- Email: [email protected]
Shoulder muscle activity during pushing, pulling, elevation and overhead throw
Journal of Electromyography and Kinesiology 15 (2005) 282–289 www.elsevier.com/locate/jelekin
Shoulder muscle activity during pushing, pulling, elevation and overhead throw ´ rpa´d Illye´s a, Rita M. Kiss A
b,*
a
b
Semmelweis University, Department of Orthopaedics, 1113 Budapest, Karolina u´t 27, Hungary Hungarian Academy of Sciences, Research Group of Structures, 1111 Budapest, Bertalan L. u. 2, Hungary Received 1 June 2004; received in revised form 5 October 2004; accepted 25 October 2004
Abstract Purpose: The aim of this study was to compare the muscle activity of recreational athletes and professional javelin throwers during pull, push, and elevation of upper extremities and during overhead throw. Scope: Nine professional javelin throwers and 16 recreational athletes without shoulder problems were studied. Signals were recorded by surface EMG from eight different muscles. The results obtained from the muscles of upper extremities of throwers were compared with those of recreational athletes. Conclusion: The different neuromuscular contol of professional throwers caused a more profitable muscle activity. Differences during the overhead throw were more significant. The deltoid muscle and rotator cuff of recreational athletes showed stronger activity than those of throwers during pull, push and elevation. The deltoid muscle and the rotator cuff of professional throwers showed stronger activity during overhead throw. Studying the detailed characteristics of muscle activity pattern (differences in length of activity periods, MVC% of muscles and time broadness among peak muscle activities in percent of total time of a movement cycle) may provide a basis for better understanding improved performance and help in planning proper rehabilitation protocol. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Shoulder; Electromyography; Biomechanics; Overhead throw
1. Introduction Electromyography as a tool for the study of muscle function has been in use since the mid-1900s. Since then, both normal and pathological muscle functions have been examined by this method. Electromyography has been used to quantify muscle activity patterns during shoulder rehabilitation protocols [8] as well as to analyze shoulder muscle activity and coordination during sports activity [8,13] and all-day work [19]. For more sufficient data to obtain there have been numerous studies performed with intramuscular electrodes [7,12] examining shoulder muscles in a dynamic *
Corresponding author. Tel.: +36 1 463 1738; fax: +36 1 463 1784. E-mail address: [email protected] (R.M. Kiss).
1050-6411/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jelekin.2004.10.005
way. Jobe et al. [12] determined muscle firing order and activity grade within the different phases of throwing movement. Gowan [7] defined two types of muscle activity during baseball pitching. Group I muscles (supra- and infraspinatus, biceps brachii) were more active during the early and late cocking phase, while Group II muscles (subcapularis and latissimus dorsi) were more active in the acceleration phase of pitching. He stated that amateurs tend to use more the muscles of the rotator cuff during the acceleration phase of pitching. Heise [8] suggests that EMG amplitudes of assistive muscles may change rather than those of primary agonists. The relationship between EMG activity and force is multifactorial, but during isometric conditions EMG signal increases with increasing force. In dynamic conditions the EMG activity of muscles also increases with
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289
increasing tension but the relationship is more complex [1,10]. The functions of shoulder muscles during various activities have been widely studied by EMG and these provide a basis for designing rehabilitation protocols as well as following up the rehabilitation program of glenohumeral and scapulothoracal muscles [2,14,15,21]. In a number of studies, researchers have used dynamic EMG to examine shoulder muscle activity during overhead sports activities, predominantly overhead baseball pitching [5,7,8]. Among overhead athletes the risk of shoulder injury may be increased with the level of athlete, the style of throwing, the length of the throw and the level of associated muscle fatigue that occurs throughout practices. Developmental instability may appear after several years of heavy trainings that leads to different shoulder problems developing during the career of overhead thrower athletes. Injuries of the rotator cuff are the most common ones while disorders (rupture, tendinitis, etc.) of biceps tendon and pectoralis major can also be observed [13]. Increasing the strength of muscles responsible for stability in the shoulder joint can lead to injury prevention by maintaining humeral head in the glenoid. Detailed defining activation patterns of various muscles may help in planning the rehabilitation process as the accurate simulation and training program of the injured and/or affected muscles can properly be planned and regularly and accurately followed up with EMG measurements. Earlier EMG studies indicated that the subscapularis muscle is important for anterior stability and the infraspinatus for posterior stability [11,17,16]. The subscapularis muscle also plays a main stabilizing role in abduction, rotation and flexion, while the infraspinatus muscle is active in abduction and flexion, and the supraspinatus muscle in extension [14,18]. The purposes of this study were to define a detailed sequence of muscular activity patterns in selected shoulder girdle muscles during pull, push, and elevation and during overhead throw and to analyze the characteristics of overhead throw in professional javelin throwers. An improved understanding of muscle activity patterns during different movements may benefit many aspects of athletic training, injury prevention, and even rehabilitation after injury.
