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Journal of Bodywork & Movement Therapies (2013) xx, 1e6
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/jbmt
MUSCLE PHYSIOLOGY
The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises* Khosro Khademi Kalantari, PhD PT a,1, Simin Berenji Ardestani, BSc in Physiotherapy, MSc in Exercise Physiology and Sport Science b,* a Department of Physiotherapy, Faculty of Rehabilitation, Shahid Beheshti University of Medical Sciences (SBMU), Damavand Ave., 16169 Tehran, Iran b Department of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, NO, Norway
Received 1 September 2012; received in revised form 14 August 2013; accepted 27 August 2013
KEYWORDS Shoulder; Closed kinetic chain; Stability; Exercise
Summary Method: A total of thirty eligible subjects (17 female and 13 male, age Z 22.26 0.99 years, height Z 170.96 8.42 cm, weight Z 61.63 9.92 kg) were tested in six different randomly ordered positions. Surface Electromyography (EMG) was recorded from the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), long head of the biceps (LB), teres major (TM) and posterior deltoid (PD) muscles in the dominant shoulder in 6 different closed kinetic chain (CKC) positions. Objective: To investigate changes in muscular activity of the shoulder muscles at different base of support stability levels. Results: Muscle activity was greater in the most stable position for all muscles except UT (P < 0.01). Conclusion: Shoulder muscle activity did not increase in parallel with a reduction in base of support stability in the present study. ª 2013 Elsevier Ltd. All rights reserved.
* The project should be attributed to: The Physiotherapy Department, Shahid Beheshti University of Medical Sciences (SBMU), Tehran, Iran. [email protected], www.sbmu.ac. * Corresponding author. Tel.: þ47 41011703. E-mail addresses: [email protected] (K. Khademi Kalantari), [email protected], [email protected] (S. Berenji Ardestani). 1 Tel.: þ98 21 77561411; fax: þ98 21 77561406.
1360-8592/$ - see front matter ª 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jbmt.2013.08.005
Please cite this article in press as: Khademi Kalantari, K., Berenji Ardestani, S., The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises, Journal of Bodywork & Movement Therapies (2013), http://dx.doi.org/10.1016/ j.jbmt.2013.08.005
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Introduction The use of axial load exercises, which are known as closed kinetic chain (CKC) exercises, has grown considerably in recent years. Biomechanically, the function of each segment of the body is considered in relation to other interconnected segments. The whole body is considered as a chain with movement of one part affecting the others. The term “kinetic chain” is used to describe how the body moves, with the limbs functioning either in an open kinetic chain (OKC) or a closed kinetic chain (CKC) condition. The difference between these two conditions is determined by whether the terminal ending of the limb is free or fixed, for example, whether it is moving against a hard or soft surface. During CKC exercises a group of muscles and joints works simultaneously, whereas in OKC exercises they work separately, for example: shoulder abduction and knee extension. Examples of CKC exercises are push-ups, pullups, squats and lunges. All types of CKC exercises may be performed with or without weights. There is a considerable amount of research to indicate that CKC exercises are safer and more efficient than OKC exercises for both patients and healthy subjects, especially in the early stage of rehabilitation (Fitzgerald, 1997). The majority of everyday activities and sports activities are examples of CKC exercises (Prokopy et al., 2008). During CKC exercises, compressive force, which is the result of terminal limb section stabilization, decreases the amount of shear force in active joints. During OKC exercises, the shear stress present during movement exposes the joints and muscles to risk (Graham et al., 1993). Traumatic and non-traumatic shoulder injuries lead to functional instability in the shoulder complex. In general, coordination between mechanical (i.e. capsuloligamentous, articular, and musculotendinous structures) and dynamic restraint (i.e. shoulder muscle contraction) promotes functional shoulder stability. The sensorimotor system plays an important role in producing shoulder muscle coordination. It has been demonstrated that shoulder instability is due to a deficit in both mechanical and sensorimotor elements (Cuomo et al., 2005; Machner et al., 2003; Zuckerman et al., 2003; Barden et al., 2004). Improvement of proprioception in periarticular shoulder muscles is one of the main factors that can increase functional shoulder stability. It has been reported that the axial load present during CKC exercises could simulate biomechanical situations that promote muscle co-activation and a significant increase of proprioceptive stimulation, compared with OKC exercises (Kibler, 1998; Wilk and Arrigo, 1993). There is solid evidence of the beneficial effects of CKC exercises (such as squat and bridging exercises) using an unstable base of support in lower-body and trunk rehabilitation, whereas the evidence for upper-limb rehabilitation is limited (Escamilla et al., 1998; Uhl et al., 2003). Facilitation of muscle activation and proprioception by means of CKC exercises has been shown in a number of studies (Ubinger et al., 1999; Timothy et al., 2001). Generally, CKC exercises are performed with a stable or unstable base of support. Most of the literature recommends the use of a stable base of support in the early phases of shoulder rehabilitation when these exercises are safer for the individual. However, similar exercises with a relatively unstable base of support, for example a medicine ball or wobble
K. Khademi Kalantari, S. Berenji Ardestani board, are usually made use of in the advanced phases of a rehabilitation programme (Wilk and Arrigo, 1993). It is assumed that CKC exercises using an unstable base of support make greater demands on the neuromuscular system and thus will lead to an increase in joint stability, proprioception, muscle control and muscle co-activation (Lephart and Henry, 1996; Ellenbecker and Cappel, 2000; Andrade et al., 2011). CKC exercises with an unstable base of support generate a series of patterns of movement due to the sudden changes in the direction of movement. This perturbation stimulates mechanoreceptors and results in increased joint stabilization (McMahon et al., 1996). In recent years, research involving shoulder muscle activity during CKC exercises has been compared with respect to the use of stable and unstable surfaces using the same volunteers. The results from EMG recordings in these studies showed greater muscle activity during CKC exercises on an unstable surface. It should be noted that in the majority of these studies, shoulder muscle activity was compared during different upper limb CKC exercises, for example bench-press, wall-press and push-ups. However, there is a lack of studies using both a stable and unstable base of support during exercises that generate the same biomechanical patterns addressing load direction and intensity in upper limbs (Anderson and Behm, 2005; Marshall and Murphy, 2005). The purpose of the present study was to determine the differences between shoulder muscle activity during CKC exercises performed with and without a stable base of support. The aim was to improve our knowledge of progressive shoulder rehabilitation in order to provide better treatment recommendations.
