645
Journal of Back and Musculoskeletal Rehabilitation 28 (2015) 645–649 DOI 10.3233/BMR-140560 IOS Press
Effects of bridge exercises with a sling and vibrations on abdominal muscle thickness in healthy adults Won-tae Gong Department of Physical Therapy, Korea Nazarene University, Wolbong Ro 48, Seobuk-gu, Cheonan-Si, Chungcheongnam-do 330-718, Korea Tel.: +82 41 570 4286; Fax: +82 41 570 7925; E-mail: [email protected]
Abstract. In the present study, we aimed to examine the changes in the thickness of the transversus abdominis (TrA) and internal oblique (Io) muscles using ultrasonography in adults who performed bridge exercises with the abdominal drawing-in maneuver and a sling and received micro vibrations. In total, 32 subjects were divided into a therapy (n = 16) and control (n = 16) groups. The therapy group completed nine sets, with four repetitions, of bridge exercises with the sling and received vibrations. The control group completed nine sets, with four repetitions, of bridge exercises with the sling and did not receive vibrations. The thicknesses of the TrA and Io muscles were measured in both groups using ultrasonography before and after therapy. According to the pressure applied to the biofeedback unit, both groups showed significant changes in the thicknesses of the TrA and Io muscles after therapy (P < 0.05). The change in the thickness of the TrA muscle after therapy was significantly different between the 2 groups when the pressures applied at 38, 42, and 46 mmHg (P < 0.05). Moreover, the change in the thickness of the Io muscle did not significantly different between the 2 groups at any of the pressures applied (P > 0.05). These findings indicate that approximately 15 minutes of vibrations during bridge exercises on unstable surfaces with a sling facilitates the activation of the deep trunk muscles and further enhances the activation of the TrA. Keywords: Bridge exercise, ultrasonography, transversus abdominis, vibration
1. Introduction Low back pain (LBP) is a musculoskeletal system disease that frequently occurs in modern society. Most people experience LBP at least once during their lifetime, and recurrence is common even after treatment. Compared to healthy individuals, patients with LBP have atrophied deep trunk muscles and declined proprioception. These conditions cause problems in spinal stability, which leads to the recurrence of pain [1]. Therefore, the recovery of spinal stability is important in the treatment and prevention of LBP. The improvement of lumbar stability is effective in treating LBP and prevents recurrences regardless of the cause or the results of the pain [2]. Bridge exercises are closed kinetic chain exercises. They can improve lumbar stability and are effective in
recovering the ability to control trunk muscles because they induce contraction and improve coordination of the transversus abdominis (TrA) as well as the superficial muscles of the trunk [3]. Muscles that contribute to lumbar stability include the TrA, internal oblique (Io), and external oblique (Eo) muscles in the abdomen as well as the quadratus lumborum, multifidus, and pelvic floor muscles [4]. It has been reported that movement causes the activation of the TrA at an earlier stage as compared to other muscles, thus contributing to trunk stability [5]. Many studies have investigated the function of the TrA in relation to lumbar stabilization and balanceas well as the effects of these parameters on muscle thickness. A previous study indicated that lumbar stabilization exercises increase the thickness of the TrA [6]. Recently, studies investigating lumbar stabilization ex-
c 2015 – IOS Press and the authors. All rights reserved ISSN 1053-8127/15/$35.00
646
W. Gong / Effects of bridge exercises with a sling and vibrations on abdominal muscle thickness in healthy adults
ercises have utilized various devices, such as unstable surfaces, balance disks, therapeutic balls, and sponge pads. O’Sullivan et al. [7] stated that performing stabilization exercises in a dynamic environment (e.g. therapeutic balls) rather than in a static environment maximizes balancing ability, and Page [8] suggested that exercises utilizing unstable devices were effective in recovering postural control and proprioception. Using ultrasonography, Saliba et al. [9] showed that bridge exercises with hip abduction on unstable surfaces with slings were more effective in activating the TrA compared to bridge exercises with hip abduction on stable surfaces. Previous studies reported that bridge exercises improved lumbar stability by activating the TrA and were also effective in changing its thickness. However, to our knowledge, no previous studies have investigated the effect of bridge exercises, along with abdominal drawing-in maneuver, with a sling and micro vibration application, on TrA activation. In the present study, we hypothesized that bridge exercises with a sling, along with the abdominal drawing-in maneuver,and micro vibrationswould be effective for TrA activation.Therefore, in the present study, using ultrasonography, we aimed to assess the changes in TrA activation, which is a measure of lumbar stability, following the application of bridge exerciseswith a sling, along with the abdominal drawing-in maneuver, and micro vibrations in healthy adults.