2. Material and methods 2.1. Subjects Professional javelin throwers and a comparison group of healthy subjects took part in the study. The professional athletes were all trained by a top trainer of the national team, which ensured the same training protocol for all the athletes. The comparison group
283
was selected from among university students, so as the age, body height and weight, BMI were comparable to those of professional athletes. All subjects were screened for musculoskeletal pain or disorders of the upper limbs by an experienced medical doctor. Subjects were excluded if they reported any type of previous disorders or symptoms within the past year. Out of 15 professional javelin throwers seven male (age 21.2 ± 3.1 years, height 185.3 ± 12.1 cm, weight 79.1 ± 4.1 kg) and two female (age 19.9 ± 2.38 years, height 176.9 ± 12.4 cm, weight 62.3 ± 7.3 kg) athletes were selected for the measurement. Out of 20 of the comparison group 12 males (age 22.1 ± 1.1 years, height 182.9 ± 23.9 cm, weight 72.1 ± 3.4 kg) and four females (age 22.6 ± 2.12 years, height 164.1 ± 33.3 cm, weight 61.1 ± 4.5 kg) remained in the study. The Constant score was 100/100 in all cases [3,4]. Each subject provided informed consent before participation and signed a consent form approved by the Hungarian Human Subjects Compliance Committee. 2.2. Procedures and instrumentation The following movements were investigated: (Fig. 1) (a) pull; (b) push; (c) elevation; (d) slow and (e) fast overhead throw. Subjects were standing during the measurement. Each movement was repeated at least three times one after the other, the movement series was continuous. Before the measurement the end points of the movements and the movement itself were taught to the subjects so as they could repeat the movement in the same manner. Each phase of the pull, push and elevation exercises was performed at 40 beats per minute, standardized with the aid of a metronome. Exercises involving the use of elastic resistance were performed at a distance away from the point of fixation, where the subject could perform at least three repetitions while maintaining consistent metronome speed. The exercises were performed as follows. At the starting position of pull in the saggital plane the arm was in approximately 45° of anteflexion with extended elbow and the forearm in 90° of supination. From this position all subjects performed pull against the same minimal resistance administered by a rubber band. The end point of pull was at approximately 10° of dorsiflexion with 100° of flexion of the elbow, and the forearm still in 90° of supination. At the starting position of push in the saggital plane the upper arm was in neutral position beside the trunk with the elbow in 90° of flexion, the forearm in 90° of pronation and the wrist in 30° of dorsiflexion. The end-point of pushing was at approximately 70° of anteflexion with the elbow in full extension and forearm and wrist in the same supination and dorsiflexion position as at the starting point.
284
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289
Fig. 1. Type of movements: (a) pull, (b) push, (c) elevation, (d) overhead throw.
The plane of elevation was in approximately 20° of anteflexion to the frontal plane. The elbow and the wrist were extended during the movement. Elevation started from a neutral position of the upper extremity. The end point was at approximately 140° of elevation. A tennis ball was used for overhead throw, whereas performing slow overhead pitch muscles were investigated during target throw. The target was 5 m away. The fast overhead throw was performed with maximal speed. During the fast pitch subjects were asked to throw the ball as fast as they can, in the position as it was natural for them, into a large ‘‘golf’’-net allowing the subjects to throw into a direction and with the technique as they wished. Activity from: (1) pectoralis major, (2) infraspinatus, (3–5) anterior, middle and posterior deltoid, (6) supraspinatus with trapesius (upper trapesius), (7) biceps brachii, and (8) triceps brachii were recorded in parallel. Ag–AgCl mono-polar surface electrodes (blue sensor P-00-S, Germany) were attached to the skin over the muscle belly, in the main direction of muscle fibers with an interelectrode center-to-center distance of 30 mm. The reference electrode was taped to the seventh cervical spine process and to the acromion. Electrodes were placed using the recommendations of SENIAM [9]. The locations of electrodes are shown in Fig. 2. EMG
investigation was performed on the dominant side. The electrodes were connected to an eight-channel EMG amplifier (Zebris CMS-HS motion analyzing system, Germany). The sampling rate was 1000 Hz. The amplitude of the raw EMG signal is quasi stochastic (random) and can be represented by a Gaussian distribution function: the amplitude ranges from 2000 to +2000 mV and the usable energy of the signal is limited to the frequency spectrum of 10–500 Hz. The accuracy of the differential amplifier is measured by the Common Mode Rejection Ratio (CMRR > 80, dBnoise <2 lV). ANVOLCOM model was used to check the cross-talk of different muscles [9]. The root mean square (RMS) values of EMG signals were calculated for consecutive segments of 50 ms. In order to allow comparison of the activity in specific muscles and the activity in specific muscles among different individuals the EMG was normalized. Maximum EMG reference values were calculated for each muscle by using the maximum of five peaks EMG signals to represent 100% MVC. [14,19,20]. Muscle activity was categorized as minimal (0–39.9%), moderate (40–74.9%) or marked (75–100%) [13]. The analysis was also made for movement type, whereas the activity pattern of different muscles could
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289
285
differences between the two groups are summarized in Table 1. 3.1. Pull In the comparison group, mainly the posterior deltoid took part in the motion, it demonstrated maximal activity. Activity of the anterior and middle deltoid, supraspinatus, infraspinatus, biceps brachii, and triceps brachii was moderate. In javelin throwers, approximately all investigated muscles took part in the same ratio in generating the movement; the activity level of each muscle was minimal, except for the posterior deltoid, infraspinatus and triceps brachii, which were moderately active. In the comparison group, the middle and posterior deltoid, the supraspinatus, infraspinatus, biceps brachii and triceps brachii took part in generating the pull, while the anterior deltoid was active solely in the deference phase, rarely cooperating with pectoralis major. In javelin throwers, the posterior deltoid, the supraspinatus, infraspinatus, and biceps brachii – and rarely the middle deltoid – were active in the pull phase. In the deference phase, the pectoralis major, the anterior deltoid, and the triceps brachii were mainly active. Significant differences could be observed between the two groups in the MVC% of the middle and posterior deltoid, the supraspinatus and infraspinatus as well as between their ratios to each other (Table 1). Fig. 2. Locations of surface EMG electrodes.