Methods and materials A total of thirty eligible subjects e students at a medical university (class of 2005) e (17 females and 13 males, age Z 22.26 0.99 years, height Z 170.96 8.42 cm, weight Z 61.63 9.92 kg) participated in the present study. The inclusion criteria for subjects were: no history of orthopaedic and/or neurological disorders in the neck, shoulders or upper limbs during the preceding year and no recent pain or discomfort in upper limbs. The study was approved by the state research ethics board in Iran. Subjects gave their written informed consent prior to participation.
Testing conditions The six different test positions described in the next paragraph were randomly ordered and divided into two categories based on the amount of stability in the base support. The first category consisted of 3 different test positions with a stable base of support (the feet on the ground). The second category consisted of the same 3 different positions, but with an unstable base of support (the lower limbs were on a Swiss ball). The six positions were numbered from most stable (Position 1) to most unstable (Position 6) (see Figure 1): Position 1: both hands and feet on the ground Position 2: dominant hand on a wobble board and feet on the ground
Please cite this article in press as: Khademi Kalantari, K., Berenji Ardestani, S., The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises, Journal of Bodywork & Movement Therapies (2013), http://dx.doi.org/10.1016/ j.jbmt.2013.08.005
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The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises
Figure 1
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The six test positions utilising different support surface stability under the dominant hand.
Position 3: dominant hand on a small ball centred on a wobble board and feet on the ground Position 4: both hands on the ground and legs on a Swiss ball
Position 5: dominant hand on a wobble board and legs on a Swiss ball Position 6: dominant hand on a ball centred on a wobble board and legs on a Swiss ball
Please cite this article in press as: Khademi Kalantari, K., Berenji Ardestani, S., The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises, Journal of Bodywork & Movement Therapies (2013), http://dx.doi.org/10.1016/ j.jbmt.2013.08.005
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K. Khademi Kalantari, S. Berenji Ardestani
The subjects were asked to place themselves in each test position with 90 shoulder flexion, no internal or external rotation and elbows at full extension. The subjects’ bodies were aligned so that the middle finger was located under the acromioclavicular joint and the head was kept in line with the trunk and vertebral column. To ensure that both dominant and non-dominant shoulders were at the same level, a platform that could be adjusted was used for Positions 2, 3, 5 and 6.
EMG recording Upon arrival at the laboratory, the subject’s physical data were recorded and the test protocol explained. Before the test, each subject performed a 5 min warm-up consisting of stretching and gentle upper limb exercises. The electromyography (EMG) signals were recorded by means of surface EMG (Biometric Ltd, Gwent, South Wales, UK) of the dominant shoulder. The muscles recorded were the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), long head of biceps (LB), teres major (TM) and posterior deltoid (PD). Prior to electrode placement, the skin was shaved, abraded and cleaned with alcohol to reduce the amount of skin resistance. The surface electrodes (Biometrics Ltd, electrode model SX230, 20 38 mm) were placed according to SEINAM (surface EMG for non-invasive assessment of muscles) recommendations. To obtain a measurement, EMG was recorded continuously for 10 s. The subjects were given 5-min rest periods between each of the test positions in order to prevent muscle fatigue. The root mean square (RMS) values of EMG signals (EMGRMS) were calculated for the middle 3-s period. The intensity of muscular activity was expressed as the ratio of the EMGRMS in each particular test position compared to the most stable position (Position 1). All the data were normalized compared to Position 1.
Data analysis Statistical analysis was performed using SPSS 18 software (Statistical Package for Social Science, Chicago, IL). A one way repeated measure analysis of variance (rANOVA) was performed to compare the shoulder muscles’ activity between two categories: positions with a stable base of support (Positions 1e3) and positions with an unstable base of support (Positions 4e6). Differences were considered significant at P < 0.05 level. If significant differences were
Table 1
detected, a Bonferroni correction was carried out to identify group differences. Differences were considered significant at P < 0.01. A Pearson correlation coefficient test was used to identify the possible co-activation of the muscles across the positions. The results are presented as mean standard deviation (SD).
