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Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension
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Journal of Bodywork & Movement Therapies (2014) xx, 1e7
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/jbmt
SPINAL PHYSIOLOGY STUDY
Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension Tadanobu Suehiro, M.Sc, PT a,b,*, Masatoshi Mizutani, PhD a, Susumu Watanabe, PhD, PT b, Hiroshi Ishida, PhD, PT b, Kenichi Kobara, PhD, PT b, Hiroshi Osaka, M.Sc, PT b a Graduate School of Health Sciences, Kibi International University, 8, Iga-machi, Takahashi City, Okayama 716-8508, Japan b Department of Rehabilitation, Faculty of Health Science and Technology, Kawasaki University of Medical Welfare, 288, Matsushima, Kurashiki City, 701-0193, Japan
Received 10 March 2014; received in revised form 25 March 2014; accepted 7 April 2014
KEYWORDS Lumbopelvic stabilization maneuver; Prone hip extension; Muscle activity; Spine motion
Summary The aim of this study was to examine the effects of lumbopelvic stabilization maneuvers on spine motion and trunk muscle activity during prone hip extension (PHE). In this study, 14 healthy male volunteers (mean age, 21.2 2.6 years) were instructed to perform PHE without any maneuvers (control), with abdominal hollowing (AH), and with abdominal bracing (AB). Surface electromyography data were collected from the trunk muscles and the lumbopelvic motion was measured. Lumbar extension and anterior pelvic tilt degree were significantly lower in the AH and AB than in the control condition during PHE (p < 0.001). Lumbar extension and anterior pelvic tilt degree did not differ significantly between the AH and AB (p > 0.05). Global muscle group activity such as external obliques was lower in the AH than in the AB. These findings suggest that PHE with AH effectively minimizes unwanted lumbopelvic motion which does not result in global muscle activation. ª 2014 Elsevier Ltd. All rights reserved.
* Corresponding author. Department of Rehabilitation, Faculty of Health Science and Technology, Kawasaki University of Medical Welfare, 288, Matsushima, Kurashiki City, 701-0193, Japan. Tel.: þ81 86 462 1111; fax: þ81 86 464 1109. E-mail address: [email protected] (T. Suehiro). http://dx.doi.org/10.1016/j.jbmt.2014.04.012 1360-8592/ª 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Suehiro, T., et al., Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension, Journal of Bodywork & Movement Therapies (2014), http://dx.doi.org/ 10.1016/j.jbmt.2014.04.012
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T. Suehiro et al.
Introduction Prone hip extension (PHE) is often performed in the rehabilitation of individuals with back or hip pathologies. In addition to hip extensions, this exercise is reported to cause excessive anterior pelvic tilt as well as excessive lumbar spine movement (Liebenson, 2004; Page et al., 2009). Patients with low back pain (LBP) demonstrated excessive erector spinae (ES) activity during PHE (Arab et al., 2011; Kim et al., 2013). Dominant ES muscle activity may contribute to excessive anterior pelvic tilt during PHE (Comerford and Mottram, 2001). O’Sullivan (2005) reported that reduced movement control and excessive lumbar spine motion induced pain in patients with back pain. Richardson et al. (2004) suggested that abnormally large motions compress or stretch neural structures or cause abnormal deformation of the ligaments and pain sensitive structures. Furthermore, Sahrmann (2002) suggests in her theory of “relative flexibility” that movement occurs through the pathway of least resistance, e.g. if hip motion is relatively stiff compared to that of the low back, then movement is more likely to occur in the back, leading to a back pain problem related to the direction of that particular movement. Controlling the lumbar neutral zone has been reported to decrease low back pain and improve self-evaluated work ability (Suni et al., 2006, 2013). From these observations, stabilizing the lumbopelvic region in a neutral state during hip extension exercise is important for preventing low back pain. Abdominal hollowing (AH) and abdominal bracing (AB) maneuvers are widely used clinical lumbopelvic stabilization maneuvers. In AH, the abdomen is drawn in without moving the lumbar spine or pelvis. The AH maneuver has been suggested to be a preferential contraction exercise for deep muscles such as the transverse abdominal (TrA), internal oblique (IO), lumbar multifidus (LM), and diaphragm (Allison et al., 1998; Matthijs et al., 2014; Richardson et al., 2004). The TrA co-operates with the pelvic floor muscles and the diaphragm to elevate intra-abdominal pressure and contribute to stability (Critchley, 2002; Hodges and Cholewicki, 2007; Hodges et al., 2003; Sapsford and Hodges, 2001). The TrA and IO contribute to lumbopelvic stability by contributing to intra-abdominal pressure, creating tension of the thoracolumbar fascia, and compressing the sacroiliac joints (Arjmand et al., 2001; Richardson et al., 2004; Snijders et al., 1998). The LM reportedly has better segmental support and control capabilities (Richardson et al., 2004). In contrast, the AB maneuver does not focus on specific muscle recruitment; rather, it involves contracting all abdominal and low back muscles including the deep muscles such as the TrA and LM (Grenier and McGill, 2007; Juker et al., 1998; Matthijs et al., 2014; Vera-Garcia et al., 2007). In trunk muscle co-contraction AB is theorized to provide increased stability in all directions and in various types of movements by promoting spinal stiffness to help minimize low back pain (Grenier and McGill, 2007; Stanton and Kawchuk, 2008; Vera-Garcia et al., 2006, 2007). Studies have shown that AH and AB suppress spinal movements during lower limb exercises (Cynn et al., 2006; Liebenson et al., 2009; Oh et al., 2007; Park et al., 2011).
Figure 1 (a) The right lower fiber of the internal oblique and external oblique were monitored for visual electromyogram biofeedback. (b) Spinal curvature was measured using the “Spinal Mouse” to calculate spine motion.
Studies comparing AH and AB have also investigated the effect of lumbar spine movement on sudden rearward load or posteroanterior (PA) loads applied to the spinous processes (Stanton and Kawchuk, 2008; Vera-Garcia et al., 2007). However, although these maneuvers are used to suppress lumbopelvic motion during hip extension, no quantitative analyses comparing the effectiveness of AH and AB for reducing lumbopelvic motion have been performed. The purposes of this study were to compare spine motion and trunk muscle activity between AH and AB maneuvers during PHE. We hypothesized that lumbopelvic motion is significantly lower in AH and AB than in the lack of a stabilization maneuver. Moreover, we hypothesized that lumbopelvic motion is significantly lower in AB than in AH.
