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Tuesday, June 6, 2023

Co-contraction of Ankle Dorsiflexors and Transverse Abdominis in Patients with Low Back Pain

Brent Brookbush

Brent Brookbush


Research Review: Co-Contraction of Ankle Dorsiflexors with the Abdominal Draw-in Maneuver Increases Transverse Abdominis Recruitment and Functional Outcome Markers in Individuals with Chronic Low Back Pain

By Nicholas Rolnick SPT, MS, CSCS

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

Original Citation: Chon SC, You JH, Saliba SA. (2012). Cocontraction of ankle dorsiflexors and transversus abdominis function in patients with low back pain. Journal of Athletic Training. 47(4): 379-389. ABSTRACT.

Illustration of the Transverse Abdominis and the Rectus Sheath from Gray's Anatomy 20th Ediction
Caption: Illustration of the Transverse Abdominis and the Rectus Sheath from Gray's Anatomy 20th Ediction

By modified by Uwe Gille - Gray397.png, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2601348

Why is this relevant?: Transverse abdominis (TrA) dysfunction has been implicated in patients experiencing low back pain (LBP). Occurrence of mechanical LBP has been thought to arise from inadequate neuromuscular control of the force coupling between TrA and the deep multifidus . This aberrant control leads to diminished stability of the lumbopelvic complex, predisposing the spine to increased anterior shear forces generated by synergistically dominant erector spinae and iliopsoas muscles. Training the TrA is a prominent component of treatment for mechanical LBP. The abdominal draw-in manuever (ADIM) is the most common exercise that is prescribed to increase recruitment of TrA but is usually performed with the intent of isolation, i.e. minimal activation from other musculature (for example, rectus abdominis and external obliques ). The current study paired the ADIM with co-contraction of tibialis anterior (TA) and rectus femoris (RF) to determine its influence on pain and function in patients with LBP.

Study Summary

Study Design Case-Control Study
Level of Evidence Level 3: Observational Studies with Controls
Subject Demographics
    • Age:
      • Experimental: 27.20 +/- 6.46 years old
      • Control: 24.25 +/- 1.59 years old

    • Gender:
      • Experimental: 7 M, 13 F
      • Control: 9 M, 11 F

    • Characteristics:
      • Height
        • Experimental: 166.25 +/- 8.70 cm
        • Control: 168.00 +/- 8.89 cm

      • Mass
        • Experimental: 58.10 +/- 11.81 kg
        • Control: 60.65 +/- 11.99 kg

    • Experimental:
      • Both groups underwent a pre-test:
        • Pain, muscle thickness ratio (ultrasound), muscle activation (electromyographic, EMG) monitor
          • Pain and function assessed in LBP group only with visual analog scale (VAS), the Pain Disability Index (PDI), and the Low Back Pain Rating Scale (LBPRS)
            • VAS - 1-10, higher numbers signify increased levels of pain
            • PDI - 0-70, higher scores signify greater levels of reported disability
            • LBPRS - 0-130, higher scores signify greater levels of disability and impairment

          • Muscle thickness ratio was assessed using a sonography system to test the thickness of the transverse abdominis (TrA), the internal oblique (IO), and the external obliques (EO).
            • TrA ratio was measured by the TrA contracted/TrA at rest using the abdominal draw-in manuever (ADIM)
              • Individuals were in a hook-lying position (lying on their back, hip and knees bent to between 40-80°)
              • Biofeedback unit placed under 5th lumbar vertebrae and inflated to 40-70 mm Hg. Participant was instructed to draw in navel gradually while maintaining target pressure without any pelvic motion
              • Dominant side was used for ultrasound imaging, and was determined in the LBP group by which side was more painful; in the healthy controls by which side they used to kick a ball
              • Ultrasound was performed transversely, 25 mm anteromedial to the midway point between the 12th rib and the iliac crest, and was maneuvered until the clearest image of the lateral abdominal wall was seen. Identical placement for each participant throughout the trial was ensured by utilization of a transparent sheet and a permanent marker on the skin
              • A test-retest reliability assessment was also performed to assess the ability of the ultrasound to measure changes in the muscle sizes in both groups

