Activity Analysis of Trunk and Leg Muscles During Whole Body Tilt Exercise

Transcription

1 Bio-Medical Materials and Engineering 24 (2014) DOI /BME IOS Press Activity Analysis of Trunk and Leg Muscles During Whole Body Tilt Exercise Chang Ho Yu a, Sun Hye Shin b, Ho Choon Jeong c, Deung Young Go d a,e* and Tae Kyu Kwon a Division of Biomedical Engineering, Chonbuk National University, Deokjin-Dong 1-Ga, Jeonju, Jeonbuk , South Korea b Department of Healthcare Engineering, Chonbuk National University, Deokjin-Dong 1-Ga, Jeonju, Jeonbuk , South Korea c CyberMedic Co, Iksan, Jeonbuk, South Korea d Department of Junior Secondary School Special Education, Kangnam University, 40 Gangnam-ro, Giheung-gu, Yongin, Gyeonggi , South Korea e Bioengineering Research Center for the Aged, Chonbuk National University, Jeonju, Jeonbuk , South Korea Abstract. The objectives were to assess the trunk and leg muscle activities during the trunk tilt exercise by a 3D dynamic exercise device capable of active and passive movements, to study the evaluation of Root Mean Squire (RMS), and to investigation the influence of the trunk positions on these muscle activities. Eighteen healthy volunteers were selected. None of the subjects had any history of lumber and trunk muscle problems. Rotation capability was enabled for the investigation of A (anterior), R (right), P (posterior), L (left), AR (anterior right), AL (anterior left), PR (posterior right), PL (posterior left) tilt directions. EMG signals of trunk (rectus abdominis, external obliques, latissimus dorsi, erector spinae) muscles and leg (rectus femoris, Biceps femoris, Tibialis Anterior, gastrocnemius) muscles were taken out. Root Mean Squire (RMS) values were calculated. The results of this study indicate that different exercise patterns can be applied depending on the exercise types, which are appropriate and necessary to each user. We believe that the human body can be maintained in equilibrium through the interaction between the position and movement execution of the human body, contributing to the improvement of body balance control. Further quantitative data collection and analysis related to the development of various spinal stabilization exercise programs is required. In the near future, we will conduct a study concerning the effects of trunk tilt exercise in active and passive modes on the strength of the tilting muscles and postural balancing ability. Keywords: Trunk stabilization exercise, whole body tilt, active Tilt, passive tilt, EMG 1. Introduction Eighty percent of people in a modern society, who spend most of their time sitting, are experienced back pain; 15% of these people suffered chronic low back pain. Moreover, low back pain creates many problems in regard to the patients physical function and moving capacity which limits the patients working ability to a great extent, leading to great social economic loss[1-2]. In other words, low back pain is a common disease among humans, and it is one of the main causes of labor losses [3-5]. Spine *Corresponding author. kwon10@jbnu.ac.kr /14/$ IOS Press and the authors. All rights reserved

2 246 C.H. Yu et al. / Activity analysis of trunk and leg muscles during whole body tilt exercise stabilization is defined as a person s ability to make large or subtle movements of the spinal joints, both consciously and unconsciously [6, 7]. Currently, it is known to be an essential approach for the treatment of patients with low back pain [8-9]. Spinal stability is believed to play an important role in the prevention and rehabilitation of lumbar spine injury. Therefore, exercises for improving spinal stability are performed widely in sports and rehabilitation. Spinal stabilization exercises include the pelvic tilt exercise, which can activate areas around the spine; naval contraction, where selective abdominal muscle contraction is possible without any movement in the spine; and other exercises using mats, treatment with tables, balls, dumbbells, balance plates, etc. [10-13]. In recent years, isometric exercises have been used to achieve spinal stabilization through the trunk tilt movement in a standing position by using three-dimensional (3D) motion. These exercises contribute to both low back pain reduction and postural balance through strengthening of the trunk muscles. Many studies about these exercises are currently being conducted. Koh et al. [14] analyzed the results regarding the balancing ability of older women and the changes in the thickness of the transversus abdominis muscle and multifidus muscle brought about by an 8- week lumbar stabilization exercise program by using a 3D Pegasus system. It is reported that the exercise contributed to positive effects on isometric strength as well as the enhancement of balancing ability. Kim et al. (2011) [15] conducted an experiment for chronic low back pain patients in their 20s by dividing them into 2 groups: a lumbar stabilization exercise group using typical exercise balls, and a group using a 3D air balance system (SNS Korea Co., Korea). After the 2 groups completed the lumbar stabilization training, the visual pain scale scores, limitation on daily life, weight shift angles in 8 directions, and postural disturbance during weight shift were assessed. Then, the effects of these 4 variables on the patients postural sway and weight distribution were analyzed. According to the results, in terms of the patients muscle balance during active weight shift in the left, right, and diagonal directions, lumbar stabilization exercise using the 3D air balance system was more effective for coordinated movements than that performed using exercise balls. Moreover, 3D exercise was effective for the reduction of posture sway during active weight shift. The 3D isometric exercise equipment examined in existing studies is divided into two movements: a self-generated active movement in the angle and direction steered by the user, and a passive movement generated by the driving of the equipment. However, the exercise equipment used in the current study enables the conversion between active and passive movements. Active and passive movements stimulate different locations of muscle mass and physical characteristics; however, only the effects of 3D exercise equipment on muscle strength were discussed in the research to date regardless the different modes of exercise. Therefore, in this study, we aimed to compare and analyze the differences in trunk muscle strength caused by the body tilt movements with active and passive exercise modes. 2. Experimental methods 2.1. Subjects In this study, eighteen healthy volunteers (18 males, height 176±2.3 cm; mass 69.9±2.7 kg; age 24.7±0.5 years) were investigated. Conforming to the Declaration of Helsinki (1964), written informed consent was obtained from all subjects. None of the subjects had any history of lumber and trunk muscle problems. The investigation was performed in a device for trunk muscle diagnosis and treatment (SpaceBlance 3D, CyberMedic Co. & Chonbuk National Univ., Korea ; Fig.1(a)).