Methods Subjects Fourteen male university students volunteered for this study. Because sex-dependent differences have been reported to influence lumbopelvic stability differences between men and women (Cynn et al., 2006), we chose only male subjects. The exclusion criteria were: subjects who had experienced musculoskeletal pain in the past 12 months, back pain; history of surgery on the lower limbs, spine, or pelvis; and flexion contracture of the muscles of the hip joint. This study was performed with approval from the Kawasaki University of Medical Welfare Ethics Committee (approval number: 356). We obtained written informed consent from all participants after a complete explanation of the study.
Procedure Measurements were made under 3 conditions: without any awareness (control), during drawing in of the abdomen while maintaining normal respiration (AH), and during general contraction of all trunk muscles (i.e., abdominal and back muscles) without drawing in or pushing out (AB). Before testing, the subjects were familiarized with PHE
Please cite this article in press as: Suehiro, T., et al., Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension, Journal of Bodywork & Movement Therapies (2014), http://dx.doi.org/ 10.1016/j.jbmt.2014.04.012
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Comparison of spine motion and trunk muscle activity using lumbopelvic stabilization maneuvers. The training session was approximately 15-min in duration. Each subject practiced lumbopelvic stabilization maneuvers under the supervision of an experienced physical therapist. For PHE, the indicator bar was set such that the extension angle of the hip was 10 from the prone position (Oh et al., 2007; Sahrmann, 2002). Hip extensions were performed with the knee extended until the popliteal region of the dominant leg touched the indicator bar. The dominant leg was determined by asking the subject to kick a soccer ball. The kicking leg was determined to be the dominant leg (Van Deun et al., 2007). All participants were right-leg dominant. PHE was performed twice for each measurement condition. In order to avoid influencing natural trunk muscle contraction, we started testing with control measurements before AH or AB. The AB and AH measurements were then taken at random. We allowed participants a 5-min rest period between each measurement to compensate for the effects of fatigue. A surface electromyograph set to biofeedback mode (Myosystem 1200, Noraxon) was used to control the pattern and intensity of lumbopelvic stabilization maneuvers during measurements for both AH and AB (Vera-Garcia et al., 2006, 2007). The right lower part fiber of the IO was monitored for visual electromyogram biofeedback (Fig. 1) because the TrA, the key to lumbopelvic stability, could not be measured on surface electromyography since it was deep within the human trunk, while the activity within the lower fiber of the IO resembled that of the TrA (Juker et al., 1998; Miller and Medeiros, 1987). In order to fix the amount of effort in the IO during AH and AB, we adjusted the maximum voluntary contraction (MVC) to 15%; we chose this number on the basis of previous reports suggesting the level of simultaneous activation of trunk muscles required for appropriate daily activity is 10e15% (Cholewicki and McGill, 1996; Richardson et al., 1999; Vera-Garcia et al., 2006, 2007). We also monitored external obliques (EO) to better differentiate between the AH and AB maneuvers (Fig. 1). Unlike AB, the objective of AH is to activate the deep abdominal muscles with a minimum level of EO activation. In order to confirm that the lumbopelvic stabilization maneuvers were performed correctly, we calculated the ratio of activation of the right IO and EO (Stevens et al., 2007; Vera-Garcia et al., 2007).
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EMG recording and data analysis The muscle activities of the trunk muscles were measured using a surface electromyograph (Myosystem 1200, Noraxon) with a 1000-Hz sampling frequency. The following muscles were measured (Fig. 2): right rectus abdominis muscle (RA: about 2e3 cm lateral to the umbilical region); bilateral EO (inferior and lateral to the 8th rib); IO (2 cm medial to and 2 cm distal to the anterior superior iliac spine); right lumbar erector spinae (ES: at the L1 level, 2e3 cm lateral to the spinous process); and the LM (at the L5/S1 level, immediately lateral to the spinous process). Disposable electrodes (Blue Sensor M-00-S, Ambu) were applied after appropriate skin preparation. Interelectrode gaps were set to 2.5 cm, and the reference electrode was attached to the right styloid process of the ulna. Trunk muscle activity was measured for 5 s at the end of PHE. All electromyograph waveforms were processed through a band-pass filter (10e500 Hz). Full-wave rectification was subsequently performed, and the average amplitudes of 5-s intervals were determined. In order to reduce the variability of each measured muscle, we took the average of 2 measurements for each condition as a representative value and normalized that to the average amplitude during MVC as %MVC. The MVC of each trunk muscle was measured using the manual muscle testing method described by Hislop and Montgomery (2007).
Spine motion Spinal curvature was measured using the “Spinal Mouse” (Idiag, Fehraltorf, Switzerland) during upright standing and PHE (Fig. 1). In many forms of exercise, the closer the movement of the lumbar spine is to the middle position, the more stably positioned it is (Suni et al., 2006, 2013). Therefore, curvature measured during upright standing was defined as neutral spine position (Harris-Hayes et al., 2005; Park et al., 2012; Suni et al., 2006), and the difference in spinal curvature between upright standing and PHE was defined as spine motion. In this way, thoracic and lumbar spine motions were defined as the difference between thoracic and lumbar spine curvature during upright standing and PHE, respectively. A positive difference in
Figure 2 Electrode placement on the muscles: (a) rectus abdominis, (b) external oblique, (c) internal oblique, (d) lumbar erector spinae, (e) lumbar multifidus; and (f) reference electrode.
Please cite this article in press as: Suehiro, T., et al., Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension, Journal of Bodywork & Movement Therapies (2014), http://dx.doi.org/ 10.1016/j.jbmt.2014.04.012
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T. Suehiro et al. Table 1
Spine motion during prone hip extension ( ). Control
AH
AB
Comparison
Thoracic
2.5 9.2
4.1 8.1
5.0 8.9
None
Lumbar
7.3 3.5
0.5 3.8
0.1 3.4
5.4 3.3
0.0 4.0
0.5 3.1
Control-AH* Control-AB* Control-AH* Control-AB*
Pelvic
95% CI Lower
Upper
4.9 5.3 7.3 6.8
8.7 9.1 3.4 2.9
Mean SD, *p < 0.001. AH: abdominal hollowing, AB: abdominal bracing, CI: confidence intervals. Negative values reflect spinal flexion or anterior pelvic tilt. Positive values reflect spinal extension or posterior pelvic tilt.
thoracic and lumbar spine motion indicated extension movement, while a negative difference indicated flexion movement. The angle formed between the surface of the dorsal sacral bone and the plumb line was measured as sacral inclination angle. Therefore, considering the difference in posture, we defined pelvic motion as the difference between sacral inclination angle during upright standing and PHE plus 90 . Positive pelvic motion indicated posterior pelvic tilt, while negative motion indicated anterior pelvic tilt.