          • Electromyographic Measurement (EMG)
            • Surface electrodes were used for TrA/IO, tibialis anterior (TA), and rectus femoris (RF)
              • TrA/IO electrode placement was 20 mm medial and inferior to the anterosuperior iliac spine
              • TA electrode placement was 20 mm distal and lateral from the tibial tubercle
              • RF electrode placement was halfway between the anterosuperior iliac spine and the superior part of the patella

            • Activation protocol
              • Max EMG maximum isometric voluntary contraction (MVIC) for each muscle group was determined
              • 30% MVIC has been previously reported to be the best activation level for TrA/IO activation so this was used in the EMG biofeedback part of the protocol as the goal
              • Onset latencies for the muscles were also calculated for each group
              • EMG's used for first two sessions in the first week as well as second two sessions in the second week to facilitate proper sequence of activation for training
              • Co-contraction training consisted of - 30% MVIC TrA/50% TA, RF for 3 seconds then rest for 5 seconds and initiated by an auditory cue

    • Testing protocol
      • Both groups received ultrasound-guided and EMG-guided visual biofeedback for 30 minutes, 5x/week over a two week period
      • ADIM protocol (described above) plus static co-contraction of TA and RF (50% MVIC) induced by a fixed strap band
      • Successful performance of the ADIM was validated by visual, tactile feedback (if necessary), ultrasound, and EMG measurements

    • Statistical Analyses
      • Computations of means and standard deviations, a mixed 2 x 2 analysis of variance (ANOVA), 2 tailed paired-samples t-test, Intra-class coefficients (ICC), and standard error of measurement (SEM)
      • Independent variables - group and time factors
      • Dependent variables - VAS, PDI, LBPRS, muscle thickness, EMG peak and mean amplitude, onset time, and latency
      • Post-hoc Tukey's was performed if significant effects were obtained in the ANOVA

  • Inclusion Criteria:
    • For LBP Group:
      • Clinical assessment of mechanical LBP, periods of LBP within the 6 to 12 months before the study, and a current level of pain ranging from 4-8 on a visual analog scale of 10
      • Mechanical LBP defined as intermittent pain that gradually develops later in the day, pain when standing or sitting for a long period of time, pain upon trunk flexion (or occasional extension), and pain when driving long distances or getting in and out of a car
        • Diagnosis was made by one author with 10 years of orthopedic experience whereas the medical diagnosis was made by attending orthopedist or physician who was not an author of the study

    • For Control Group:
      • No known medical problems or history of LBP

  • Exclusion Criteria:
    • A history of osteoporosis, structural deformity, systemic inflammatory disease, nerve-root compression, facet osteophytes, prolonged severe pain, problems with the neuromusculoskeletal system, and history of spinal surgery

Outcome Measures
    •  Participants
      • Baseline comparisons and pain pre- and post-test measures

    • Ultrasound Imaging Data
      • Resting muscle thickness for TrA, EO, IO and muscle thickness ratios for each group

    • EMG Data
      • Peak EMG amplitudes for TrA/IO, TA, RF
      • Mean EMG amplitudes was observed for TrA/IO, TA, and RF
      • Differences in mean onset time for TrA/IO, TA, and RF
      • Differences in mean latencies for TrA/IO-TA, TA-RF (P = 0.14), and TrA/IO-RF

    • Test-Retest Reliability for Ultrasound

  •  Participants
    • No significant differences in age, height, or mass (P > 0.05 for all) between LBP and controls
    • Significant differences reported in the LBP group for pre- and post-test differences in VAS (P < 0.001), PDI (P < 0.001), LBPRS (P = 0.02)
      • All showed group mean differences for decreases in pain and perceived disability in the LBP group

