Effect of the Abdominal Hollowing and Bracing Maneuvers
on Activity Pattern of the Lumbopelvic Muscles During
Prone Hip Extension in Subjects With or Without
Chronic Low Back Pain: A Preliminary StudyThis section is compiled by Frank M. Painter, D.C.
Send all comments or additions to: Frankp@chiro.org
FROM: J Manipulative Physiol Ther. 2017 (Feb); 40 (2): 106–117
Amir H. Kahlaee, PhD, Leila Ghamkhar, MSc, Amir M. Arab, PhD
Department of Physical Therapy,
University of Social Welfare and Rehabilitation Science,
Evin, Tehran, Iran.
arabloo_masoud@hotmail.com
OBJECTIVE: The purpose of this study was to compare the effect of abdominal hollowing (AH) and abdominal bracing (AB) maneuvers on the activity pattern of lumbopelvic muscles during prone hip extension (PHE) in participants with or without nonspecific chronic low back pain (CLBP).
METHODS: Twenty women with or without CLBP participated in this cross-sectional observational study. The electromyographic activity (amplitude and onset time) of the contralateral erector spinae (CES), ipsilateral erector spinae (IES), gluteus maximus, and biceps femoris muscles was measured during prone hip extension (PHE) with and without abdominal maneuvers. A 3-way mixed model analysis of variance and post hoc tests were used for statistical analysis.
RESULTS: Between-group comparisons showed that the contralateral erector spinae (CES) onset delay during prone hip extension (PHE) alone was greater (P = .03) and the activity level of IES, CES, and biceps femoris in all maneuvers (P < .05) was higher in patients with CLBP than in asymptomatic participants. In asymptomatic participants, PHE + AH significantly decreased the signal amplitude (AMP) of ipsilateral erector spinae (IES) (P = .01) and contralateral erector spinae (CES) (P = .02) muscles. In participants with CLBP, IES muscle AMP was lower during PHE + AH compared with PHE + AB and PHE alone. With regard to onset delay, the results also showed no significant difference between maneuvers within either of the 2 groups (P > .05).
CONCLUSIONS: Performance of the AH maneuver decreased the erector spinae muscle AMP in both groups, and neither maneuver altered the onset delay of any of the muscles in either group. The low back pain group showed higher levels of activity in all muscles (not statistically significant in gluteus maximus during all maneuvers). The groups were similar according to the onset delay of any of the muscles during either maneuver.
KEYWORDS: Abdominal Muscles; Biofeedback; Chronic Low Back Pain; Diagnostic Test; Exercise Therapy; Hip; Paraspinal Muscles; Pressure; Response Latency; Surface Electromyography
From the FULL TEXT Article:
Introduction
Low back pain (LBP) is among the most prevalent and costly health problems. [1] The prevalence of LBP is higher in women, and women are more likely to suffer from functional disability because of LBP. [2, 3] Among the various factors associated with chronic low back pain (CLBP), attention has been drawn to the changes in motor control and trunk muscle function within the past decade. Muscle imbalance (not becoming active at the right moment with adequate intensity) of the lumbopelvic region may lead to LBP by imposing undue stress and compression on the vertebrae. [4, 5] Reduced or delayed activity of the multifidus [6, 7] and transversus abdominis (TrA) [8, 9] and change from tonic to phasic activity of the TrA [10] are noticeable behaviors in people with LBP. A number of studies have shown higher levels of erector spinae (ES) activity during various tasks in patients with LBP compared with non-LBP subjects. [11-13] Different muscle recruitment strategies may be used to increase trunk stiffness (in terms of resistance to vertebral displacement [14]) and to enhance spinal stability in patients with lumbopelvic pain, possibly as a compensation to counteract impaired spine stability. [15, 16]
