Effects of different gait velocity between treadmill and ground walking on trunk muscle activation in normal adults

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1 Volume 120 No , ISSN: (on-line version) url: Effects of different gait velocity between treadmill and ground walking on trunk muscle activation in normal adults Ji-Yun Ryu 1, Jin-Seop Kim 2, Sang-Hyuk Park 3, Dong-Yeop Lee 4, Ji-Heon Hong 5 and Jae-Ho Yu 6 1, 2,3,4,5,6 Department of Physical Therapy, Sunmoon University, Korea cjsduszhffk@naver.com, skylove3373@sunmoon.ac.kr, parkpark9@naver.com,leedy@sunmoon.ac.kr, hgh1020@sunmoon.ac.kr, naresa@sunmoon.ac.kr Abstract Background/Objectives: The main purpose of this study is to identify the difference of trunk muscle activation between the walking environment and the gait velocity. Methods/Statistical Analysis: The subjects were 30 healthy adults who had no spinal surgery or disease. Electrodes were attached on the external oblique, the internal oblique, the transverse abdominis, the rectus abdominis, the erector spinae and the multifidus muscles, and the muscle activations while both treadmill walking and walking on the ground at the speed of 0.7 m/s, 1.4 m/s and 2.8 m/s were measured. Each value was analyzed by tow way- ANOVA. Findings: In comparison of the two conditions, the abdominal muscle activation in walking on the ground was significantly higher than on the treadmill, and the muscle activation in the treadmill walking was significantly high in the dorsal parts of the muscles (p<.05). In the speed conditions, significant differences were detected only in the lumbar erector spinae muscle (p<.05). Improvements/Applications: Thus, this study suggests that selective applications of the walking exercises for 5751

2 low back pain could be resulting in a better effect. Key Words : Treadmill, Overground, Gait Speed, Muscle Activation, Electromyography(EMG), Trunk Muscle. 1 Introduction The back pain is one of the common musculoskeletal diseases that causes social and economical issues and is approximately 80% of the world population suffers from. And it is one of the major causes that impoverish quality of life [1]. In trunk muscles, muscles near the lumbar vertebrae play important roles for the posture maintenance and balance control, and as for daily life, they also play an important role for stability of the trunk and spine [2,3]. It has been well-known that spinal instability caused by atrophy and decreased muscle activation of the deep muscles, such as the multifidus and transverse abdominis, is one of the major causes of chronic low back pain [4]. Also, forward bending posture during the long-time work pressures the back part of the vertebrae and brings about the disturbance of blood supply and the lack of nutrition supply to the vertebrae and the surface of the fascia. As a result, it could accelerate the weakening of the lumbar extensors [5]. Thus, the lumbar strength in low-back pain patients shows a lower level of muscle activation than healthy adults who has no back pain. Therefore, the tension of the lumbar region and the incidence of low-back pain get to increase [6]. Also, the weakening of muscle strength could be accelerated as the patients with low-back pain tend to minimize the movement of the trunk to relieve pain in the region of the lumbar vertebrae [7]. The management programs for low-back pain are McKenzie exercise, William s exercise, the lumbar stabilization exercise, core exercise, and cardiovascular exercises such as walking. Among them, some studies showed that therapeutic exercises, like McKenzie exercise and William s exercise, are effective on patients with chronic low-back pain, whereas there are conflicting opinions that some of them give the mechanical stress on muscle and thus are ineffectual in enhancing endurance and strength of the trunk [8]. It is wellknown, unlike these exercises, that walking is relatively safe and doable exercise in daily life and can prevent from overweight and 5752

