Journal of Electromyography and Kinesiology xxx (2014) xxx–xxx
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Isometric hip abduction using a Thera-Band alters gluteus maximus muscle activity and the anterior pelvic tilt angle during bridging exercise Sil-Ah Choi, Heon-Seock Cynn ⇑, Chung-Hwi Yi, Oh-Yun Kwon, Tae-Lim Yoon, Woo-Jeong Choi, Ji-Hyun Lee Applied Kinesiology and Ergonomic Technology Laboratory, Department of Physical Therapy, The Graduate School, Yonsei University, 1 Yonseidae-gil, Wonju-si, Gangwon-do 220-710, South Korea
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Article history: Received 7 February 2014 Received in revised form 3 June 2014 Accepted 1 September 2014 Available online xxxx Keywords: Bridging Gluteus maximus Preactivation Thera-Band
a b s t r a c t The purpose of this study was to investigate the effects of bridging with isometric hip abduction (IHA) using the Thera-Band on gluteus maximus (GM), hamstring (HAM), and erector spinae (ES) muscle activity; GM/HAM and GM/ES ratios; and the anterior pelvic tilt angle in healthy subjects. Twenty-one subjects participated in this study. Surface EMG was used to collect EMG data of GM, HAM, and ES muscle activities, and Image J software was used to measure anterior pelvic tilt angle. A paired t-test was used to compare GM, HAM, and ES muscle activity; the GM/HAM and GM/ES ratios; and the anterior pelvic tilt angle with and without IHA during the bridging exercise. GM muscle activity increased significantly and the anterior pelvic tilt angle decreased significantly during bridging with IHA using the Thera-Band (p < 0.05). However, there were no significant differences in the activity of the HAM and ES and the GM/HAM and GM/ES ratios between bridging with and without IHA (p > 0.05). The results of this study suggest that bridging with IHA using the Thera-Band can be implemented as an effective method to facilitate GM muscle activity and reduce the anterior pelvic tilt angle. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction The gluteus maximus (GM) is one of the largest and strongest muscles in the body. The GM originates from the posterior sacrum and coccyx as well as the posterior gluteal line of the ilium and inserts on the iliotibial tract and gluteal tuberosity of the femur (Frank and Netter, 1987). The GM is a powerful extensor and external rotator of the hip, and the superior part of the GM acts as a hip abductor because muscle fibers in the GM are directed downward and outward (Frank and Netter, 1987; Long et al., 1993). Hip extensors, especially the GM, are important for many functional activities of daily living such as moving from sitting to standing, climbing stairs, and maintaining an upright posture during walking (Winter, 1991). Because the direction of the GM muscle fibers, especially deep sacral fibers of the GM, are perpendicular to the sacroiliac (SI) joint, GM contraction improves SI joint stability and plays a part in force transmission from the lower extremity
⇑ Corresponding author. Tel.: +82 33 760 2427; fax: +82 33 760 2496. E-mail addresses: [email protected] (S.-A. Choi), [email protected] (H.-S. Cynn), [email protected] (C.-H. Yi), [email protected] (O.-Y. Kwon), [email protected] (T.-L. Yoon), [email protected] (W.-J. Choi), rapa60@ naver.com (J.-H. Lee).
to the pelvis during ambulation (Hossain and Nokes, 2005; Leinonen et al., 2000; Mooney et al., 2001). However, the GM is frequently weak and lengthened because many people spend a great amount of time remaining seated (Sahrmann, 2002). Decreased activity of the GM is one cause of low back pain (LBP) and results in SI joint instability and dysfunction (van Wingerden et al., 2004). In addition, hamstring (HAM) tightness can be observed as a compensatory mechanism for a weak GM (Massoud Arab et al., 2011; van Wingerden et al., 2004). Also, excessive anterior pelvic tilt, lumbar lordosis with dominant erector spinae (ES), and lumbar rotation occur in place of a weak GM or delayed GM activation during hip extension (Chaitow, 1996; Sahrmann, 2002). Bridging exercises are the most commonly used by people with weak hip extensors and trunk muscles in physical therapy programs. However, bridging exercises are associated with a risk of dominant HAM and ES activity and excessive anterior pelvic tilt as a compensation for GM weakness regardless of the type of bridging exercise performed. Therefore, bridging exercise with isometric hip abduction (IHA) using a Thera-Band (Hygenic Corp., Akron, OH, USA) was devised in this study. No previous studies have compared GM with HAM and ES muscle activity and pelvic kinematics during bridging with IHA using the Thera-Band. Thus, the purpose of this study was to investigate the effects of bridging
http://dx.doi.org/10.1016/j.jelekin.2014.09.005 1050-6411/Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Choi S-A et al. Isometric hip abduction using a Thera-Band alters gluteus maximus muscle activity and the anterior pelvic tilt angle during bridging exercise. J Electromyogr Kinesiol (2014), http://dx.doi.org/10.1016/j.jelekin.2014.09.005
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S.-A. Choi et al. / Journal of Electromyography and Kinesiology xxx (2014) xxx–xxx
with IHA using the Thera-Band on GM, HAM, and ES muscle activity; GM/HAM and GM/ES ratios; and the anterior pelvic tilt angle in healthy subjects. It was hypothesized that bridging with IHA using the Thera-Band would result in increased GM muscle activity, increased GM/HAM and GM/ES ratios, and a decreased anterior pelvic tilt angle. 2. Methods
subjects failed to perform the standardized position and maintain the position during the exercise period, data collection was immediately stopped. Subjects performed two conditions (with IHA and without IHA) of the same bridging exercise twice and maintained each position for 5-s. Bridging without IHA was followed by bridging with IHA to minimize the carry over or learning effect (Park et al., 2013). A 5-min rest between the two conditions and a 1-min rest between every two trials was given to avoid muscle fatigue.
2.1. Subjects A power analysis was performed with G*power software ver. 3.1.2 (Franz Faul, University of Kiel, Kiel, Germany) using the results of a pilot study involving five subjects. The calculation of sample size was carried out with a power of 0.80, alpha level of 0.05, and effect size of 0.89. This provided a necessary sample size of ten subjects for this study. Twenty-one healthy subjects (6 males, 15 females) were recruited from a university population (age = 22.5 ± 1.0 years, height = 165.3 ± 7.1 cm, weight = 57.5 ± 8.7 kg, and body mass index = 20.9 ± 1.8 kg/m2). The exclusion criteria were: (1) limitations in range of motion of the bilateral hip, knee, and ankle joints; (2) a history of LBP or lower extremity dysfunctions such as iliotibial band friction syndrome, patellofemoral pain syndrome, anterior cruciate ligament sprains, or chronic ankle instability (Cichanowski et al., 2007; Fredericson et al., 2000; Friel et al., 2006; Hewett et al., 2006; Ireland et al., 2003) in the past 12 months; (3) iliopsoas, rectus femoris, or tensor fasciae latae tightness as evidenced by the Thomas test, Ely’s test, or modified Ober’s test, respectively (Kendall et al., 2005; Magee, 2007); and (4) lumbopelvic instability demonstrated by performing the active straight leg raising test with a pressure biofeedback unit (Liebenson, 2004; Mens et al., 1999). Prior to collecting data, the examiner informed the subjects of the study procedures and each subject completed an informed consent form. The study protocol was approved by the Yonsei University Wonju Institutional Review Board. 2.2. Exercise procedures Subjects underwent a familiarization period of approximately 20 min to achieve a proper exercise performance capability. When
2.2.1. Bridging without isometric hip abduction The subjects were placed in a supine position. Both knees were flexed at 90°, the feet were hip-width apart while resting on the floor, and the toes were facing forward. The arms were crossed over the chest to minimize arm support (Fig. 1). Two plastic poles were placed vertically along the lateral aspect of the bilateral knee joint to maintain hip abduction of 30°. A wooden target bar was placed at the height of the middle point of the thigh between the greater trochanter and femoral condyle when the trunk, pelvis, and thigh were aligned in a straight line (hip extension of 0°). A universal goniometer was used for knee and hip angle measurements. The subject was instructed to lift his pelvis comfortably at a self-selected speed while maintaining contact between the lateral aspects of the bilateral knee joint and vertically placed plastic poles. When both thighs touched the wooden target bar during bridging, the subject was asked not to lift his pelvis further and to hold the bridging position for 5-s without pelvic or thigh movement (Fig. 2). 2.2.2. Bridging with isometric hip abduction Bridging with IHA followed the same procedure as bridging without IHA, with the exception of the application of a blue-colored Thera-Band, which is recommended by the manufacturer for an intermediate or advanced workout level. The Thera-Band was wrapped around both thighs just proximal to the knees, providing consistent resistance to IHA. Tension was controlled by lengthening or shortening the Thera-Band. The tension in the Thera-Band was determined when the subject was able to perform more than ten repetitions of hip abduction of 30° in hook-lying position using the Thera-Band (Decker et al., 1999; Park et al., 2013) (Fig. 3).
