Pediatric Postural Development: Is Fidgeting In Kids Behavioral Or Biomechanical?

When a child struggles to sit upright in class, at the dinner table, or during therapy sessions, the default explanation is often behavioral. Maybe the child is restless or lacks attention. Maybe they simply don’t want to participate. But what if the inability to sit still or maintain upright posture isn’t about behavior at all?

As pediatric therapists, you’re trained to recognize postural control challenges, motor delays, and sensory processing issues. Yet there’s a deeper layer often overlooked: pediatric postural development, and how the pelvic floor and diaphragm work together to create core stability and support sustained function.

When these systems aren’t working together, the child may appear fidgety, fatigued, or inattentive. This may not be due to a lack of motivation, but rather because their body doesn’t have the biomechanical support it needs.

In this blog, we’ll explore how inefficient postural and pressure systems can contribute to fidgeting and poor sitting tolerance, why it’s essential to look beyond behavior, and how a deeper understanding of the pelvic floor and diaphragm can expand your clinical toolbox.

When a child collapses into a slouched posture or constantly shifts in their seat, you may think of weak “core muscles.” But pediatric postural development is not just about core strength. It’s about pressure regulation and system integration.

The diaphragm, rib cage, abdominal wall, and pelvic floor create a pressure system that supports spinal alignment, trunk control, and endurance for upright sitting. When one part of this cylinder is compromised, such as restricted ribcage movement or pelvic floor tension, the child has to work harder to stay upright.

The result? Fidgeting, shifting, and moving. Not because they don’t want to pay attention, but because their postural development hasn’t provided them with the structural support they need.

Take a moment to observe how a child breathes while supine, sitting, and in standing. Many will show minimal lateral rib expansion, instead relying on shallow, anterior-posterior chest movements. Or conversely, some children have too much lateral expansion, making it difficult to engage the abdominal muscles.

Without proper ribcage mobility, the diaphragm can’t descend fully, and the abdominal wall cannot engage as effectively. Not only does this inefficient breathing strategy limit oxygenation, it also disrupts postural stability.

When the diaphragm isn’t moving efficiently, the pelvic floor may compensate by becoming underactive or hypertonic. This imbalance affects intra-abdominal pressure and interferes with postural development and stability, making it difficult for a child to sustain upright sitting.

For the child, this translates into discomfort. They may constantly adjust, arch, or slump to find a position where breathing feels easier. What looks like distractibility may actually be their body working around a faulty breathing strategy. Identifying and addressing these faulty patterns early is essential for you to help your kids build strong foundations for their postural development.

You may not associate the pelvic floor with a child’s ability to sit still, but it plays a crucial role in stabilizing the pressure system. The pelvic floor responds dynamically to changes in breath and posture, providing a base of support for upright sitting.

In children with delayed postural developmental, gastrointestinal dysfunction, or even prolonged postural habits like gaming slouch, the pelvic floor may not coordinate well with the diaphragm. Rather than moving with the diaphragm, the pelvic floor may be held in tension or fail to engage properly when required. When this neuromuscular communication is disrupted, children lose the automatic, reflexive support that should underlie postural control and continence

This mismatch means the child’s sitting posture lacks true support from below. Without the foundation, children find many ways to compensate, including fidgeting, leaning, or propping themselves up on external supports.

As a pediatric therapist, it’s tempting to interpret restlessness through a behavioral or sensory lens. While these factors certainly play a role, it’s essential to ask: Is this child’s postural development mature enough to sustain upright sitting in the first place?

Some common postural patterns you may notice in children who struggle with sitting still:

• Collapsed rib cage and abdominal wall – limiting expansion and causing pressure to bear down or bulge forward.
• Forward head, rounded shoulders – classic “gaming posture” that strains the diaphragm and pelvic floor relationship.
• Hanging on ligaments in standing or sitting – thorax displaced behind the pelvis, hyperlordotic lumbar spine, no active postural engagement.
• Horizontal creases in the abdominal wall – evidence of sustained pressure against a collapsed trunk.

Each of these patterns represents an inefficient use of the body’s pressure system. Without intervention, they often persist into later childhood and adolescence, appearing as poor endurance, constipation, or pelvic floor dysfunction.

A thorough assessment would include:

• Observation of breathing mechanics in different positions: rib cage excursion, use of accessory muscles, diaphragm movement.
• Assessment of postural alignment: fascial systems span the entire body, so look from foot to head.
• Abdominal wall and diastasis rectus abdominis screening: how is pressure distributed?
• Pelvic floor coordination: does the pelvic floor relax and engage in coordination with the breath?

By reframing sitting challenges as potential biomechanical issues, you can move beyond compensatory strategies and toward interventions that address the root cause. This perspective expands your clinical reasoning and helps you move past compensations toward meaningful, lasting outcomes.

If you want to learn how to assess and treat these systems comprehensively, I provide practical tools and strategies for pediatric PTs and OTs in my online course, Pediatric Pelvic Floor, Diaphragm, and Postural Development.

This beginner-level course is perfect for non-pelvic floor therapists who want to:

• Understand pediatric postural development in depth
• Assess posture, breathing, and pelvic floor function as one system
• Apply practical interventions for motor development and visceral health
• Gain tools you can use immediately in the clinic to improve kids’ motor development, bowel and bladder health, and quality of life

Join us live on September 21, 2025!

If you can’t join us live on September 21st, then be sure to check out the pre-recorded course on Teachable.