Results EMG measurement indicated a significant change in the extent of muscle activation within the same muscle between the stable and unstable categories. With respect to the two categories (with and without the Swiss ball), a significant decrease in activity (P < 0.001) in TM, PD, LT and LB muscles was observed in the first category when compared to the second category. Table 1 shows the mean and SD of muscle activity from EMGRMS measurement at each position. Pair-wise comparison reveals a significant difference in muscle activity (except in UT and LB) between Position 1 and other Positions (P < 0.01). In UT and SA activity the differences were just significant between Position 1 and the last 3 positions (with Swiss ball) (P < 0.01). Muscle activity in LT, TM, PD and SA decreased significantly from Position 1 to Position 6 (P < 0.01). A similar change was observed from Position 2 to Position 6 in UT and LB activities (P < 0.01). Another finding from EMG measurement after applying the Pearson correlation across shoulder muscles’ activity (see Table 2) was that strong correlations were found between UT and TM (r Z 0.76, P < 0.01), LB and UT (r Z 0.73, P < 0.01) and LB and TM (r Z 0.75, P < 0.01).
Discussion The main finding of this study was that decreased stability of support in CKC exercises is not associated with an increase in activity of shoulder muscles. The finding of the present study contrasts with that in more recent literature showing dominant shoulder muscle activity during CKC exercises with an unstable base of support (Naughton et al., 2005; de Oliveira et al., 2008; Anderson and Behm, 2004). In the present study, the highest muscle activity (except in UT) was observed in the two stable positions (Positions 1 and 2). Similar results have been reported previously by other authors. It seems that the unstable base of support is not the only factor affecting muscle activity during CKC
The ratio of muscle activity (EMGRMS) related to Position 1.
Positions
SA
1 2 3 4 5 6
100% 112 79 89 61 49
LB 2% 2% 1% 2% 2%
100% 12 65 54 55 57
PD 2% 2% 2% 2% 2%
100% 67 16 44 29 12
TM 2% 2% 2% 2% 1%
100% 74 48 42 42 55
LT 2% 2% 2% 3% 2%
100% 84 61 64 69 57
UT 2% 2% 2% 2% 2%
100% 93 79 75 78 94
3% 3% 3% 3% 2%
Data are presented in mean SD. SA, serratus anterior; LB, long head of biceps; PD, posterior deltoid; TM, teres major; LT, lower trapezius; UT, upper trapezius.
Please cite this article in press as: Khademi Kalantari, K., Berenji Ardestani, S., The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises, Journal of Bodywork & Movement Therapies (2013), http://dx.doi.org/10.1016/ j.jbmt.2013.08.005
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The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises Table 2 activity.
Pearson correlation across the shoulder muscles’
Muscles
SA
LB
PD
TM
LT
UT
SA LB PD TM LT UT
1 0.73
0.01 1
0.52 0.11 1
0.10 0.75 0.11 1
0.15 0.02 0.37 0.05 1
0.16 0.73 0.07 0.76 0.15 1
Data are presented as the correlation. SA, serratus anterior; LB, long head of biceps; PD, posterior deltoid; TM, teres major; LT, lower trapezius; UT, upper trapezius.
exercises (Anderson and Behm, 2004). With respect to the differences noted in UT activity, Lehman et al. (2008) found that an increase in UT activity was observed during pushups on an unstable base of support (Swiss ball) compared to a stable surface (bench) (Lehman et al., 2008). The shoulder is one of the most mobile joints in the human body. Generally, shoulder stability depends primarily on muscles. According to the findings in the present study and other recent publications, an increase in activity of the shoulder muscles is not the only response to the perturbation of an unstable base of support under the shoulder. It seems that wrist and elbow strategy is more important than shoulder strategy in upper limb stability. Although there is a large amount of weight on the shoulder, the elbow and wrist could be more important factors than decreased stability in the base of support in activating muscles. In the present experiment, the lowest amount of shoulder muscle activity was observed in Positions 4, 5 and 6. Using the Swiss ball under the legs may decrease the amount of weight on wrist and elbow joints. Recently, the use of external loads during push-ups has been shown to cause significant muscle activity during CKC exercises (Vaseghi et al., 2012; Lehman et al., 2008). Furthermore, these authors showed that if the feet are raised off the ground by means of a small bench, more scapulothoracic muscle activity will be recorded. The significant role of CKC exercises in the improvement of proprioception has been frequently reported. Following shoulder injury, both mechanical (casule-ligamentus, articular and musculo-tendinous) and sensorimotor (proprioception, motor and central integration) factors should be improved in order to re-establish functional shoulder stability (Myers and Lephart, 2000; McMahon et al., 1996; Kronberg et al., 1991). Co-activation in periarticular shoulder muscles is known to be a major factor in improving proprioception (Miller and Croce, 2007; Myers and Lephart, 2000). Correlations between UT and LB as well as TM and LB have also been demonstrated following CKC exercises in the present study. Among the shoulder muscles, the rotator cuff and LB are the primary factors (Labriola et al., 2005; Norkin and Levangie, 2011) and SA, UT and LT are the secondary factors influencing shoulder stability (Ludewig and Cook, 2000). In the present study, a correlation was found between UT and SA, which are attached to the scapula, and between TM and LB, which are attached to the humerus. The simultaneous contraction in these groups of muscles
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may explain the role of the scapula in shoulder stability. During exercises, the superior rotatory forces of UT may eliminate the downward rotatory forces of LB and lead to an appropriate positioning of the scapula. It seems that when more stability around the shoulder is required, the more important roles of these muscles are to align the glenoid cavity in a proper position and decrease the excessive superior translation of the head of the humerus (Ginn and Cohen, 2005). It should be noted that in the present study shoulder muscle activity was recorded in static positions. Different results may perhaps be obtained if recording is done during dynamic activities performed on an unstable base of support.