Fig. 1. Starting position of bridging exercise.
Fig. 2. Bridging without isometric hip abduction.
Please cite this article in press as: Choi S-A et al. Isometric hip abduction using a Thera-Band alters gluteus maximus muscle activity and the anterior pelvic tilt angle during bridging exercise. J Electromyogr Kinesiol (2014), http://dx.doi.org/10.1016/j.jelekin.2014.09.005
S.-A. Choi et al. / Journal of Electromyography and Kinesiology xxx (2014) xxx–xxx
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Fig. 3. Bridging with isometric hip abduction using the Thera-Band.
2.3. Surface electromyography and data processing Electromyographic (EMG) data were collected using a wireless TeleMyo DTS (Noraxon Inc., Scottsdale, AZ, USA) and Myo-Research Master Edition 1.06 XP software was used for analyzing EMG data. The EMG signals were sampled at 1000 Hz. A band pass filter was used between 20 and 450 Hz and notch filter was preset to reject 60 Hz. The raw data were processed into the root mean square (RMS) with a window of 50 ms. The electrode sites were shaved and then rubbing alcohol was used to reduce skin impedance. Two surface electrodes with an interelectrode distance of 2 cm were positioned on the upper fibers of GM, the general part of HAM, and ES muscle bilaterally. Electrodes were placed in the middle of each muscle belly and parallel to the direction of each muscle fiber. In this study, all subjects should maintain the standardized position of bridging with hip abduction of 30° for comparing bridging with IHA and without IHA. In this reason, we chose the upper fibers of the as representative of the GM because they anatomically act as hip abductor more than lower fiber (Criswell, 2011; Frank and Netter, 1987; Kang et al., 2013). The electrode for the upper GM was placed half the distance between the trochanter and sacral vertebrae in the middle of the muscle at an oblique angle at the level of the trochanter. For recordings of the general part of HAM, the electrode was placed parallel to the muscle in the center of the back of the thigh, approximately half the distance from the gluteal fold to the back of the knee. The electrode for the ES was placed parallel to the spine at the level of the iliac crest, approximately 2 cm apart from the spine over the muscle mass (Criswell, 2011). EMG data were collected for the mean value of bilateral GM, HAM, and ES because there was no significant difference between right and left of GM, HAM, and ES muscle activity when we conducted an independent t-test (p > 0.05). Normalization was needed to minimize variables or differences between different recoding sites and individuals. The maximal voluntary isometric contraction (MVIC) normalization method was applied to each tested muscle and MVIC was recorded during a manual muscle test (MMT) in the positions described by Kendall et al. (2005). To collect MVIC data, subjects maintained the MMT position of each tested muscle against manual resistance for 5-s twice. The middle 3-s contraction, excluding each 1-s at the
beginning and end, was used for data analysis, and a 30-s rest was given between the two trials (Bolgla and Uhl, 2007; Bolgla et al., 2010). The mean value of middle 3-s contraction of the two trials for the maximal contraction in each muscle was taken as the MVIC. All EMG data during two conditions of bridging exercise were recorded for 5-s twice and calculated from the middle 3-s isometric phase except for each 1-s at the beginning and end. The mean value of the middle 3-s contraction of the two trials for each condition was used for data analysis. To calculate the GM/HAM and GM/ES ratios, the normalized GM amplitude was divided by the normalized HAM and the normalized GM was divided by the normalized ES amplitude, respectively. 2.4. Measurement of anterior pelvic tilt angle To obtain pelvic kinematic data, two reflective markers were placed on specific anatomical landmarks; namely, the anterior superior iliac spine (ASIS) and posterior superior iliac spine (PSIS). In this study, the anterior pelvic tilt was defined as an angle between a line joining the ASIS, PSIS, and the vertical line from the ASIS (Fig. 4). The examiner took a picture of the subject’s pelvis with a digital camera when the subject maintained the position under two conditions of bridging exercises. The location of the digital camera and distance from the digital camera to the subject were consistent. These pictures were then transferred to Image J software (National Institutes of Health, Bethesda, MD, USA) and used to measure the anterior pelvic tilt angle. 2.5. Statistical analysis A Kolmogorov–Smirnov Z-test was performed to confirm a normal distribution. Test–retest reliability of EMG and pelvic tilt measurements in two conditions (with IHA and without IHA) of bridging exercises was assessed by intra-class correlation (ICC), 95% confidence interval (CI), the standard error of measurement (SEM), and minimal detectable difference (MDC). SEM was calculated for each measurement to assess absolute consistency pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi [SEM = SD 1 ICC. MDC (95% confidence interval) [MDC95 = p SEM ⁄ 1.96 2] was calculated (Ries et al., 2009). Effect size index (ESI) is calculated to determine meaningful changes between the
Fig. 4. Measurement of anterior pelvic tilt angle.
Please cite this article in press as: Choi S-A et al. Isometric hip abduction using a Thera-Band alters gluteus maximus muscle activity and the anterior pelvic tilt angle during bridging exercise. J Electromyogr Kinesiol (2014), http://dx.doi.org/10.1016/j.jelekin.2014.09.005
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bridging exercise with and without IHA [Mean of the bridging exercise with IHA – Mean of the bridging exercise without IHA/ standard deviation of the bridging exercise without IHA]. A oneway, repeated-measures analysis of variance (ANOVA) was used to access the statistical significance of the GM, HAM, and ES muscle activity; the GM/HAM and GM/ES ratios; and the anterior pelvic tilt angle during the bridging exercise with and without IHA. Statistical significance was set at 0.05. If a significant difference was found, a Bonferroni correction was performed (a = 0.025). All statistical analyses were performed using PASW Statistics ver. 18.0 (SPSS, Inc., Chicago, IL, USA). 3. Results The test–retest reliabilities for EMG measurement of GM, HAM, and ES muscle were substantial in both bridging with and without IHA. (Bridging with IHA: ICC = 0.98, 95% CI = 0.97–0.99, SEM = 1.72, and MDC = 4.77 for GM, and ICC = 0.96, 95% CI = 0.93–0.99, SEM = 3.38, and MDC = 9.37 for HAM, and ICC = 0.96, 95% CI = 0.93–0.99, SEM = 3.88, and MDC = 10.76 for ES; Bridging without IHA: ICC = 0.93, 95% CI = 0.85–0.99, SEM = 3.44, and MDC = 9.54 for GM, ICC = 0.95, 95% CI = 0.89–0.99, SEM = 4.52, and MDC = 12.53 for HAM, and ICC = 0.98, 95% CI = 0.97–0.99, SEM = 2.60, and MDC = 7.21 for ES). 3.1. Gluteus maximus, hamstrings, and erector spinae muscle activity In terms of muscle activity, there was a significant difference in GM muscle activity between bridging with IHA using the TheraBand and without IHA (F1,20 = 9.098, P = .007, ESI = .365). Bridging with IHA using the Thera-Band resulted in significantly greater GM muscle activity than bridging without IHA (P = .007) (Fig. 5). However, there were no significant differences in the activity of the HAM (F1,20 = 4.163, P = .055, ESI = .247) and ES (F1,20 = 0.319, P = .578, ESI = .064) between bridging with and without IHA. 3.2. Gluteus maximus/hamstrings and gluteus maximus/erector spinae muscle activity ratios In terms of muscle ratios, there were no significant differences in the GM/HAM (F1,20 = .014, P = .906) and GM/ES (F1,20 = .559.163, P = .463) ratios between bridging with and without IHA. 3.3. Anterior pelvic tilt angle With regard to pelvic kinematics, there was a significant difference in the anterior pelvic tilt angle between with IHA using the Thera-Band and without IHA (F1,20 = 15. 624, P = .001). Bridging
Fig. 5. Comparison of gluteus maximus muscle activity between bridging exercise with and without isometric hip abduction (GM: Gluteus maximus, IHA: Isometric hip abduction). ⁄p < 0.05.
