Stabilizing Function of the Diaphragm: Upper Extremity versus Lower Extremity Movement

Research Review: Stabilizing Function of the Diaphragm: Upper Extremity versus Lower Extremity Movement

By Jinny McGivern DPT, PT, Certified Yoga Instructor

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

Original Citation: Kolar, P., Sulc, J., Kyncl, M., Sanda, J., Neuwirth, J., Bokarius, A. V., Kriz, J. & Kobesova, A. (2010). Stabilizing function of the diaphragm: dynamic MRI and synchronized spirometric assessment. Journal of Applied Physiology, 109(4), 1064-1071. ARTICLE

Note the movement of the diaphragm from its inferior position during inhalation (contracted state) to a more superior position during exhalation (relaxed state).

Image courtesy of http://solidglow.com/online-courses/online-courses/tag/breathing/

Why is this relevant?: The importance of core stabilization and how to improve it are topics of perpetual discussion within the community of human movement professionals. The diaphragm is often included in the group of muscles that make up our deep core stabilizers (Intrinsic Stabilization Subsystem (ISS) ). Exactly how the diaphragm contributes to the function of core stabilization is not widely understood. This research provides direct evidence of a changes in the behavior of the diaphragm with muscle contraction of the upper extremity and lower extremity, versus rest conditions.

Study Summary

Note the right and left crus of the diaphragm and their attachments to the lumbar spine. The authors of this study (Kolar et al.) report observing greater movement of the crural diaphragm during muscle activation of the limbs as opposed to movement of the costal diaphragm (the outer portion attached to the ribs). In a different research study, Hodges et al . report that they did not observe separate functions of different regions of the diaphragm. It is possible that these differing observations are related to different methods of measurement of diaphragm movement (dynamic MRI versus ultrasound/needle EMG). More research is needed to resolve the question of whether the diaphragm functions as 1 unit for all functions or as regional units for different functions.

Image courtesy of https://brentbrookbush.com/online-courses/articles/muscular-anatomy/psoas/

Review & Commentary:

Kolar et al utilized a particularly rigorous method of selecting subjects to participate in this study. Medical histories were collected to screen individuals for any conditions that might impact respiratory function. This was followed up by pulmonary function tests to confirm that all subjects possessed optimal respiratory function. The researchers did not assume that because the subjects reported "normal" respiratory function, that they actually demonstrated efficient function of this system. The researchers recruited a sample size of 30 individuals. This group was considerably larger than the sample of 5 participating in the research performed by Hodges et al . While having more subjects is always better, no power analysis was mentioned; therefore, it is not possible to know if this was an appropriate subject number to determine statistical significance for the outcome measures assessed. With regards to procedure, the same physiotherapist performed all assessments to assure consistency during data collection. Like Hodges et al., Kolar et al. performed direct observation of the behavior of the diaphragm (as opposed to a test of a theoretical model), albeit via different means. The current study observed diaphragm movement measured via dynamic MRI and lung volumes via spirometric assessment, whereas Hodges et al., utilized needle EMG, ultrasound and pressure transducers to perform their observations. These 2 studies taken together provide a multi-faceted view of the behavior of the diaphragm as a core muscle.

Although this study utilized a strong methodology, it also had limitations. Imaging of the diaphragm was only performed in the sagittal plane. Additional imaging in the coronal plane would have provided further information on the movement of the diaphragm. Measurements of diaphragm movement were performed with the subject in the supine position. While this position may have been necessary due to the equipment utilized for data collection, it is not "against gravity" nor is it a particularly demanding position for our core stabilizing system. To create a challenge, one of the researchers applied a manual force (described as being the equivalent of a manual muscle test 4/5) to the subject's bilateral UE, followed by the LE while the subject remained in supine. Manual application of force, even by the same rater, leaves room for error & subjectivity to be introduced. Standardization of force application via use of a percentage of maximum voluntary contraction may be beneficial for use in future studies.

The information provided by the results of this research is valuable, but we must be cautious with our interpretation. It is difficult to say that this research explicitly demonstrates support of the diaphragm's function in "postural stabilization". The performance of isometric contractions in the supine position is not a particularly demanding task for our stabilization system. However, this position may be more accurate to conclude the behavior change of the diaphragm in response to muscle activity of the UE and LE compared to rest conditions, as the stabilization required for upright posture may further confound data. It is likely that these behavior changes are part of the diaphragm's role as stabilizer; but further, research will be needed to conclude the role of the diaphragm in functional activities, comparing the findings of this study to UE and LE excursion in upright positures.

Why is this study important?

This research provides further evidence of the diaphragm's role in stabilization during limb muscle contraction. Furthermore, this research clarifies how the behavior of the diaphragm changes with respect to UE versus LE muscle activity.

How does it affect practice?

This study indicates that challenges to the LE result in greater changes in diaphragm behavior than challenges to the UE. When considering program design and exercise progression for core musculature, it would make sense to start with UE challenges and progress to LE challenges, as these appear to be more demanding activities.

How does it relate to Brookbush Institute Content?

As discussed in the research review The Role of the Diaphragm in Stabilization , research supports the inclusion of the diaphragm in the Intrinsic Stabilization Subsystem (ISS) , along with the Transverse Abdominis  (TVA), Multifidus , the Transversospinales , and the pelvic floor muscles. Because this subsystem is often observed to be underactive in all predictive models of postural dysfunction , Brookbush Institute interventions target activation and integration of the ISS . The Brookbush Institute utilizes the activation of the TVA as a method of activating the entire ISS subsystem. Note: in the video below, this exercise is progressed by starting with UE movements and then moving on to LE movements for an added challenge (as supported by this study). In the following video, appropriate regression/progression of a basic plank further utilizes the concept of the progression of UE challenge to LE challenge (knees down -> knees straight -> 1 leg). The following three videos describe core reactive integration exercises to promote efficient function of the ISS in conjunction with the rest of our global core musculature in a "timely fashion" (Anterior Oblique Subsystem , Posterior Oblique Subsystem , etc), with the first 2 videos focused on UE challenges and the final video focusing on a LE challenge.

Transverse Abdominis TVA Isolated Activation

Plank

Core Reactive Integration Crunch and Catch

Static Up Chop aka Lift

Modified Mountain Climbers for Core Reactive Stabilization

© 2014 Brent Brookbush

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