Conclusion Although the present study confirmed previous reports on marked improvement in proprioception in shoulder joints following CKC exercises, shoulder muscle activity did not increase in parallel with a reduction in base support stability in the present study. According to the American Centers for Disease Control and Prevention, about 4 million people in the United States seek medical care each year for sprains, strains, dislocations or other problems in the shoulder complex. Each year, shoulder problems account for about 1.5 million visits to orthopaedic surgeons/doctors. Functional stability of the shoulder has been shown by several studies to be affected by traumatic or non-traumatic shoulder injury. Any unsuccessful shoulder treatment exposes the joint to a greater chance of re-injury. More consideration should be given to rehabilitation for more physically active groups (such as athletes) in terms of increasing proprioceptive awareness, dynamic stabilization and restoration of functional movement patterns (Lephart and Henry, 1996; Myers and Lephart, 2000). It has been suggested by different scientists that CKC exercises simulate functional activities. This group of exercises leads to significant joint stability due to the re-establishment of joint congruency and articular mechanoreceptor stimulation (Ubinger et al., 1999; Timothy et al., 2001). In conclusion, the findings in the present study are that the CKC exercises using an unstable base of support did not increase the muscle activity compared to the CKC exercises with a stable base of support. Further studies are required in order to explore which of these two categories of exercises is safer to use in the early stage of shoulder rehabilitation.
References Anderson, K., Behm, D.G., 2005. Trunk muscle activity increases with unstable squat movements. Can J. Appl. Physiol. 30 (1), 33e45. Anderson, K.G., Behm, D.G., 2004. Maintenance of EMG activity and loss of force output with instability. J. Strength Cond Res. 18 (3), 637e640. http://dx.doi.org/10.1519/1533-4287(2004) 182.0.co;2. Andrade, R., Araujo, R.C., Tucci, H.T., Martins, J., Oliveira, A.S., 2011. Coactivation of the shoulder and arm muscles during
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6 closed kinetic chain exercises on an unstable surface. Singapore Med. J. 52 (1), 35e41. Barden, J.M., Balyk, R., Raso, V.J., Moreau, M., Bagnall, K., 2004. Dynamic upper limb proprioception in multidirectional shoulder instability. Clin. Orthop. Relat. Res. 420, 181e189. Cuomo, F., Birdzell, M.G., Zuckerman, J.D., 2005. The effect of degenerative arthritis and prosthetic arthroplasty on shoulder proprioception. J. Shoulder Elbow Surg. 14 (4), 345e348. http: //dx.doi.org/10.1016/j.jse.2004.07.009. de Oliveira, A.S., de Morais Carvalho, M., de Brum, D.P., 2008. Activation of the shoulder and arm muscles during axial load exercises on a stable base of support and on a medicine ball. J. Electromyogr. Kinesiol. 18 (3), 472e479. http: //dx.doi.org/10.1016/j.jelekin.2006.09.009. Ellenbecker, T., Cappel, K., 2000. Clinical application of closed kinetic chain exercises in the upper extremities. Orthop. Clin. North Am. 9, 231e245. Escamilla, R.F., Fleisig, G.S., Zheng, N., Barrentine, S.W., Wilk, K.E., Andrews, J.R., 1998. Biomechanics of the knee during closed kinetic chain and open kinetic chain exercises. Med. Sci. Sports Exerc. 30 (4), 556e569. Fitzgerald, G.K., 1997. Open versus closed kinetic chain exercise: issues in rehabilitation after anterior cruciate ligament reconstructive surgery. Phys. Ther. 77 (12), 1747e1754. Ginn, K.A., Cohen, M.L., 2005. Exercise therapy for shoulder pain aimed at restoring neuromuscular control: a randomized comparative clinical trial. J. Rehabil. Med. 37 (2), 115e122. http://dx.doi.org/10.1080/16501970410023443. Graham, V.L., Gehlsen, G.M., Edwards, J.A., 1993. Electromyographic evaluation of closed and open kinetic chain knee rehabilitation exercises. J. Athl. Train. 28 (1), 23e30. Kibler, W.B., 1998. The role of the scapula in athletic shoulder function. Am. J. Sports Med. 26 (2), 325e337. Kronberg, M., Brostrom, L.A., Nemeth, G., 1991. Differences in shoulder muscle activity between patients with generalized joint laxity and normal controls. Clin. Orthop. Relat. Res. 269, 181e192. Labriola, J.E., Lee, T.Q., Debski, R.E., McMahon, P.J., 2005. Stability and instability of the glenohumeral joint: the role of shoulder muscles. J. Shoulder Elbow Surg. 14 (1 Suppl S), 32Se38S. http://dx.doi.org/10.1016/j.jse.2004.09.014. Lehman, G.J., Gilas, D., Patel, U., 2008. An unstable support surface does not increase scapulothoracic stabilizing muscle activity during push up and push up plus exercises. Man Ther. 13 (6), 500e506. http://dx.doi.org/10.1016/j.math.2007.05.016. Lephart, S.M., Henry, T., 1996. The physiological basis for open and closed kinetic chain rehabilitation for the upper extremity. J. Sport Rehabil. 5 (1), 71e78. Ludewig, P.M., Cook, T.M., 2000. Alterations in shoulder kinematics and associated muscle activity in people with