3 obesity. Also, a walking exercise helps strengthen muscles around the spinal vertebrae so that it is an efficient exercise on the treatment and prevention of low-back pain. WHO recommends walking as an easy exercise for everyone in the treatment and prevention of low-back pain. The treadmill is mostly used for walking exercise since it has the benefit of the control of gait speed and the high amount of exercise can be achieved in a small area [9]. Although there are many researches on the differences between walking on ground and on a treadmill, it has been still controversial on this issue. According to Murray, it was reported that walking on a treadmill showed the shorter stride length, higher walking rate, shorter swing phase and longer double limb support period than on ground. However, no significant difference was revealed in other muscle groups except for the activation of the quadriceps femoris muscle [10]. Lee reported that a few differences in the joint moment and lower extremity strength were found in the sagittal plane [9]. The change in gait speed should be regarded as one of the key components in walking exercise as it accompanies the change in the gate time and distance, energy consumption and muscle activation. According to Kirtley, the gait speed affects the gait pattern and movement, thus a big change in walking pattern is made and the movement of the body becomes bigger when the speed gets accelerated [8]. Also Jansen (1978) suggested that the vertical reaction force increases as the gait speed is augmented, and the proportional increase of anterior and posterior strength was found as increasing speed [11]. Previous studies on the gait pattern and change of gait ability based on environmental conditions were mostly about the improvement of gait ability in patients with neurological diseases (stroke, spinal cord injury. and Parkinson s disease). However, researches on the activation of the trunk muscle in healthy adults have not been studied. There were studies on the difference based on speed, whereas on the change of the trunk muscle activation according to the speed and environmental conditions have been insufficient. This study was performed to identify the impact of the speed change in each condition on the trunk muscle activation. 5753

4 2 Materials and Methods 2.1 Participant The subjects were healthy male students who attend S university which is located in Asan-city, South Chungcheong province. The aims and method of this study were explained to all the participants, and a prior consent was obtained from all patients after explanation. Thirty healthy males who are in their twenties were selected except for those who had had a spinal surgery history, gait impairment or any disease. The general characteristics of the subjects are described in table 1. The institutional review board of Sunmoon University granted approval for the method and purpose of this study. 2.2 Experimental Protocol To reduce the skin resistance of the body part, shaving was performed before the experiment. The dead tissue was removed by sandpaper and then wiped by alcohol cotton. The height and weight were measured by body composition analyzer. Before intervention, a period of five minutes was given to the subjects for more accurate and stable gait, and the EMG electrode pads were placed over the rectus abdominis, transverse abdominis, internal oblique, external oblique, multifidus and erector spinae muscles to see muscle activation. First, walking on the treadmill for 5 minutes at the speed of 1.4m/s. Measurement of muscle activation was conducted 3 times, 5754

5 and one minute intermission was given to avoid muscle fatigue. After that, muscle activation was measured at 2.8m/s and 0.7m/s in the same manner. Walking speed on ground was measured by setting up the number of beats per minute with the step speed on the treadmill, and walking on ground was gauged indoor with sufficient space. The whole research process is shown in Figure 1. Figure 1: Research Procedure 2.3 Instrumentation In this study, the treadmill in figure 2 was used as a gait tool to compare with walking on ground, and QUS100 (Zero WIRE EMG, Italy, 2009) in figure 2 was used to measure the muscle activation 5755

6 of the following muscles: the rectus abdominis (2 cm lateral to the umbilicus), the transverse abdominis, internal oblique (2 cm medial to the anterior superior iliac spine), the external oblique (15 cm lateral to the umbilicus), the mutifidus (2 cm lateral to L4 spinous process), the erector spinae (the lumbar region: 5 cm lateral to L2 spinous process, the thoracic region: 4 cm lateral to T12 spinous process). The EMG electrode placement is shown in figure 3. In EMG measurement, the sampling rate was set at 1000HZ, and the frequency bandpass filter was set at 20 to 450 HZ. Figure 2: Electromyography and Treadmill Figure 3: Attachment Site of Electromyography 5756

7 2.4 Data Analysis SPSS/PC ver.22.0 for windows program (SPSS INC. Chicago. IL) was used to analyze the data. MVIC of the trunk muscles was measured, and then the quantification was performed by dividing the muscle activation on the treadmill and ground at each speed by MVIC value. The quantification represents the percentage (%MVIC). Two-way ANOVA was used to compare the muscle activation in each group, and ShapiroWilk was used for normality tests. The normality was satisfied. A post-hoc test was performed using the Bonferroni method. The significance level was set at p <