2. Methods 2.1. Participants Thirty-two university students participated in the study. The subjects were randomly assigned to either a therapy group (16 subjects; 8 men and 8 women) or control group (16 subjects; 8 men and 8 women). The mean age of the therapy group was 23.17 ± 2.14 years with a mean height and weight of 169.61 ± 7.26 cm and 65.83 ± 13.17 kg, respectively. The mean age of the control group was 23.72 ± 1.40 years with a mean height and weight of 169.38 ± 10.96 cm and 63.55 ± 13.30 kg, respectively. There were no statistically significant differences between the two groups (P > 0.05). Only healthy adult male and female subjects were included in the study. Individuals with muscular, skeletal, or nervous system problems or individuals who could not perform the bridge exercises due to chronic pain in the waist, pelvis, knee, or ankle were
excluded. All the participants understood the purpose of this study and provided written informed consent prior to their participation, in accordance with the ethical standards of the Declaration of Helsinki. 2.2. Intervention The therapy group performed bridge exercises with a sling and received vibrations, and the control group performed the bridge exercises with a sling only. Two types of bridge exercises were completed, including a supine position bridge exercise and a prone position bridge exercise. Before the exercises, the abdominal drawing-in maneuver was applied to enhance the stability of the trunk [10]. During the supine position bridge exercise, each subject was placed in the supine position on the table with both hands on their chest and both feet in a narrow sling. The sling suspension point was placed on a line perpendicular to the calcaneus, and the height of the sling was adjusted so that the hip and knee joints were at an angle of 90◦ before the bridge exercises were initiated. The exercises were then completed by extending the legs. During the exercise, the weight was loaded on both the lower limbs without any pelvic tilt and the trunk, pelvis, and lower limbs were lifted so that they were in a straight line. During the prone position bridge exercise, each subject was placed in the prone position on the table, with their weight on the elbows, and while maintaining a 90◦ angle at the shoulder and elbow joints. The distal part of both tibias were then placed in a narrow sling. The sling suspension point was then placed on a line perpendicular to the distal part of both tibias, and the height of the sling was adjusted so that the lateral malleolus and scapula were horizontal to each other before the bridge exercise was initiated. During the exercise, the weight was loaded on both the lower limbs without any pelvic tilt, and the trunk, pelvis, and lower limbs were lifted so that they were in a straight line. The supine and prone position bridge exercises were repeated four times per set, and each bridge position was maintained for approximately 2 seconds followed by a 3 seconds rest period. In total, nine sets of the exercises were performed for approximately 15 minutes with a 1-minute rest period between each set. For the therapy group, the vibration equipment R Stimula, Norway) was installed on ropes (Redcord on both sides of the sling that supported both lower limbs, and microvibrations were applied to the trunk. The vibrations were applied only while the bridge exercise was performed, by operating a switch. The vi-
W. Gong / Effects of bridge exercises with a sling and vibrations on abdominal muscle thickness in healthy adults
647
Fig. 1. Bridge exercise and vibration equipment.
tanooga Group, Australia) was placed below the waist and the subject was instructed by a physical therapist (with more than 10 years of clinical experience)to increase the pressure of the PBU to 30, 34, 38, 42, and 46 mmHg. The thicknesses of the TrA and Io muscles were measured at each pressure value. 2.4. Analysis
Fig. 2. Measurement of TrA and Io.
brations were not applied during the rest period. A vibration frequency of 15 Hz was applied during the first three exercise sets, a vibration frequency of 20 Hz was applied during the three middle exercise sets, and a vibration frequency of 30 Hz was applied during the final three exercise sets (Fig. 1).