  • Ultrasound Imaging Data
    • ANOVA 2x2 showed a group by intervention interaction (P = 0.01) and an intervention main effect for TrA ratio (P = 0.001) but insignificant for IO (P = 0.83) and EO (P = 0.53) ratios
    • Tukey's showed that LBP group had greater improvement in the TrA muscle thickness ratio after training than the control group (P = 0.03)
    • Independent samples t-test showed differences in baseline (resting) muscle thickness for TrA (0.001), IO (0.02), and EO (0.001) between the groups at the pre-test but no changes in muscle thickness ratio (contracted/rest) were observed (P > 0.05) between the groups

  • EMG Data
    • Independent samples t-test showed differences in peak EMG amplitudes for TrA/IO (P = 0.001), TA (P = 0.004), and RF (P = 0.003) but not for co-contracted TrA/IO (P = 0.07) between the LBP and the control groups
      • LBP group had smaller peak EMG amplitudes for TrA/IO than healthy controls when ADIM was done in isolation
      • Peak EMG amplitudes were similar between groups when co-contraction was added

    • Differences in mean EMG amplitudes was observed for TrA/IO (P = 0.001), TA (P = 0.003), and RF (P = 0.001) but not for co-contracted TrA/IO (P = 0.08) between the LBP and the control groups
      • Mean amplitudes were similar between groups when co-contraction was added

    • Differences in mean onset time was observed for TrA/IO (P = 0.009) and TA (P = 0.007) but not RF (P = 0.11) between the LBP and the control groups
      • LBP group had increased latencies in TrA/IO contraction when compared to healthy controls

    • No differences in mean latencies for TrA/IO-TA (P = 0.48), TA-RF (P = 0.14), or TrA/IO-RF (P = 0.06) were found between the LBP and the control groups
      • Latencies were similar between groups when co-contraction was added

  • Test-Retest Reliability
    • ICC (1,3) of 0.99 for TrA, 0.95 for IO, and 0.96 for EO signifying high test-retest reliability

  •  ADIM can be used to provide sequential motor recruitment and muscle thickness in the abdominal muscles of healthy adults and those with chronic LBP
Conclusions of the Researchers
  •  The ADIM followed by co-contraction of TA stimulated selective recruitment of the TrA and IO muscles possibly leading to reduction of LBP by facilitating TrA's central action in the lumbopelvic region.
  • Co-contraction can further facilitate TrA activation and could be used to augment its function in providing core stability.

Tibialis Anterior Activation with Cueing for a quad set and increased quadriceps activation and pressing the heel Into the table for increased gluteus maximus activation.
Caption: Tibialis Anterior Activation with Cueing for a quad set and increased quadriceps activation and pressing the heel Into the table for increased gluteus maximus activation.

Tibialis Anterior Activation with Cueing for a Quad Set and increased Rectus Femoris Activation.

Review & Commentary:

Altered neuromuscular control of the transverse abdominis (TrA) has been proposed as a primary mechanism for mechanical LBP. Previous research has implicated TrA dysfunction in LBP by showing delays in EMG activation, decreases in peak EMG activation and decreases in cross-sectional area of the TrA when compared to healthy controls (1-2). This study supports previous literature in that chronic LBP patients exhibited delays in EMG activation, a smaller EMG activation peak, and smaller cross-sectional areas of the abdominal musculature when compared to age-matched healthy controls.

As the TrA’s proposed function is to stabilize the lumbar spine, the sacroiliac joint (SIJ), and the pubic symphysis via increasing intra-abdominal pressure and tensioning of the thoracodorsal fascia , research has been conducted to determine its contribution to these mechanisms. The Brookbush Institute has conducted several research reviews investigating TrA's purported function - lumbopelvic hip complex research reviews.

One study compared abdominal hollowing (drawing in stomach without inhaling to minimize rectus abdominis and external oblique contractions) to abdominal bracing (co-contraction of all abdominal muscles) while holding no weight, a 10 kg weight in the dependent position, and lifting a 10 kg weight and its influence on lumbar stability in 8 healthy young individuals without LBP (3 ). The study concluded that abdominal bracing was more effective in generating compressive lumbar stability than abdominal hollowing, but used complex equations to estimate TrA’s role in lumbar stability (which was estimated to be 0.14% of compressive forces) and inferred its activation based on activation of the internal obliques (IO). Furthermore, abdominal hollowing is not a similar TrA recruitment exercise as the ADIM, so direct comparisons are difficult to make.

