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Tuesday, June 6, 2023

Role of the Diaphragm in Stabilization

Brent Brookbush

Brent Brookbush


Research Review: Role of the Diaphragm in Stabilization

By Jinny McGivern DPT, PT, Certified Yoga Instructor

Edited by Brent Brookbush DPT, PT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Hodges, P. W., Butler, J. E., McKenzie, D. K., & Gandevia, S. C. (1997). Contraction of the human diaphragm during rapid postural adjustments. The Journal of physiology, 505(Pt 2), 539-548. - ABSTRACT

Kinesiology taping to promote diaphragm facilitation.
Caption: Kinesiology taping to promote diaphragm facilitation.

Kinesiology taping to promote diaphragm facilitation.

Why is this relevant?: The diaphragm is often described as a core stabilizing muscle, working in conjunction with the transverse abdominis (TVA) , pelvic floor and multifidi to provide stability to the spine & trunk. The exact nature of how the diaphragm functions as a core muscle is not often described in detail. This research provides direct evidence of diaphragm muscle contraction related to postural stabilization, not respiratory function. Furthermore this research provides support that the diaphragm functions synergistically with another core stabilizing muscle, the TVA .

Study Summary

Study Design Cross sectional laboratory study - Descriptive study
Level of Evidence Level VI - Evidence from a single descriptive or qualitative study
Subject Demographics
  • Age: 25 - 44 years
  • Gender: 4 male, 1 female
  • Characteristics: Healthy
  • Inclusion Criteria: n/a
  • Exclusion Criteria: Significant respiratory or neurological condition
Outcome Measures

This study consisted of 3 different protocols where 3 different sets of outcome measures were examined.#1 The following were collected during  20 reps of standing shoulder flexion to 90 degrees performed "as fast as possible" in response to a random visual stimulus:

EMG readings and onset of timing of:

  • Right (R) costal hemi diaphragm (5 subjects)
    • Needle electrodes

  • Crural diaphragm
    • Gastro-esophogeal Catheter

  • Rights (R) TVA (2 subjects)
    • Needle electrodes

  • Left (L) Deltoid
    • Surface electrodes

Pressures (collected using a gastro-esophogeal catheter):

  • Esophogeal pressure
  • Gastric pressure
  • Transdiaphragmatic pressure (Difference between Esophogeal & Gastric)

Respiratory cycle (measured via inductance plethysmograph)

  • Movement of the chest wall

#2 The following was collected from 2 subjects during 10 reps of fast as possible movement for each body part cued by a visual stimulus:

EMG readings for the onset of each of the following segment movement, as well as diaphragm:

  • Shoulder flexion
  • Elbow flexion
  • Wrist & finger extension
  • Thumb abduction

# 3 The following was collected for 4 subjects via ultrasound during 10 reps of shoulder flexion  and at resting end expiratory volume:

Diaphragm motion in response to shoulder 

  • Measurement of the length of the zone of apposition  of the costal diaphragm (indicative of total length of diaphragm) both before (at end of exhalation at rest) & during shoulder flexion task.
Results #1 Responses to shoulder flexion
  • Onset of activity in the costal diaphragm (attachment to ribs) preceded activity in the deltoid by 18 +/- 3 ms (significantly earlier in 4/5 subjects).
  • Onset of EMG in the crural diaphragm (attachment to vertebral column) preceded activity in deltoid by 17 +/-3 ms.
  • Mean difference in onset times between the 2 portions of the diaphragm was not significant.
  • Onset of diaphragm activity in response to shoulder flexion was not affected by the phase of respiration of the subject.
  • Onset of activity in the costal diaphragm preceded movement of the arm by 112 +/-8 ms. (delay of 96 +/- 6ms between onset of deltoid EMG & movement of arm is consistent with previous research on this muscle).
  • Latency between visual stimulus & onset of diaphragm activity was 122 +/- 7 ms.
  • Latency between visual stimulus & onset of deltoid activity was 140 +/- 6 ms.
  • Latency between visual stimulus & arm movement was 229 +/- 6 ms.
  • Onset of TVA activity preceded that of deltoid by 19 +/- 3 ms.
  • Mean difference between onset of TVA & diaphragm activity was  5 +/- 2ms.
  • Initiation of arm movement was preceded by an increase in gastric & trans diaphragmatic pressures by 63 +/- 7 ms.
  • The delay between onset of diaphragmatic activity & change in pressure was 49 +/- 4 ms & is consistent with previously observed results in the literature.
  • At onset of arm movement trans diaphragmatic pressure was 25% +/- 3% of peak.
  • Peak trans diaphragmatic pressure occurred at 120 +/- 7 ms after the onset of limb movement.
  • Peak increase of gastric pressure was 13.5 +/- 1.8 cm H2O
  • Peak increase in esophogeal pressure was .3 +/- 1.8 cm H2O (not significantly different from 0).
  • Peak increase trans diaphragmatic pressure was 13.8 +/- 1.9 cm H2O (mainly related to changes in gastric pressure)