The therapy results were analyzed using SPSS 12.0 KO (SPSS, Chicago, IL, USA). After the general characteristics of the subjects were assessed, repeated oneway analysis of variance was performed to examine the thicknesses of the TrA and Io in each group in relation to the pressures applied. Paired t-tests were used to compare the pre-test and post-test thicknesses of the TrA and Io in each group. The differences between the 2 groups were tested using independent t-tests. The statistical significance level, α, was set at 0.05.
2.3. Outcome measures
3. Results
Ultrasonography (MysonoU5, Samsung Medison, Korea) was used to examine the changes in the thicknesses of the TrA and Io before and after the bridge exercises using a 12-MHz linear probe. Ultrasonography was conducted by a clinician who was experienced in ultrasonic imaging. First, the subject was instructed to lie comfortably in a supine position. A triangular pillow was then placed below the knee joints to relax the lower limbs, and the probe was placed transversely on the top of the right iliac crest and moved toward the center of the abdomen. The probe was adjusted until the Eo, TrA, and Io were completed observed. The muscle thicknesses of TrA and Io were measured on the ultrasonography monitor for approximately 5 minutes at a point 13 mm away from where the fascia of the Io and TrA meet [11] (Fig. 2). When the TrA and Io muscle thicknesses were being measured, a pressure biofeedback unit (PBU) (Chat-
The changes in the thickness of the TrA and Io muscles before and after therapy were significantly increase in both groups when the pressures applied to the PBU were increased (P < 0.05). Moreover, the change in thickness of the TrA after therapy was significantly different between the groups when the pressures applied to the PBU at 38, 42 and 46 mmHg (P < 0.05). However, the change in the thickness of the Io after therapy did not significantly differ between the 2 groups at any of the pressures applied to the PBU (P > 0.05) (Table 1).
4. Discussion The results of the present study indicated that the TrA and Io muscle thicknesses increased as pressure applied to the waist increased. In particular, the addi-
648
W. Gong / Effects of bridge exercises with a sling and vibrations on abdominal muscle thickness in healthy adults
Table 1 Comparison of changes in the muscle thicknesses of the TrA and the Io in the therapy group and the control group in relation to the pressure applided (unit: pressure-MHg) Period Muscle Group 30 Tra pre Exp* 0.32 Cont* 0.35 post Exp* 0.34 Cont* 0.36 Io
pre post
Exp* Cont* Exp* Cont*
0.52 0.51 0.55 0.53
34 0.40 0.42 0.42 0.43
38 0.45 0.43 0.53 0.46p
42 0.46 0.46 0.58 0.46p
46 0.48 0.49 0.62 0.52p
0.60 0.59 0.61 0.61
0.66 0.66 0.72 0.66
0.73 0.71 0.79 0.73
0.81 0.79 0.84 0.82
Tra: transverse abdominis muscle, Io: internal oblique muscle,Ther: therapy group, Cont: control group; ∗ significantly different for pres† sure (repeated one way ANOVA); significantly different for group (independent t-test); significantly different for period (paired ttest).