A test commonly used for evaluation of the recruitment pattern [17] and stability of lumbopelvic muscles in CLBP (with or without leg pain) [18] is prone hip extension (PHE), a maneuver developed by Janda. The muscle activity pattern during this movement has been theorized to simulate those used during functional activities, such as gait. [19] It is thought that changes in this pattern can decrease the stability of the lumbopelvic region during walking, which could be a risk factor for the initiation or exacerbation of LBP. [20] The most common sign of a faulty recruitment pattern (although seriously challenged recently) has been proposed to be [18, 21] alteration in the timing or activity level, or both, of the tested muscles. This test is also commonly used as a therapeutic exercise in patients with LBP to strengthen the trunk and hip extensors and stretch the hip flexors. Despite a lack of strong evidence, altered muscle recruitment pattern within the back and hip extensors during PHE has been proposed as a prevalent dysfunctional pattern [19, 22] in patients with LBP, which possibly contributes to reduced lumbopelvic stability. [23] A recent study has attributed the higher activity in ES, gluteus maximus (GM), and biceps femoris (BF) to spinal instability [24] in patients with LBP compared with asymptomatic participants. Vogt et al. have proposed that alterations in the timing of trunk and hip extensors during walking decrease the stability of the lumbar spine and pelvis, which might lead to the development of low back pain. [20] Coordinated back and hip extensor activity have also been proposed to be crucial to the stability of the lumbopelvic region during PHE. [11, 25]
Spinal stability (or instability) is a complex concept that is being approached from both mechanical (radiographic) and functional (clinical) points of view. [16, 26] Mechanical instability is attributed to excessive spinal segmental movement and is confirmed by radiography. [26] Functional instability is defined as a failure in the maintenance of intervertebral neutral zones under loaded conditions, which results in pain and disability. [16] It has been hypothesized that increased muscular activity in patients with LBP may be required to compensate for reduced spinal stability, [27, 28] which comes with the cost of increased spinal compression. Lumbar stabilization exercises have been recommended to improve motor control of the lumbopelvic region. [29] It is also hypothesized that unwanted increased lumbar global muscle activity may be prevented or decreased if adequate stability is provided.
The role of abdominal muscles (both deep and superficial) in the stabilization of the spine has been well established. [30] abdominal hollowing (AH) and abdominal bracing (AB) maneuvers are commonly used to activate abdominal muscles to increase spinal stability. Abdominal hollowing is performed to activate the deep abdominal muscles — namely, transversus abdominis (TrA) and the internal oblique abdominal muscle — while minimizing superficial global muscle activity [30] and thus seems effective in preserving the motor patterns of abdominal muscles and consequently enhancing spinal stability. [31, 32]
Abdominal bracing focuses on activation of all abdominal wall muscles. According to McGill, [33] sufficient stability of the lumbar spine is achieved with modest levels of simultaneous activation in all trunk muscles. Recently, it has been suggested that AH is suitable for treatment of unstable spine with altered abdominal muscle recruitment pattern, whereas AB might be more suitable for use in healthy participants, [34] although this hypothesis needs further investigation to be applied clinically. Some previous studies reported alterations in electromyography (EMG) signal amplitude (AMP) [35, 36] and timing [37] of the lumbopelvic muscles during hip extension and abduction in healthy participants when these movement were accompanied by AH. Performance of AH and AB maneuvers in asymptomatic participants have been reported to reduce EMG activity of lumbar ES muscles. The authors suggested that the effective stabilization provided by this maneuver reduced the need for increased global muscle activity. [38] It thus seems worthwhile to investigate the effects of clinically relevant and frequently used abdominal maneuvers on the recruitment pattern of lumbopelvic muscles (as a determining factor for spinal stability) during PHE. Despite the inherent discrepancies the 2 tasks have in terms of body posture and gravity influences, lumbopelvic muscle activity during PHE has been proposed to mimic muscle activity during gait. [37, 39] To the best of our knowledge, no study has directly compared the effect of abdominal stabilizing maneuvers on the trunk muscular activation patterns (EMG AMP and onset time), which have been suggested to reflect motor control strategy, in participants with LBP.
Therefore, the objectives of this study were to
compare the activation pattern of the ipsilateral and contralateral ES (IES and CES, respectively), GM, and BF muscles during PHE between asymptomatic participants and patients with CLBP and
assess the effect of AH and AB maneuvers on the EMG signal AMP and timing of these muscles in both groups.