3.2. Push be compared by muscles whereas the participation of different muscles in each movement type could be compared. 2.3. Data analysis Statistical analysis was carried out using the MS Excel Analysis ToolPak. The mean and standard deviation of MVC% were determined for each muscle during the different movement types. The time broadness among peak muscle activities in percent of total time of a movement cycle was calculated separately at each subject [22]. The mean and standard deviation of time broadness were determined by groups. Comparisons of MVC% and the time broadness among peak muscle activities between the two groups were made by unpaired t-test with a set at 0.05. 3. Results The mean values of MVC%, standard deviation (SD), grading of activity of each muscle group and significant
During push the anterior deltoid was maximally active while pectoralis major, middle deltoid, infraspinatus, biceps brachii and triceps brachii were moderately active in the comparison group. On the other hand, the anterior and middle deltoid, the pectoralis major, infraspinatus and the biceps brachii demonstrated moderate activity, all other muscles were minimally active in javelin throwers. In the comparison group, the pectoralis major, the anterior and middle deltoid, the infraspinatus, and the triceps brachii were achieving their maximal activity level in the pushing phase, whereas the posterior deltoid, the supraspinatus, and the biceps brachii were active in the deference phase. In the push phase at the javelin throwers, the pectoralis major, the anterior and middle deltoid, the infraspinatus, and biceps brachii were taking part, while in the deference phase the supraspinatus and the biceps brachii achieved maximum level of activity. Significant difference could be observed between the two groups in the MVC% of the posterior deltoid and supraspinatus (Table 1).
99.80 (0.63), +++
3.3. Elevation In the comparison group all three parts of the deltoid and the supraspinatus demonstrated maximum activity while infraspinatus, biceps brachii and triceps brachii were moderately active and pectoralis major minimally active. In javelin throwers, the anterior and middle deltoid and the supraspinatus were maximally active and the posterior head of deltoid, the infraspinatus and biceps brachii demonstrated moderate activity. All muscles achieved the maximum level of their activity in the elevation phase. Significant differences between the two groups could only be observed in the MVC% of the posterior deltoid. The activity level of the muscle was maximum in the comparison group, while in javelin throwers it was moderate (Table 1). 3.4. Slow overhead throw (as goal oriented movement) All muscles of the subjects in both groups were moderately active except for the biceps brachii, which was minimally active in the comparison group. No significant differences were observed within the group of subjects (Table 1). The mean maximum time broadness among peak muscle activities was 24.5% in the comparison group, while it was 21.9% at javelin throwers if we consider the total time of a throw to be 100%. No significant differences were observed within the group of subjects (p = 0.73) (Table 1).
Activity level: +, minimal; ++, moderate; +++, maximal.