8 Figure 4: Comparison of muscle activity by walking type according to speed p <.05, MVIC : Maximum voluntary isometric contraction 3 Results and Discussion The muscle activation of abdominal muscles was statistically and significantly increased in ground walking compared to the treadmill walking (p<.05) in table 2. The muscle activation of abdominal muscles was not statistically significant (p>.05) in table 2, figure 4. The multifidus and erector spinae muscles were statistically and significantly increased in the treadmill walking compared to the ground walking (p<.05) in table 2, figure 4. There was a significant increase in the muscle activation of the lumbar erector spinae muscle at different speeds (p<.05), and the thoracic erector spinae and multifidus muscle were not statistically significant (p>.05) in table 2, figure 4. The rectus abdominis, transverse abdominis, internal oblique, external oblique, multifidus and erector spinae muscles were not statistically significant in the interaction between types of exercise and speed (p>.05) in table 2, figure 4. The purpose of the study was to compare the treadmill walking and ground walking in two different conditions and to identify the impact on the trunk muscle activation at three different speeds: slow-paced, medium-paced, and fast-paced in the two conditions. As a result, the abdominal muscles showed higher muscle activation in the ground walking than walking on the treadmill. And, the dorsal muscles, the lumbar and thoracic erector spinae and multifidus muscles, revealed higher muscle activation in treadmill walking. Although there have been many previous studies on the mechanical difference of the treadmill and ground walking, the conclusion is 5758

9 still controversial. Alton et al suggested that the treadmill walking has higher walking rate and shorter stance phase than the ground walking, and these high walking rate and short stance phase could be presented due to psychological urgency that happened on the rail of the treadmill during swing phase [12]. Similarly, Lee and Hidler and Watt et al reported that high walking rate and short stride were appeared, and there were decreases in the joint angle and moment [9] [13]. However, in the study of previous study, the walking rate was decreased by 12%, and stance phase was increased by 11% in the treadmill walking. And pelvic movement was decreased compared to the ground walking [14,15]. An increase of the muscle activation was shown in the lumbar and thoracic erector spinae and multifidus muscles. It is assumed that the dorsal muscle groups were activated to increase the stability of the trunk on an unstable ground, thus the decreased movement of the pelvis made the stride decreased and the walking rate increased. The decrease of the pelvic movement and stride relatively induce upright position that causes the shift of center of gravity backwards and upwards. So, the activation of the dorsal muscle group is increased, and ground reaction forces in the treadmill walking are increased due to the vertical change of center of gravity [16]. It seemed that the increase of the moment of the hip joint caused the significantly high muscle activation of the abdominal muscles on ground. Previous study, it was found out that the joint moment and muscle activation are closely related each other, and the maximum flexion moment of the hip joint was significantly high in the ground walking related to the treadmill walking. [9]. The period of muscle activation for the abdominal muscles are at 20 to 40% and 70 to 90%. Thus, it is believed that the activation of the abdominal muscles was increased to provide a stable fixed-point as stabilizing the pelvis and waist for the increased activation of the hip flexors during flexion of the hip joint.[17]. In comparison with the trunk muscle activation at different speeds, significant differences were found in the lumbar erector spinae muscle, whereas there was no significant difference in the thoracic eretor spinae, rectus abdominis, transverse abdominis, internal oblique, external oblique and multifidus muscles. According to Anders et al, in the analysis of the muscle activation pattern in the trunk muscle during gait, the trunk muscle activation was 5759

10 increased by same amount during stance phase as the speed was augmented[1]. The lumbar erector spinae muscle showed a matched result of the study. However, no significant difference in the muscle activation was detected in the thoracic erector spinae, rectus abdominis, transverse abdominis, internal oblique, external oblique and multifidus muscles. Motor units for the activation of muscle contraction were almost similar in comparison with a slow-paced and mid-paced speed. Thus, it was due to the fact that could not reach the threshold level for the increment of the muscle activation. The stability of the trunk was highly relevant than the lower extremity muscles that are directly involved in the movement and speed during gait. And, it seemed that no significant difference was found in a slow-paced, mid-paced and fast-paced speeds since the trunk muscle activation is relatively low. The study has a few limitations. Firstly, the muscle activation was measured from the subjects who were healthy males in their twenties, thus it cannot be generalized in all age and sex. Secondly, we proceeded this research by setting up the three types of speed: slow-paced, mid-paced and fast-paced speed. However there was no significant difference in the muscle activation at each speed. Thus, researches on gait at more various speeds are needed. Thirdly, the measurement of the ground walking was taken by setting a metronome at the speed of gait on the treadmill. A tool for more precise measurement of speed is needed. Thus, these limitations should be supplemented in further studies. 4 Conclusion The study was to compare the trunk muscle activation in the ground walking and treadmill walking at slow-paced, mid-paced and fastpaced speeds. As a result, there was a difference only in the lumbar erector spinae muscle. Higher activation levels in the ground walking were showed in the abdominal muscles: the external oblique, rectus abdominis, internal oblique and transverse abdominis muscles. In the treadmill walking, the dorsal msucles, the erector spinae and multifidus muscles, revealed higher muscle activation levels than the ground walking. Patients with low-back pain suffer from muscle atrophy in the spinal muscles as well as the trans- 5760