tion of micro vibrations to the lumbar stabilization exercises on an unstable surface with a sling (to facilitate the stimulation of the deep muscles) further increased the TrA muscle thickness compared to the same exercises with a sling on a similar surface without the application of vibrations. These results indicate that healthy adults who performed bridge exercises with a sling, along with the abdominal drawing-in maneuver, and received micro vibrations showed improved activation and contraction of the TrA (a deep muscle) by facilitating proprioception. Lumbar stabilization exercises are used to treat patients with LBP, and can reduce instability and repetitive damage to the muscles around the spine; these exercises may also protect the vertebral joints and can help recover the capability for spinal adjustment. It has been reported that lumbar stability is improved through co-contraction of trunk muscles [12]. To improve lumbar stability, different bridge exercises have been developed, such as supine position bridge, prone position bridge, both-legs support bridge, one-leg support bridge, bridge with hip abduction, bridge with hip adduction, bridge on a stable surface, and bridge on an unstable surface. In the present study, the changes in the muscle thickness of the TrA caused by bridge exercises, along with the abdominal drawing-in maneuver,on unstable surfaces with a sling and micro vibrations were examined using ultrasonography. Ultrasonography can provide visual biofeedback, is portable, and not only enables muscle activity imaging in real time [13] but also the selective measurement of deep muscles [14]. The abdominal drawing-in method was applied during the bridge exercises because this can increase the activation of the TrA, and thus reduce hyper lordosis [15]. Previous studies reported that the muscle activity of the trunk and thickness of the deep abdominal mus-
cles increased to a greater extent when lumbar stability exercises were performed on unstable surfaces than when these exercises were performed on stable surfaces. Gregory et al. [16] stated that the addition of unstable surfaces to existing exercises further enhanced the activation of many muscles. Using ultrasonography, Saliba et al. [9] showed that bridge exercises performed on unstable surfaces using a sling were more effective for TrA activation than bridge exercises on stable surfaces in 51 patients with chronic LBP. In addition, Brumagne et al. [17] measured the lumbo-sacral position sensein 23 young patients with LBP and 21 control subjects when lumbar paraspinal muscle vibrations were applied. They found that position sense was improved in the LBP group because the vibrations improved proprioception and enhanced local muscle control. These results are partially consistent with the results of the present study, which indicated that micro vibrations are effective inactivating the TrA.
5. Conclusion In the present study, the changes in the muscle thickness of the TrA caused by bridge exercises, along with the abdominal drawing-in maneuver, on unstable surfaces with a sling and micro vibrations were examined using ultrasonography. Thirty-two healthy university students were selected and randomly divided into a therapy (n = 16) and control (n = 16) group. The therapy group performed bridge exercises with a sling and received vibrations, and the control group performedbridge exercises with a sling only. A higher pressure applied to the waist results in a greater activation of the TrA and Io muscles. In addition, the muscle thickness of TrA was greater in the therapy group in which the micro vibrations were applied than in the control group. In conclusion, adding micro vibrations during bridge exercises on unstable surfaces with a sling facilitates the activation of the deep trunk muscles, thus enhancing the muscle thickness of the TrA. Therefore, applying micro vibrations during bridge exercises with a sling for lumbar stability in clinics is recommended for the enhancement of TrA muscle thickness.
Acknowledgment This research was supported by the Korea Nazarene University Research Grants in 2015.
W. Gong / Effects of bridge exercises with a sling and vibrations on abdominal muscle thickness in healthy adults
References [9] [1]
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O’Sullivan PB, Burnett A, Floyd AN, Gadsdon K, Logiudice J, Miller D, Quirke H. Lumbar repositioning deficit in a specific low back pain population. Spine (Phila Pa 1976). 2003 May 15; 28(10): 1074-9. Luoto S, Aalto H, Taimela S, Hurri H, Pyykkö I, Alaranta H. One-footed and externally disturbed two-footed postural control in patients with chronic low back pain and healthy control subjects. A controlled study with follow-up. Spine. 1998; 23(19): 2081-90. Stevens VK, Coorevits PL, Bouche KG, Mahieu NN, Vanderstraeten GG, Danneels LA. The influence of specific training on trunk muscle recruitment patterns in healthy subjects during stabilization exercises. Man Ther. 2007; 12(3): 271-9. O’Sullivan PB, Grahamslaw KM, Kendell M, Lapenskie SC, Möller NE, Richards KV. The effect of different standing and sitting postures on trunk muscle activity in a pain-free population.Spine. 2002; 27(11): 1238-44. Hodges PW, Richardson CA. Inefficient Muscular Stabilization of the Lumbar Spine Associated With low back pain: A Motor Control Evaluation of TransversusAbdominis. Spine. 1996; 21(22): 2640-2650. Hides J, Wilson S, Stanton W, McMahon S, Keto H, McMahon K, Bryant M, Richardson C. An MRI investigation into the function of the transversusabdominis muscle during “rawing-in” of the abdominal wall. Spine. 2006; 31(6): E175E178. O’Sullivan PB, Phyty GD, Twomey LT, Allison GT. Evaluation of specific stabilizing exercise in the treatment of chronic low back pain with radiologic diagnosis of spondylolysis or spondylolisthesis. Spine. 1997; 22(24): 2959-67. Page P. Sensorimotor training: A “global” approach for bal-