94.7 (8.81), +++ 93.40 (9.86), +++ 100.00 (0.00), +++ 84.10 (17.30), +++ 92.50 (15.30), +++
93.50 (15.17), +++
86.6 (21.45), +++
96.87 (10.36), +++
53.40 (18.15), ++
87.27 (17.89), +++ 89.33 (16.68), +++ 81.27 (17.23), +++
87.73 (22.51), +++
57.20 (18.55), ++ 65.00 (21.66), ++ 41.20 (22.88), ++ 66.60 (18.89), ++ 69.20 (20.36), ++
76.93 (19.40), +++
51.20 (25.10), ++
Comparison group, n = 16 Javelin throwers, n = 9 Fast overhead throw
87.07 (23.34), +++
82.80 (15.73), +++
43.20 (19.84), ++
53.07 (15.72), ++
29.10 (19.24), + 71.10 (35.30), ++ 71.70 (30.78), ++
54.20 (24.10), ++
79.60 (24.67), +++
68.27 (21.40), ++
95.90 (6.17), +++
46.00 (25.97), ++
Comparison group, n = 16 Javelin throwers, n = 9 Slow overhead throw
28.20 (24.36), +
51.60 (21.79), ++
52.9 (26.77), ++
40.67 (27.30), ++
83. 90 (19.95), +++
52.93 (24.82), ++
33.20 (21.65), +
32.30 (28.53), + 53.20 (23.40), ++ 44.80 (20.51), ++
68.60 (26.08), ++ 80.13 (19.44), +++ 89.67 (21.22), +++
19.30 (16.09), + 14.70 (11.11), + 40.30 (27.09), ++
90.00 (14.64), +++
65.50 (26.06), ++
31.93 (26.68), +
47.60 (33.44), ++
Comparison group, n = 16 Javelin throwers, n = 9 Elevation
75.13 (19.35), +++
Comparison group, n = 16 Javelin throwers, n = 9 Push
58.67 (30.85), ++
80.73 (28.50), +++
27.53 (17.28), + 53.87 (27.36), ++
58.47 (23.43), ++
50.67 (28.70), ++ 55.53 (29.95), ++ 50.27 (23.21), ++ 34.13 (16.57), +
44.30 (30.31), ++ 50.90 (23.97), ++ 24.30 (14.20), + 19.20 (6.12), +
32.60 (26.67), +
28.40 (20.63), + 39.60 (16.26), ++ 22.00 (10.42), +
Triceps brachii
49.80 (27.82), ++ 45.60 (25.00), ++ 59.60 (28.03), ++ 52.07 (25.71), ++ 95.60 (7.23), +++ 65.47 (27.81), ++
Biceps brachii Infraspinatus Supraspinatus Posterior deltoid Middle deltoid
37.67 (24.16), ++
Anterior deltoid Pectoralis major
30.47 (22.86), +
Comparison group, n = 16 Javelin throwers, n = 9 Pull
Table 1 Average MVC% (standard deviation) of the muscles examined of the comparison group and javelin throwers; grading of activity level of muscles during: (a) pull, (b) push, (c) elevation, (d) slow overhead throw, (e) maximal speed overhead throw
47.33 (26.94), ++
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289
286
3.4.1. Fast overhead throw (as goal oriented movement with maximum speed) All muscles of the subjects of both groups were maximally active. Significant differences could be observed in the activity of the posterior deltoid (Table 1). Longer time broadness among peak muscle activities could be observed in the comparison group comparing to the javelin throwers (Fig. 3). In javelin throwers the difference was minimal (Fig. 3(b)). The mean of time broadness among peak muscle activities was 13.1% in the comparisons and 10.6% in javelin throwers if we considered the total time of a throw to be 100%. The difference was not significant (p = 0.44).
4. Discussion The presumable selective use of certain muscles to throw a ball determines the quality of a thrower. Throw is a complex act that uses the muscles of the lower extremities, the trunk, the shoulder, the elbow, the wrist and the fingers. The skilled thrower throws a ball accurately, quickly and repetitively because
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289
Fastoverhead throw -Comparisongroup 100 Pectoralis major
90
Infraspinatus
MVC%
80
Anterior deltoid
70
Middle deltoid
60
Posterior deltoid Supraspinatus
50
Biceps brachii
40
Ttriceps brachii
30 20 10 0 0
20
(a)
40
60
80
100
Percent of movement cycle[%]
Fast overhead throw -Javelin throwers 100 Pectorolalis major
90
Infraspinatus
80
Anterior deltoid Middle deltoid
70
Posterior deltoid
MVC%
60
Supraspinatus Biceps brachii
50
Triceps brachii
40 30 20 10 0 0
(b)
20
40
60
80
100
Percent of movement cycle [%]
Fig. 3. Normalized EMG curve of the muscles examined, during maximal speed overhead throw: (a) comparison group, (b) javelin throwers.