Fig. 6. Comparison of anterior pelvic tilt angle between bridging exercise with and without isometric hip abduction (IHA: Isometric hip abduction). ⁄p < 0.05.
with IHA using the Thera-Band showed significantly lesser anterior pelvic tilt angle than bridging without IHA (P = .001) (Fig. 6). 4. Discussion To our knowledge, this study is the first to evaluate the effect of IHA with the Thera-Band on GM muscle activity and pelvic kinematics during a bridging exercise. The results partially supported the research hypothesis. GM activity increased significantly by 21.1% during bridging with IHA using the Thera-Band, supporting the research hypothesis. A possible explanation is that applying IHA with the TheraBand during bridging and maintaining hip abduction of 30° induced facilitation of the GM in advance before initiation of the bridging movement, consequently increasing GM muscle activity. Our present finding is in agreement with those of previous studies demonstrating the effect of muscle preactivation on muscle firing or force. Kyrolaïnen et al. (1999) emphasized the importance of the preactivation of leg extensor for increasing running speed. Specifically, preactivity of the gastrocnemius muscle functioned as a preparatory requirement to enhance muscle activity and the timing of muscular action with respect to ground contact during the running cycle. Mrdakovic et al. (2008) confirmed that when a knee extensor bench exercise was performed before a leg press exercise by means of muscle preactivation, an increased EMG signal was recorded from the vastus lateralis muscle. This result indicates that preactivation performance by a single-joint exercise increases the number of motor units recruited during a multi-joint exercise. The GM is quadrilateral in shape, and its fibers are obliquely directed inferiorly and laterally. It functions not only as a hip extensor, but also as a hip abductor and external rotator (Frank and Netter, 1987; McAndrew et al., 2006). In this study, hip abduction of 30° was sustained by two plastic poles placed vertically along the lateral aspect of the bilateral knee joints. Such hip abduction during bridging might facilitate GM activity in terms of the action of the GM as a hip abductor and external rotator. In a previous study, Kang et al. (2013) reported that the GM EMG amplitude was greatest at 30° of hip abduction during prone hip extension with knee flexion. Because the GM is a fusiform muscle that is optimized when the direction of muscle pull is parallel to the muscle fiber, hip abduction during prone hip extension with knee flexion leads to an increased EMG amplitude of the GM. It was expected that HAM and ES activity would be reduced when GM activity was increased by applying IHA with the TheraBand during bridging exercise. This hypothesis was based on the findings of previous studies demonstrating that synergistic muscles work together to perform the same range of motion (Jonkers et al., 2003; Kang et al., 2013; Park et al., 2013). Based on these findings, synergistic muscles during bridging (i.e., trunk extensors
Please cite this article in press as: Choi S-A et al. Isometric hip abduction using a Thera-Band alters gluteus maximus muscle activity and the anterior pelvic tilt angle during bridging exercise. J Electromyogr Kinesiol (2014), http://dx.doi.org/10.1016/j.jelekin.2014.09.005
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such as the GM, HAM, and ES) can affect one another during bridging: increased GM activity could reduce HAM and ES activity. Although GM activity was significantly increased in this study, it failed to elicit significant changes in the GM/HAM and GM/ES ratios between bridging with and without IHA. The unexpected findings in this study may be the result of several differences from previous studies. First, healthy subjects participated in the present study and exhibited HAM or ES activity that was dominant to (or greater than) the GM activity at the beginning of the study. In many previous studies that investigated GM activity during various bridging or prone hip extension exercises in healthy subjects, the mean activity levels of the ES and HAM at baseline (i.e., before the intervention) were less than or similar to the mean value for the GM (Ekstrom et al., 2007, 2008; Kang et al., 2013; Sakamoto et al., 2009). However, because the mean value of HAM and ES muscle activity was about 1.8 and 2.5 times that of the GM, respectively, during bridging without IHA in this study (without intervention or at entry), bridging with IHA would not likely lead to significant decreases in the dominant HAM and ES in a crosssectional study. Second, because a wooden target bar was used to control pelvic lift during bridging, increased activation of the HAM and ES was not likely to occur in the present study. No previous studies have recommended the most appropriate level of pelvic lifting during bridging during bridging can be disadvantageous due to potential overactivation of the already-dominant HAM and ES; thus, a wooden target bar was placed to provide contact, cueing the subjects not to over-lift the pelvis while performing the two types of bridging. However, this valid use of a wooden target bar could have limited the level of the lumbopelvis and consequently might have prevented overactivation of the HAM and ES during bridging. Thus, HAM and ES activity may have differed if the subjects had performed bridging without a wooden target bar. The anterior pelvic tilt angle decreased significantly by 20.5% during bridging with IHA using the Thera-Band, supporting the research hypothesis. Although the change of anterior pelvic tilt angle was small, it could be a meaningful result in consideration of measurement position because anterior pelvic tilt was measured in bridging position in this study. Lembeck et al. (2005) reported that average pelvic tilt angle in the lying position was lower than standing position. Thus, bridging with IHA using a Thera-Band resulted in facilitation of the GM in advance, and the increased GM activity could have contributed to reduce anterior pelvic tilt. In other words, when the femur was fixed, such as bridging position, contraction of the GM induced the pelvis to move posteriorly and decrease anterior pelvic tilt and lumbar lordosis. Many previous studies have emphasized that an important function of the GM is to maintain pelvic stability. Oh et al. (2007) suggested that performance of the abdominal drawing-in maneuver during prone hip extension encouraged activation of the hip extensors while decreasing activation of the ES and reducing the anterior pelvic tilt. They explained that increased GM muscle activity could be affected by biomechanical alterations such as a reduced anterior pelvic tilt. Tateuchi et al. (2012) focused on improvements in hip muscle balance between agonists and antagonists, which could reduce the anterior pelvic tilt. An altered balance in muscle activation, especially a hip flexor (tensor fasciae latae) dominant to the hip extensors (GM and semitendinosus), during prone hip extension resulted in abnormal movement patterns, such as anterior pelvic tilt and excessive lumbar extension. Our study has several limitations. First, measurement errors were likely to have occurred when measuring the pelvic kinematics because this study used only two-dimensional image processing software. A three-dimensional or real-time measuring system will be needed to improve the precision of measurement in future studies. Second, the findings of this study are difficult to generalize