K. Khademi Kalantari, S. Berenji Ardestani symptoms of shoulder impingement. Phys. Ther. 80 (3), 276e291. Machner, A., Merk, H., Becker, R., Rohkohl, K., Wissel, H., Pap, G., 2003. Kinesthetic sense of the shoulder in patients with impingement syndrome. Acta Orthop. Scand. 74 (1), 85e88. http://dx.doi.org/10.1080/00016470310013716. Marshall, P.W., Murphy, B.A., 2005. Core stability exercises on and off a Swiss ball. Arch. Phys. Med. Rehabil. 86 (2), 242e249. http://dx.doi.org/10.1016/j.apmr.2004.05.004. McMahon, P.J., Jobe, F.W., Pink, M.M., Brault, J.R., Perry, J., 1996. Comparative electromyographic analysis of shoulder muscles during planar motions: anterior glenohumeral instability versus normal. J. Shoulder Elbow Surg. 5 (2 Pt 1), 118e123. Miller, J.P., Croce, R.V., 2007. Analyses of isokinetic and closed chain movements for hamstring reciprocal coactivation. J. Sport Rehabil. 16 (4), 319e325. Myers, J.B., Lephart, S.M., 2000. The role of the sensorimotor system in the athletic shoulder. J. Athl. Train. 35 (3), 351e363. Naughton, J., Adams, R., Maher, C., 2005. Upper-body wobbleboard training effects on the post-dislocation shoulder. Phys. Ther. Sport 6 (1), 31e37. Norkin, C., Levangie, P., 2011. Joint Structure and Function. Prokopy, M.P., Ingersoll, C.D., Nordenschild, E., Katch, F.I., Gaesser, G.A., Weltman, A., 2008. Closed-kinetic chain upperbody training improves throwing performance of NCAA division I softball players. J. Strength Cond Res. 22 (6), 1790e1798. http://dx.doi.org/10.1519/JSC.0b013e318185f637. Timothy, J.H., Scott, M.L., Jorge, G., 2001. The Effect of Muscle Fatigue on Muscle Force-couple Activation of the Shoulder. Sport Studies and Physical Education Faculty Publications. Ubinger, M., Prentice, W.E., Guskiewicz, K.M., 1999. Effect of closed kinetic chain training on neuromuscular control in the upper extremity. J. Sport Rehabil. 8 (3). Uhl, T.L., Carver, T.J., Mattacola, C.G., Mair, S.D., Nitz, A.J., 2003. Shoulder musculature activation during upper extremity weight-bearing exercise. J. Orthop. Sports Phys. Ther. 33 (3), 109e117. Vaseghi, B., Jaberzadeh, S., Kalantari, K.K., Naimi, S.S., 2012. The impact of load and base of support on electromyographic onset in the shoulder muscle during push-up exercises. J. Bodyw. Mov. Ther. 17 (2), 192e199. Wilk, K.E., Arrigo, C., 1993. Current concepts in the rehabilitation of the athletic shoulder. J. Orthop. Sports Phys. Ther. 18 (1), 365e378. Zuckerman, J.D., Gallagher, M.A., Cuomo, F., Rokito, A., 2003. The effect of instability and subsequent anterior shoulder repair on proprioceptive ability. J. Shoulder Elbow Surg. 12 (2), 105e109. http://dx.doi.org/10.1067/mse.2003.4.
Please cite this article in press as: Khademi Kalantari, K., Berenji Ardestani, S., The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises, Journal of Bodywork & Movement Therapies (2013), http://dx.doi.org/10.1016/ j.jbmt.2013.08.005
MODEL
Journal of Bodywork & Movement Therapies (2013) xx, 1e6
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/jbmt
MUSCLE PHYSIOLOGY
The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises* Khosro Khademi Kalantari, PhD PT a,1, Simin Berenji Ardestani, BSc in Physiotherapy, MSc in Exercise Physiology and Sport Science b,* a Department of Physiotherapy, Faculty of Rehabilitation, Shahid Beheshti University of Medical Sciences (SBMU), Damavand Ave., 16169 Tehran, Iran b Department of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, NO, Norway
Received 1 September 2012; received in revised form 14 August 2013; accepted 27 August 2013
KEYWORDS Shoulder; Closed kinetic chain; Stability; Exercise
Summary Method: A total of thirty eligible subjects (17 female and 13 male, age Z 22.26 0.99 years, height Z 170.96 8.42 cm, weight Z 61.63 9.92 kg) were tested in six different randomly ordered positions. Surface Electromyography (EMG) was recorded from the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), long head of the biceps (LB), teres major (TM) and posterior deltoid (PD) muscles in the dominant shoulder in 6 different closed kinetic chain (CKC) positions. Objective: To investigate changes in muscular activity of the shoulder muscles at different base of support stability levels. Results: Muscle activity was greater in the most stable position for all muscles except UT (P < 0.01). Conclusion: Shoulder muscle activity did not increase in parallel with a reduction in base of support stability in the present study. ª 2013 Elsevier Ltd. All rights reserved.