these muscles are well-coordinated and well-conditioned. In our study only the muscle activity of the shoulder is investigated. The goal of our study was to examine how the muscle activity pattern depends on the quality of throwers. The muscle activity pattern was characterized by maximal value of contraction and by time broadness in the percent of the movement cycle. Surface EMG electrodes were used, neither of them caused pain or restricted subjectsÕ movements. The amplifiersÕ bandwidth was sufficient for both type of motion (isokinetic and dynamic). Processing the data, we used the MVC% of each muscle to compare various muscle activities of different subjects during several movements. The advantage of this type of normalizing method is that it belongs to a dynamic condition and a second set is not needed for determining the RVC. Average activity period of mus-
287
cles during the movement cycle and mean time broadness in the percent of the movement cycle were calculated by analyzing all cycles. These two parameters should be considered in evaluating muscle activity pattern. The pattern is different in case there is a difference in any of the parameters above. The rationale for using EMG to study muscle activation during elementary motion and during throwing movement is to provide a better understanding of muscle firing patterns during these shoulder movements. The movements of pull, push and elevation were isokinetic as the same speed during various movements at different subjects was ensured with metronome. The overhead throw was dynamic motion. Two different types of movements gave us an opportunity to analyze the effect of speed on muscle activity. In our experience, professional javelin throwers and recreational athletes were examined and compared to each other. Gowan et al. [7] and Kelly et al. [13] have defined two groups of muscles. Infraspinatus, supraspinatus, three part of deltoid defined as stabilizers. Subscapularis, pectoralis major, latissimus dorsi and triceps brachii defined as accelerators. On the basis of our study this definition could be use not only for throw, but it could be used for pull, push and elevation as well. During pull and push, the activity of all muscles of recreational athletes is higher than that of professional athletesÕ (Table 1). Significant differences could be observed between the two groups of the middle and posteror deltoid, supra- and infraspinatus (Table 1). The difference is best visible during elevation, as in the comparison group the activity of all three parts of the deltoid and the supraspinatus is maximum while in javelin throwers the anterior and middle deltoid and the supraspinatus demonstrate maximal activity (Table 1). This indicates that coordination in muscle contraction plays a significant role in stabilizing the shoulder joint, and the role of the muscles mentioned above is higher in recreational athletes during pull, push and elevation than in qualifier throwers. During overhead throw in the comparison group, the activity level of one head of the deltoid is much higher than that of the other muscles while in javelin throwers besides the deltoid the activity level of one of the rotator cuff muscles is higher than the othersÕ (Table 1). During slow overhead throw, there was no significant difference in the maximum contraction of the muscles between the two groups (Table 1). We suppose that this type of motion was equally unknown for both groups and this is the reason why the supposedly more developed neuromuscular comparison of the athletes was not obvious. During maximum speed overhead throw, there was significant difference between the two groups in the activity of the posterior deltoid (Table 1). This indicates that during overhead throw
288
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289
of professional athletes an additional muscle (posterior deltoid) has to be involved to ensure proper stability of the shoulder joint as forces generated during fast speed throw requires this. On basis of the results it could be determined the peak muscle activity is significantly higher during the dynamic motion, as the overhead throw than during the isokinetic motion. Peak muscle activity depends on force, on speed and on proprioception level of muscles. In the comparison group, 3–4 muscles achieve nearly 100% MVC value, while in javelin throwers 5–8 muscles achieve nearly 100% MVC value. In javelin throwers, the standard deviation of MVC values of the muscles is significantly higher than that of the comparison group (p = 0.007) (Table 1). These findings are correlated by results of Hintermeister et al. [10]. The other parameter for the characteristics of muscle activity pattern is the time broadness in the percent of the movement cycle. In javelin throwers that of the agonist and antagonist muscles are minimal, while in the comparison subjects the time broadness is wider; however, the difference between the groups is not significant (Table 1). This can be well observed during fast overhead throw (Fig. 3). This suggests that different neuromuscular control and proprioception of javelin throwers cause different muscle coordination during throwing. The comparison of results of MVC% and time broadness in the percent of the movement cycle may strengthen our belief that the different motion patterns could be characterized by MVC and by time broadness in the percent of the movement cycle. The observations above resulted from different motion patterns in the two groups that may refer to the learned character of overhead throw, which is correlated by findings of earlier studies [5–8,12,13]. Muscle activity patterns have clinical implications for both the training and rehabilitation protocol: 1. By knowing the manner in which different muscles fire during various motions (pull, push, elevation and throw), muscle-specified conditioning protocols could be provided. The demonstration of distinct patterns of muscle activation may have further implications for changes in training and rehabilitation protocols. 2. The maximal activation documented during the different movement in all muscles tested suggests the mechanism of muscle injury. Movements execute with low peak amplitudes may minimize the risk of damage for initial muscular training. This is useful in the first part of rehabilitation and for strengthening stabilizer muscles. Large peak amplitudes may exceed the maximal load that repaired and injured muscles can withstand. Exercises with
large peak amplitudes can be used in the last period of rehabilitation and the strengthening of accelerator muscles. The data collected in this study enhance the knowledge of the muscle activity used during pull, push, elevation and throw.
Acknowledgements This work was supported in part by the Hungarian Scientific Found T034150 by Stipendium Istva´n Sze´chenyi (Rita Kiss,) and by the Research Group of Hungarian Academy of Sciences.
