The Effects of Sling Exerci Using Vibration on
Trunk Muscle Activities of Healthy Adults
Y oungin C hoi, MSc, PT1), h YungkYu k ang, PhD, PT2)*
1) Department of Physical Therapy, the Graduate School, Hano University, Republic of Korea
2) Department of Physical Therapy, College of Natural Sciences, Kyungnam University: 449
Woryeong-dong, Masanhappo-gu, Changwon-si, Gyeongsangnam-do 631-701, Republic of Korea
Abstract.[Purpo] This study compared the effects of sling exercis with and without vibration on the muscu-lar activity of the internal oblique (IO), rectus abdominis (RA), multifidus (MF), and erector spinae (ES) muscles of healthy adults. [Methods] Eleven healthy university students (11 men) with a mean age of 22.8 years were enrolled in this study. Subjects performed supine and prone bridge exercis with the knees flexed using a sling suspen-sion system with and without vibration. The amplitudes of the EMG activities of lected trunk muscles (internal oblique, rectus abdominis, erector spinae, multifidus) were recorded. Two types of exerci conditions were ex-ecuted in a random quence for 5 conds each. The signals detected from the middle 3 conds (after discarding the sig
nals of the first and the last one conds) were ud in the analysis. A 3-minute break was given after each exerci to minimize muscle fatigue. [Results] During the supine bridge exerci with vibration, the activities of the IO, RA, MF, and ES muscles were significantly higher than tho of the supine bridge exerci without vibra-tion. Additionally, during the prone bridge exerci with vibration, the activities of the IO, RA, MF, and ES were significantly higher than tho of the prone bridge exerci without vibration. [Conclusion] Sling exercis with vibration improved the trunk muscle activities of healthy adults compared to the sling exercis without vibration.
The information prented here is important for clinicians who u lumbar stabilization exercis as an evaluation tool or a rehabilitation exerci.
Key words: Sling exerci, Vibration, Trunk muscle公共场所吸烟
(This article was submitted Apr. 8, 2013, and was accepted May 20, 2013)
INTRODUCTION
Stabilization exercis are exerci methods that focus on co-contraction of deep trunk muscles and improvement of spinal stability1). Stabilization exercis not only the im-prove strength and enduran
ce of deep trunk muscles, but also have the effect of maintaining dynamic stability by improving neuromuscular control2). Conquently, they are ud in a wide range of rehabilitation therapies for individu-als with low back pain3–5).
Coordination promotions between local and global mus-cles are necessary factors of efficient lumbar stabilization6). Activities of a single muscle do not systematically influence trunk stabilization6–9). Therefore, for an adequate level of stability maintenance, integration of local and global mus-cle is required10, 11).
Sling therapy is performed by suspending part of body in a sling12). It was reported that sling therapy has the ad-vantage of facilitating exerci by decreasing the load on the body12, 13). Sling therapy also facilitates neuromuscular control of the extremities14). Vibratory stimulation can im-prove muscle contraction by stimulating muscle hypertro-phy, thereby affecting the muscle spindles15). Type Ia af-ferent fibers are co-activated by α-γ motor neurons. They are activated during isometric contraction, and vibratory stimulation improves the strength of the muscular contrac-tion by increasing the firing rate of Type Ia fibers, and the excitability of α motor neuron16).
Sling exerci therapy with vibration should improve lumbar stability by increasing trunk muscle activ
ity. How-ever, only a limited number of studies have investigated the effects of sling exerci therapy using vibration on trunk muscles activation. Therefore, this study investigated the effect of sling exerci therapy with and without vibration on trunk muscles, activation and their ratios to elucidate an effective lumbar stabilization training method.
SUBJECTS AND METHODS
Eleven healthy adults (11 men) were recruited from A university through a leaflet explaining the details of the study. The general characteristics of the subjects are shown in Table 1. Subject inclusion criteria were a normal body weight and no limitation of motion of the hip or knee joints. Subject exclusion criteria were congenital malformation, neurological or orthopedic symptoms, or low back pain. All subjects included in this study were given a complete ex-planation of the study and voluntarily signed participation connt forms before participating in the experiment. The study was approved by the human rearch ethics commit-
J. Phys. Ther. Sci.
25: 1291–1294, 2013
*To whom correspondence should be addresd. E-mail: hkkang@kyungnam.ac.kr
J. Phys. Ther. Sci. Vol. 25, No. 10, 2013 1292
tees of all the participating institutions.