* The project should be attributed to: The Physiotherapy Department, Shahid Beheshti University of Medical Sciences (SBMU), Tehran, Iran. [email protected], www.sbmu.ac. * Corresponding author. Tel.: þ47 41011703. E-mail addresses: [email protected] (K. Khademi Kalantari), [email protected], [email protected] (S. Berenji Ardestani). 1 Tel.: þ98 21 77561411; fax: þ98 21 77561406.
1360-8592/$ - see front matter ª 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jbmt.2013.08.005
Please cite this article in press as: Khademi Kalantari, K., Berenji Ardestani, S., The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises, Journal of Bodywork & Movement Therapies (2013), http://dx.doi.org/10.1016/ j.jbmt.2013.08.005
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Introduction The use of axial load exercises, which are known as closed kinetic chain (CKC) exercises, has grown considerably in recent years. Biomechanically, the function of each segment of the body is considered in relation to other interconnected segments. The whole body is considered as a chain with movement of one part affecting the others. The term “kinetic chain” is used to describe how the body moves, with the limbs functioning either in an open kinetic chain (OKC) or a closed kinetic chain (CKC) condition. The difference between these two conditions is determined by whether the terminal ending of the limb is free or fixed, for example, whether it is moving against a hard or soft surface. During CKC exercises a group of muscles and joints works simultaneously, whereas in OKC exercises they work separately, for example: shoulder abduction and knee extension. Examples of CKC exercises are push-ups, pullups, squats and lunges. All types of CKC exercises may be performed with or without weights. There is a considerable amount of research to indicate that CKC exercises are safer and more efficient than OKC exercises for both patients and healthy subjects, especially in the early stage of rehabilitation (Fitzgerald, 1997). The majority of everyday activities and sports activities are examples of CKC exercises (Prokopy et al., 2008). During CKC exercises, compressive force, which is the result of terminal limb section stabilization, decreases the amount of shear force in active joints. During OKC exercises, the shear stress present during movement exposes the joints and muscles to risk (Graham et al., 1993). Traumatic and non-traumatic shoulder injuries lead to functional instability in the shoulder complex. In general, coordination between mechanical (i.e. capsuloligamentous, articular, and musculotendinous structures) and dynamic restraint (i.e. shoulder muscle contraction) promotes functional shoulder stability. The sensorimotor system plays an important role in producing shoulder muscle coordination. It has been demonstrated that shoulder instability is due to a deficit in both mechanical and sensorimotor elements (Cuomo et al., 2005; Machner et al., 2003; Zuckerman et al., 2003; Barden et al., 2004). Improvement of proprioception in periarticular shoulder muscles is one of the main factors that can increase functional shoulder stability. It has been reported that the axial load present during CKC exercises could simulate biomechanical situations that promote muscle co-activation and a significant increase of proprioceptive stimulation, compared with OKC exercises (Kibler, 1998; Wilk and Arrigo, 1993). There is solid evidence of the beneficial effects of CKC exercises (such as squat and bridging exercises) using an unstable base of support in lower-body and trunk rehabilitation, whereas the evidence for upper-limb rehabilitation is limited (Escamilla et al., 1998; Uhl et al., 2003). Facilitation of muscle activation and proprioception by means of CKC exercises has been shown in a number of studies (Ubinger et al., 1999; Timothy et al., 2001). Generally, CKC exercises are performed with a stable or unstable base of support. Most of the literature recommends the use of a stable base of support in the early phases of shoulder rehabilitation when these exercises are safer for the individual. However, similar exercises with a relatively unstable base of support, for example a medicine ball or wobble
K. Khademi Kalantari, S. Berenji Ardestani board, are usually made use of in the advanced phases of a rehabilitation programme (Wilk and Arrigo, 1993). It is assumed that CKC exercises using an unstable base of support make greater demands on the neuromuscular system and thus will lead to an increase in joint stability, proprioception, muscle control and muscle co-activation (Lephart and Henry, 1996; Ellenbecker and Cappel, 2000; Andrade et al., 2011). CKC exercises with an unstable base of support generate a series of patterns of movement due to the sudden changes in the direction of movement. This perturbation stimulates mechanoreceptors and results in increased joint stabilization (McMahon et al., 1996). In recent years, research involving shoulder muscle activity during CKC exercises has been compared with respect to the use of stable and unstable surfaces using the same volunteers. The results from EMG recordings in these studies showed greater muscle activity during CKC exercises on an unstable surface. It should be noted that in the majority of these studies, shoulder muscle activity was compared during different upper limb CKC exercises, for example bench-press, wall-press and push-ups. However, there is a lack of studies using both a stable and unstable base of support during exercises that generate the same biomechanical patterns addressing load direction and intensity in upper limbs (Anderson and Behm, 2005; Marshall and Murphy, 2005). The purpose of the present study was to determine the differences between shoulder muscle activity during CKC exercises performed with and without a stable base of support. The aim was to improve our knowledge of progressive shoulder rehabilitation in order to provide better treatment recommendations.
Methods and materials A total of thirty eligible subjects e students at a medical university (class of 2005) e (17 females and 13 males, age Z 22.26 0.99 years, height Z 170.96 8.42 cm, weight Z 61.63 9.92 kg) participated in the present study. The inclusion criteria for subjects were: no history of orthopaedic and/or neurological disorders in the neck, shoulders or upper limbs during the preceding year and no recent pain or discomfort in upper limbs. The study was approved by the state research ethics board in Iran. Subjects gave their written informed consent prior to participation.