11 verse abdominis muscle which contributes to the trunk stabilization. Therefore, in the application of walking exercise programs for patients with low-back pain, it would have better effects if selective application for patients condition and demand are considered. References [1] Anders, C., Scholle, H. C., Wagner, H., Puta, C., Grassme, R., & Petrovitch, A. (2005). Trunk muscle co-ordination during gait: Relationship between muscle function and acute low back pain. Pathophysiology, 12(4), [2] Beimborn, D. S., & Morrissey, M. C. (1988). A review of the literature related to trunk muscle performance. Spine, 13(6), [3] Shumway-Cook, A., & Horak, F. B. (1990). Rehabilitation strategies for patients with vestibular deficits. Neurol Clin, 8(2), [4] Panjabi, M. M. (2003). Clinical spinal instability and low back pain. J Electromyogr Kinesiol, 13(4), [5] Takemitsu, Y., Harada, Y., Iwahara, T., Miyamoto, M., & Miyatake, Y. (1998). Lumbar degenerative kyphosis: Clinical, radiological and epidemiological studies. Spine, 13(11), [6] Cassisi, J. E., Robinson, M. E., O Conner, P., & Macmillan, M. (1993). Trunk strenght and lumbar paraspinal muscle activity during isometric exercise in chronic low back pain patients and controls. Spine, 18(2), [7] Cooper, R. G., St Clair, Forbes, W., & Jayson, M. I. (1992). Radiographic demonstration of paraspinal muscle wasting in patients with chronic low back pain. Br J Rheumatol, 31(6), [8] Kirtley, C., Whittle, M. W., & Jefferson, R. J. (1985). Influence of walking speed on gait parameters. J Biomed Eng, 7(4),

12 [9] Lee, S. J., & Hidler, J. (2008). Biomechanics of overground vs treadmill walking in healthy individuals. J Appl Physiol (1985), 104(3), [10] Murray, M. P., Spurr, G. B., Sepic, S. B., Gardner, G. M., & Mollinger, L. A. (1985). Treadmill vs floor walking: kinematics, electromyogram, and heart rate. J Appl Physiol (1985), 59(1), [11] Jansen, E. C., & Jansen, K. F. (1978). Vis-velocitas-via: Alteration of foot-to-ground forces during increasing speed of gait. Biomechanics. University ParkPressLondon. [12] Alton, F., Baldey, L., Caplan, S., & Morrissey, M. C. (1998). A kinematic comparison of overground and treadmill walking. Clin Biomech (Bristol, Avon), 13(6), [13] Watt, J. R., Franz, J. R., Jackson, K., Dicharry, J., Riley, P. O., & Kerrigan, D. C. (2010). A three-dimensional kinematic and kinetic comparison of overground and treadmill walking in healthy elderly subjects. Clin Biomech (Bristol, Avon), 2010, 25(5), [14] Chockalingam, N., Chatterley, F., Healy, A. C., Greenhalgh, A., & Branthwaite, H. R. (2012). Comparison of pelvic complex kinematics during treadmill and overground walking. Arch Phys Med Rehabil, 93(12), [15] Wall, J. C., & Charteris, J. (1981). A kinematic study of longterm habituation to treadmill walking. Ergonomics, 24(7), [16] James, C. R., Atkins, L. T., Yang, H. S., Dufek, J. S., & Bates, B. T. (2015). Kinematic and groun reaction force accommodation during weighted walking. Hum Mov Sci, 44, [17] Neumann, D. A. (2010). Kinesiology of the musculoskeletal system: foundation for rehabilitation. Mosby Inc London. 5762

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