In this study, we measured trunk muscle activation in two sling exercis with and without vibration.
A surface electromyography (sEMG) system (Telemyo 2400T-G2 Telemetry EMG system; Noraxon,
USA) with disposable bipolar surface EMG electrodes and MyoR-earch Master Edition 1.06 XP software were ud for data collection. We ud 4 active electrodes and a refer-ence electrode. The maximum spacing between the record-ing electrodes was 2.0 cm. The sampling frequency was 1,024 Hz. The raw data were band-pass filtered between 20 and 500 Hz and full-wave rectified by the analysis software. During each exerci with and without vibration, the root mean square was calculated over 3 conds. For normal-ization, EMG signals were recorded during maximum vol-untary isometric contraction (MVIC). The EMG signal of each muscle was measured for 5 conds and the average value of the middle 3 conds (excluding the first and last one conds) was ud in the analysis after normalization to %MVIC. Surface EMG of the internal oblique (IO), rec-tus abdominis (RA), multifidus (MF), and erector spinae (ES) were measured on the subjects’ dominant side. Hair was removed from the measurement sites, and the skin was cleaned with alcohol before electrode placement to reduce the skin impedance. The reference electrode was placed over the superior aspect of the left iliac crest. The electrode placement for the muscles were as follows: IO, midway between the anterior iliac spine and symphysis pubis and above the inguinal ligament; RA, 3 cm lateral to the um-bilicus; MF, lateral to the midline of the body and above and below the line connecting both posterior superior iliac spines; ES, 2 cm lateral to the L2 level.
For the quantification of RA, IO, ES, MF muscles action potential, MVIC was measured. Measurement of MVIC was performed using the method of Daniels and Worthing-ham17) and measurements lasting 5 conds were performed 3 times. The maximum value of the 3- cond signal exclud-ing first and last one conds was ud.
Two sling exercis were performed as follows. Supine bridge exerci with the knees flexed: Subjects had their heels suspended in sling in the supine position. With the palms on the ground, the shoulders in 30° abduction and the pelvis maintained in the neutral position, subjects raid their hips on the auditory cue “go”. When the flexion angle of both knees as measured by a goniometer was 90°, sub-jects maintained this position. Prone bridge exerci with the knees flexed: Subjects had their ankles suspended in slings in the prone position. They raid their hips on the auditory cue “go” and maintained the pelvis in the neutral position. When the flexion angle of both knees as measured by a goniometer was 90°, subjects maintained this position. To get ud to the exerci method, the subjects practiced after being given an explanation of how to perform the ex-erci. The exercis were performed in a random manner. Each exerci was performed 3 times. Measurements lasted for 5 conds. The middle 3 conds of data, after discard-ing the first and last one conds, were ud in the analysis. In order to minimize muscle fatigue, a 3-minute break w
as taken after each exerci. Manual vibration was applied for 5 conds with amplitude with cord within 5 cm when expert physical therapist maintains exerci position. The SPSS 12.0 program was ud for data analysis. Wilcoxon’s signed-rank test was ud to compare the differences in trunk muscle activities of each sling exerci with and with-out vibration. The significance level was chon as p<0.05.
RESULTS
The mean EMG amplitudes of the different trunk mus-cle activations during the supine bridge exerci with and without vibration are prented in Table 2. The mean EMG amplitudes of the different trunk muscle activations dur-ing the prone bridge exerci with and without vibration are prented in Table 3.