Testing conditions The six different test positions described in the next paragraph were randomly ordered and divided into two categories based on the amount of stability in the base support. The first category consisted of 3 different test positions with a stable base of support (the feet on the ground). The second category consisted of the same 3 different positions, but with an unstable base of support (the lower limbs were on a Swiss ball). The six positions were numbered from most stable (Position 1) to most unstable (Position 6) (see Figure 1): Position 1: both hands and feet on the ground Position 2: dominant hand on a wobble board and feet on the ground
Please cite this article in press as: Khademi Kalantari, K., Berenji Ardestani, S., The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises, Journal of Bodywork & Movement Therapies (2013), http://dx.doi.org/10.1016/ j.jbmt.2013.08.005
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The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises
Figure 1
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The six test positions utilising different support surface stability under the dominant hand.
Position 3: dominant hand on a small ball centred on a wobble board and feet on the ground Position 4: both hands on the ground and legs on a Swiss ball
Position 5: dominant hand on a wobble board and legs on a Swiss ball Position 6: dominant hand on a ball centred on a wobble board and legs on a Swiss ball
Please cite this article in press as: Khademi Kalantari, K., Berenji Ardestani, S., The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises, Journal of Bodywork & Movement Therapies (2013), http://dx.doi.org/10.1016/ j.jbmt.2013.08.005
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K. Khademi Kalantari, S. Berenji Ardestani
The subjects were asked to place themselves in each test position with 90 shoulder flexion, no internal or external rotation and elbows at full extension. The subjects’ bodies were aligned so that the middle finger was located under the acromioclavicular joint and the head was kept in line with the trunk and vertebral column. To ensure that both dominant and non-dominant shoulders were at the same level, a platform that could be adjusted was used for Positions 2, 3, 5 and 6.
EMG recording Upon arrival at the laboratory, the subject’s physical data were recorded and the test protocol explained. Before the test, each subject performed a 5 min warm-up consisting of stretching and gentle upper limb exercises. The electromyography (EMG) signals were recorded by means of surface EMG (Biometric Ltd, Gwent, South Wales, UK) of the dominant shoulder. The muscles recorded were the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), long head of biceps (LB), teres major (TM) and posterior deltoid (PD). Prior to electrode placement, the skin was shaved, abraded and cleaned with alcohol to reduce the amount of skin resistance. The surface electrodes (Biometrics Ltd, electrode model SX230, 20 38 mm) were placed according to SEINAM (surface EMG for non-invasive assessment of muscles) recommendations. To obtain a measurement, EMG was recorded continuously for 10 s. The subjects were given 5-min rest periods between each of the test positions in order to prevent muscle fatigue. The root mean square (RMS) values of EMG signals (EMGRMS) were calculated for the middle 3-s period. The intensity of muscular activity was expressed as the ratio of the EMGRMS in each particular test position compared to the most stable position (Position 1). All the data were normalized compared to Position 1.
Data analysis Statistical analysis was performed using SPSS 18 software (Statistical Package for Social Science, Chicago, IL). A one way repeated measure analysis of variance (rANOVA) was performed to compare the shoulder muscles’ activity between two categories: positions with a stable base of support (Positions 1e3) and positions with an unstable base of support (Positions 4e6). Differences were considered significant at P < 0.05 level. If significant differences were
Table 1
detected, a Bonferroni correction was carried out to identify group differences. Differences were considered significant at P < 0.01. A Pearson correlation coefficient test was used to identify the possible co-activation of the muscles across the positions. The results are presented as mean standard deviation (SD).
Results EMG measurement indicated a significant change in the extent of muscle activation within the same muscle between the stable and unstable categories. With respect to the two categories (with and without the Swiss ball), a significant decrease in activity (P < 0.001) in TM, PD, LT and LB muscles was observed in the first category when compared to the second category. Table 1 shows the mean and SD of muscle activity from EMGRMS measurement at each position. Pair-wise comparison reveals a significant difference in muscle activity (except in UT and LB) between Position 1 and other Positions (P < 0.01). In UT and SA activity the differences were just significant between Position 1 and the last 3 positions (with Swiss ball) (P < 0.01). Muscle activity in LT, TM, PD and SA decreased significantly from Position 1 to Position 6 (P < 0.01). A similar change was observed from Position 2 to Position 6 in UT and LB activities (P < 0.01). Another finding from EMG measurement after applying the Pearson correlation across shoulder muscles’ activity (see Table 2) was that strong correlations were found between UT and TM (r Z 0.76, P < 0.01), LB and UT (r Z 0.73, P < 0.01) and LB and TM (r Z 0.75, P < 0.01).
Discussion The main finding of this study was that decreased stability of support in CKC exercises is not associated with an increase in activity of shoulder muscles. The finding of the present study contrasts with that in more recent literature showing dominant shoulder muscle activity during CKC exercises with an unstable base of support (Naughton et al., 2005; de Oliveira et al., 2008; Anderson and Behm, 2004). In the present study, the highest muscle activity (except in UT) was observed in the two stable positions (Positions 1 and 2). Similar results have been reported previously by other authors. It seems that the unstable base of support is not the only factor affecting muscle activity during CKC
The ratio of muscle activity (EMGRMS) related to Position 1.