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to the entire patient population because only healthy and young subjects participated. Subjects with a broad age range and clinical symptoms such as GM weakness should be investigated in future to strengthen the clinical implications of this study. Third, this study did not perform force measurement. It could help to further differentiate between the two exercise protocols and EMG/force data would be interesting indications for future studies in this filed. Finally, this study used a cross-sectional design. Future longitudinal studies are necessary to identify distinct differences and the long-term effects of facilitation of the GM on HAM and ES activity. 5. Conclusion This study investigated the effects of bridging with IHA using a Thera-Band on GM, HAM, and ES activity; the GM/HAM and ES ratios; and the anterior pelvic tilt angle. GM muscle activity increased significantly and the anterior pelvic tilt angle decreased significantly during bridging with IHA using a Thera-Band. These findings indicate that the application of a Thera-Band facilitates the GM in advance before the initiation of bridging, consequently enhances GM activity, and prevents excessive anterior pelvic tilt during bridging. Therefore, bridging with IHA using the Thera-Band can be implemented as an effective method to facilitate GM muscle activity and reduce the anterior pelvic tilt angle. Conflict of interest The authors declare that they have no conflict of interest. References Bolgla LA, Uhl TL. Reliability of electromyographic normalization methods for evaluating the hip musculature. J Electromyogr Kinesiol 2007;17(1):102–11. Bolgla LA, Malone TR, Umberger BR, Uhl TL. Reliability of electromyographic methods used for assessing hip and knee neuromuscular activity in females diagnosed with patellofemoral pain syndrome. J Electromyogr Kinesiol 2010;20:142–7. Chaitow L. Muscle energy techniques. London (UK): Churchill Livingstone; 1996. Cichanowski HR, Schmitt JS, Johnson RJ, Niemuth PE. Hip strength in collegiate female athletes with patellofemoral pain. Med Sci Sports Exerc 2007;39(8): 1227–32. Criswell E. Cram’s introduction to surface electromyography. 2nd ed. Sudbury (MA): Jones and Bartlett Publishers; 2011. Decker MJ, Hintermeister RA, Faber KJ, Hawkins RJ. Serratus anterior muscle activity during selected rehabilitation exercises. Am J Sports Med 1999;27(6):784–91. Ekstrom RA, Donatelli RA, Carp KC. Electromyographic analysis of core trunk, hip, and thigh muscles during 9 rehabilitation exercises. J Orthop Sports Phys Ther 2007;37(12):754–62. Ekstrom RA, Osborn RW, Hauer PL. Surface electromyographic analysis of the low back muscles during rehabilitation exercises. J Orthop Sports Phys Ther 2008;38(12):736–45. Frank H, Netter R. The CIBA collection of medical illustrations: musculoskeletal system. vol. 8. Summit, NJ: Ciba-Geigy Corp; 1987. Fredericson M, Cookingham CL, Chaudhari AM, Dowdell BC, Oestreicher N, Sahrmann SA. Hip abductor weakness in distance runners with iliotibial band syndrome. Clin J Sport Med 2000;10(3):169–75. Friel K, McLean N, Myers C, Caceres M. Ipsilateral hip abductor weakness after inversion ankle sprain. J Athl Train 2006;41(1):74–8. Hewett TE, Myer GD, Ford KR. Anterior cruciate ligament injuries in female athletes: Part 1, mechanisms and risk factors. Am J Sports Med 2006;34(2):299–311. Hossain M, Nokes LD. A model of dynamic sacroiliac joint instability from malrecruitment of gluteus maximus and biceps femoris muscles resulting in low back pain. Med Hypotheses 2005;65(2):278–81. Ireland ML, Willson JD, Ballantyne BT, Davis IM. Hip strength in females with and without patellofemoral pain. J Orthop Sports Phys Ther 2003;33(11):671–6. Jonkers I, Stewart C, Spaepen A. The complementary role of the plantar flexors, hamstrings and gluteus maximus in the control of stance limb stability during gait. Gait Posture 2003;17:264–72. Kang SY, Jeon HS, Kwon O, Cynn HS, Choi BR. Activation of the gluteus maximus and hamstring muscles during prone hip extension with knee flexion in three hip abduction positions. Man Ther 2013;18(4):303–7. Kendall FP, McCreary EK, Provance PG. Muscles: Testing and Function With Posture and Pain. 5th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2005. Kyrolaïnen H, Komi PV, Belli A. Changes in muscle activity patterns and kinetics with increasing running speed. J Strength Cond Res 1999;13(4):400–6.
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Sil-Ah Choi received her B.S. degree in Physical Therapy from Yonsei University, and M.S. degree in Physical Therapy from Yonsei University. She is a member of applied kinesiology and ergonomic technology laboratory. Her research focuses on the musculoskeletal problems and movement disorders, especially in muscle imbalance and dysfunction of hip, knee, and shoulder joint, using the electromyograpic system.
Heon-Seock Cynn is a professor in the Department of Physical Therapy at the College of Health Science of Yonsei University. He received B.S. degree in Physical Therapy from Yonsei University, M.A. degree in Physical Therapy from New York University, and Ph.D. degree in Physical Therapy from Yonsei University. He was a full time lecturer of Seoul Health College and an associate professor of Hanseo University. He is a director of applied kinesiology and ergonomic technology laboratory, and his research interests are identification of etiologic factors, classification, and intervention approaches for movement disorders and musculoskeletal diseases.
Chung-Hwi Yi received his Ph.D. degree in physical therapy from Yonsei University in 1990. He joined the Department of Rehabilitation Therapy of Yonsei University in 1993. He was a president of The Korean Academy of University Trained Physical Therapists. From 1993 onwards he has been employed as a professor in the Department of Physical Therapy at the College of Health Science of Yonsei University. His research interests include motion, posture analysis, and the development of outcome measures for evaluating disability.
Oh-Yun Kwon is a professor in the Department of Physical Therapy at the College of Health Science of Yonsei University. He received his B.S. degree in Physical therapy and M.P.H. degree from Yonsei University in 1986 and 1992 respectively, and Ph.D. degree from Keimyung University in 1998. He had research experience in Program in Physical Therapy at Washington University in St Louis as a Post Doctoral Fellow. He is a director in Lab of Kinetic Ergocise based on Movement Analysis (KEMA). He is interested in the mechanisms of movement impairment, movement analysis, and prevention and management of the work related musculoskeletal pain syndrome.
Tae-Lim Yoon is a professor in the Department of Physical Therapy at the College of Health and Wallfare of Woosong University and Ph.D. Candidate in the Department of Physical Therapy at the Graduate School of Yonsei University. He received B.S. degree in Physical Therapy from Yonsei University, M.A. degree in Physical Therapy from New York University. He is a member of applied kinesiology and ergonomic technology laboratory, and his research interests are movement analysis, human factors and ergonomics, and prevention and management of musculoskeletal problems.
Woo-Jeong Choi is a M.S. Student in the Department of Physical Therapy at the Graduate School of Yonsei University. She received B.S. degree in Physical Therapy from Yonsei University in 2013. She is a member of applied kinesiology and ergonomic technology laboratory. Her research interests include electromyographic and kinematic analysis of therapeutic exercise for musculoskeletal syndromes, including scapular dyskinesis.
Ji-Hyun Lee is a Ph.D. Student in the Department of Physical Therapy at the Graduate School of Yonsei University. She received B.S. degree in Physical Therapy from Hanseo University, M.S. degree in Physical Therapy from Yonsei University. She is a member of applied kinesiology and ergonomic technology laboratory, and she is a part time lecturer of Yonsei University. Her main research interests are shoulder and hip assessment and treatment strategy. Her papers have been published in several international journals in these fields.
