The following reference list highlights research articles which are relevant to studies completed on the transversus abdominis and its relationship to low back pain.
[Updated December, 2004]

Articles 1-10 | Next 10 »

1. McMeeken JM, Beith ID, Newham DJ, Milligan P, Critchley DJ.
The relationship between EMG and change in thickness of transversus
abdominis.
Clin Biomech ( Bristol , Avon ). 2004 May;19(4):337-42. >> summary article

2. Bunce SM, Hough AD, Moore AP.
Measurement of abdominal muscle thickness using M-mode ultrasound imaging
during functional activities.
Man Ther. 2004 Feb;9(1):41-4. >> summary article

3. Bo K, Sherburn M, Allen T.
Transabdominal ultrasound measurement of pelvic floor muscle activity when
activated directly or via a transversus abdominis muscle contraction.
Neurourol Urodyn. 2003;22(6):582-8. >> summary article

4. Kladny B, Fischer FC, Haase I.
[Evaluation of specific stabilizing exercise in the treatment of low back pain and
lumbar disk disease in outpatient rehabilitation]
Z Orthop Ihre Grenzgeb. 2003 Jul-Aug;141(4):401-5. >> summary article

5. Hodges PW, Moseley GL, Gabrielsson A, Gandevia SC.
Experimental muscle pain changes feedforward postural responses of the trunk
muscles.
Exp Brain Res. 2003 Jul;151(2):262-71. Epub 2003 Jun 03. >> summary article

6. Hodges PW, Pengel LH, Herbert RD , Gandevia SC.
Measurement of muscle contraction with ultrasound imaging.
Muscle Nerve. 2003 Jun;27(6):682-92. >> summary article

7: Critchley D.
Instructing pelvic floor contraction facilitates transversus abdominis thickness increase during low-abdominal hollowing.
Physiother Res Int. 2002;7(2):65-75. >> summary article

8: Allison GT, Henry SM.
The influence of fatigue on trunk muscle responses to sudden arm movements,
a pilot study.
Clin Biomech ( Bristol , Avon ). 2002 Jun;17(5):414-7.  >> summary article

9: Neumann P, Gill V.
Pelvic floor and abdominal muscle interaction: EMG activity and intra-abdominal
pressure.
Int Urogynecol J Pelvic Floor Dysfunct. 2002;13(2):125-32. >> summary article

10: Bunce SM, Moore AP, Hough AD.
M-mode ultrasound: a reliable measure of transversus abdominis thickness?
Clin Biomech ( Bristol , Avon ). 2002 May;17(4):315-7.  >> summary article

» Next 10

:: Summary &/or Abstract of Research Articles

1: Clin Biomech ( Bristol , Avon ). 2004 May;19(4):337-42.

The relationship between EMG and change in thickness of transversus
abdominis.

McMeeken JM, Beith ID, Newham DJ, Milligan P, Critchley DJ.

School of Physiotherapy , The University of Melbourne , Melbourne , Victoria
3010, Australia.

OBJECTIVE: To investigate the relationship between changes in thickness and EMG activity in the transversus abdominis muscle of healthy subjects and the reliability of ultrasound measurements using different modes and transducers. DESIGN: Convenience sampling. BACKGROUND: Chronic low back pain is associated with transversus abdominis dysfunction but EMG studies of this muscle are restricted to invasive techniques. Since the thickness of transversus abdominis changes with activity, such changes measured from ultrasound images might provide insight into this muscle's function non- invasively. In addition, little is known about the comparability of ultrasound measurements from different modes and transducers, nor the reliability of transversus abdominis measurements. METHODS: In 9 healthy subjects (aged 29-52 years, four male) transversus abdominis was studied at rest and during activity (5-80% max) with simultaneous EMG and ultrasound (M mode, 5 MHz curvilinear transducer) measurements. Intra-rater reliability for thickness measurements was studied on 13 subjects using 7.5 MHz linear and 5 MHz curvilinear transducers in B and M modes. RESULTS: Muscle thickness changes correlated well with EMG activity (P < 0.001, R2 = 0.87) and there were no significant differences between subjects (P > 0.05). Using 7.5 MHz head, the ICC for B mode was 0.989 and for M mode was 0.981 for between days reliability. The ICC for between transducer reliability was 0.817. CONCLUSIONS:
Changes in thickness of transversus abdominis can be used to indicate changes in the electrical activity in this muscle. RELEVANCE: Ultrasound scanning can be used in the clinical setting to provide objective information about transversus abdominis function.

2: Man Ther. 2004 Feb;9(1):41-4. 

Measurement of abdominal muscle thickness using M-mode ultrasound imaging during functional activities.