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ancetraining. K Body MovTher. 2006; 10(1): 77-84. Saliba SA, Croy T, Guthrie R, Grooms D, Weltman A, Grindstaff TL.Differences in transverse abdominis activation with stable and unstable bridging exercises in individuals with low back pain.North American Journal of Sports Physical Therapy. 2010; 5(2): 63-73. Liebenson C. Spinal stabilization training: the transverse abdominus. Journal of Bodywork and Movement Therapies. 1998; 2(4): 218-223. Endleman I, Critchley DJ: Transversusabdominis and obliquusinternus activity during pilates exercises: measurement with ultrasound scanning. Arch Phys Med Rehabil, 2008; 89(11): 2205-2212. Stevens VK, Coorevits PL, Bouche KG et al. Theinfluence of specific training on trunk muscle recruitment patterns in healthy subjects during stabilization exercises. Man Ther. 2007; 12(3): 271-279. Kermode F. Benefits of utilising real-time ultrasound imaging in the rehabilitation of the lumbar spine sabilising muscles following low back injury in the elite athlete-a single case study. Physical Therapy in sport, 2004; 5(1): 13-16. Whittaker JL. Ultrasound imaging for rehabilitation of the lumbopelvicregion: A clinical approach. Edinburgh: Elsevier science; 2007. Panjabi MM. Clinical spinal instability and low back pain. J Electromyogr Kinesiol. 2003; 13(4): 371-379. Lehman GJ, Hoda W, Oliver S. Trunk muscle activity during ridging exercises on and off a Swissball. Chiropractic & Osteopathy. 2005; 13(14): 1-8. Brumagne S, Cordo P, Lysens R, Verschueren, S, Swinnen S. The role of paraspinal muscle spindles in umbosacral position sense in individuals with and without low back pain.Spine. 2000; 25(8): 989-994.
Journal of Back and Musculoskeletal Rehabilitation 28 (2015) 645–649 DOI 10.3233/BMR-140560 IOS Press
Effects of bridge exercises with a sling and vibrations on abdominal muscle thickness in healthy adults Won-tae Gong Department of Physical Therapy, Korea Nazarene University, Wolbong Ro 48, Seobuk-gu, Cheonan-Si, Chungcheongnam-do 330-718, Korea Tel.: +82 41 570 4286; Fax: +82 41 570 7925; E-mail: [email protected]
Abstract. In the present study, we aimed to examine the changes in the thickness of the transversus abdominis (TrA) and internal oblique (Io) muscles using ultrasonography in adults who performed bridge exercises with the abdominal drawing-in maneuver and a sling and received micro vibrations. In total, 32 subjects were divided into a therapy (n = 16) and control (n = 16) groups. The therapy group completed nine sets, with four repetitions, of bridge exercises with the sling and received vibrations. The control group completed nine sets, with four repetitions, of bridge exercises with the sling and did not receive vibrations. The thicknesses of the TrA and Io muscles were measured in both groups using ultrasonography before and after therapy. According to the pressure applied to the biofeedback unit, both groups showed significant changes in the thicknesses of the TrA and Io muscles after therapy (P < 0.05). The change in the thickness of the TrA muscle after therapy was significantly different between the 2 groups when the pressures applied at 38, 42, and 46 mmHg (P < 0.05). Moreover, the change in the thickness of the Io muscle did not significantly different between the 2 groups at any of the pressures applied (P > 0.05). These findings indicate that approximately 15 minutes of vibrations during bridge exercises on unstable surfaces with a sling facilitates the activation of the deep trunk muscles and further enhances the activation of the TrA. Keywords: Bridge exercise, ultrasonography, transversus abdominis, vibration
1. Introduction Low back pain (LBP) is a musculoskeletal system disease that frequently occurs in modern society. Most people experience LBP at least once during their lifetime, and recurrence is common even after treatment. Compared to healthy individuals, patients with LBP have atrophied deep trunk muscles and declined proprioception. These conditions cause problems in spinal stability, which leads to the recurrence of pain [1]. Therefore, the recovery of spinal stability is important in the treatment and prevention of LBP. The improvement of lumbar stability is effective in treating LBP and prevents recurrences regardless of the cause or the results of the pain [2]. Bridge exercises are closed kinetic chain exercises. They can improve lumbar stability and are effective in
recovering the ability to control trunk muscles because they induce contraction and improve coordination of the transversus abdominis (TrA) as well as the superficial muscles of the trunk [3]. Muscles that contribute to lumbar stability include the TrA, internal oblique (Io), and external oblique (Eo) muscles in the abdomen as well as the quadratus lumborum, multifidus, and pelvic floor muscles [4]. It has been reported that movement causes the activation of the TrA at an earlier stage as compared to other muscles, thus contributing to trunk stability [5]. Many studies have investigated the function of the TrA in relation to lumbar stabilization and balanceas well as the effects of these parameters on muscle thickness. A previous study indicated that lumbar stabilization exercises increase the thickness of the TrA [6]. Recently, studies investigating lumbar stabilization ex-