3 C.H. Yu et al. / Activity analysis of trunk and leg muscles during whole body tilt exercise 247 Fig. 1.(a) 3D dynamic exercise device (SpaceBalance 3D, CyberMedic Co. &Chonbuk National Univ., Korea), (b) Explanation of 8 tilting directions during the trunk tilt exercise modes of the SpaceBalance 3D. (c) Passive tilt mode of the Space- Balance 3D. (d) Active tilt mode of the SpaceBalance 3D 2.2. System configuration As shown in Fig. 1.(b), the trunk and leg muscles generated by tilting in 8 different directions such as A (anterior), R (right), P (posterior), L (left), AR (anterior right), AL (anterior left), PR (posterior right), PL (posterior left) were measured during the trunk tilt exercise modes of a 3D dynamic exercise device. This device applies forces on the trunk by tilting the whole body from a neutral upright position. Subjects are fixed at their feet and hips, but the trunk remains unsupported. During the different tilt positions, the subject has to simply stabilize his or her upper body in the body axis. For this investigation, subjects held their arms crossed against their chests. Exact body and arm positioning throughout the whole investigation was controlled by the examiner. This 3D dynamic equipment was capable of moving 100 degrees in the A-P direction, 180 degrees in the L-R direction, 100 degrees in the AR- PL direction and 100 degrees in the AL-PR direction since it can be rotated in 3D space. For the recording of the EMG signals, an 8-channel surface EMG system was used (Bignoli system, Delsys. Inc., USA). All raw EMG signals were band pass-filtered between 6 to 400 Hz and amplified. The sampling rate was 1000 Hz and the signals were converted from an analogue voltage to a digital signal at 1000Hz (A/D conversion) before being transformed into a personal computer. The electrode was attached after removing the keratinous skin layer with sterilization alcohol to reduce the skin resistance against the surface EMG signals. We measured trunk (rectus abdominis, external obliques, latissimus dorsi, erector spinae) muscles and leg (rectus femoris, Biceps femoris, Tibialis Anterior, gastrocnemius) muscles during these exercise. Root mean squire (RMS) values were used for the analysis method. RMS values were calculated to quantify the amplitude of the EMG signals Experimental equipment and procedures This device (Space Blance 3D, CyberMedic Co. &Chonbuk National Univ., Korea) has active and passive tilt modes according to the driven approach in Fig. 1(c), and (d). This device is divided into two exercise modes: a self-generated active movement in the angle and direction steered by the user (active tilt mode), and a passive movement generated by the driving of the equipment (passive tilt

