomes essential. 

Pelvic floor physical therapists are uniquely trained to assess and treat the deep core system holistically. Here’s how PFPT can help: 

1. Assessment of the Entire Core Unit 

PFPTs don’t just look at the pelvic floor in isolation. They evaluate breathing patterns, postural alignment, TrA and multifidus activation, and the functional coordination between all core muscles. This whole-system approach helps uncover the root of the dysfunction. 

2. Retraining Motor Control 

Therapists use techniques such as ultrasound imaging, verbal or manual cueing, and exercise to help patients feel and activate the correct muscles. For example, many individuals unknowingly hold their breath or brace their superficial abs instead of using the diaphragm and TrA appropriately. Correcting these patterns can drastically reduce symptoms. 

3. Progressive Strength and Coordination 

Once the patient can correctly engage the deep core, exercises are progressed to incorporate dynamic movement, load, and functional tasks—like lifting a child, squatting, or running. The goal is not just pain relief, but return to full, confident movement. 

4. Pain Reduction through Neuromuscular Re-education 

By improving core coordination and reducing compensatory muscle tension, PFPT can significantly decrease pain. Many patients report improvements in symptoms such as: 

• Low back stiffness or aching during prolonged standing 

• SI joint sharp pain during transitional movements (e.g., rolling in bed, stepping up) 

• Pelvic pressure or urinary leakage during exercise 

• Hip tightness or groin pain that wasn’t relieved by stretching alone 

Whether it’s an athlete wanting to get back to sport, a postpartum mom navigating physical recovery, or someone living with persistent back or pelvic pain, pelvic floor physical therapy offers a science-backed, personalized path to healing. 

By restoring the foundational coordination of the deep core system, PFPT doesn’t just mask symptoms—it addresses the root cause. Patients often express how surprising it is that something as “simple” as breathing better or learning how to activate a muscle they never thought about could lead to profound improvements in pain, posture, continence, and confidence. 

The multifidus, transverse abdominis, diaphragm, and pelvic floor muscles are more than just anatomical components—they are a team. Their coordinated activation is essential for spinal and pelvic stability. When dysfunction or poor motor planning disrupts this team, the result can be pain, limited mobility, and frustration. Fortunately, pelvic floor physical therapy offers targeted strategies to restore this system, reduce pain, and help people return to the activities they love—with strength and resilience. 

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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.