c 2015 – IOS Press and the authors. All rights reserved ISSN 1053-8127/15/$35.00
646
W. Gong / Effects of bridge exercises with a sling and vibrations on abdominal muscle thickness in healthy adults
ercises have utilized various devices, such as unstable surfaces, balance disks, therapeutic balls, and sponge pads. O’Sullivan et al. [7] stated that performing stabilization exercises in a dynamic environment (e.g. therapeutic balls) rather than in a static environment maximizes balancing ability, and Page [8] suggested that exercises utilizing unstable devices were effective in recovering postural control and proprioception. Using ultrasonography, Saliba et al. [9] showed that bridge exercises with hip abduction on unstable surfaces with slings were more effective in activating the TrA compared to bridge exercises with hip abduction on stable surfaces. Previous studies reported that bridge exercises improved lumbar stability by activating the TrA and were also effective in changing its thickness. However, to our knowledge, no previous studies have investigated the effect of bridge exercises, along with abdominal drawing-in maneuver, with a sling and micro vibration application, on TrA activation. In the present study, we hypothesized that bridge exercises with a sling, along with the abdominal drawing-in maneuver,and micro vibrationswould be effective for TrA activation.Therefore, in the present study, using ultrasonography, we aimed to assess the changes in TrA activation, which is a measure of lumbar stability, following the application of bridge exerciseswith a sling, along with the abdominal drawing-in maneuver, and micro vibrations in healthy adults.
2. Methods 2.1. Participants Thirty-two university students participated in the study. The subjects were randomly assigned to either a therapy group (16 subjects; 8 men and 8 women) or control group (16 subjects; 8 men and 8 women). The mean age of the therapy group was 23.17 ± 2.14 years with a mean height and weight of 169.61 ± 7.26 cm and 65.83 ± 13.17 kg, respectively. The mean age of the control group was 23.72 ± 1.40 years with a mean height and weight of 169.38 ± 10.96 cm and 63.55 ± 13.30 kg, respectively. There were no statistically significant differences between the two groups (P > 0.05). Only healthy adult male and female subjects were included in the study. Individuals with muscular, skeletal, or nervous system problems or individuals who could not perform the bridge exercises due to chronic pain in the waist, pelvis, knee, or ankle were
excluded. All the participants understood the purpose of this study and provided written informed consent prior to their participation, in accordance with the ethical standards of the Declaration of Helsinki. 2.2. Intervention The therapy group performed bridge exercises with a sling and received vibrations, and the control group performed the bridge exercises with a sling only. Two types of bridge exercises were completed, including a supine position bridge exercise and a prone position bridge exercise. Before the exercises, the abdominal drawing-in maneuver was applied to enhance the stability of the trunk [10]. During the supine position bridge exercise, each subject was placed in the supine position on the table with both hands on their chest and both feet in a narrow sling. The sling suspension point was placed on a line perpendicular to the calcaneus, and the height of the sling was adjusted so that the hip and knee joints were at an angle of 90◦ before the bridge exercises were initiated. The exercises were then completed by extending the legs. During the exercise, the weight was loaded on both the lower limbs without any pelvic tilt and the trunk, pelvis, and lower limbs were lifted so that they were in a straight line. During the prone position bridge exercise, each subject was placed in the prone position on the table, with their weight on the elbows, and while maintaining a 90◦ angle at the shoulder and elbow joints. The distal part of both tibias were then placed in a narrow sling. The sling suspension point was then placed on a line perpendicular to the distal part of both tibias, and the height of the sling was adjusted so that the lateral malleolus and scapula were horizontal to each other before the bridge exercise was initiated. During the exercise, the weight was loaded on both the lower limbs without any pelvic tilt, and the trunk, pelvis, and lower limbs were lifted so that they were in a straight line. The supine and prone position bridge exercises were repeated four times per set, and each bridge position was maintained for approximately 2 seconds followed by a 3 seconds rest period. In total, nine sets of the exercises were performed for approximately 15 minutes with a 1-minute rest period between each set. For the therapy group, the vibration equipment R Stimula, Norway) was installed on ropes (Redcord on both sides of the sling that supported both lower limbs, and microvibrations were applied to the trunk. The vibrations were applied only while the bridge exercise was performed, by operating a switch. The vi-
W. Gong / Effects of bridge exercises with a sling and vibrations on abdominal muscle thickness in healthy adults
647
Fig. 1. Bridge exercise and vibration equipment.