4 248 C.H. Yu et al. / Activity analysis of trunk and leg muscles during whole body tilt exercise mode). Our experimental procedures were conducted by explaining the analysis of trunk and leg muscle activities generated by 30 degrees in 8 tilting directions with both the active and passive tilt modes. The applied tilting directions are A (anterior), R (right), P (posterior), L (left), AR (anterior right), AL (anterior left), PR (posterior right), and PL (posterior left).the subject then maintained their COG (center of gravity) to the appointed 8 tilting directions twice for 10 sec, respectively. 20 seconds of relaxation was allotted during targeting change. To recover the muscular strength, 20 minutes of relaxation was allotted between the active tile and passive tile modes. As shown in Fig. 2, the electrode was attached after removing the keratinous skin layer with sterilization alcohol to reduce the skin resistance against the surface EMG signals. The trunk (rectus abdominis, external obliques, latissimus dorsi, erector spinae) muscles and leg (rectus femoris, Biceps femoris, Tibialis Anterior, gastrocnemius) muscles were measured during these exercise Data analysis Fig. 2.Muscle measured in upper and lower limbs for verifying muscular activities Data analysis was completed using the statistical software program SPSS PASW statistics 18(SPSS Inc., Chicago, IL, USA) for Windows Ver The Kolmogorov-Smirnov test (K S test) was used to evaluate the differences in EMG activity between the active mode and passive mode for changes in the measured parameters. A P value of less than 0.05 was considered statistically significant. 3. Results 3.1. Analysis of trunk muscle activities Figures 3 6 illustrate trunk muscle activities according to the active and passive movements generated by tilting in 8 directions. The y-axes represent Root Mean Square (RMS) values converted from the electromyography (EMG) data, and the x-axes indicate the 8 directions. Figure 3 represents the RMS values of the left and right sides of the rectus abdominis. In the case of the left rectus abdominis, muscle activity maintaining the active tilt mode in the P and PL directions was higher than that in the passive tilt mode. In the case of the right rectus abdominis, muscle activity in the active tilt mode in the P and PR directions was significantly higher. Rectus abdominis muscle activities during the active and passive tilt modes demonstrated significantly higher RMS values in the

5 C.H. Yu et al. / Activity analysis of trunk and leg muscles during whole body tilt exercise 249 P direction than those in the A direction, regardless whether the muscle was in the active or passive mode. Figure 4 illustrates the RMS values of the left and right external oblique. In the case of the left external oblique, maintaining the passive tilt mode in the AR and AL directions resulted in significantly higher values, whereas in the case of the right external oblique, maintaining the passive tilt mode in the PL direction resulted in higher values (p < 0.05). In terms of external oblique muscle activity in both the active and passive tilt modes by direction, tilting in the PR and R directions caused much higher values of muscle activity than tilting in the PL and L directions in the case of the left muscle. In contrast, in the case of the right muscle, the opposite tendency was observed: tilting in the PL and L directions caused much higher values than tilting in the PR and R directions. Fig. 3.Rectus abdominis of RMS in passive and active tilt training in eight directions Fig. 4.External oblique of RMS in passive and active tilt training in eight directions According to the RMS values of the left and right latissimus dorsi shown in Figure 5, muscle activities in the passive tilt mode showed higher values in all directions except for the A and PL directions in the case of the left latissimus dorsi. Muscle activities in the passive tilt mode were higher in the P, L, and AL directions in the case of the right latissimus dorsi. However, there were no significant differences in the muscle activities in different directions.

6 250 C.H. Yu et al. / Activity analysis of trunk and leg muscles during whole body tilt exercise Fig. 5.Latissimus dorsi of RMS in passive and active tilt training in eight directions 3.2. Analysis of leg muscle activities Fig. 6.Erector spinae of RMS in passive and active tilt training in eight directions As shown in Fig. 7, there was no significant tilting mode-related difference in the muscle activities of the left rectus femoris. In the case of the right rectus femoris, the muscle activities generated by maintaining the passive tilting mode in the PR and PL directions were significantly lower than those generated by maintaining the active tilting mode in the same directions (p<0.05). Fig. 8 shows the RMS values of the left and right biceps femoris. Significantly higher values of muscle activity were obtained in the left biceps femoris in the passive tilting mode in the A, P, and AL directions, as well as in the right biceps femoris in the A, R, and P directions (p< 0.05). In terms of the tibialis anterior muscle activities shown in Figure 9, there were no significant tilting mode-related differences in the RMS values of the left and right tibialis anterior. The RMS values for the muscle activities of the left and right gastrocnemius did not show any significant differences depending on the tilting mode either, as indicated in Figure 10. In addition, no significant differences were shown in leg muscle activities related to the tilting direction.