Please cite this article in press as: Choi S-A et al. Isometric hip abduction using a Thera-Band alters gluteus maximus muscle activity and the anterior pelvic tilt angle during bridging exercise. J Electromyogr Kinesiol (2014), http://dx.doi.org/10.1016/j.jelekin.2014.09.005
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Isometric hip abduction using a Thera-Band alters gluteus maximus muscle activity and the anterior pelvic tilt angle during bridging exercise Sil-Ah Choi, Heon-Seock Cynn ⇑, Chung-Hwi Yi, Oh-Yun Kwon, Tae-Lim Yoon, Woo-Jeong Choi, Ji-Hyun Lee Applied Kinesiology and Ergonomic Technology Laboratory, Department of Physical Therapy, The Graduate School, Yonsei University, 1 Yonseidae-gil, Wonju-si, Gangwon-do 220-710, South Korea
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Article history: Received 7 February 2014 Received in revised form 3 June 2014 Accepted 1 September 2014 Available online xxxx Keywords: Bridging Gluteus maximus Preactivation Thera-Band
a b s t r a c t The purpose of this study was to investigate the effects of bridging with isometric hip abduction (IHA) using the Thera-Band on gluteus maximus (GM), hamstring (HAM), and erector spinae (ES) muscle activity; GM/HAM and GM/ES ratios; and the anterior pelvic tilt angle in healthy subjects. Twenty-one subjects participated in this study. Surface EMG was used to collect EMG data of GM, HAM, and ES muscle activities, and Image J software was used to measure anterior pelvic tilt angle. A paired t-test was used to compare GM, HAM, and ES muscle activity; the GM/HAM and GM/ES ratios; and the anterior pelvic tilt angle with and without IHA during the bridging exercise. GM muscle activity increased significantly and the anterior pelvic tilt angle decreased significantly during bridging with IHA using the Thera-Band (p < 0.05). However, there were no significant differences in the activity of the HAM and ES and the GM/HAM and GM/ES ratios between bridging with and without IHA (p > 0.05). The results of this study suggest that bridging with IHA using the Thera-Band can be implemented as an effective method to facilitate GM muscle activity and reduce the anterior pelvic tilt angle. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction The gluteus maximus (GM) is one of the largest and strongest muscles in the body. The GM originates from the posterior sacrum and coccyx as well as the posterior gluteal line of the ilium and inserts on the iliotibial tract and gluteal tuberosity of the femur (Frank and Netter, 1987). The GM is a powerful extensor and external rotator of the hip, and the superior part of the GM acts as a hip abductor because muscle fibers in the GM are directed downward and outward (Frank and Netter, 1987; Long et al., 1993). Hip extensors, especially the GM, are important for many functional activities of daily living such as moving from sitting to standing, climbing stairs, and maintaining an upright posture during walking (Winter, 1991). Because the direction of the GM muscle fibers, especially deep sacral fibers of the GM, are perpendicular to the sacroiliac (SI) joint, GM contraction improves SI joint stability and plays a part in force transmission from the lower extremity
⇑ Corresponding author. Tel.: +82 33 760 2427; fax: +82 33 760 2496. E-mail addresses: [email protected] (S.-A. Choi), [email protected] (H.-S. Cynn), [email protected] (C.-H. Yi), [email protected] (O.-Y. Kwon), [email protected] (T.-L. Yoon), [email protected] (W.-J. Choi), rapa60@ naver.com (J.-H. Lee).
to the pelvis during ambulation (Hossain and Nokes, 2005; Leinonen et al., 2000; Mooney et al., 2001). However, the GM is frequently weak and lengthened because many people spend a great amount of time remaining seated (Sahrmann, 2002). Decreased activity of the GM is one cause of low back pain (LBP) and results in SI joint instability and dysfunction (van Wingerden et al., 2004). In addition, hamstring (HAM) tightness can be observed as a compensatory mechanism for a weak GM (Massoud Arab et al., 2011; van Wingerden et al., 2004). Also, excessive anterior pelvic tilt, lumbar lordosis with dominant erector spinae (ES), and lumbar rotation occur in place of a weak GM or delayed GM activation during hip extension (Chaitow, 1996; Sahrmann, 2002). Bridging exercises are the most commonly used by people with weak hip extensors and trunk muscles in physical therapy programs. However, bridging exercises are associated with a risk of dominant HAM and ES activity and excessive anterior pelvic tilt as a compensation for GM weakness regardless of the type of bridging exercise performed. Therefore, bridging exercise with isometric hip abduction (IHA) using a Thera-Band (Hygenic Corp., Akron, OH, USA) was devised in this study. No previous studies have compared GM with HAM and ES muscle activity and pelvic kinematics during bridging with IHA using the Thera-Band. Thus, the purpose of this study was to investigate the effects of bridging
http://dx.doi.org/10.1016/j.jelekin.2014.09.005 1050-6411/Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Choi S-A et al. Isometric hip abduction using a Thera-Band alters gluteus maximus muscle activity and the anterior pelvic tilt angle during bridging exercise. J Electromyogr Kinesiol (2014), http://dx.doi.org/10.1016/j.jelekin.2014.09.005
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with IHA using the Thera-Band on GM, HAM, and ES muscle activity; GM/HAM and GM/ES ratios; and the anterior pelvic tilt angle in healthy subjects. It was hypothesized that bridging with IHA using the Thera-Band would result in increased GM muscle activity, increased GM/HAM and GM/ES ratios, and a decreased anterior pelvic tilt angle. 2. Methods
subjects failed to perform the standardized position and maintain the position during the exercise period, data collection was immediately stopped. Subjects performed two conditions (with IHA and without IHA) of the same bridging exercise twice and maintained each position for 5-s. Bridging without IHA was followed by bridging with IHA to minimize the carry over or learning effect (Park et al., 2013). A 5-min rest between the two conditions and a 1-min rest between every two trials was given to avoid muscle fatigue.
2.1. Subjects A power analysis was performed with G*power software ver. 3.1.2 (Franz Faul, University of Kiel, Kiel, Germany) using the results of a pilot study involving five subjects. The calculation of sample size was carried out with a power of 0.80, alpha level of 0.05, and effect size of 0.89. This provided a necessary sample size of ten subjects for this study. Twenty-one healthy subjects (6 males, 15 females) were recruited from a university population (age = 22.5 ± 1.0 years, height = 165.3 ± 7.1 cm, weight = 57.5 ± 8.7 kg, and body mass index = 20.9 ± 1.8 kg/m2). The exclusion criteria were: (1) limitations in range of motion of the bilateral hip, knee, and ankle joints; (2) a history of LBP or lower extremity dysfunctions such as iliotibial band friction syndrome, patellofemoral pain syndrome, anterior cruciate ligament sprains, or chronic ankle instability (Cichanowski et al., 2007; Fredericson et al., 2000; Friel et al., 2006; Hewett et al., 2006; Ireland et al., 2003) in the past 12 months; (3) iliopsoas, rectus femoris, or tensor fasciae latae tightness as evidenced by the Thomas test, Ely’s test, or modified Ober’s test, respectively (Kendall et al., 2005; Magee, 2007); and (4) lumbopelvic instability demonstrated by performing the active straight leg raising test with a pressure biofeedback unit (Liebenson, 2004; Mens et al., 1999). Prior to collecting data, the examiner informed the subjects of the study procedures and each subject completed an informed consent form. The study protocol was approved by the Yonsei University Wonju Institutional Review Board. 2.2. Exercise procedures Subjects underwent a familiarization period of approximately 20 min to achieve a proper exercise performance capability. When
2.2.1. Bridging without isometric hip abduction The subjects were placed in a supine position. Both knees were flexed at 90°, the feet were hip-width apart while resting on the floor, and the toes were facing forward. The arms were crossed over the chest to minimize arm support (Fig. 1). Two plastic poles were placed vertically along the lateral aspect of the bilateral knee joint to maintain hip abduction of 30°. A wooden target bar was placed at the height of the middle point of the thigh between the greater trochanter and femoral condyle when the trunk, pelvis, and thigh were aligned in a straight line (hip extension of 0°). A universal goniometer was used for knee and hip angle measurements. The subject was instructed to lift his pelvis comfortably at a self-selected speed while maintaining contact between the lateral aspects of the bilateral knee joint and vertically placed plastic poles. When both thighs touched the wooden target bar during bridging, the subject was asked not to lift his pelvis further and to hold the bridging position for 5-s without pelvic or thigh movement (Fig. 2). 2.2.2. Bridging with isometric hip abduction Bridging with IHA followed the same procedure as bridging without IHA, with the exception of the application of a blue-colored Thera-Band, which is recommended by the manufacturer for an intermediate or advanced workout level. The Thera-Band was wrapped around both thighs just proximal to the knees, providing consistent resistance to IHA. Tension was controlled by lengthening or shortening the Thera-Band. The tension in the Thera-Band was determined when the subject was able to perform more than ten repetitions of hip abduction of 30° in hook-lying position using the Thera-Band (Decker et al., 1999; Park et al., 2013) (Fig. 3).