During the supine bridge exerci with vibration, the muscle activities of the IO, RA, MF, and ES were signifi-
Table 1. General characteristics of the subjects
Gender Age (years)Height (cm)Weight (kg) Subjects (n=11)11 males22.83 ± 1.65173.67 ± 6.8669.48 ± 14.55
All values are mean±standard deviation (SD)
Table 2. Comparison of trunk muscle activities during su-
死得其所的意思是什么pine bridge exerci with and without vibration
SBE (M ± SD)
SBEV (M ± SD)
IO**11.52 ± 9.2517.90 ± 12.61
RA* 2.46 ± 1.99 3.78 ± 3.12
MF**30.05 ± 5.1336.53 ± 6.05
ES**24.87 ± 8.0231.01 ± 8.56
All values are mean±SD. SBE: supine bridge exerci. SBEV: supine bridge exerci with vibration, IO: internal oblique, RA: rectus abdominis, MF: multifidus, ES: erector spinae. * p<0.05, ** p<0.01Table 3. Comparison of trunk muscle activities during prone bridge exerci with and without
vibration
PBE
(M ± SD)
PBEV
(M ± SD)
IO*37.04 ± 9.2549.21 ± 22.65
RA*17.82 ± 12.8123.44 ± 16.00
MF**12.53 ± 5.7521.77 ± 18.01
ES*9.49 ± 4.0610.55 ± 5.15
All values are mean±SD. PBE: prone bridge exerci, PBEV: prone bridge exerci with vibration. IO: internal oblique, RA: rectus abdominis, MF: multifidus, ES: erector spinae. * p<0.05, ** p<0.01
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cantly higher than tho during the supine bridge exerci without vibration (p<0.05). Moreover, during the prone bridge exerci with vibration, the muscle activities of the IO, RA, MF, and ES were significantly higher than tho during the prone bridge exerci without vibration (p<0.05).
DISCUSSION
Sling therapy is performed with the pelvis suspended in a sling. Since the load of gravity is reduced, subjects are better able to control the level of exerci, and can carry out the exerci to suit themlves for a more effective ap-proach12, 13). The principle of the therapy is to carry out each treatment pain free, and in order to maintain balance13–16, 18), the stabilization muscles are activated according to the in-crea in physical demand12). Many previous studies have provided empirical evidence that vibratory stimulation is effective for pain relief and enhancement of muscle activa-tion15, 16, 19, 20). Pain relief occurs through the cretion of enkephalin from inhibitory interneurons, which are stimu-lated by vibration, which suppress the pain. The enhance-ment of muscle activation occurs through effects on the muscle spindle system21). The muscle spindle is contained in the muscular fiber and consists of two afferent and one efferent fiber. Not only is it nsitive to muscle stretch, but it also n the γ-motor signal during contraction22, 23). The type Ia afferent fiber is connected in monosynaptic form to the motor neuron, which can change muscle c
ontraction de-pending on the rate of firing, and due to the co-activation of alpha-gamma motor neurons, type Ia fibers can be aroud even during isometric contraction16, 19, 20, 22, 23). Therefore when doing sling exercis, the added vibratory stimulation increas the firing rate of type Ia fibers and allows addi-tional muscle contraction.
Sling therapy and vibratory stimulation are recognized as effective methods of physical muscle activation; how-ever, previous rearch has experienced difficulties in re-producing effects induced in clinical practice by mechani-cal vibration. This study was carried out to test what effect vibration has on trunk muscles during sling exerci. Roel-ants et al. carried out a study with 15 healthy adults. They measured their leg muscle activation in three different squat postures, with and without the application of vibration19). Vibration incread leg muscle activation in all of the pos-tures. Another study showed that resistance exerci using heavy load with vibration is effective for decrea of the muscle atrophy generating by a bet rest during a long time. Bosco et al. propod that vibratory stimulation has a posi-tive influence on the power of the upper limbs of boxers24). The prent study showed that during each exerci, vibra-tion stimulation significantly enhanced the activation of all the trunk muscles. Therefore, manual vibration has a better intervention effect in clinical practice, rather than mechan-ic vibration. In addition, the prent study ud bridging exercis
es with the knees flexed, and compared to the typi-cal bridging posture, as performed in a study by Stenvens, we showed that the multifidus, internal abdominal oblique and abdominal rectus muscles were much more activated8). Compared with Lehman’s rearch25), there was a differ-ence of activation in the internal abdominal oblique and erector spine muscles. Therefore, the exerci in the bridg-ing posture with the knees bent and vibratory stimulation enables the trunk muscles to be effectively activated and is a method propod to patients suffering back pains for mediation.
A limitation of this study was the u of surface EMG to measure the activity of the multifidus muscle. Also, the effect of the movement of muscles on the EMG signals, due to the, could not be eliminated. In addition, the lack of kine-matics equipment made it difficult to control the spinal pos-ture, and there could have been additional effects, becau the frequency of vibration was not consistent. Therefore, in further studies, the vibratory stimulation and spine posture need to be controlled and during sling exerci, the effect of vibration duration on the activity ratio of the trunk muscles should be rearched.
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