#2 EMG activity of diaphragm as related to motion of specific segment of the UE.

  • Neither rapid movement of thumb abduction nor wrist extension had any impact on diaphragm activity.
  • Both rapid movement of the elbow & shoulder were preceded by anticipatory contractions of the diaphragm.

#3 Length changes of diaphragm relative to timing of shoulder movement

  • Mean length of the zone of apposition was 70 mm at resting functional residual capacity (end of a normal exhale).
  • Onset of shortening was a mean 30 ms prior to limb movement
  • Peak shortening (8% of initial length) occurred at a mean of 71 ms after onset of limb movement.
  • Shortening was followed by a lengthening to a 12% increase over initial length (The researchers explain that initially the diaphragm was able to contract & shorten due to low intra-abdominal pressure.  As the activity of abdominal muscles increased during limb movement, intra-abdominal pressure increased and additional diaphragm contraction was eccentric).
ConclusionsThis research supports the inclusion of the diaphragm as a member of our "core" musculature based on its co-contraction with other members of the intrinsic stabilization subsystem in response to a challenge to postural stability.  The mechanism by which the diaphragm aids in creating core stability is by increasing intra-abdominal pressure to increase support of the spine.
Conclusions of the Researchers The findings of this study indicate that the diaphragm contracts with the TVA prior to movement of the upper limb (larger movements, not fine motor), regardless of the phase of respiration.  Because the diaphragm's response appears to be dependent on the scale of the movement performed, this indicates a role as a stabilizing postural muscle.

Image of the inferior aspect of the diaphragm with sternal, costal and crural (right crus & left crus) sections indicated - https://anatomytopics.wordpress.com/files/2009/01/diaphragm-inf-view.jpg

Review & Commentary:

There were many features of this study that contributed to it's strong methodology. The researchers elected to observe the behavior of two members of the "core" or "deep stabilizers," in response to postural perturbations related to upper extremity movement. As a lack of core stabilization is typically cited as a contributing factor to many movement impairments, this study illustrates the role the TVA and Diaphragm may play. With respect to data collection, the use of surface EMG readings was not an option. The diaphragm & TVA are deep structures with layers of overlying muscle that would have interfered with the accurate assessment of muscle activity. Needle electrodes were used with exact placement determined by ultrasound imaging and confirmed with EMG readings. To make their study multi-dimensional, the authors observed the onset of electrical activity of the diaphragm (EMG readings), it's mechanical behavior (shortening and lengthening), and the changes in pressure in the thorax and abdomen. By examining all of these components simultaneously, the researchers were able to study how these different components were inter-related.

A major limitation of this study was its small sample size and differing numbers of subjects for different components of the research study. The largest number of individuals for any 1 set of data was 5 and the lowest was 2. It would have been beneficial if all data points could have been collected from all 5 subjects. It would be ideal if future researchers could reproduce this methodology with a larger sample size. In terms of subject selection, the individuals chosen were screened for neurologic and respiratory conditions that might impact results. The researchers do not mention screening subjects for any orthopedic conditions, in particular low back pain. Other research reviews on this website have focused on how core musculature can become inhibited in the event of injury, pain or pathology. Could the diaphragm's function as a core stabilizer become inhibited in similar ways to multifidi or TVA ? Future research is needed to examine the effect of pain on the diaphragm.

