When physical therapists think about core stability, the focus often turns to individual muscles such as the transversus abdominis, multifidus, or pelvic floor. Yet at the center of this intricate system lies the diaphragm, a key player in the generation and modulation of intra-abdominal pressure (IAP). The ability to coordinate the diaphragm with the abdominals and pelvic floor through effective IAP regulation is critical not only for postural control but also for spine protection and efficient movement strategies.

IAP refers to the pressure within the abdominal cavity, bounded superiorly by the diaphragm, inferiorly by the pelvic floor, and circumferentially by the abdominal wall and spine. As the diaphragm contracts and descends during inhalation, it compresses the abdominal contents, while the pelvic floor and abdominal wall counteract this pressure to maintain balance. This pressurization acts as an internal stabilizer, creating a dynamic support system that reduces shear and bending stress on the lumbar spine. Recent biomechanical modeling by Murray and colleagues (2025) highlighted that IAP’s stabilizing role becomes particularly significant when external mechanical loads shift rapidly, emphasizing its importance for both daily and athletic movements.

Emerging evidence reinforces that IAP is not a passive byproduct of breathing; it is an active mechanism of stabilization. Kawabata and Shima (2023) demonstrated that breathing patterns and postural orientation strongly influence IAP and abdominal muscle recruitment. Their cross-sectional study revealed that forced exhalation in supine produced significant transversus abdominis and internal oblique activation, while exertion inhalation during a plank posture elicited similar effects, confirming that posture and breath type dictate how effectively the core musculature contributes to trunk stiffness.

Sembera et al. (2023) added an intriguing layer by showing that abdominal bracing, although stabilizing, can compromise respiration during lifting tasks. Their findings indicated that bracing reduces lung volumes even when diaphragmatic excursion increases, suggesting a necessary balance between spinal stability and ventilatory function. Clinically, this underscores the need to coach patients on modulating (not maximizing) IAP, to avoid respiratory compromise while preserving spinal support.

When the diaphragm, abdominal wall, and pelvic floor fail to coordinate efficiently, IAP regulation becomes dysfunctional. Patients with chronic low back pain often exhibit altered breathing strategies or underuse IAP mechanisms, relying instead on excessive paraspinal activation. Similarly, postpartum individuals with diastasis recti or individuals with pelvic floor dysfunction may struggle to modulate IAP effectively, resulting in impaired load transfer and increased spinal demand. In patients with respiratory disorders such as asthma or COPD, restricted diaphragmatic excursion can further limit the ability to generate stabilizing intra-abdominal pressure.

Recent clinical studies support the integration of breathing and core training in rehabilitation. Li et al. (2025) found that individuals with chronic non-specific low back pain who engaged in core training combined with breathing exercises demonstrated greater improvements in pain, function, and strength than those performing core training alone.

Likewise, Seo et al. (2024) reported that diaphragmatic strengthening within a core training protocol enhanced diaphragm thickness, respiratory pressure, and postural stability compared to traditional training methods. Together, these findings affirm that targeted interventions to optimize IAP and diaphragmatic coordination can yield meaningful functional benefits.

While the science of IAP is growing, the clinical application remains refreshingly practical. The following cues can help practitioners integrate IAP-based interventions into patient care.

Clinical Cues & Strategies: How to “Use IAP” Without Overdoing It

1. Start with breathing awareness
   • Use diaphragmatic or “belly” breathing cues in supine/recumbent first, encouraging gentle expansion in all directions.
     Use ultrasound or palpation (if available) to see diaphragm descent or amplitude changes.
2. Introduce gentle co-activation
   • Once diaphragm movement seems adequate, cue light abdominal engagement (e.g., light TrA) while breathing to gently harness IAP.
     Avoid immediate high bracing; the goal is dynamic modulation, not always maximal stiffening.
3. Progress posture + load
   • Move from supine → quadruped → half-kneel → standing → loaded tasks (bird-dog, dead bug, split stance).
     In each, cue breathing + abdominal co-activation together in a coordinated rhythm, not sequentially.
4. Load under breathing constraints
   • Challenge patients to maintain coordinated breathing + IAP during functional tasks: lifts, carries, squats.
     Use feedback (tactile cue, visual diaphragm ultrasound, breathing sensors) if possible.
5. Monitor for compensation
   • Watch for breath holds, neck accessory overuse, scapular shrugging, or paradoxical breathing.
     If compensations appear, regress posture or reduce load.
6. Balance ventilation and stability
   • Be cautious in populations with respiratory compromise, too much bracing may reduce lung capacity.
     When in doubt, prioritize breathing first, then layer in stabilization.

In summary, intra-abdominal pressure serves as a powerful yet nuanced mechanism of spinal protection. The coordinated activity of the diaphragm, abdominals, and pelvic floor forms an adaptable cylinder that stabilizes the spine, enhances postural control, and supports efficient movement. Current research emphasizes that effective IAP regulation requires both breath control and muscular timing, skills that can be refined through intentional training. Clinicians who integrate IAP strategies into their treatment approaches are better positioned to optimize function and alleviate pain across a wide spectrum of patients, from postpartum individuals to high-performance athletes.

Register Now: Breathing and the Diaphragm - December 6
For clinicians ready to deepen their understanding of the diaphragm and its vital relationship with IAP, join us on December 6 for Breathing and the Diaphragm, an interactive Zoom-based continuing education course.

Learn evidence-based assessment and treatment techniques that connect the diaphragm, abdominals, and pelvic floor to optimize intra-abdominal pressure, postural control, and functional performance. Perfect for clinicians treating patients with pelvic pain, diastasis, incontinence, spinal dysfunction, or athletes seeking enhanced stability.

Don’t miss this opportunity to translate current research into practical, evidence-based interventions that enhance your patients’ stability and performance.

References

1. Kawabata, M., & Shima, N. (2023). Interaction of breathing pattern and posture on abdominal muscle activation and intra-abdominal pressure in healthy individuals: A comparative cross-sectional study. Scientific Reports, 13(1), 1-9. https://doi.org/10.1038/s41598-023-37629-5
2. Li, Y., Zhao, Q., Zhang, X., E, Y., & Su, Y. (2025). The impact of core training combined with breathing exercises on individuals with chronic non-specific low back pain. Frontiers in Public Health, 13, 1518612. https://doi.org/10.3389/fpubh.2025.1518612
3. Murray SA, Driscoll M. Finite element investigation of the intrinsic stiffness contribution of intra-abdominal pressure in a transient spine and trunk model. Comput Biol Med. 2025 Sep;196(Pt A):110549. doi: 10.1016/j.compbiomed.2025.110549. Epub 2025 Jul 3. PMID: 40614524. https://pubmed.ncbi.nlm.nih.gov/40614524/
4. Sembera, M., Busch, A., Kobesova, A. et al.The effect of abdominal bracing on respiration during a lifting task: a cross-sectional study. BMC Sports Sci Med Rehabil 15, 112 (2023). https://doi.org/10.1186/s13102-023-00729-w
5. Seo, H., Jeong, G., & Chun, B. (2024). Impact of Diaphragm-Strengthening Core Training on Postural Stability in High-Intensity Squats. Life, 14(12), 1612. https://doi.org/10.3390/life14121612