Fig. 1. Starting position of bridging exercise.
Fig. 2. Bridging without isometric hip abduction.
Please cite this article in press as: Choi S-A et al. Isometric hip abduction using a Thera-Band alters gluteus maximus muscle activity and the anterior pelvic tilt angle during bridging exercise. J Electromyogr Kinesiol (2014), http://dx.doi.org/10.1016/j.jelekin.2014.09.005
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Fig. 3. Bridging with isometric hip abduction using the Thera-Band.
2.3. Surface electromyography and data processing Electromyographic (EMG) data were collected using a wireless TeleMyo DTS (Noraxon Inc., Scottsdale, AZ, USA) and Myo-Research Master Edition 1.06 XP software was used for analyzing EMG data. The EMG signals were sampled at 1000 Hz. A band pass filter was used between 20 and 450 Hz and notch filter was preset to reject 60 Hz. The raw data were processed into the root mean square (RMS) with a window of 50 ms. The electrode sites were shaved and then rubbing alcohol was used to reduce skin impedance. Two surface electrodes with an interelectrode distance of 2 cm were positioned on the upper fibers of GM, the general part of HAM, and ES muscle bilaterally. Electrodes were placed in the middle of each muscle belly and parallel to the direction of each muscle fiber. In this study, all subjects should maintain the standardized position of bridging with hip abduction of 30° for comparing bridging with IHA and without IHA. In this reason, we chose the upper fibers of the as representative of the GM because they anatomically act as hip abductor more than lower fiber (Criswell, 2011; Frank and Netter, 1987; Kang et al., 2013). The electrode for the upper GM was placed half the distance between the trochanter and sacral vertebrae in the middle of the muscle at an oblique angle at the level of the trochanter. For recordings of the general part of HAM, the electrode was placed parallel to the muscle in the center of the back of the thigh, approximately half the distance from the gluteal fold to the back of the knee. The electrode for the ES was placed parallel to the spine at the level of the iliac crest, approximately 2 cm apart from the spine over the muscle mass (Criswell, 2011). EMG data were collected for the mean value of bilateral GM, HAM, and ES because there was no significant difference between right and left of GM, HAM, and ES muscle activity when we conducted an independent t-test (p > 0.05). Normalization was needed to minimize variables or differences between different recoding sites and individuals. The maximal voluntary isometric contraction (MVIC) normalization method was applied to each tested muscle and MVIC was recorded during a manual muscle test (MMT) in the positions described by Kendall et al. (2005). To collect MVIC data, subjects maintained the MMT position of each tested muscle against manual resistance for 5-s twice. The middle 3-s contraction, excluding each 1-s at the
beginning and end, was used for data analysis, and a 30-s rest was given between the two trials (Bolgla and Uhl, 2007; Bolgla et al., 2010). The mean value of middle 3-s contraction of the two trials for the maximal contraction in each muscle was taken as the MVIC. All EMG data during two conditions of bridging exercise were recorded for 5-s twice and calculated from the middle 3-s isometric phase except for each 1-s at the beginning and end. The mean value of the middle 3-s contraction of the two trials for each condition was used for data analysis. To calculate the GM/HAM and GM/ES ratios, the normalized GM amplitude was divided by the normalized HAM and the normalized GM was divided by the normalized ES amplitude, respectively. 2.4. Measurement of anterior pelvic tilt angle To obtain pelvic kinematic data, two reflective markers were placed on specific anatomical landmarks; namely, the anterior superior iliac spine (ASIS) and posterior superior iliac spine (PSIS). In this study, the anterior pelvic tilt was defined as an angle between a line joining the ASIS, PSIS, and the vertical line from the ASIS (Fig. 4). The examiner took a picture of the subject’s pelvis with a digital camera when the subject maintained the position under two conditions of bridging exercises. The location of the digital camera and distance from the digital camera to the subject were consistent. These pictures were then transferred to Image J software (National Institutes of Health, Bethesda, MD, USA) and used to measure the anterior pelvic tilt angle. 2.5. Statistical analysis A Kolmogorov–Smirnov Z-test was performed to confirm a normal distribution. Test–retest reliability of EMG and pelvic tilt measurements in two conditions (with IHA and without IHA) of bridging exercises was assessed by intra-class correlation (ICC), 95% confidence interval (CI), the standard error of measurement (SEM), and minimal detectable difference (MDC). SEM was calculated for each measurement to assess absolute consistency pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi [SEM = SD 1 ICC. MDC (95% confidence interval) [MDC95 = p SEM ⁄ 1.96 2] was calculated (Ries et al., 2009). Effect size index (ESI) is calculated to determine meaningful changes between the
Fig. 4. Measurement of anterior pelvic tilt angle.
Please cite this article in press as: Choi S-A et al. Isometric hip abduction using a Thera-Band alters gluteus maximus muscle activity and the anterior pelvic tilt angle during bridging exercise. J Electromyogr Kinesiol (2014), http://dx.doi.org/10.1016/j.jelekin.2014.09.005
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bridging exercise with and without IHA [Mean of the bridging exercise with IHA – Mean of the bridging exercise without IHA/ standard deviation of the bridging exercise without IHA]. A oneway, repeated-measures analysis of variance (ANOVA) was used to access the statistical significance of the GM, HAM, and ES muscle activity; the GM/HAM and GM/ES ratios; and the anterior pelvic tilt angle during the bridging exercise with and without IHA. Statistical significance was set at 0.05. If a significant difference was found, a Bonferroni correction was performed (a = 0.025). All statistical analyses were performed using PASW Statistics ver. 18.0 (SPSS, Inc., Chicago, IL, USA). 3. Results The test–retest reliabilities for EMG measurement of GM, HAM, and ES muscle were substantial in both bridging with and without IHA. (Bridging with IHA: ICC = 0.98, 95% CI = 0.97–0.99, SEM = 1.72, and MDC = 4.77 for GM, and ICC = 0.96, 95% CI = 0.93–0.99, SEM = 3.38, and MDC = 9.37 for HAM, and ICC = 0.96, 95% CI = 0.93–0.99, SEM = 3.88, and MDC = 10.76 for ES; Bridging without IHA: ICC = 0.93, 95% CI = 0.85–0.99, SEM = 3.44, and MDC = 9.54 for GM, ICC = 0.95, 95% CI = 0.89–0.99, SEM = 4.52, and MDC = 12.53 for HAM, and ICC = 0.98, 95% CI = 0.97–0.99, SEM = 2.60, and MDC = 7.21 for ES). 3.1. Gluteus maximus, hamstrings, and erector spinae muscle activity In terms of muscle activity, there was a significant difference in GM muscle activity between bridging with IHA using the TheraBand and without IHA (F1,20 = 9.098, P = .007, ESI = .365). Bridging with IHA using the Thera-Band resulted in significantly greater GM muscle activity than bridging without IHA (P = .007) (Fig. 5). However, there were no significant differences in the activity of the HAM (F1,20 = 4.163, P = .055, ESI = .247) and ES (F1,20 = 0.319, P = .578, ESI = .064) between bridging with and without IHA. 3.2. Gluteus maximus/hamstrings and gluteus maximus/erector spinae muscle activity ratios In terms of muscle ratios, there were no significant differences in the GM/HAM (F1,20 = .014, P = .906) and GM/ES (F1,20 = .559.163, P = .463) ratios between bridging with and without IHA. 3.3. Anterior pelvic tilt angle With regard to pelvic kinematics, there was a significant difference in the anterior pelvic tilt angle between with IHA using the Thera-Band and without IHA (F1,20 = 15. 624, P = .001). Bridging
Fig. 5. Comparison of gluteus maximus muscle activity between bridging exercise with and without isometric hip abduction (GM: Gluteus maximus, IHA: Isometric hip abduction). ⁄p < 0.05.