tanooga Group, Australia) was placed below the waist and the subject was instructed by a physical therapist (with more than 10 years of clinical experience)to increase the pressure of the PBU to 30, 34, 38, 42, and 46 mmHg. The thicknesses of the TrA and Io muscles were measured at each pressure value. 2.4. Analysis
Fig. 2. Measurement of TrA and Io.
brations were not applied during the rest period. A vibration frequency of 15 Hz was applied during the first three exercise sets, a vibration frequency of 20 Hz was applied during the three middle exercise sets, and a vibration frequency of 30 Hz was applied during the final three exercise sets (Fig. 1).
The therapy results were analyzed using SPSS 12.0 KO (SPSS, Chicago, IL, USA). After the general characteristics of the subjects were assessed, repeated oneway analysis of variance was performed to examine the thicknesses of the TrA and Io in each group in relation to the pressures applied. Paired t-tests were used to compare the pre-test and post-test thicknesses of the TrA and Io in each group. The differences between the 2 groups were tested using independent t-tests. The statistical significance level, α, was set at 0.05.
2.3. Outcome measures
3. Results
Ultrasonography (MysonoU5, Samsung Medison, Korea) was used to examine the changes in the thicknesses of the TrA and Io before and after the bridge exercises using a 12-MHz linear probe. Ultrasonography was conducted by a clinician who was experienced in ultrasonic imaging. First, the subject was instructed to lie comfortably in a supine position. A triangular pillow was then placed below the knee joints to relax the lower limbs, and the probe was placed transversely on the top of the right iliac crest and moved toward the center of the abdomen. The probe was adjusted until the Eo, TrA, and Io were completed observed. The muscle thicknesses of TrA and Io were measured on the ultrasonography monitor for approximately 5 minutes at a point 13 mm away from where the fascia of the Io and TrA meet [11] (Fig. 2). When the TrA and Io muscle thicknesses were being measured, a pressure biofeedback unit (PBU) (Chat-
The changes in the thickness of the TrA and Io muscles before and after therapy were significantly increase in both groups when the pressures applied to the PBU were increased (P < 0.05). Moreover, the change in thickness of the TrA after therapy was significantly different between the groups when the pressures applied to the PBU at 38, 42 and 46 mmHg (P < 0.05). However, the change in the thickness of the Io after therapy did not significantly differ between the 2 groups at any of the pressures applied to the PBU (P > 0.05) (Table 1).