Statistical analysis SPSS Ver. 21 for Windows was used for all of the statistical analyses. We confirmed the normality of the spine motion data as well as muscle activity of each trunk muscle using the ShapiroeWilk test to decide whether to use a parametric or nonparametric test. Differences among the experimental maneuvers in terms of spine motion and muscle activity were analyzed by p values (p < 0.05) and the calculation of 95% confidence intervals of the differences. We also used the G-power software (Franz Faul, Univesitat Kiel, Germany) to calculate the effect size and the actual power of the sample. Spine motion Spine motion is presented as mean standard deviation (SD). One-way analysis of variance with repeated measures was used to detect differences in spine motion between the experimental conditions (control, AH, and AB). Where applicable, post-hoc analyses were performed using Tukey’s honestly significant difference test. The significance level was set at 0.05.
Results Subject characteristics Fourteen healthy male volunteers participated in the study (age, 20e30 years [mean SD, 21.2 2.6. years]; height, 160e177 cm [mean, 170.8 4.2 cm]; body weight, 55e80 kg [66.6 8.7 kg]). All 14 subjects completed the experiment and no data were missing.
Spine motion As illustrated in Table 1, lumbar extension showed the lowest measurement in AB (0.1 3.4 ), followed by AH (0.5 3.8 ). The control condition had the highest lumbar extension measurement (7.3 3.5 ). Significant differences were found between the control and AH (p < 0.001) as well as the control and AB conditions (p < 0.001). Lumbar extension did not differ significantly between the AH and AB (p > 0.05). The degree of anterior pelvic tilt was the smallest in AH (0.0 4.0 ), followed by AB (0.5 3.1 ). The control had the largest degree of anterior pelvic tilt (5.4 3.3 ). Significant differences were seen between the control and AH (p < 0.001) as well as the control and AB (p < 0.001). The degree of anterior pelvic did not differ significantly between the AH and AB (p > 0.05). Sample actual power of lumbar and pelvic motion was determined as 1.00, with large effect size. No significant difference was observed with respect to thoracic spine motion (p > 0.05).
Muscle activity Muscle activity Muscle activity is presented as median [interquartile range]. Friedman repeated measures analysis of variance was used to detect differences in muscle activity among the three experimental conditions (control, AH, and AB). The significance level was set at 0.05. Where applicable, post-hoc analysis with Wilcoxon signed-rank tests was conducted with a Bonferroni correction (or adjustment) applied, resulting in a significance level set at p < 0.017.
As shown in Table 2, the abdominal muscle group showed the highest EMG activity levels in AB followed by AH and control. Significant differences were found between the control and AH (p < 0.001) as well as the control and AB (p < 0.001). Furthermore, activation of the EO muscles was significantly higher in AB than in AH (p < 0.017). The right ES showed the highest EMG activity levels in the control (14.0 [10.2] %), followed by AB (6.5 [10.1] %) and AH (5.7 [13.8] %). Significant differences were found between the
Please cite this article in press as: Suehiro, T., et al., Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension, Journal of Bodywork & Movement Therapies (2014), http://dx.doi.org/ 10.1016/j.jbmt.2014.04.012
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Comparison of spine motion and trunk muscle activity Table 2
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EMG activity during prone hip extension (%MVC). Control
AH
AB
Comparison
rt RA
0.7 (0.8)
0.9 (1.0)
1.1 (1.8)
rt EO
1.1 (1.5)
6.1 (4.7)
11.1 (5.2)
rt IO
2.0 (2.3)
14.8 (1.5)
15.3 (2.2)
lt EO
1.1 (1.0)
2.9 (3.3)
4.3 (5.5)
lt IO
2.2 (4.6)
13.5 (9.0)
16.3 (6.8)
rt ES
14.0 (10.2)
5.7 (13.8)
6.5 (10.1)
rt LM
21.7 (10.6)
23.3 (11.2)
23.8 (16.7)
1.8 (3.0)
2.3 (1.9)
1.3 (0.8)
rt IO/rt EO
Control-AH* Control-AB* Control-AH* Control-AB* AH-AB* Control-AH* Control-AB* Control-AH* Control-AB* AH-ABy Control-AH* Control-AB* Control-AHy
95% CI Lower
Upper
0.2 0.2 2.4 6.0 2.6 10.8 11.4 0.8 1.7 0.4 8.3 9.3 7.2
0.6 0.8 6.0 14.1 8.5 13.8 14.0 3.5 6.5 4.2 15.4 17.6 1.7
0.1
2.1
None AH-AB*
Median (interquartile range), *p < 0.001, yp Z 0.006. rt: right, lt: left, RA: rectus abdominus, EO: external oblique, IO: internal oblique, ES: lumbar erector spinae, MF: lumbar multifidus, AH: abdominal hollowing, AB: abdominal bracing, and CI: confidence intervals.
control and AH (p Z 0.006). The ratio of activation of the IO muscles to the EO muscles was significantly higher in the AH (2.3 [1.9]) than in the AB (1.3 [0.8]) (p < 0.001). Sample actual power of EO, IO and ES activity was determined as 0.99 to 1.00 with a large effect size. Sample actual power of RA muscle activity was determined as 0.46 with a medium effect size.