Fig. 6. Comparison of anterior pelvic tilt angle between bridging exercise with and without isometric hip abduction (IHA: Isometric hip abduction). ⁄p < 0.05.
with IHA using the Thera-Band showed significantly lesser anterior pelvic tilt angle than bridging without IHA (P = .001) (Fig. 6). 4. Discussion To our knowledge, this study is the first to evaluate the effect of IHA with the Thera-Band on GM muscle activity and pelvic kinematics during a bridging exercise. The results partially supported the research hypothesis. GM activity increased significantly by 21.1% during bridging with IHA using the Thera-Band, supporting the research hypothesis. A possible explanation is that applying IHA with the TheraBand during bridging and maintaining hip abduction of 30° induced facilitation of the GM in advance before initiation of the bridging movement, consequently increasing GM muscle activity. Our present finding is in agreement with those of previous studies demonstrating the effect of muscle preactivation on muscle firing or force. Kyrolaïnen et al. (1999) emphasized the importance of the preactivation of leg extensor for increasing running speed. Specifically, preactivity of the gastrocnemius muscle functioned as a preparatory requirement to enhance muscle activity and the timing of muscular action with respect to ground contact during the running cycle. Mrdakovic et al. (2008) confirmed that when a knee extensor bench exercise was performed before a leg press exercise by means of muscle preactivation, an increased EMG signal was recorded from the vastus lateralis muscle. This result indicates that preactivation performance by a single-joint exercise increases the number of motor units recruited during a multi-joint exercise. The GM is quadrilateral in shape, and its fibers are obliquely directed inferiorly and laterally. It functions not only as a hip extensor, but also as a hip abductor and external rotator (Frank and Netter, 1987; McAndrew et al., 2006). In this study, hip abduction of 30° was sustained by two plastic poles placed vertically along the lateral aspect of the bilateral knee joints. Such hip abduction during bridging might facilitate GM activity in terms of the action of the GM as a hip abductor and external rotator. In a previous study, Kang et al. (2013) reported that the GM EMG amplitude was greatest at 30° of hip abduction during prone hip extension with knee flexion. Because the GM is a fusiform muscle that is optimized when the direction of muscle pull is parallel to the muscle fiber, hip abduction during prone hip extension with knee flexion leads to an increased EMG amplitude of the GM. It was expected that HAM and ES activity would be reduced when GM activity was increased by applying IHA with the TheraBand during bridging exercise. This hypothesis was based on the findings of previous studies demonstrating that synergistic muscles work together to perform the same range of motion (Jonkers et al., 2003; Kang et al., 2013; Park et al., 2013). Based on these findings, synergistic muscles during bridging (i.e., trunk extensors
Please cite this article in press as: Choi S-A et al. Isometric hip abduction using a Thera-Band alters gluteus maximus muscle activity and the anterior pelvic tilt angle during bridging exercise. J Electromyogr Kinesiol (2014), http://dx.doi.org/10.1016/j.jelekin.2014.09.005
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such as the GM, HAM, and ES) can affect one another during bridging: increased GM activity could reduce HAM and ES activity. Although GM activity was significantly increased in this study, it failed to elicit significant changes in the GM/HAM and GM/ES ratios between bridging with and without IHA. The unexpected findings in this study may be the result of several differences from previous studies. First, healthy subjects participated in the present study and exhibited HAM or ES activity that was dominant to (or greater than) the GM activity at the beginning of the study. In many previous studies that investigated GM activity during various bridging or prone hip extension exercises in healthy subjects, the mean activity levels of the ES and HAM at baseline (i.e., before the intervention) were less than or similar to the mean value for the GM (Ekstrom et al., 2007, 2008; Kang et al., 2013; Sakamoto et al., 2009). However, because the mean value of HAM and ES muscle activity was about 1.8 and 2.5 times that of the GM, respectively, during bridging without IHA in this study (without intervention or at entry), bridging with IHA would not likely lead to significant decreases in the dominant HAM and ES in a crosssectional study. Second, because a wooden target bar was used to control pelvic lift during bridging, increased activation of the HAM and ES was not likely to occur in the present study. No previous studies have recommended the most appropriate level of pelvic lifting during bridging during bridging can be disadvantageous due to potential overactivation of the already-dominant HAM and ES; thus, a wooden target bar was placed to provide contact, cueing the subjects not to over-lift the pelvis while performing the two types of bridging. However, this valid use of a wooden target bar could have limited the level of the lumbopelvis and consequently might have prevented overactivation of the HAM and ES during bridging. Thus, HAM and ES activity may have differed if the subjects had performed bridging without a wooden target bar. The anterior pelvic tilt angle decreased significantly by 20.5% during bridging with IHA using the Thera-Band, supporting the research hypothesis. Although the change of anterior pelvic tilt angle was small, it could be a meaningful result in consideration of measurement position because anterior pelvic tilt was measured in bridging position in this study. Lembeck et al. (2005) reported that average pelvic tilt angle in the lying position was lower than standing position. Thus, bridging with IHA using a Thera-Band resulted in facilitation of the GM in advance, and the increased GM activity could have contributed to reduce anterior pelvic tilt. In other words, when the femur was fixed, such as bridging position, contraction of the GM induced the pelvis to move posteriorly and decrease anterior pelvic tilt and lumbar lordosis. Many previous studies have emphasized that an important function of the GM is to maintain pelvic stability. Oh et al. (2007) suggested that performance of the abdominal drawing-in maneuver during prone hip extension encouraged activation of the hip extensors while decreasing activation of the ES and reducing the anterior pelvic tilt. They explained that increased GM muscle activity could be affected by biomechanical alterations such as a reduced anterior pelvic tilt. Tateuchi et al. (2012) focused on improvements in hip muscle balance between agonists and antagonists, which could reduce the anterior pelvic tilt. An altered balance in muscle activation, especially a hip flexor (tensor fasciae latae) dominant to the hip extensors (GM and semitendinosus), during prone hip extension resulted in abnormal movement patterns, such as anterior pelvic tilt and excessive lumbar extension. Our study has several limitations. First, measurement errors were likely to have occurred when measuring the pelvic kinematics because this study used only two-dimensional image processing software. A three-dimensional or real-time measuring system will be needed to improve the precision of measurement in future studies. Second, the findings of this study are difficult to generalize