Why is this study important?

This study is important because it provides evidence to support established theory of the diaphragm's role as a deep core stabilizing muscle, and potentially targeted assessment and intervention.

How does it affect practice?

This study in particular does not provide much direct insight into the practical applications of improving the diaphragm's function as a core stabilizer; however, it does encourage the human movement professional to take note of this muscle. One method of assessing the diaphragm's function is to observe breathing. Although this article focuses on the stabilizing role of the diaphragm, it is reasonable to consider - if the muscle is impaired in its respiratory function, it may be impaired in it's stabilizing function as well.

The Assessment: Have your patient or client lie on their back with their knees bent and feet flat on the floor. Ask them to take a deep breath. Observe where you see movement. Is it primarily in the upper chest, lateral rib cage or is the gentle rise of the abdomen? You know that your client is breathing diaphragmatically if you see a gentle expansion of the abdomen and lower rib cage. If you don't see any movement of the abdomen on inhalation, it may be presumed that the diaphragm is not functioning optimally.

The Intervention: Ask your client to place 1 hand on their chest & 1 hand on their abdomen as they breathe. Encourage him or her to notice where the most movement is happening. Then, ask your client to gently breathe into their abdomen (One cue that works well is "Imagine you are inflating a balloon"). Some individuals will try to push their abdomen out. This is not the goal looking for - reset, re-cue a gentle, broadly distributed expansion of the abdomen, and reassess.

On a personal note, with a background as a yoga instructor, I have always been interested in the "breath" and how it has the capacity to influence movement. I frequently incorporate the above intervention into my patient/client's home exercise program, especially those with low back pain. Patients have reported that this technique was helpful in managing their pain. It is difficult to say (in this very unscientific, non-controlled observation) if it was the improved function of the diaphragm as stabilizer, or if this reduction in pain was related to relaxation, enhanced parasympathetic nervous system activity, or other factors.

How does it relate to Brookbush Institute Content?

This research supports the inclusion of the diaphragm in the Intrinsic Stabilization Subsystem (ISS) , as described by the Brookbush Institute (influenced by the work of Richardson, Hodges and Vleeming). Within the paradigm of subsystems tending toward overactivity or under-activity based on observed movement impairment and predictive models of postural dysfunctions , the ISS is believed to adopt a compensation pattern that includes relative under-activity in all predictive models of postural dysfunctions . This often results in synergistic dominance of other subsystems (i.e. the Anterior Oblique Subsystem (AOS) ) as they attempt to compensate for impaired trunk and spine stabilization. This often has ramification on movement (i.e. compensations) at peripheral joints. Based on this, activation activities are essential to increase neural drive to the muscles included in this subsystem. These activities are typically performed during a corrective exercise routine/integrated warm-up, or at the beginning of a performance enhancement routine so that the core is involved from the start of a workout. ISS activation activities are especially important to the predictive models of postural dysfunction intimately related to the trunk and spine, i.e. Lumbo Pelvic Hip Complex Dysfunction and Sacroiliac Dysfunction. It is not far fetched to reason that individuals with Upper Body Dysfunction and Lower Leg Dysfunction might also demonstrate inhibition of the ISS , although other interventions that more directly address those dysfunctions are typically employed first.

The Brookbush Institute primarily addresses the ISS via activation exercises targeted for TVA  (specifically the "Quadruped") (although there may be more to come in the future). Below are videos with details of these exercises as well as a video with a brief explanation of subsystems.

Transverse Abdominis TVA Isolated Activation

TVA and Gluteus Maximus Activation and Progressions

Hardest Quadruped Progression Ever Challenge

Review of Core Subsystems

© 2014 Brent Brookbush

Questions, comments, and criticisms are welcomed and encouraged -