References [1] J.V. Basmajian, C.J. DeLuca, Muscles Alive: Their Functions Revealed by Electromyography, fifth ed., Williams & Wilkins, Baltimore, 1985. [2] J.P. Bradley, J.E. Tibone, Electromyographic analysis of muscles action about the shoulder, Clin. Sports Med. 10 (1991) 789–805. [3] C.R. Constant, A.H.G. Murley, A clinical method of functional assessment of the shoulder, Clin. Orthop. 214 (1987) 160–164. [4] C.R. Constant, Assessment of the shoulder function, in: D.F. Gazielly, P. Gleyze, P. Thomas (Eds.), The Cuff, Elsevier, Paris, 1997, pp. 39–44. [5] G. David, M.E. Magarey, M.A. Jones, Z. Dvir, K.S. Tu¨rker, M. Sharpe, EMG and strength correlates of selected shoulder muscles during rotations of the glenohumeral joint, Clin. Biomech. 15 (2000) 95–102. [6] M.J. Decker, J.M. Tokish, H.B. Ellis, M.R. Torry, R.J. Hawkins, Subscapularis muscle activity during selected rehabilitation exercises, Am. J. Sports Med. 31 (2003) 126–134. [7] I.D. Gowan, F.W. Jobe, J.E. Tibone, J. Perry, D.R. Moynes, A comparative electromyographic analysis of the shoulder during pitching, Am. J. Sports Med. 15 (1987) 586– 590. [8] G.D. Heise, EMG changes in agonist muscles during practice of a multijoint throwing skill, J. Electromyogr. Kinesiol. 5 (1995) 81– 94. [9] H.J. Hermes, B. Freriks, R. Merletti, D. Stegemann, J. Blok, G. Rau, C. Disselhorst-Klug, G. Hagg, European Recommendations for Surface Electromyography, Results of the SENIAM project Roessingh Research and Development b.v., Enschede, The Netherlands, 1999. [10] R.A. Hintermeister, G.W. Lange, J.M. Schulteis, M.J. Bey, R.J. Hawkins, Electromyographic activity and applied load during shoulder rehabilitation exercises using elastic resistance, Am. J. Sports Med. 26 (1998) 210–219. [11] L. Hovelius, Anterior dislocation of the shoulder. PhD thesis. Linko¨ping University No. 139, Linko¨ping, Sweden, 1982. [12] F.V. Jobe, D.R. Moynes, Tibone, J. Perry, An EMG analysis of the shoulder in pitching. A second report, Am. J. Sports Med. 12 (1984) 218–220. [13] B.T. Kelly, S.I. Backus, R.D. Warren, R.J. Williems, Electromyographic analysis and phase definition of the overhead football throw, Am. J. Sports Med. 30 (2002) 837–847.
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289 [14] M. Kronberg, G. Ne´meth, L.A. Brostro¨m, Muscle activity and coordination in the normal shoulder, Clin. Orthop. Rel. Res. 257 (1990) 76–85. [15] J.B. Moseley Jr., F.W. Jobe, M. Pink, J. Perry, J. Tibone, EMG analysis of the scapular muscles during a shoulder rehabilitation program, Am. J. Sports Med. 20 (1992) 128– 134. [16] J. Ovensen, S. Nielsen, Posterior instability of the shoulder joint, Acta Othop. Scand. 57 (1986) 436. [17] J. Ovensen, S. Nielsen, Stability of the shoulder joint, Acta Othop. Scand. 56 (1985) 149. [18] A.K. Saha, Dynamic stability of the glenohumeral joint, Acta Othop. Scand. 42 (1971) 491. [19] K. Schu¨ldt, J. Ekholm, K. Harms-Ringdahl, U.P. Arborelius, G. Ne´meth, Influence of sitting postures on neck and shoulder emg during arm-hand work movement, Clin. Biomech. 2 (1987) 126. [20] G.L. Soderberg, T.M. Cook, An electromyographic analysis of quadriceps femoris muscle setting and straight leg rising, Phys. Ther. 63 (1983) 1434. [21] H. Townsend, F.W. Jobe, M. Pink, J. Perry, Electromyographic analysis of the glenohumeral muscles during a baseball rehabilitation program, Am. J. Sports Med. 19 (1991) 264– 272. [22] D.A. Winter, Biomechanics and motor control of human movement, second ed., Wiley, New York, 1990.
289
Kiss, Rita PhD, senior research fellow, member of HAS-BUTE Research Group of Structures, working at Biomechanical Lab. Graduated from the Faculty of Civil Engineering of the Technical University of Budapest as qualified civil engineer in 1991. Main research area: analysis of human motion mechanics. From 2001: Sze´che´nyi grant holder. Member of several – domestic and international – scientific and educational bodies/committees. Published a number of special articles, methodology guides, and conference lectures in the past years. ´ rpa´d MD, orthopaedic surgeon, Illye´s, A traumatologist. Graduated from the Faculty of General Medicine of Debrecen University of Medical Sciences in 1992; passed special examination of traumatology in 1998 and of orthopaedy in 2001. Main research areas: conservative and operative treatment/rehabilitation of injuries, sports surgery analysis of sports movements. Published a number of special articles, methodology guides, and conference lectures in the past years.