4. Discussion The results of the present study indicated that the TrA and Io muscle thicknesses increased as pressure applied to the waist increased. In particular, the addi-
648
W. Gong / Effects of bridge exercises with a sling and vibrations on abdominal muscle thickness in healthy adults
Table 1 Comparison of changes in the muscle thicknesses of the TrA and the Io in the therapy group and the control group in relation to the pressure applided (unit: pressure-MHg) Period Muscle Group 30 Tra pre Exp* 0.32 Cont* 0.35 post Exp* 0.34 Cont* 0.36 Io
pre post
Exp* Cont* Exp* Cont*
0.52 0.51 0.55 0.53
34 0.40 0.42 0.42 0.43
38 0.45 0.43 0.53 0.46p
42 0.46 0.46 0.58 0.46p
46 0.48 0.49 0.62 0.52p
0.60 0.59 0.61 0.61
0.66 0.66 0.72 0.66
0.73 0.71 0.79 0.73
0.81 0.79 0.84 0.82
Tra: transverse abdominis muscle, Io: internal oblique muscle,Ther: therapy group, Cont: control group; ∗ significantly different for pres† sure (repeated one way ANOVA); significantly different for group (independent t-test); significantly different for period (paired ttest).
tion of micro vibrations to the lumbar stabilization exercises on an unstable surface with a sling (to facilitate the stimulation of the deep muscles) further increased the TrA muscle thickness compared to the same exercises with a sling on a similar surface without the application of vibrations. These results indicate that healthy adults who performed bridge exercises with a sling, along with the abdominal drawing-in maneuver, and received micro vibrations showed improved activation and contraction of the TrA (a deep muscle) by facilitating proprioception. Lumbar stabilization exercises are used to treat patients with LBP, and can reduce instability and repetitive damage to the muscles around the spine; these exercises may also protect the vertebral joints and can help recover the capability for spinal adjustment. It has been reported that lumbar stability is improved through co-contraction of trunk muscles [12]. To improve lumbar stability, different bridge exercises have been developed, such as supine position bridge, prone position bridge, both-legs support bridge, one-leg support bridge, bridge with hip abduction, bridge with hip adduction, bridge on a stable surface, and bridge on an unstable surface. In the present study, the changes in the muscle thickness of the TrA caused by bridge exercises, along with the abdominal drawing-in maneuver,on unstable surfaces with a sling and micro vibrations were examined using ultrasonography. Ultrasonography can provide visual biofeedback, is portable, and not only enables muscle activity imaging in real time [13] but also the selective measurement of deep muscles [14]. The abdominal drawing-in method was applied during the bridge exercises because this can increase the activation of the TrA, and thus reduce hyper lordosis [15]. Previous studies reported that the muscle activity of the trunk and thickness of the deep abdominal mus-
cles increased to a greater extent when lumbar stability exercises were performed on unstable surfaces than when these exercises were performed on stable surfaces. Gregory et al. [16] stated that the addition of unstable surfaces to existing exercises further enhanced the activation of many muscles. Using ultrasonography, Saliba et al. [9] showed that bridge exercises performed on unstable surfaces using a sling were more effective for TrA activation than bridge exercises on stable surfaces in 51 patients with chronic LBP. In addition, Brumagne et al. [17] measured the lumbo-sacral position sensein 23 young patients with LBP and 21 control subjects when lumbar paraspinal muscle vibrations were applied. They found that position sense was improved in the LBP group because the vibrations improved proprioception and enhanced local muscle control. These results are partially consistent with the results of the present study, which indicated that micro vibrations are effective inactivating the TrA.
5. Conclusion In the present study, the changes in the muscle thickness of the TrA caused by bridge exercises, along with the abdominal drawing-in maneuver, on unstable surfaces with a sling and micro vibrations were examined using ultrasonography. Thirty-two healthy university students were selected and randomly divided into a therapy (n = 16) and control (n = 16) group. The therapy group performed bridge exercises with a sling and received vibrations, and the control group performedbridge exercises with a sling only. A higher pressure applied to the waist results in a greater activation of the TrA and Io muscles. In addition, the muscle thickness of TrA was greater in the therapy group in which the micro vibrations were applied than in the control group. In conclusion, adding micro vibrations during bridge exercises on unstable surfaces with a sling facilitates the activation of the deep trunk muscles, thus enhancing the muscle thickness of the TrA. Therefore, applying micro vibrations during bridge exercises with a sling for lumbar stability in clinics is recommended for the enhancement of TrA muscle thickness.
Acknowledgment This research was supported by the Korea Nazarene University Research Grants in 2015.
W. Gong / Effects of bridge exercises with a sling and vibrations on abdominal muscle thickness in healthy adults
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