Discussion Abnormal movements such as excessive lumbar extension and anterior pelvic tilt are frequently observed during PHE. These excessive movements of the lumbar spine and pelvis can lead to compression and extension stress on the vertebrae and surrounding soft tissue, causing low back pain (Gardner-Morse et al., 1995; McGill, 2007; Richardson et al., 2004). Therefore, many researchers recommend the facilitation of abdominal muscles to control excessive movements of the lumbar spine and pelvis during hip extension (Oh et al., 2007; Sahrmann, 2002). However, no studies have determined whether AB or AH during hip extension is more stabilizing for the lumbar spine and pelvis. Hence, we investigated which lumbopelvic stabilization maneuver is most appropriate for maintaining a neutral position during PHE with the least amount of motion of the lumbar spine and pelvis. In order to confirm whether AH and AB were performed correctly, the activity ratio was calculated between the local muscle (IO) and global muscle (EO). The results show that the ratio was significantly higher in AH than AB, suggesting both AH and AB were performed correctly. AH resulted in a reduction of lumbar extension and the amount of anterior pelvic tilt compared to the control,
suggesting AH confers greater stability. This result is similar to that reported by Oh et al. (2007), who compared pelvic motion in AH without lumbopelvic stabilization maneuvers. Furthermore, they measured EMG signal amplitude of the erector spinae, gluteus maximus, and medial hamstrings and found increased gluteus maximus activity, increased medial hamstring activity, and decreased ES activity during AH. In the present study, AH led to significant increases in the activities of abdominal muscles, particularly the IO; this contributes to the reduced lumbar extension and amount of anterior pelvic tilt. Studies have also shown that AH increases the activities of the TrA muscle and the lower fibers of the IO muscle and increases spinal stability during lower limb movements (Cynn et al., 2006; Jull et al., 1993). In the present study, TrA and IO muscle contractions were believed to have increased the tension of the thoracolumbar fascia and the intra-abdominal pressure to enhance spinal stability. In addition, although we did not measure lower limb muscle activity, on the basis of the findings of Oh et al. (2007), we infer that the muscle activities of the gluteus maximus and medial hamstrings, which belong to the hip joint extensor group, increased to enable hip extension to the indicator bar under conditions of minimal lumbopelvic motion. Moreover, the activity of the ES, which normally compensates for hip extension, decreased due to increases in hip extensor muscle group activity. The reduction of movement of the lumbar spine and pelvis after AH might also be explained by the findings of Bruno et al. (2008) and Chance-Larsen et al. (2010). Bruno et al. (2008) used healthy subjects to investigate excessive movement of the lumbar spine between PHE as well as the onset time for muscle activity and demonstrated that excessive movement of the lumbar spine between PHE sessions is related to delayed activity of the
Please cite this article in press as: Suehiro, T., et al., Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension, Journal of Bodywork & Movement Therapies (2014), http://dx.doi.org/ 10.1016/j.jbmt.2014.04.012
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6 gluteus maximus. Chance-Larsen et al. (2010) reported that performing AH significantly accelerated the onset time for gluteus maximus activity between PHE. Accordingly, the reduction in excessive movements of the lumbar spine and pelvis with AH in the present study might be attributed to the fact that, although it was not measured, the gluteus maximus activity contracted earlier. AB also resulted in a significant reduction of the lumbar extension and amount of anterior pelvic tilt compared to the control. Increases in the activity level of the abdominal muscle group led to reductions in lumbar extension and amount of anterior pelvic tilt. No significant difference was observed between AH and AB with respect to spine motion or pelvic motion. This finding contradicts our hypothesis that lumbopelvic motion is lower in the AB than in the AH. Vera-Garcia et al. (2007) investigated whether AH or AB is more stable in response to sudden backward stimuli on the basis of lumbar spine motion and a stability index. Their results suggest AB is more stable than AH. Furthermore, Grenier and McGill (2007) performed simulations to determine whether AH or AB is more stable from a standing position with a weighted load, and found that AB is more stable than AH. Thus, the conclusions of the present and previous studies differ. We believe this difference can be explained by the differences in load during these activities. McGill (2007) suggests all muscles contribute to stability differently depending on the demands of each task. In the present study, the load when performing hip extension exercises was relatively light. As a result, a small amount of trunk muscle activity such as that in AH was able to stabilize the lumbopelvic region. This is possibly why no difference was observed between AB and AH with respect to spine motion. There was no significant difference between AH and AB with respect to spine motion during PHE. In addition, global muscle group activity such as that of the EO was significantly higher in AB than AH. Previous studies suggest that an increase in global muscle activity leads to increased compressive stress on the spine, exacerbating low back pain (Radebold et al., 2000; Thelen et al., 1995). Moreover, excessive activity of the ES during PHE in people with lumbar pain has been reported (Arab et al., 2011; Kim et al., 2013). Increased ES activity could cause pain in the muscles themselves and contribute to a vicious painespasmepain cycle. Therefore, if PHE is used for therapeutic exercise, AH is a more appropriate exercise because it suppresses excessive lumbopelvic motion and does not result in global muscle activation (i.e., of the EO and ES muscles). This study has several limitations. First, because sample size was small and all subjects participating in the study were healthy young men, our results cannot be generalized to other populations. Therefore, the benefits of the lumbopelvic stabilization maneuvers used in this study should be confirmed in future investigations of a larger more representative sample. Second, we did not measure the muscle activation of the TrA, hip joint flexor, or extensor muscle group. Third, although we only investigated movements in the sagittal plane, lumbopelvic movements during hip extension can also impact the horizontal and frontal planes.
T. Suehiro et al.
Conclusion This study examined the effects of lumbopelvic stabilization maneuvers on the EMG signal amplitude of the trunk muscles and lumbopelvic motion during PHE. Spine motion did not differ between the AH and AB. However, global muscle group activity was lower in the AH than in the AB. Therefore, use of the AH maneuver is recommended to effectively stabilize the lumbopelvic region during PHE.
Source of funding No external funding was received for this study.
Conflict of interest There is no conflict of interest.
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7 electromyographic activity, lumbopelvic and knee motion during seated knee extension in subjects with hamstring shortness. J. Phys. Ther. Sci. 24, 17e22. Radebold, A., Cholewicki, J., Panjabi, M.M., Patel, T.C., 2000. Muscle response pattern to sudden trunk loading in healthy individuals and in patients with chronic low back pain. Spine 25, 947e954. Richardson, C., Hodges, P., Hides, J., 2004. Therapeutic Exercise for Lumbopelvic Stabilization. Churchill Livingstone, Edinburgh. Richardson, C.A., Jull, G., Hodges, P., Hides, J., 1999. Therapeutic Exercise for Spinal Segmental Stabilization in Low Back Pain: Scientific Basis and Clinical Approach. Churchill Livingstone, Sydney. Sahrmann, S., 2002. Diagnosis and Treatment of Movement Impairment Syndromes. Mosby, St Louis. Sapsford, R.R., Hodges, P.W., 2001. Contraction of the pelvic floor muscles during abdominal maneuvers. Arch. Phys. Med. Rehabil. 82, 1081e1088. Snijders, C.J., Ribbers, M.T., de Bakker, H.V., Stoeckart, R., Stam, H.J., 1998. EMG recordings of abdominal and back muscles in various standing postures: validation of a biomechanical model on sacroiliac joint stability. J. Electromyogr. Kinesiol. 8, 205e214. Stanton, T., Kawchuk, G., 2008. The effect of abdominal stabilization contractions on posteroanterior spinal stiffness. Spine 33, 694. Stevens, V.K., Coorevits, P.L., Bouche, K.G., Mahieu, N.N., Vanderstraeten, G.G., Danneels, L.A., 2007. The influence of specific training on trunk muscle recruitment patterns in healthy subjects during stabilization exercises. Man. Ther. 12, 271e279. Suni, J., Rinne, M., Natri, A., Statistisian, M.P., Parkkari, J., Alaranta, H., 2006. Control of the lumbar neutral zone decreases low back pain and improves self-evaluated work ability: a 12-month randomized controlled study. Spine 31, E611eE620. Suni, J.H., Taanila, H., Mattila, V.M., Ohrankammen, O., Vuorinen, P., Pihlajamaki, H., Parkkari, J., 2013. Neuromuscular exercise and counseling decrease absenteeism due to low back pain in young conscripts: a randomized, population-based primary prevention study. Spine 38, 375e384. Thelen, D., Schultz, A., Ashton-Miller, J., 1995. Co-contraction of lumbar muscles during the development of time-varying triaxial moments. J. Orthop. Res. 13, 390e398. Van Deun, S., Staes, F.F., Stappaerts, K.H., Janssens, L., Levin, O., Peers, K.K., 2007. Relationship of chronic ankle instability to muscle activation patterns during the transition from doubleleg to single-leg stance. Am. J. Sports Med. 35, 274e281. Vera-Garcia, F.J., Brown, S.H.M., Gray, J.R., McGill, S.M., 2006. Effects of different levels of torso coactivation on trunk muscular and kinematic responses to posteriorly applied sudden loads. Clin. Biomech. 21, 443e455. Vera-Garcia, F.J., Elvira, J.L.L., Brown, S.H.M., McGill, S.M., 2007. Effects of abdominal stabilization maneuvers on the control of spine motion and stability against sudden trunk perturbations. J. Electromyogr. Kinesiol. 17, 556e567.