7 C.H. Yu et al. / Activity analysis of trunk and leg muscles during whole body tilt exercise 251 Fig. 7.Rectus femoris of RMS in passive and active tilt training in eight directions Fig. 8.Biceps femoris of RMS in passive and active tilt training in eight directions Fig. 9.Tibialis anterior of RMS in passive and active tilt training in eight directions

8 252 C.H. Yu et al. / Activity analysis of trunk and leg muscles during whole body tilt exercise Fig. 10. Gastrocnemius of RMS in passive and active tilt training in eight directions 4. Discussion This study conducted basic research to compare differences in muscle activities according to the different movement methods on spinal stabilization devices. The spine supports the torso and enables forward, backward and rotating movements as well as side bending. Moreover, the spine comprises a series of irregular vertebrae, discs consisting of fibrous cartilage, ligaments that hold the spine in place, and muscles that maintain movements. As the muscles on the spine allow the trunk to bend, twist, and pull, it strongly supports posture when people sit or stand [16]. The muscles on the spine can be divided into 2 categories: movers, which work during joint movements; and stabilizers, which protect the body tissues from collisions. Spinal movements usually involve the erector spinae, rectus abdominis, internal and external oblique, latissimus, etc., which are located near the body surface. Spinal stabilization is ensured by multifidus muscles located deep in the spine as well as the transversus abdominis muscle [5-6, 17]. Trunk stabilization exercises that strengthen these muscles play an important role in patients with low back pain and spinal disease by preventing spinal pain and strengthening the muscles surrounding the spine. Recently, spinal stabilization exercise programs, including ball exercises, sling movements, and 3D spinal stabilization devices, have been introduced [18]. Spinal stabilization devices are categorized into those with a human-generated active mode and those with a motor-generated passive mode. In the present study, the muscle activities of the lower limb muscles, erector spinae, rectus abdominis, external oblique, latissimus dorsi, biceps femoris, tibialis anterior, and gastrocnemius were measured in order to compare muscle contraction during the trunk tilt movement in active and passive modes. The results showed that, in all directions except for rearward backward tilt, active tilt training showed higher values for muscle movements than passive tilt training. This may be ascribed to the fact that in the case of active tilt, tilting is maintained through the coordinated movements of muscles after moving the body s center of gravity; thus, the measured values for the muscle movements are low. In contrast, in the case of passive tilt, tilting is maintained with excessive force through involuntary movements regardless the alignment of the body; thus, the measured values for the muscle movements are high. When tilting in a rearward direction, rectus abdominis muscle activity demonstrated higher values in the active mode than that in the passive mode, which can be explained by the fact that in

9 C.H. Yu et al. / Activity analysis of trunk and leg muscles during whole body tilt exercise 253 rearward tilt, not only excessive force is used in order to maintain tilting, but also it is difficult to move the body without using the device. In addition, the results for muscle movements according to direction, regardless of active or passive tilting mode, showed that erector spinae muscle movements had higher values in forward tilting, whereas rectus abdominis muscle movements revealed higher values in rearward tilting. These results were similar to those of previous studies [19-21]. When tilting to the right, numerous muscles on the left side of the body were used. On the other hand, a lot of muscles on the right side were used when tilting to the left, which could be attribute to the fact that the muscles located on the side opposite to the direction of trunk tilt are activated; thus, interaction between the position and movement execution environment of the human body is achieved, enabling the body s equilibrium. By contrast, the leg muscles were not affected by any specific direction of tilt. This is considered to be due to the fact that the subject was irregularly correcting their lower body posture while standing on the device and maintaining the tilting position. Kim(2011) [20] suggested that the angle and direction can lead to a coordinated contraction of those muscles, which are integral to the lumbar and lower body. It is reported that tilting exercises are not an appropriate method to improve imbalance of the lower body, although they bring about balanced muscle development of the trunk. In other words, passive mode exercises only require users to keep their body straight since the angle and direction are fixed to the device, while active mode exercises require users to both achieve the exact angle and direction and maintain this position. Hence, body coordination occurs not only in the muscles but also in the visual and vestibular sensory nervous system, which leads to the optimally using of muscles in the passive mode in terms of muscle activity [22]. Also, when the body tilts, the muscles located on the side opposite to the tilting direction are activated, leading to coordination between the position and movement execution environment of the human body, enabling the body's equilibrium. 5. Conclusion This study was designed to compare and analyze the trunk and leg muscle contraction patterns generated by means of the trunk tilting movement in active and passive modes by using a 3D dynamic exercise device, with which both active and passive movements are possible. The results of this study indicate that different exercise patterns can be applied depending on the exercise types, which are appropriate and necessary to each user. We believe that the human body can be maintained in equilibrium through the interaction between the position and movement execution of the human body, contributing to the improvement of body balance control. Further quantitative data collection and analysis related to the development of various spinal stabilization exercise programs is required. And in the near future, we will conduct a study regarding the effects of trunk tilt exercise in active and passive modes on the strength of the tilting muscles and postural balancing ability. 6. Acknowledgment This work was supported by Ministry of Knowledge Economy (QoLT Technology Development, No ) and also supported by the 2013 Small &Medium Technology Development of Small &Medium Business Administration (SA113693).

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