Shoulder muscle activity during pushing, pulling, elevation and overhead throw ´ rpa´d Illye´s a, Rita M. Kiss A
b,*
a
b
Semmelweis University, Department of Orthopaedics, 1113 Budapest, Karolina u´t 27, Hungary Hungarian Academy of Sciences, Research Group of Structures, 1111 Budapest, Bertalan L. u. 2, Hungary Received 1 June 2004; received in revised form 5 October 2004; accepted 25 October 2004
Abstract Purpose: The aim of this study was to compare the muscle activity of recreational athletes and professional javelin throwers during pull, push, and elevation of upper extremities and during overhead throw. Scope: Nine professional javelin throwers and 16 recreational athletes without shoulder problems were studied. Signals were recorded by surface EMG from eight different muscles. The results obtained from the muscles of upper extremities of throwers were compared with those of recreational athletes. Conclusion: The different neuromuscular contol of professional throwers caused a more profitable muscle activity. Differences during the overhead throw were more significant. The deltoid muscle and rotator cuff of recreational athletes showed stronger activity than those of throwers during pull, push and elevation. The deltoid muscle and the rotator cuff of professional throwers showed stronger activity during overhead throw. Studying the detailed characteristics of muscle activity pattern (differences in length of activity periods, MVC% of muscles and time broadness among peak muscle activities in percent of total time of a movement cycle) may provide a basis for better understanding improved performance and help in planning proper rehabilitation protocol. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Shoulder; Electromyography; Biomechanics; Overhead throw
1. Introduction Electromyography as a tool for the study of muscle function has been in use since the mid-1900s. Since then, both normal and pathological muscle functions have been examined by this method. Electromyography has been used to quantify muscle activity patterns during shoulder rehabilitation protocols [8] as well as to analyze shoulder muscle activity and coordination during sports activity [8,13] and all-day work [19]. For more sufficient data to obtain there have been numerous studies performed with intramuscular electrodes [7,12] examining shoulder muscles in a dynamic *
Corresponding author. Tel.: +36 1 463 1738; fax: +36 1 463 1784. E-mail address: [email protected] (R.M. Kiss).
1050-6411/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jelekin.2004.10.005
way. Jobe et al. [12] determined muscle firing order and activity grade within the different phases of throwing movement. Gowan [7] defined two types of muscle activity during baseball pitching. Group I muscles (supra- and infraspinatus, biceps brachii) were more active during the early and late cocking phase, while Group II muscles (subcapularis and latissimus dorsi) were more active in the acceleration phase of pitching. He stated that amateurs tend to use more the muscles of the rotator cuff during the acceleration phase of pitching. Heise [8] suggests that EMG amplitudes of assistive muscles may change rather than those of primary agonists. The relationship between EMG activity and force is multifactorial, but during isometric conditions EMG signal increases with increasing force. In dynamic conditions the EMG activity of muscles also increases with
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289
increasing tension but the relationship is more complex [1,10]. The functions of shoulder muscles during various activities have been widely studied by EMG and these provide a basis for designing rehabilitation protocols as well as following up the rehabilitation program of glenohumeral and scapulothoracal muscles [2,14,15,21]. In a number of studies, researchers have used dynamic EMG to examine shoulder muscle activity during overhead sports activities, predominantly overhead baseball pitching [5,7,8]. Among overhead athletes the risk of shoulder injury may be increased with the level of athlete, the style of throwing, the length of the throw and the level of associated muscle fatigue that occurs throughout practices. Developmental instability may appear after several years of heavy trainings that leads to different shoulder problems developing during the career of overhead thrower athletes. Injuries of the rotator cuff are the most common ones while disorders (rupture, tendinitis, etc.) of biceps tendon and pectoralis major can also be observed [13]. Increasing the strength of muscles responsible for stability in the shoulder joint can lead to injury prevention by maintaining humeral head in the glenoid. Detailed defining activation patterns of various muscles may help in planning the rehabilitation process as the accurate simulation and training program of the injured and/or affected muscles can properly be planned and regularly and accurately followed up with EMG measurements. Earlier EMG studies indicated that the subscapularis muscle is important for anterior stability and the infraspinatus for posterior stability [11,17,16]. The subscapularis muscle also plays a main stabilizing role in abduction, rotation and flexion, while the infraspinatus muscle is active in abduction and flexion, and the supraspinatus muscle in extension [14,18]. The purposes of this study were to define a detailed sequence of muscular activity patterns in selected shoulder girdle muscles during pull, push, and elevation and during overhead throw and to analyze the characteristics of overhead throw in professional javelin throwers. An improved understanding of muscle activity patterns during different movements may benefit many aspects of athletic training, injury prevention, and even rehabilitation after injury.
2. Material and methods 2.1. Subjects Professional javelin throwers and a comparison group of healthy subjects took part in the study. The professional athletes were all trained by a top trainer of the national team, which ensured the same training protocol for all the athletes. The comparison group
283
was selected from among university students, so as the age, body height and weight, BMI were comparable to those of professional athletes. All subjects were screened for musculoskeletal pain or disorders of the upper limbs by an experienced medical doctor. Subjects were excluded if they reported any type of previous disorders or symptoms within the past year. Out of 15 professional javelin throwers seven male (age 21.2 ± 3.1 years, height 185.3 ± 12.1 cm, weight 79.1 ± 4.1 kg) and two female (age 19.9 ± 2.38 years, height 176.9 ± 12.4 cm, weight 62.3 ± 7.3 kg) athletes were selected for the measurement. Out of 20 of the comparison group 12 males (age 22.1 ± 1.1 years, height 182.9 ± 23.9 cm, weight 72.1 ± 3.4 kg) and four females (age 22.6 ± 2.12 years, height 164.1 ± 33.3 cm, weight 61.1 ± 4.5 kg) remained in the study. The Constant score was 100/100 in all cases [3,4]. Each subject provided informed consent before participation and signed a consent form approved by the Hungarian Human Subjects Compliance Committee. 2.2. Procedures and instrumentation The following movements were investigated: (Fig. 1) (a) pull; (b) push; (c) elevation; (d) slow and (e) fast overhead throw. Subjects were standing during the measurement. Each movement was repeated at least three times one after the other, the movement series was continuous. Before the measurement the end points of the movements and the movement itself were taught to the subjects so as they could repeat the movement in the same manner. Each phase of the pull, push and elevation exercises was performed at 40 beats per minute, standardized with the aid of a metronome. Exercises involving the use of elastic resistance were performed at a distance away from the point of fixation, where the subject could perform at least three repetitions while maintaining consistent metronome speed. The exercises were performed as follows. At the starting position of pull in the saggital plane the arm was in approximately 45° of anteflexion with extended elbow and the forearm in 90° of supination. From this position all subjects performed pull against the same minimal resistance administered by a rubber band. The end point of pull was at approximately 10° of dorsiflexion with 100° of flexion of the elbow, and the forearm still in 90° of supination. At the starting position of push in the saggital plane the upper arm was in neutral position beside the trunk with the elbow in 90° of flexion, the forearm in 90° of pronation and the wrist in 30° of dorsiflexion. The end-point of pushing was at approximately 70° of anteflexion with the elbow in full extension and forearm and wrist in the same supination and dorsiflexion position as at the starting point.