Please cite this article in press as: Suehiro, T., et al., Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension, Journal of Bodywork & Movement Therapies (2014), http://dx.doi.org/ 10.1016/j.jbmt.2014.04.012
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Journal of Bodywork & Movement Therapies (2014) xx, 1e7
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SPINAL PHYSIOLOGY STUDY
Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension Tadanobu Suehiro, M.Sc, PT a,b,*, Masatoshi Mizutani, PhD a, Susumu Watanabe, PhD, PT b, Hiroshi Ishida, PhD, PT b, Kenichi Kobara, PhD, PT b, Hiroshi Osaka, M.Sc, PT b a Graduate School of Health Sciences, Kibi International University, 8, Iga-machi, Takahashi City, Okayama 716-8508, Japan b Department of Rehabilitation, Faculty of Health Science and Technology, Kawasaki University of Medical Welfare, 288, Matsushima, Kurashiki City, 701-0193, Japan
Received 10 March 2014; received in revised form 25 March 2014; accepted 7 April 2014
KEYWORDS Lumbopelvic stabilization maneuver; Prone hip extension; Muscle activity; Spine motion
Summary The aim of this study was to examine the effects of lumbopelvic stabilization maneuvers on spine motion and trunk muscle activity during prone hip extension (PHE). In this study, 14 healthy male volunteers (mean age, 21.2 2.6 years) were instructed to perform PHE without any maneuvers (control), with abdominal hollowing (AH), and with abdominal bracing (AB). Surface electromyography data were collected from the trunk muscles and the lumbopelvic motion was measured. Lumbar extension and anterior pelvic tilt degree were significantly lower in the AH and AB than in the control condition during PHE (p < 0.001). Lumbar extension and anterior pelvic tilt degree did not differ significantly between the AH and AB (p > 0.05). Global muscle group activity such as external obliques was lower in the AH than in the AB. These findings suggest that PHE with AH effectively minimizes unwanted lumbopelvic motion which does not result in global muscle activation. ª 2014 Elsevier Ltd. All rights reserved.
* Corresponding author. Department of Rehabilitation, Faculty of Health Science and Technology, Kawasaki University of Medical Welfare, 288, Matsushima, Kurashiki City, 701-0193, Japan. Tel.: þ81 86 462 1111; fax: þ81 86 464 1109. E-mail address: [email protected] (T. Suehiro). http://dx.doi.org/10.1016/j.jbmt.2014.04.012 1360-8592/ª 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Suehiro, T., et al., Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension, Journal of Bodywork & Movement Therapies (2014), http://dx.doi.org/ 10.1016/j.jbmt.2014.04.012
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Introduction Prone hip extension (PHE) is often performed in the rehabilitation of individuals with back or hip pathologies. In addition to hip extensions, this exercise is reported to cause excessive anterior pelvic tilt as well as excessive lumbar spine movement (Liebenson, 2004; Page et al., 2009). Patients with low back pain (LBP) demonstrated excessive erector spinae (ES) activity during PHE (Arab et al., 2011; Kim et al., 2013). Dominant ES muscle activity may contribute to excessive anterior pelvic tilt during PHE (Comerford and Mottram, 2001). O’Sullivan (2005) reported that reduced movement control and excessive lumbar spine motion induced pain in patients with back pain. Richardson et al. (2004) suggested that abnormally large motions compress or stretch neural structures or cause abnormal deformation of the ligaments and pain sensitive structures. Furthermore, Sahrmann (2002) suggests in her theory of “relative flexibility” that movement occurs through the pathway of least resistance, e.g. if hip motion is relatively stiff compared to that of the low back, then movement is more likely to occur in the back, leading to a back pain problem related to the direction of that particular movement. Controlling the lumbar neutral zone has been reported to decrease low back pain and improve self-evaluated work ability (Suni et al., 2006, 2013). From these observations, stabilizing the lumbopelvic region in a neutral state during hip extension exercise is important for preventing low back pain. Abdominal hollowing (AH) and abdominal bracing (AB) maneuvers are widely used clinical lumbopelvic stabilization maneuvers. In AH, the abdomen is drawn in without moving the lumbar spine or pelvis. The AH maneuver has been suggested to be a preferential contraction exercise for deep muscles such as the transverse abdominal (TrA), internal oblique (IO), lumbar multifidus (LM), and diaphragm (Allison et al., 1998; Matthijs et al., 2014; Richardson et al., 2004). The TrA co-operates with the pelvic floor muscles and the diaphragm to elevate intra-abdominal pressure and contribute to stability (Critchley, 2002; Hodges and Cholewicki, 2007; Hodges et al., 2003; Sapsford and Hodges, 2001). The TrA and IO contribute to lumbopelvic stability by contributing to intra-abdominal pressure, creating tension of the thoracolumbar fascia, and compressing the sacroiliac joints (Arjmand et al., 2001; Richardson et al., 2004; Snijders et al., 1998). The LM reportedly has better segmental support and control capabilities (Richardson et al., 2004). In contrast, the AB maneuver does not focus on specific muscle recruitment; rather, it involves contracting all abdominal and low back muscles including the deep muscles such as the TrA and LM (Grenier and McGill, 2007; Juker et al., 1998; Matthijs et al., 2014; Vera-Garcia et al., 2007). In trunk muscle co-contraction AB is theorized to provide increased stability in all directions and in various types of movements by promoting spinal stiffness to help minimize low back pain (Grenier and McGill, 2007; Stanton and Kawchuk, 2008; Vera-Garcia et al., 2006, 2007). Studies have shown that AH and AB suppress spinal movements during lower limb exercises (Cynn et al., 2006; Liebenson et al., 2009; Oh et al., 2007; Park et al., 2011).