On the basis of previous findings, we hypothesized that
the lumbopelvic muscle activity level during PHE is higher in patients with CLBP compared with asymptomatic participants,
performance of abdominal stabilizing maneuvers will reduce EMG activity level and onset time delay in lumbopelvic muscles during PHE, and
the EMG AMP and onset delay are significantly lower in AH than in AB.
Investigation of the differences between groups and maneuvers may provide beneficial information for clinicians who engage in exercise prescription for patients with CLBP and those susceptible to low back dysfunction.
Discussion
The major aim of this study was to investigate the effect of AH and AB maneuvers on the EMG signal AMP and timing of the lumbopelvic muscles in participants with nonspecific CLBP and those without nonspecific CLBP.
Electromyography AMP in lumbopelvic muscles was found to be higher in participants with nonspecific CLBP. This finding is consistent with previous studies that reported higher levels of activity in global trunk muscles in patients with LBP. [11, 56] Chronic low back pain has been suggested to be associated with lumbopelvic stability. [57] Although lumbopelvic instability was not measured in this study, the higher activation level of the back and hip extensors in the LBP group might indicate greater need for muscular activation in the presence of instability. This finding is consistent with a recent study that reported higher activation of the ES, GM, and BF in participants with lumbar segmental instability compared with asymptomatic participants during PHE. [24] Panjabi theorized that enhanced muscle activation is likely to compensate for the passive subsystem dysfunction resulting from CLBP. [16] The central nervous system protects the spine from further pain and injury via increased activity of global trunk muscles. [15] Investigators have attributed the increased activity of trunk muscles in patients with CLBP to functional adaptations designed to cope with reduced spinal stability [28] by simultaneous contraction of trunk muscles and increased trunk stiffness. [58, 59] Because experimental pain induction in non-LBP subjects has also been shown to increase trunk muscle activity, [60] it cannot be concluded with certainty that the increased muscular activity level in patients with CLBP is a response to spinal instability.
The second finding of the current study was that the activity level of the ES muscle in healthy participants was decreased when PHE was accompanied by the AH maneuver, whereas AB did not alter its activity level. Similar findings have been reported elsewhere. It has been shown that the AH exercise can decrease the EMG signal AMP of the ES muscles during PHE [61] and quadratus lumborum during hip abduction. [36] Healthy participants have revealed lower degrees of lumbar extension and anterior pelvic tilt during both the AH and AB maneuvers, but the activity level of ES has only been observed to decrease during AH. [38] Decreased activity of ES muscle during AH might be associated with the enhanced stability of the lumbopelvic region provided by this maneuver. Because AH incorporates a precisely controlled contraction of the deep abdominal muscles, such as TrA and the internal oblique abdominal muscle, independently of global abdominal muscles, it has thus been proposed to be effective in controlling intervertebral motion and enhancing intersegmental stability. [57]
Addition of either maneuver to PHE did not alter the EMG AMP of ES muscles in patients with LBP. One of the major findings in CLBP sufferers is reduced and delayed activity of the deep trunk muscles. Performance of AH or AB in patients with LBP may not be as efficient as that in asymptomatic participants in decreasing the need for increased ES activity. In the current study, the participants were only instructed on the abdominal maneuvers within the test session, so only the immediate effect of these maneuvers was investigated. Practicing the maneuver for sufficiently lengthy periods as a treatment might help patients benefit from these maneuvers in terms of enhanced stability and decreased need for global muscle activation. This hypothesis needs to be investigated in a clinical trial.
The stability provided by the instant application of AH might not be sufficient to eliminate the need for stiffening of global muscles. During AB, simultaneous activation of global trunk muscles provides 360-degree spinal stiffness. [62] Increased stability during AB is provided at the expense of augmentation of global muscle activity, namely that of ES, and increased compressive load on the spine. In the current study, AB maneuver had no effect on the activity pattern of muscles in either the asymptomatic group or the patient group. This might have resulted from the simultaneous contraction of abdominal and ES muscles that occurs during AB.