Bunce SM, Hough AD, Moore AP.

Clinical Research Centre for Health Professions, University of Brighton , Aldro Building 49 Darley Road , Eastbourne BN20 7UR , UK.

Ultrasound imaging has been previously utilized in the measurement of muscle thickness and cross-sectional area in research studies, and advocated as a clinical biofeedback tool in the rehabilitation of transversus abdominis function following episodes of low back pain. This paper describes how the thickness of the abdominal muscles can be quantified with a new measurement technique using M-mode ultrasound. The technique uses a custom-made transducer holder that facilitates measurement of muscle thickness changes during functional activity. Limitations of the technique and potential future applications are discussed. The M-mode ultrasound technique may provide an effective method for the non-invasive measurement of abdominal muscle thickness during functional activities.

3: Neurourol Urodyn. 2003;22(6):582-8. 

Transabdominal ultrasound measurement of pelvic floor muscle activity when
activated directly or via a transversus abdominis muscle contraction.

Bo K, Sherburn M, Allen T.

The Norwegian University of Sport and Physical Education, Ulleval Stadion, Oslo , Norway

AIMS: The purpose of the present study was to compare the effectiveness of
instruction to contract the pelvic floor muscles (PFM), the transversus abdominis (TrA), and the TrA + PFM visualized as displacement of the pelvic floor by ultrasound. MATERIALS AND METHODS: Twenty female physical therapists, mean age 41.1 years (range 26-56) participated in the study. A 3.5 MHz 35 mm curved linear array ultrasound transducer (Dornier Medtech) was placed in the mid-sagittal plane immediately suprapubically, angled at 15-30 degrees from the vertical depending on subcutaneous fat and anatomical variations, to image the pelvic floor. Six trials of three maneuvers in random order were performed: contraction of PFM, TrA, and TrA + PFM. RESULTS: In spite of correct contractions assessed by palpation and clinical observation, one subject demonstrated a downward movement of the pelvic floor during PFM contraction on ultrasound. Six subjects (30%) showed a downward movement during a TrA- contraction, and two during the combined TrA + PFM contraction. Instruction to contract PFM produced significantly greater mean displacement: 11.2 mm (95% CI 7.2-15.3) than TrA 4.3 mm (95% CI -0.2-8.8), P < 0.01, and combination: 8.5 mm (95% CI 5.2-12), P = 0.04. Hence, instruction of PFM contraction produced a 61.6% greater displacement of the pelvic floor in the correct direction than a TrA contraction. CONCLUSIONS: It is concluded that ultrasound is a more valid method than palpation and clinical observation to assess PFM function, and that instruction to contract the PFM produces a significantly more effective pelvic floor muscle contraction than instruction to perform a TrA contraction. Copyright 2003 Wiley-Liss, Inc.

4: Z Orthop Ihre Grenzgeb. 2003 Jul-Aug;141(4):401-5. 

Evaluation of specific stabilizing exercise in the treatment of low back pain and
lumbar disk disease in outpatient rehabilitation

Kladny B, Fischer FC, Haase I.

Fachklinik Herzogenaurach, Abteilung fur Orthopadie , Germany.

AIM: The aim of the study was to evaluate the outcome of outpatient
rehabilitation in patients with low back pain and lumbar disk disease with a
specific stabilizing exercise of the M. multifidus and M. transversus abdominis.
METHOD: 99 outpatients admitted to a rehabilitation unit were included in a
prospective randomized controlled interventional trial. The interventional group
consisted of 50 patients (34 male, 16 female; mean age 41.1 +/- 9.1, range; 21 -
54 years), 49 patients (31 male, 18 female; mean age 37.9 +/- 9.5, range; 19 -
55 years) were in the control group. Outcomes were assessed at the beginning
and the end of the treatment and at a three month follow-up with the Oswestry
Low Back Pain Disability Questionnaire, the Hannover Functional Ability
Questionnaire FFbH-R, the pain scale SES and a numeric rating scale. RESULTS:
In both groups there was a significant functional improvement as measured with
the Oswestry Score and the FFbH-R. The interventional group showed better
values at the end of the treatment. Pain as well could be reduced significantly
by the treatment, but no differences were noted between the two groups.
CONCLUSION: Outpatient rehabilitation improved functional capacity and pain in
both groups. Advantages could be seen in the interventional group concerning
functional status. The specific stabilizing exercise approach appears to be
effective in conservative treatment programs of low back pain and lumbar disk
disease.

5: Exp Brain Res. 2003 Jul;151(2):262-71. Epub 2003 Jun 03.

Experimental muscle pain changes feedforward postural responses of the trunk
muscles.