Figure 1 (a) The right lower fiber of the internal oblique and external oblique were monitored for visual electromyogram biofeedback. (b) Spinal curvature was measured using the “Spinal Mouse” to calculate spine motion.
Studies comparing AH and AB have also investigated the effect of lumbar spine movement on sudden rearward load or posteroanterior (PA) loads applied to the spinous processes (Stanton and Kawchuk, 2008; Vera-Garcia et al., 2007). However, although these maneuvers are used to suppress lumbopelvic motion during hip extension, no quantitative analyses comparing the effectiveness of AH and AB for reducing lumbopelvic motion have been performed. The purposes of this study were to compare spine motion and trunk muscle activity between AH and AB maneuvers during PHE. We hypothesized that lumbopelvic motion is significantly lower in AH and AB than in the lack of a stabilization maneuver. Moreover, we hypothesized that lumbopelvic motion is significantly lower in AB than in AH.
Methods Subjects Fourteen male university students volunteered for this study. Because sex-dependent differences have been reported to influence lumbopelvic stability differences between men and women (Cynn et al., 2006), we chose only male subjects. The exclusion criteria were: subjects who had experienced musculoskeletal pain in the past 12 months, back pain; history of surgery on the lower limbs, spine, or pelvis; and flexion contracture of the muscles of the hip joint. This study was performed with approval from the Kawasaki University of Medical Welfare Ethics Committee (approval number: 356). We obtained written informed consent from all participants after a complete explanation of the study.
Procedure Measurements were made under 3 conditions: without any awareness (control), during drawing in of the abdomen while maintaining normal respiration (AH), and during general contraction of all trunk muscles (i.e., abdominal and back muscles) without drawing in or pushing out (AB). Before testing, the subjects were familiarized with PHE
Please cite this article in press as: Suehiro, T., et al., Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension, Journal of Bodywork & Movement Therapies (2014), http://dx.doi.org/ 10.1016/j.jbmt.2014.04.012
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Comparison of spine motion and trunk muscle activity using lumbopelvic stabilization maneuvers. The training session was approximately 15-min in duration. Each subject practiced lumbopelvic stabilization maneuvers under the supervision of an experienced physical therapist. For PHE, the indicator bar was set such that the extension angle of the hip was 10 from the prone position (Oh et al., 2007; Sahrmann, 2002). Hip extensions were performed with the knee extended until the popliteal region of the dominant leg touched the indicator bar. The dominant leg was determined by asking the subject to kick a soccer ball. The kicking leg was determined to be the dominant leg (Van Deun et al., 2007). All participants were right-leg dominant. PHE was performed twice for each measurement condition. In order to avoid influencing natural trunk muscle contraction, we started testing with control measurements before AH or AB. The AB and AH measurements were then taken at random. We allowed participants a 5-min rest period between each measurement to compensate for the effects of fatigue. A surface electromyograph set to biofeedback mode (Myosystem 1200, Noraxon) was used to control the pattern and intensity of lumbopelvic stabilization maneuvers during measurements for both AH and AB (Vera-Garcia et al., 2006, 2007). The right lower part fiber of the IO was monitored for visual electromyogram biofeedback (Fig. 1) because the TrA, the key to lumbopelvic stability, could not be measured on surface electromyography since it was deep within the human trunk, while the activity within the lower fiber of the IO resembled that of the TrA (Juker et al., 1998; Miller and Medeiros, 1987). In order to fix the amount of effort in the IO during AH and AB, we adjusted the maximum voluntary contraction (MVC) to 15%; we chose this number on the basis of previous reports suggesting the level of simultaneous activation of trunk muscles required for appropriate daily activity is 10e15% (Cholewicki and McGill, 1996; Richardson et al., 1999; Vera-Garcia et al., 2006, 2007). We also monitored external obliques (EO) to better differentiate between the AH and AB maneuvers (Fig. 1). Unlike AB, the objective of AH is to activate the deep abdominal muscles with a minimum level of EO activation. In order to confirm that the lumbopelvic stabilization maneuvers were performed correctly, we calculated the ratio of activation of the right IO and EO (Stevens et al., 2007; Vera-Garcia et al., 2007).
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EMG recording and data analysis The muscle activities of the trunk muscles were measured using a surface electromyograph (Myosystem 1200, Noraxon) with a 1000-Hz sampling frequency. The following muscles were measured (Fig. 2): right rectus abdominis muscle (RA: about 2e3 cm lateral to the umbilical region); bilateral EO (inferior and lateral to the 8th rib); IO (2 cm medial to and 2 cm distal to the anterior superior iliac spine); right lumbar erector spinae (ES: at the L1 level, 2e3 cm lateral to the spinous process); and the LM (at the L5/S1 level, immediately lateral to the spinous process). Disposable electrodes (Blue Sensor M-00-S, Ambu) were applied after appropriate skin preparation. Interelectrode gaps were set to 2.5 cm, and the reference electrode was attached to the right styloid process of the ulna. Trunk muscle activity was measured for 5 s at the end of PHE. All electromyograph waveforms were processed through a band-pass filter (10e500 Hz). Full-wave rectification was subsequently performed, and the average amplitudes of 5-s intervals were determined. In order to reduce the variability of each measured muscle, we took the average of 2 measurements for each condition as a representative value and normalized that to the average amplitude during MVC as %MVC. The MVC of each trunk muscle was measured using the manual muscle testing method described by Hislop and Montgomery (2007).
Spine motion Spinal curvature was measured using the “Spinal Mouse” (Idiag, Fehraltorf, Switzerland) during upright standing and PHE (Fig. 1). In many forms of exercise, the closer the movement of the lumbar spine is to the middle position, the more stably positioned it is (Suni et al., 2006, 2013). Therefore, curvature measured during upright standing was defined as neutral spine position (Harris-Hayes et al., 2005; Park et al., 2012; Suni et al., 2006), and the difference in spinal curvature between upright standing and PHE was defined as spine motion. In this way, thoracic and lumbar spine motions were defined as the difference between thoracic and lumbar spine curvature during upright standing and PHE, respectively. A positive difference in
Figure 2 Electrode placement on the muscles: (a) rectus abdominis, (b) external oblique, (c) internal oblique, (d) lumbar erector spinae, (e) lumbar multifidus; and (f) reference electrode.