Another study investigated TrA’s role in SIJ stability in individuals who were not suffering from LBP and compared abdominal bracing to ADIM (4 ). The study defined ADIM as an isolated contraction of the TrA by pulling the navel to the spine with a decrease in waist circumference and no pelvic motion, which is similar to the methodology of the current study. The authors concluded that ADIM provided greater SIJ stability than the abdominal bracing and recommended that the ADIM be considered for any rehabilitation program for individuals with LBP or SIJ dysfunction as well as performance enhancement programs aimed to increase the efficiency of load transfer from the trunk to the lower extremities and vice versa.

And in yet another study, the Brookbush Institute investigated with respect to TrA activation was on EMG firing patterns in individuals suffering from chronic LBP (1 ). The study conclusively showed that in individuals with chronic LBP, TrA firing pattern was delayed when compared to healthy participants when performing shoulder flexion, abduction, and extension movements, suggesting disordered neuromuscular coordination. The authors posited that the disordered feed-forward control leads to improper loading and stabilization of the spine predisposing the individual to LBP.

The literature on TrA’s contribution to lumbopelvic stability has yet to be fully elucidated, but Chon, You, & Aliba’s (2012) study exhibited many strengths that continue to add more support for the important role TrA has in chronic LBP.

The current study provided a clear and comprehensive methodology for investigating their primary objective, which was to determine the efficacy of two weeks of ADIM with co-contraction on abdominal muscle thickness and activation and its effect on pain and perceived disability in chronic LBP patients. This study was the first of its kind to demonstrate that co-contraction of the ankle dorsiflexors with TrA training using the ADIM might lead to changes in thickness of the abdominal musculature and concomitant reductions in pain and perceived disability in chronic LBP patients over a two-week training period. The entire methodology was clearly defined to the reader and each recording was standardized for each participant to maximize reliability for measurement of ultrasound and EMG. Secondly, although this was a case-control design, the authors were blinded to the assignment group for each patient, minimizing potential biases in data recording. Finally, the authors conducted a reliability study on their ultrasound protocol, which added further support to the effectiveness of their treatment intervention. High test-retest values show that the measurement protocol is repeatable and returns similar values when no actual change has occurred. Without high test-retest reliability, the examiner cannot be certain if the values obtained from the exam are an artifact of the test itself, or actual changes in condition.

However, there are limitations that must be discussed before applying to clinical practice. First, TrA activation was inferred with respect to IO activation, leading the authors to conclude the efficacy of their intervention indirectly via TrA/IO EMG amplitudes and latencies. Furthermore, the authors set activation threshold for the TrA/IO complex at 30% based on previously reported literature, but it is unclear what “optimal co-contraction” between these muscles actually means. Secondly, the short duration of the study leaves many questions about its long-term efficacy. Two important exclusions worth noting were the absence of recording of the firing and measurements of the thickness of the deep multifidus musculature, and an absence of a comparison group using TrA activation without co-contraction. The deep multifidus has an important role in segmental spinal stability and is most often atrophied (much like TrA) in chronic LBP patients (5), and we cannot conclude if this technique was more effective than TrA activation alone. Finally, due to the small sample size (40 total) and case-control design, caution must be made when attempting to generalize the results to the population at large.

Why is this study important?

This study is the first of its kind to comprehensively investigate the effects of the ADIM with co-contraction from the ankle dorsiflexors and rectus femoris musculature on TrA activation and muscle thickness ratios in individuals with chronic LBP. Using ultrasound and surface EMGs, along with a standardized ADIM protocol, the authors showed short-term benefits in muscle thickness ratios of TrA, TrA/IO contraction amplitudes and latencies with co-contraction, and decreases in pain and perceived disability with two weeks of the intervention protocol (5x/week, 30 minutes/session).