Hodges PW, Moseley GL, Gabrielsson A, Gandevia SC.

Department of Physiotherapy, The University of Queensland , Brisbane, QLD
4072, Australia.

Many studies have identified changes in trunk muscle recruitment in clinical low
back pain (LBP). However, due to the heterogeneity of the LBP population these
changes have been variable and it has been impossible to identify a cause-
effect relationship. Several studies have identified a consistent change in the
feedforward postural response of transversus abdominis (TrA), the deepest
abdominal muscle, in association with arm movements in chronic LBP. This
study aimed to determine whether the feedforward recruitment of the trunk
muscles in a postural task could be altered by acute experimentally induced
LBP. Electromyographic (EMG) recordings of the abdominal and paraspinal
muscles were made during arm movements in a control trial, following the
injection of isotonic (non-painful) and hypertonic (painful) saline into the
longissimus muscle at L4, and during a 1-h follow-up. Movements included rapid
arm flexion in response to a light and repetitive arm flexion-extension. Temporal
and spatial EMG parameters were measured. The onset and amplitude of EMG
of most muscles was changed in a variable manner during the period of
experimentally induced pain. However, across movement trials and subjects the
activation of TrA was consistently reduced in amplitude or delayed. Analyses in
the time and frequency domain were used to confirm these findings. The results
suggest that acute experimentally induced pain may affect feedforward
postural activity of the trunk muscles. Although the response was variable, pain
produced differential changes in the motor control of the trunk muscles, with
consistent impairment of TrA activity.

6: Muscle Nerve. 2003 Jun;27(6):682-92. 
 
Measurement of muscle contraction with ultrasound imaging.

Hodges PW, Pengel LH, Herbert RD , Gandevia SC.

Prince of Wales Medical Research Institute and the University of New South
Wales , Sydney , New South Wales 2031, Australia.

To investigate the ability of ultrasonography to estimate muscle activity, we
measured architectural parameters (pennation angles, fascicle lengths, and
muscle thickness) of several human muscles (tibialis anterior, biceps brachii,
brachialis, transversus abdominis, obliquus internus abdominis, and obliquus
externus abdominis) during isometric contractions of from 0 to 100% maximal
voluntary contraction (MVC). Concurrently, electromyographic (EMG) activity
was measured with surface (tibialis anterior only) or fine-wire electrodes. Most
architectural parameters changed markedly with contractions up to 30% MVC
but changed little at higher levels of contraction. Thus, ultrasound imaging can
be used to detect low levels of muscle activity but cannot discriminate between
moderate and strong contractions. Ultrasound measures could reliably detect
changes in EMG of as little as 4% MVC (biceps muscle thickness), 5% MVC
(brachialis muscle thickness), or 9% MVC (tibialis anterior pennation angle).
They were generally less sensitive to changes in abdominal muscle activity, but
it was possible to reliably detect contractions of 12% MVC in transversus
abdominis (muscle length) and 22% MVC in obliquus internus (muscle
thickness). Obliquus externus abdominis thickness did not change consistently
with muscle contraction, so ultrasound measures of thickness cannot be used
to detect activity of this muscle. Ultrasound imaging can thus provide a
noninvasive method of detecting isometric muscle contractions of certain
individual muscles.

7: Physiother Res Int 2002;7(2):65-75

Instructing pelvic floor contraction facilitates transversus abdominis thickness increase during low-abdominal hollowing.

Critchley D.
Division of Physiotherapy, Guy's, King's and St Thomas' School of Biomedical Sciences, King's College, London, UK. duncan.critchley@kcl.ac.uk

BACKGROUND AND PURPOSE: Low abdominal hollowing in four-point kneeling is used clinically to test and rehabilitate transversus abdominis (TrA) but many people find this exercise difficult to perform. Contracting pelvic floor muscles (PF) during low abdominal hollowing may facilitate contraction of TrA. Thickness increase in the abdominal muscles during low abdominal hollowing has been measured with real-time ultrasound scanning and may indicate muscle contraction. The present study investigated the effect of instructing PF contraction on TrA thickness increase during low abdominal hollowing.
METHOD: Twelve females and eight males with no reported pelvic floor dysfunction or low back pain in the last two years were taught low abdominal hollowing in four-point kneeling. Subjects performed low abdominal hollowing with and without instruction to contract PF in random order. Transversus abdominis, obliquus internus (OI) and obliquus externus (OE) thickness were measured with ultrasound scanning at rest and during both tests.
RESULTS: Mean increase in TrA thickness during low abdominal hollowing was 49.71% (SD 26.76%), during low abdominal hollowing with PF it was 65.81% (SD 23.53%). Paired Student's t-tests indicated a significant difference between tests (p = 0.015). There were no significant differences between tests for OE or OI thickness increase. CONCLUSIONS: Instructing healthy subjects to co-contract PF results in greater increase in TrA thickness during low abdominal hollowing in four-point kneeling. This may indicate greater contraction of TrA and thus be useful for clinicians training TrA. Further research could investigate the validity of change of thickness as a measure of abdominal muscle contraction, investigate the effect of instructing PF co-contraction on TrA in patients with low back pain and measure PF and TrA activity simultaneously.