Positions
SA
1 2 3 4 5 6
100% 112 79 89 61 49
LB 2% 2% 1% 2% 2%
100% 12 65 54 55 57
PD 2% 2% 2% 2% 2%
100% 67 16 44 29 12
TM 2% 2% 2% 2% 1%
100% 74 48 42 42 55
LT 2% 2% 2% 3% 2%
100% 84 61 64 69 57
UT 2% 2% 2% 2% 2%
100% 93 79 75 78 94
3% 3% 3% 3% 2%
Data are presented in mean SD. SA, serratus anterior; LB, long head of biceps; PD, posterior deltoid; TM, teres major; LT, lower trapezius; UT, upper trapezius.
Please cite this article in press as: Khademi Kalantari, K., Berenji Ardestani, S., The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises, Journal of Bodywork & Movement Therapies (2013), http://dx.doi.org/10.1016/ j.jbmt.2013.08.005
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The effect of base of support stability on shoulder muscle activity during closed kinematic chain exercises Table 2 activity.
Pearson correlation across the shoulder muscles’
Muscles
SA
LB
PD
TM
LT
UT
SA LB PD TM LT UT
1 0.73
0.01 1
0.52 0.11 1
0.10 0.75 0.11 1
0.15 0.02 0.37 0.05 1
0.16 0.73 0.07 0.76 0.15 1
Data are presented as the correlation. SA, serratus anterior; LB, long head of biceps; PD, posterior deltoid; TM, teres major; LT, lower trapezius; UT, upper trapezius.
exercises (Anderson and Behm, 2004). With respect to the differences noted in UT activity, Lehman et al. (2008) found that an increase in UT activity was observed during pushups on an unstable base of support (Swiss ball) compared to a stable surface (bench) (Lehman et al., 2008). The shoulder is one of the most mobile joints in the human body. Generally, shoulder stability depends primarily on muscles. According to the findings in the present study and other recent publications, an increase in activity of the shoulder muscles is not the only response to the perturbation of an unstable base of support under the shoulder. It seems that wrist and elbow strategy is more important than shoulder strategy in upper limb stability. Although there is a large amount of weight on the shoulder, the elbow and wrist could be more important factors than decreased stability in the base of support in activating muscles. In the present experiment, the lowest amount of shoulder muscle activity was observed in Positions 4, 5 and 6. Using the Swiss ball under the legs may decrease the amount of weight on wrist and elbow joints. Recently, the use of external loads during push-ups has been shown to cause significant muscle activity during CKC exercises (Vaseghi et al., 2012; Lehman et al., 2008). Furthermore, these authors showed that if the feet are raised off the ground by means of a small bench, more scapulothoracic muscle activity will be recorded. The significant role of CKC exercises in the improvement of proprioception has been frequently reported. Following shoulder injury, both mechanical (casule-ligamentus, articular and musculo-tendinous) and sensorimotor (proprioception, motor and central integration) factors should be improved in order to re-establish functional shoulder stability (Myers and Lephart, 2000; McMahon et al., 1996; Kronberg et al., 1991). Co-activation in periarticular shoulder muscles is known to be a major factor in improving proprioception (Miller and Croce, 2007; Myers and Lephart, 2000). Correlations between UT and LB as well as TM and LB have also been demonstrated following CKC exercises in the present study. Among the shoulder muscles, the rotator cuff and LB are the primary factors (Labriola et al., 2005; Norkin and Levangie, 2011) and SA, UT and LT are the secondary factors influencing shoulder stability (Ludewig and Cook, 2000). In the present study, a correlation was found between UT and SA, which are attached to the scapula, and between TM and LB, which are attached to the humerus. The simultaneous contraction in these groups of muscles
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may explain the role of the scapula in shoulder stability. During exercises, the superior rotatory forces of UT may eliminate the downward rotatory forces of LB and lead to an appropriate positioning of the scapula. It seems that when more stability around the shoulder is required, the more important roles of these muscles are to align the glenoid cavity in a proper position and decrease the excessive superior translation of the head of the humerus (Ginn and Cohen, 2005). It should be noted that in the present study shoulder muscle activity was recorded in static positions. Different results may perhaps be obtained if recording is done during dynamic activities performed on an unstable base of support.
Conclusion Although the present study confirmed previous reports on marked improvement in proprioception in shoulder joints following CKC exercises, shoulder muscle activity did not increase in parallel with a reduction in base support stability in the present study. According to the American Centers for Disease Control and Prevention, about 4 million people in the United States seek medical care each year for sprains, strains, dislocations or other problems in the shoulder complex. Each year, shoulder problems account for about 1.5 million visits to orthopaedic surgeons/doctors. Functional stability of the shoulder has been shown by several studies to be affected by traumatic or non-traumatic shoulder injury. Any unsuccessful shoulder treatment exposes the joint to a greater chance of re-injury. More consideration should be given to rehabilitation for more physically active groups (such as athletes) in terms of increasing proprioceptive awareness, dynamic stabilization and restoration of functional movement patterns (Lephart and Henry, 1996; Myers and Lephart, 2000). It has been suggested by different scientists that CKC exercises simulate functional activities. This group of exercises leads to significant joint stability due to the re-establishment of joint congruency and articular mechanoreceptor stimulation (Ubinger et al., 1999; Timothy et al., 2001). In conclusion, the findings in the present study are that the CKC exercises using an unstable base of support did not increase the muscle activity compared to the CKC exercises with a stable base of support. Further studies are required in order to explore which of these two categories of exercises is safer to use in the early stage of shoulder rehabilitation.
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