The findings of the present study showed no difference in onset time of muscle activation across the maneuvers and between the 2 groups, with the exception of CES. Our data revealed no significant difference in GM and BF muscle activity pattern among the 3 conditions in either group. This result is in line with recent studies that investigated the muscle onset time in individuals with CLBP during PHE [51, 63, 64] and PHE while performing AH and gluteal contractions. [37] Hungerford et al. suggested that reduced and delayed activity of GM is observed in cases of SIJ pain. [45] Decrease in GM onset delay was reported when using compression force across the pelvic girdle to improve SIJ stability, possibly via the force closure mechanism. [23] These findings suggest that the recruitment pattern of GM may be mainly associated with dysfunction of SIJ rather than nonspecific LBP. Delayed activation of the GM during PHE in patients with unilateral LBP was reported in another study, albeit with no description of the SIJ status. [21] Patients with SIJ dysfunction were excluded from our study (although the screening tests were limited to only 2 of the most frequently recommended). [49, 65] Thus, absence of delayed GM cannot be considered a contradiction to reports in the existing literature.
It should be mentioned that to avoid the immediate pain interference effect and any painful movement that might cause injury to patients with LBP, those with pain intensity greater than 3 on the visual analog scale were excluded from this study. This criterion was set according to the pain intensity at the testing session, and the participants’ pain intensity was not necessarily this low in the long term; therefore, caution should be taken when generalizing the results of this study. Assuming the pain intensity of these patients to be as low as that recorded in this study, it is possible that studying patients with LBP who have more severe pain intensity would yield more pronounced differences.
This study only measured the immediate effect of performance of abdominal stabilizing maneuvers on the activation pattern of trunk muscles. Alteration of the timing pattern of the lumbopelvic muscles might require the neuromuscular adaption provided by longer durations of exercise using the performance of these maneuvers as a therapeutic intervention and not as a test trial. Further research is needed to investigate the effect of these maneuvers as an intervention and to assess the short-term and long-term outcomes to identify whether performance of these maneuvers can improve the recruitment pattern of trunk muscles. The large effect size of the maneuvers and between-group comparisons on statistically significant differences emphasizes the clinical importance of the findings of this study. In other words, the effect size analysis reveals that the statistical differences reported in this study are clinically important.
Our nonspecific CLBP group revealed delayed activity onset of CES during performance of PHE. This result is consistent with that of a recent study that reported delayed activation of CES and MF during PHE in patients with CLBP. [51] Addition of the stabilizing maneuvers to the PHE task would diminish the CES-onset delay discrepancy between groups. This addition of the stabilizing maneuvers might reflect the effective role these maneuvers play in partly compensating for the recruitment pattern deficit in participants with CLBP. Our study finding that performance of the AH and AB maneuvers could not alter the timing and activity level of the lumbopelvic muscles in patients with CLBP challenges the stabilizing role of these maneuvers, currently prescribed for these patients, and it may emphasize the need for prolonged periods of exercise to produce the necessary neuromotor adaptation to enhance spinal stability.
Limitations
Abdominal muscles were not investigated in this study, and a direct comparison of the activity patterns of the back and abdominal muscles was not possible. The long-term effect of the maneuvers as exercises were not studied here, and no direct conclusion could be made on the possible neuromotor adaptation provided by these maneuvers. The small sample size and exclusion of male participants are other limitations of our study. Long-term application of these maneuvers is necessary to evaluate their effectiveness in providing spinal stability and reducing the need for alterations in the motor control of lumbopelvic muscles.
Conclusions
This study reports that
bilateral erector spinae (ES) muscles exhibit higher levels of activation during prone hip extension (PHE) in patients with nonspecific nonspecific chronic low back pain (CLBP), and contralateral erector spinae (CES) also was delayed in these patients compared with the control participants;
AH effectively decreased the activity of ES muscles in the control group, whereas performance of any of the maneuvers produced no such an effect in patients with nonspecific CLBP; and
none of the maneuvers could alter the timing of muscle recruitment in either group.
The results of this study suggest that stabilizing maneuvers may play a differential role in participants with nonspecific CLBP and in those without nonspecific CLBP.
Practical Applications
The AH maneuver may reduce ES activity during prone hip extension
in asymptomatic individuals.Abdominal hollowing and AB maneuvers do not effectively reduce the
need for ES activity.The timing of lumbopelvic muscles did not differ between
participants with CLBP and asymptomatic participants.
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