Please cite this article in press as: Suehiro, T., et al., Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension, Journal of Bodywork & Movement Therapies (2014), http://dx.doi.org/ 10.1016/j.jbmt.2014.04.012
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T. Suehiro et al. Table 1
Spine motion during prone hip extension ( ). Control
AH
AB
Comparison
Thoracic
2.5 9.2
4.1 8.1
5.0 8.9
None
Lumbar
7.3 3.5
0.5 3.8
0.1 3.4
5.4 3.3
0.0 4.0
0.5 3.1
Control-AH* Control-AB* Control-AH* Control-AB*
Pelvic
95% CI Lower
Upper
4.9 5.3 7.3 6.8
8.7 9.1 3.4 2.9
Mean SD, *p < 0.001. AH: abdominal hollowing, AB: abdominal bracing, CI: confidence intervals. Negative values reflect spinal flexion or anterior pelvic tilt. Positive values reflect spinal extension or posterior pelvic tilt.
thoracic and lumbar spine motion indicated extension movement, while a negative difference indicated flexion movement. The angle formed between the surface of the dorsal sacral bone and the plumb line was measured as sacral inclination angle. Therefore, considering the difference in posture, we defined pelvic motion as the difference between sacral inclination angle during upright standing and PHE plus 90 . Positive pelvic motion indicated posterior pelvic tilt, while negative motion indicated anterior pelvic tilt.
Statistical analysis SPSS Ver. 21 for Windows was used for all of the statistical analyses. We confirmed the normality of the spine motion data as well as muscle activity of each trunk muscle using the ShapiroeWilk test to decide whether to use a parametric or nonparametric test. Differences among the experimental maneuvers in terms of spine motion and muscle activity were analyzed by p values (p < 0.05) and the calculation of 95% confidence intervals of the differences. We also used the G-power software (Franz Faul, Univesitat Kiel, Germany) to calculate the effect size and the actual power of the sample. Spine motion Spine motion is presented as mean standard deviation (SD). One-way analysis of variance with repeated measures was used to detect differences in spine motion between the experimental conditions (control, AH, and AB). Where applicable, post-hoc analyses were performed using Tukey’s honestly significant difference test. The significance level was set at 0.05.
Results Subject characteristics Fourteen healthy male volunteers participated in the study (age, 20e30 years [mean SD, 21.2 2.6. years]; height, 160e177 cm [mean, 170.8 4.2 cm]; body weight, 55e80 kg [66.6 8.7 kg]). All 14 subjects completed the experiment and no data were missing.
Spine motion As illustrated in Table 1, lumbar extension showed the lowest measurement in AB (0.1 3.4 ), followed by AH (0.5 3.8 ). The control condition had the highest lumbar extension measurement (7.3 3.5 ). Significant differences were found between the control and AH (p < 0.001) as well as the control and AB conditions (p < 0.001). Lumbar extension did not differ significantly between the AH and AB (p > 0.05). The degree of anterior pelvic tilt was the smallest in AH (0.0 4.0 ), followed by AB (0.5 3.1 ). The control had the largest degree of anterior pelvic tilt (5.4 3.3 ). Significant differences were seen between the control and AH (p < 0.001) as well as the control and AB (p < 0.001). The degree of anterior pelvic did not differ significantly between the AH and AB (p > 0.05). Sample actual power of lumbar and pelvic motion was determined as 1.00, with large effect size. No significant difference was observed with respect to thoracic spine motion (p > 0.05).
Muscle activity Muscle activity Muscle activity is presented as median [interquartile range]. Friedman repeated measures analysis of variance was used to detect differences in muscle activity among the three experimental conditions (control, AH, and AB). The significance level was set at 0.05. Where applicable, post-hoc analysis with Wilcoxon signed-rank tests was conducted with a Bonferroni correction (or adjustment) applied, resulting in a significance level set at p < 0.017.
As shown in Table 2, the abdominal muscle group showed the highest EMG activity levels in AB followed by AH and control. Significant differences were found between the control and AH (p < 0.001) as well as the control and AB (p < 0.001). Furthermore, activation of the EO muscles was significantly higher in AB than in AH (p < 0.017). The right ES showed the highest EMG activity levels in the control (14.0 [10.2] %), followed by AB (6.5 [10.1] %) and AH (5.7 [13.8] %). Significant differences were found between the
Please cite this article in press as: Suehiro, T., et al., Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension, Journal of Bodywork & Movement Therapies (2014), http://dx.doi.org/ 10.1016/j.jbmt.2014.04.012
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Comparison of spine motion and trunk muscle activity Table 2
5
EMG activity during prone hip extension (%MVC). Control
AH
AB
Comparison
rt RA
0.7 (0.8)
0.9 (1.0)
1.1 (1.8)
rt EO
1.1 (1.5)
6.1 (4.7)
11.1 (5.2)
rt IO
2.0 (2.3)
14.8 (1.5)
15.3 (2.2)
lt EO
1.1 (1.0)
2.9 (3.3)
4.3 (5.5)
lt IO
2.2 (4.6)
13.5 (9.0)
16.3 (6.8)
rt ES
14.0 (10.2)
5.7 (13.8)
6.5 (10.1)
rt LM
21.7 (10.6)
23.3 (11.2)
23.8 (16.7)
1.8 (3.0)
2.3 (1.9)
1.3 (0.8)
rt IO/rt EO
Control-AH* Control-AB* Control-AH* Control-AB* AH-AB* Control-AH* Control-AB* Control-AH* Control-AB* AH-ABy Control-AH* Control-AB* Control-AHy
95% CI Lower
Upper
0.2 0.2 2.4 6.0 2.6 10.8 11.4 0.8 1.7 0.4 8.3 9.3 7.2
0.6 0.8 6.0 14.1 8.5 13.8 14.0 3.5 6.5 4.2 15.4 17.6 1.7
0.1
2.1
None AH-AB*
Median (interquartile range), *p < 0.001, yp Z 0.006. rt: right, lt: left, RA: rectus abdominus, EO: external oblique, IO: internal oblique, ES: lumbar erector spinae, MF: lumbar multifidus, AH: abdominal hollowing, AB: abdominal bracing, and CI: confidence intervals.
control and AH (p Z 0.006). The ratio of activation of the IO muscles to the EO muscles was significantly higher in the AH (2.3 [1.9]) than in the AB (1.3 [0.8]) (p < 0.001). Sample actual power of EO, IO and ES activity was determined as 0.99 to 1.00 with a large effect size. Sample actual power of RA muscle activity was determined as 0.46 with a medium effect size.