Furthermore, individual statistical analyses showed that chronic LBP showed decreases in all abdominal musculature cross-sectional area pre-intervention. Increased TrA thickness has been associated with improved lumbar stiffness leading to decreases in reported pain in people with LBP (2). With intervention, chronic LBP participants increased their TrA muscle thickness with the added co-contraction from 12.00 +/- 11.7 mm to 13.6 +/- 12.0 mm (total increase of 13%) versus just 14.7 +/- 7.2 mm to 15.1 +/- 7.5 mm (total increase of 3%) in the healthy controls (P = 0.01). These results suggest that TrA muscle thickness was diminished in chronic LBP participants when compared with the healthy controls pre-intervention and the inclusion of co-contraction benefitted chronic LBP participants more than the healthy controls (13% vs. 3%).

How does it affect practice?

The study utilized the principle of irradiation from the Proprioceptive Neuromuscular Facilitation paradigm, whereby the activation of stronger muscles (TA and RF) can selectively activate recruitment of weakened or involved motor units distal to the activated muscle (TrA) (6).

The results of the current study suggest that the ADIM along with added co-contraction from TA and RF can increase recruitment of the TrA and help facilitate its central action of increasing lumbopelvic stability via tightening of the thoracodorsal fascia. The added co-contraction further increased TrA recruitment markers and resulted in decreased pain and perceived disability in chronic LBP sufferers over a two-week period.

Human movement professionals should look to utilize the ADIM with co-contraction to facilitate increases in TrA recruitment in an effort to achieve optimal spinal stability.

How does it relate to Brookbush Institute Content?

The "draw-in" verbal and manual cues as utilized by the Brookbush Institute in all activities promote optimal spinal stability by increasing intra-abdominal pressure. Isolated activation of the transverse abdominis is discussed throughout the predictive models of Lumbo Pelvic Hip Dysfunction , Sacroiliac Joint Dysfunction , and Upper Body Dysfunction . The addition of co-contraction by the ankle dorsiflexors during isolated TrA exercise can further enhance TrA recruitment.

The following videos demonstrate activation of the TrA, integration of the TrA with gluteus maximus activation , integration of the TrA with deep neck flexor activation and tibialis anterior activation .

Brookbush Institute Videos

TVA Isolated Activation

TVA and Gluteus Maximus Activation and Progressions

TVA and Deep Neck Flexor Activation and Progressions

Tibialis Anterior and Tibial Internal Rotator Activation


  1. RESEARCH REVIEW: Hodges, P., Richardson, C. (1996). Inefficient Muscular Stabilization of the Lumbar Spine Associated With Low Back Pain: A Motor Control Evaluation of Transverse Abdominis. Spine, 21(22), 2640-2650.
  2. O’Sullivan PB, Phyty GD, Twomey LT, Allison GT. (1997). Evaluation of specific stabilizing exercise in treatment of chronic low back pain with radiologic diagnosis of spondylolysis or spondylolisthesis. Spine. 22(24): 2959-2967.
  3. RESEARCH REVIEW: Grenier, S., McGill, S. (2007). Quantification of lumbar stability by using 2 different abdominal activation strategies. Archives of Physical Medicine & Rehabilitation. 88, 54-62.
  4. RESEARCH REVIEW: Richardson, C., Snijders, C., Hides, J., Damen, L., Pas, M., Storm, J. (2002) The Relation Between the Transversus Abdominis Muscles, Sacroiliac Joint Mechanics, and Low Back Pain. Spine. 27 (4), 399-405.
  5. Freeman MD, Woodham MA, Woodham AW. (2010). The role of lumbar multifidus in chronic low back pain: a review. PMR. 2: 142-146.
  6. Adler, Beckers, Buck (2014) PNF in Practice: An Illustrated Guide - 4th Edition © Springer-Verlag, Berlin Heidelberg 1993, 2000, 2008, 2014

© 2016 Brent Brookbush

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