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to the entire patient population because only healthy and young subjects participated. Subjects with a broad age range and clinical symptoms such as GM weakness should be investigated in future to strengthen the clinical implications of this study. Third, this study did not perform force measurement. It could help to further differentiate between the two exercise protocols and EMG/force data would be interesting indications for future studies in this filed. Finally, this study used a cross-sectional design. Future longitudinal studies are necessary to identify distinct differences and the long-term effects of facilitation of the GM on HAM and ES activity. 5. Conclusion This study investigated the effects of bridging with IHA using a Thera-Band on GM, HAM, and ES activity; the GM/HAM and ES ratios; and the anterior pelvic tilt angle. GM muscle activity increased significantly and the anterior pelvic tilt angle decreased significantly during bridging with IHA using a Thera-Band. These findings indicate that the application of a Thera-Band facilitates the GM in advance before the initiation of bridging, consequently enhances GM activity, and prevents excessive anterior pelvic tilt during bridging. Therefore, bridging with IHA using the Thera-Band can be implemented as an effective method to facilitate GM muscle activity and reduce the anterior pelvic tilt angle. Conflict of interest The authors declare that they have no conflict of interest. References Bolgla LA, Uhl TL. Reliability of electromyographic normalization methods for evaluating the hip musculature. J Electromyogr Kinesiol 2007;17(1):102–11. Bolgla LA, Malone TR, Umberger BR, Uhl TL. Reliability of electromyographic methods used for assessing hip and knee neuromuscular activity in females diagnosed with patellofemoral pain syndrome. J Electromyogr Kinesiol 2010;20:142–7. Chaitow L. Muscle energy techniques. London (UK): Churchill Livingstone; 1996. Cichanowski HR, Schmitt JS, Johnson RJ, Niemuth PE. Hip strength in collegiate female athletes with patellofemoral pain. Med Sci Sports Exerc 2007;39(8): 1227–32. Criswell E. Cram’s introduction to surface electromyography. 2nd ed. Sudbury (MA): Jones and Bartlett Publishers; 2011. Decker MJ, Hintermeister RA, Faber KJ, Hawkins RJ. Serratus anterior muscle activity during selected rehabilitation exercises. Am J Sports Med 1999;27(6):784–91. Ekstrom RA, Donatelli RA, Carp KC. Electromyographic analysis of core trunk, hip, and thigh muscles during 9 rehabilitation exercises. J Orthop Sports Phys Ther 2007;37(12):754–62. Ekstrom RA, Osborn RW, Hauer PL. Surface electromyographic analysis of the low back muscles during rehabilitation exercises. J Orthop Sports Phys Ther 2008;38(12):736–45. Frank H, Netter R. The CIBA collection of medical illustrations: musculoskeletal system. vol. 8. Summit, NJ: Ciba-Geigy Corp; 1987. Fredericson M, Cookingham CL, Chaudhari AM, Dowdell BC, Oestreicher N, Sahrmann SA. Hip abductor weakness in distance runners with iliotibial band syndrome. Clin J Sport Med 2000;10(3):169–75. Friel K, McLean N, Myers C, Caceres M. Ipsilateral hip abductor weakness after inversion ankle sprain. J Athl Train 2006;41(1):74–8. Hewett TE, Myer GD, Ford KR. Anterior cruciate ligament injuries in female athletes: Part 1, mechanisms and risk factors. Am J Sports Med 2006;34(2):299–311. Hossain M, Nokes LD. A model of dynamic sacroiliac joint instability from malrecruitment of gluteus maximus and biceps femoris muscles resulting in low back pain. Med Hypotheses 2005;65(2):278–81. Ireland ML, Willson JD, Ballantyne BT, Davis IM. Hip strength in females with and without patellofemoral pain. J Orthop Sports Phys Ther 2003;33(11):671–6. Jonkers I, Stewart C, Spaepen A. The complementary role of the plantar flexors, hamstrings and gluteus maximus in the control of stance limb stability during gait. Gait Posture 2003;17:264–72. Kang SY, Jeon HS, Kwon O, Cynn HS, Choi BR. Activation of the gluteus maximus and hamstring muscles during prone hip extension with knee flexion in three hip abduction positions. Man Ther 2013;18(4):303–7. Kendall FP, McCreary EK, Provance PG. Muscles: Testing and Function With Posture and Pain. 5th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2005. Kyrolaïnen H, Komi PV, Belli A. Changes in muscle activity patterns and kinetics with increasing running speed. J Strength Cond Res 1999;13(4):400–6.
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Sil-Ah Choi received her B.S. degree in Physical Therapy from Yonsei University, and M.S. degree in Physical Therapy from Yonsei University. She is a member of applied kinesiology and ergonomic technology laboratory. Her research focuses on the musculoskeletal problems and movement disorders, especially in muscle imbalance and dysfunction of hip, knee, and shoulder joint, using the electromyograpic system.
Heon-Seock Cynn is a professor in the Department of Physical Therapy at the College of Health Science of Yonsei University. He received B.S. degree in Physical Therapy from Yonsei University, M.A. degree in Physical Therapy from New York University, and Ph.D. degree in Physical Therapy from Yonsei University. He was a full time lecturer of Seoul Health College and an associate professor of Hanseo University. He is a director of applied kinesiology and ergonomic technology laboratory, and his research interests are identification of etiologic factors, classification, and intervention approaches for movement disorders and musculoskeletal diseases.
Chung-Hwi Yi received his Ph.D. degree in physical therapy from Yonsei University in 1990. He joined the Department of Rehabilitation Therapy of Yonsei University in 1993. He was a president of The Korean Academy of University Trained Physical Therapists. From 1993 onwards he has been employed as a professor in the Department of Physical Therapy at the College of Health Science of Yonsei University. His research interests include motion, posture analysis, and the development of outcome measures for evaluating disability.
Oh-Yun Kwon is a professor in the Department of Physical Therapy at the College of Health Science of Yonsei University. He received his B.S. degree in Physical therapy and M.P.H. degree from Yonsei University in 1986 and 1992 respectively, and Ph.D. degree from Keimyung University in 1998. He had research experience in Program in Physical Therapy at Washington University in St Louis as a Post Doctoral Fellow. He is a director in Lab of Kinetic Ergocise based on Movement Analysis (KEMA). He is interested in the mechanisms of movement impairment, movement analysis, and prevention and management of the work related musculoskeletal pain syndrome.
Tae-Lim Yoon is a professor in the Department of Physical Therapy at the College of Health and Wallfare of Woosong University and Ph.D. Candidate in the Department of Physical Therapy at the Graduate School of Yonsei University. He received B.S. degree in Physical Therapy from Yonsei University, M.A. degree in Physical Therapy from New York University. He is a member of applied kinesiology and ergonomic technology laboratory, and his research interests are movement analysis, human factors and ergonomics, and prevention and management of musculoskeletal problems.
Woo-Jeong Choi is a M.S. Student in the Department of Physical Therapy at the Graduate School of Yonsei University. She received B.S. degree in Physical Therapy from Yonsei University in 2013. She is a member of applied kinesiology and ergonomic technology laboratory. Her research interests include electromyographic and kinematic analysis of therapeutic exercise for musculoskeletal syndromes, including scapular dyskinesis.
Ji-Hyun Lee is a Ph.D. Student in the Department of Physical Therapy at the Graduate School of Yonsei University. She received B.S. degree in Physical Therapy from Hanseo University, M.S. degree in Physical Therapy from Yonsei University. She is a member of applied kinesiology and ergonomic technology laboratory, and she is a part time lecturer of Yonsei University. Her main research interests are shoulder and hip assessment and treatment strategy. Her papers have been published in several international journals in these fields.
Please cite this article in press as: Choi S-A et al. Isometric hip abduction using a Thera-Band alters gluteus maximus muscle activity and the anterior pelvic tilt angle during bridging exercise. J Electromyogr Kinesiol (2014), http://dx.doi.org/10.1016/j.jelekin.2014.09.005