Discussion Abnormal movements such as excessive lumbar extension and anterior pelvic tilt are frequently observed during PHE. These excessive movements of the lumbar spine and pelvis can lead to compression and extension stress on the vertebrae and surrounding soft tissue, causing low back pain (Gardner-Morse et al., 1995; McGill, 2007; Richardson et al., 2004). Therefore, many researchers recommend the facilitation of abdominal muscles to control excessive movements of the lumbar spine and pelvis during hip extension (Oh et al., 2007; Sahrmann, 2002). However, no studies have determined whether AB or AH during hip extension is more stabilizing for the lumbar spine and pelvis. Hence, we investigated which lumbopelvic stabilization maneuver is most appropriate for maintaining a neutral position during PHE with the least amount of motion of the lumbar spine and pelvis. In order to confirm whether AH and AB were performed correctly, the activity ratio was calculated between the local muscle (IO) and global muscle (EO). The results show that the ratio was significantly higher in AH than AB, suggesting both AH and AB were performed correctly. AH resulted in a reduction of lumbar extension and the amount of anterior pelvic tilt compared to the control,
suggesting AH confers greater stability. This result is similar to that reported by Oh et al. (2007), who compared pelvic motion in AH without lumbopelvic stabilization maneuvers. Furthermore, they measured EMG signal amplitude of the erector spinae, gluteus maximus, and medial hamstrings and found increased gluteus maximus activity, increased medial hamstring activity, and decreased ES activity during AH. In the present study, AH led to significant increases in the activities of abdominal muscles, particularly the IO; this contributes to the reduced lumbar extension and amount of anterior pelvic tilt. Studies have also shown that AH increases the activities of the TrA muscle and the lower fibers of the IO muscle and increases spinal stability during lower limb movements (Cynn et al., 2006; Jull et al., 1993). In the present study, TrA and IO muscle contractions were believed to have increased the tension of the thoracolumbar fascia and the intra-abdominal pressure to enhance spinal stability. In addition, although we did not measure lower limb muscle activity, on the basis of the findings of Oh et al. (2007), we infer that the muscle activities of the gluteus maximus and medial hamstrings, which belong to the hip joint extensor group, increased to enable hip extension to the indicator bar under conditions of minimal lumbopelvic motion. Moreover, the activity of the ES, which normally compensates for hip extension, decreased due to increases in hip extensor muscle group activity. The reduction of movement of the lumbar spine and pelvis after AH might also be explained by the findings of Bruno et al. (2008) and Chance-Larsen et al. (2010). Bruno et al. (2008) used healthy subjects to investigate excessive movement of the lumbar spine between PHE as well as the onset time for muscle activity and demonstrated that excessive movement of the lumbar spine between PHE sessions is related to delayed activity of the
Please cite this article in press as: Suehiro, T., et al., Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension, Journal of Bodywork & Movement Therapies (2014), http://dx.doi.org/ 10.1016/j.jbmt.2014.04.012
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6 gluteus maximus. Chance-Larsen et al. (2010) reported that performing AH significantly accelerated the onset time for gluteus maximus activity between PHE. Accordingly, the reduction in excessive movements of the lumbar spine and pelvis with AH in the present study might be attributed to the fact that, although it was not measured, the gluteus maximus activity contracted earlier. AB also resulted in a significant reduction of the lumbar extension and amount of anterior pelvic tilt compared to the control. Increases in the activity level of the abdominal muscle group led to reductions in lumbar extension and amount of anterior pelvic tilt. No significant difference was observed between AH and AB with respect to spine motion or pelvic motion. This finding contradicts our hypothesis that lumbopelvic motion is lower in the AB than in the AH. Vera-Garcia et al. (2007) investigated whether AH or AB is more stable in response to sudden backward stimuli on the basis of lumbar spine motion and a stability index. Their results suggest AB is more stable than AH. Furthermore, Grenier and McGill (2007) performed simulations to determine whether AH or AB is more stable from a standing position with a weighted load, and found that AB is more stable than AH. Thus, the conclusions of the present and previous studies differ. We believe this difference can be explained by the differences in load during these activities. McGill (2007) suggests all muscles contribute to stability differently depending on the demands of each task. In the present study, the load when performing hip extension exercises was relatively light. As a result, a small amount of trunk muscle activity such as that in AH was able to stabilize the lumbopelvic region. This is possibly why no difference was observed between AB and AH with respect to spine motion. There was no significant difference between AH and AB with respect to spine motion during PHE. In addition, global muscle group activity such as that of the EO was significantly higher in AB than AH. Previous studies suggest that an increase in global muscle activity leads to increased compressive stress on the spine, exacerbating low back pain (Radebold et al., 2000; Thelen et al., 1995). Moreover, excessive activity of the ES during PHE in people with lumbar pain has been reported (Arab et al., 2011; Kim et al., 2013). Increased ES activity could cause pain in the muscles themselves and contribute to a vicious painespasmepain cycle. Therefore, if PHE is used for therapeutic exercise, AH is a more appropriate exercise because it suppresses excessive lumbopelvic motion and does not result in global muscle activation (i.e., of the EO and ES muscles). This study has several limitations. First, because sample size was small and all subjects participating in the study were healthy young men, our results cannot be generalized to other populations. Therefore, the benefits of the lumbopelvic stabilization maneuvers used in this study should be confirmed in future investigations of a larger more representative sample. Second, we did not measure the muscle activation of the TrA, hip joint flexor, or extensor muscle group. Third, although we only investigated movements in the sagittal plane, lumbopelvic movements during hip extension can also impact the horizontal and frontal planes.
T. Suehiro et al.
Conclusion This study examined the effects of lumbopelvic stabilization maneuvers on the EMG signal amplitude of the trunk muscles and lumbopelvic motion during PHE. Spine motion did not differ between the AH and AB. However, global muscle group activity was lower in the AH than in the AB. Therefore, use of the AH maneuver is recommended to effectively stabilize the lumbopelvic region during PHE.
Source of funding No external funding was received for this study.
Conflict of interest There is no conflict of interest.
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Please cite this article in press as: Suehiro, T., et al., Comparison of spine motion and trunk muscle activity between abdominal hollowing and abdominal bracing maneuvers during prone hip extension, Journal of Bodywork & Movement Therapies (2014), http://dx.doi.org/ 10.1016/j.jbmt.2014.04.012