8: Clin Biomech ( Bristol , Avon ). 2002 Jun;17(5):414-7.

The influence of fatigue on trunk muscle responses to sudden arm movements,
a pilot study.
Allison GT, Henry SM.

Department of Surgery, The Centre for Musculoskeletal Studies, The University
of Western Australia , Rear 50 Murray Street , Level 2 Medical Research
Foundation Bldg, Perth , WA 6000, Australia.

OBJECTIVE: To examine fatigue induced changes in trunk muscle latencies following trunk muscle fatigue. DESIGN: A repeated measures within subject design. Background. Trunk muscle responses to sudden movements is of interest in clinical biomechanics and motor control. METHODS: Electromyographic profiles were recorded from transversus abdominis (finewire), internal oblique, rectus abdominis and external oblique and longissimus at the level of the 3rd lumbar vertebrae bilaterally. Four asymptomatic subjects performed arm-raising task using a visual cue before and after an isometric fatiguing trunk extension task. RESULTS: Feed-forward responses were not detected in all muscles for every trial. In general, following fatigue trunk muscle onset latencies occur earlier (left, P=0.0016; right, P=0.0475). CONCLUSIONS: Trunk muscle fatigue alters anticipatory postural adjustments in normal subjects. It remains unclear if there is a pattern for specific muscles changes between individuals and if these are reflected in individuals with low back pain. RELEVANCE: Trunk muscle fatigue and altered trunk muscles latencies to movement perturbations have been associated with low back pain. These findings suggest that there may be a link between centrally mediated response to isometric muscle fatigue and anticipatory motor control strategies.

9: Int Urogynecol J Pelvic Floor Dysfunct. 2002;13(2):125-32. 
Pelvic floor and abdominal muscle interaction: EMG activity and intra-abdominal
pressure.
Neumann P, Gill V.
School of Physiotherapy , University of South Australia , Adelaide.

Pelvic floor muscle exercises prescribed for the treatment of incontinence commonly emphasize concurrent relaxation of the abdominal muscles. The purpose of this study was to investigate the interaction between individual muscles of the abdominal wall and the pelvic floor using surface and intramuscular electromyography, and the effect of their action on intra- abdominal pressure. Four subjects were tested in the supine and standing positions. The results indicated that the transversus abdominis (TA) and the obliquus internus (OI) were recruited during all pelvic floor muscle contractions. It was not possible for these subjects to contract the pelvic floor effectively while maintaining relaxation of the deep abdominal muscles. A mean intra- abdominal pressure rise of 10 mmHg (supine) was recorded during a maximum pelvic floor muscle contraction. These results suggest that advice to keep the abdominal wall relaxed when performing pelvic floor exercises is inappropriate and may adversely affect the performance of such exercises.

10: Clin Biomech ( Bristol , Avon ). 2002 May;17(4):315-7. 

M-mode ultrasound: a reliable measure of transversus abdominis thickness?

Bunce SM, Moore AP, Hough AD.

Clinical Research Centre for Health Professions, Aldro Building , 49 Darley Road,
Eastbourne BN20 7UR , UK.

OBJECTIVE: The purpose of this study was to establish a reliable method for
measuring transversus abdominis thickness in asymptomatic human subjects in
supine lying, standing and walking. DESIGN AND METHODS: This was a single
operator reliability study using ultrasound imaging to measure 22 subjects on
three separate occasions. A purpose built high-density foam reinforced belt
was used to house and position the transducer over the mid-point of the
transversus abdominis. Each subject was imaged in supine, standing, and
treadmill walking at 3 kph. Intraclass correlation coefficients and standard error
of measurement analysis were used to measure the data. RESULTS: The
correlation coefficient data analysis resulted in intraclass correlation
coefficients of 0.94 (standard error of measurement 0.35) in supine lying, 0.88
(0.66) in standing and 0.88 (0.56) in walking. CONCLUSION: The method
described is a reliable tool for measuring changes in thickness of transversus
abdominis in supine lying, standing and walking. RELEVANCE: This procedure
has the potential to detect dysfunctional changes in abdominal muscle activity
for patients with low back pain in a functional setting.

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