284
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289
Fig. 1. Type of movements: (a) pull, (b) push, (c) elevation, (d) overhead throw.
The plane of elevation was in approximately 20° of anteflexion to the frontal plane. The elbow and the wrist were extended during the movement. Elevation started from a neutral position of the upper extremity. The end point was at approximately 140° of elevation. A tennis ball was used for overhead throw, whereas performing slow overhead pitch muscles were investigated during target throw. The target was 5 m away. The fast overhead throw was performed with maximal speed. During the fast pitch subjects were asked to throw the ball as fast as they can, in the position as it was natural for them, into a large ‘‘golf’’-net allowing the subjects to throw into a direction and with the technique as they wished. Activity from: (1) pectoralis major, (2) infraspinatus, (3–5) anterior, middle and posterior deltoid, (6) supraspinatus with trapesius (upper trapesius), (7) biceps brachii, and (8) triceps brachii were recorded in parallel. Ag–AgCl mono-polar surface electrodes (blue sensor P-00-S, Germany) were attached to the skin over the muscle belly, in the main direction of muscle fibers with an interelectrode center-to-center distance of 30 mm. The reference electrode was taped to the seventh cervical spine process and to the acromion. Electrodes were placed using the recommendations of SENIAM [9]. The locations of electrodes are shown in Fig. 2. EMG
investigation was performed on the dominant side. The electrodes were connected to an eight-channel EMG amplifier (Zebris CMS-HS motion analyzing system, Germany). The sampling rate was 1000 Hz. The amplitude of the raw EMG signal is quasi stochastic (random) and can be represented by a Gaussian distribution function: the amplitude ranges from 2000 to +2000 mV and the usable energy of the signal is limited to the frequency spectrum of 10–500 Hz. The accuracy of the differential amplifier is measured by the Common Mode Rejection Ratio (CMRR > 80, dBnoise <2 lV). ANVOLCOM model was used to check the cross-talk of different muscles [9]. The root mean square (RMS) values of EMG signals were calculated for consecutive segments of 50 ms. In order to allow comparison of the activity in specific muscles and the activity in specific muscles among different individuals the EMG was normalized. Maximum EMG reference values were calculated for each muscle by using the maximum of five peaks EMG signals to represent 100% MVC. [14,19,20]. Muscle activity was categorized as minimal (0–39.9%), moderate (40–74.9%) or marked (75–100%) [13]. The analysis was also made for movement type, whereas the activity pattern of different muscles could
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289
285
differences between the two groups are summarized in Table 1. 3.1. Pull In the comparison group, mainly the posterior deltoid took part in the motion, it demonstrated maximal activity. Activity of the anterior and middle deltoid, supraspinatus, infraspinatus, biceps brachii, and triceps brachii was moderate. In javelin throwers, approximately all investigated muscles took part in the same ratio in generating the movement; the activity level of each muscle was minimal, except for the posterior deltoid, infraspinatus and triceps brachii, which were moderately active. In the comparison group, the middle and posterior deltoid, the supraspinatus, infraspinatus, biceps brachii and triceps brachii took part in generating the pull, while the anterior deltoid was active solely in the deference phase, rarely cooperating with pectoralis major. In javelin throwers, the posterior deltoid, the supraspinatus, infraspinatus, and biceps brachii – and rarely the middle deltoid – were active in the pull phase. In the deference phase, the pectoralis major, the anterior deltoid, and the triceps brachii were mainly active. Significant differences could be observed between the two groups in the MVC% of the middle and posterior deltoid, the supraspinatus and infraspinatus as well as between their ratios to each other (Table 1). Fig. 2. Locations of surface EMG electrodes.
3.2. Push be compared by muscles whereas the participation of different muscles in each movement type could be compared. 2.3. Data analysis Statistical analysis was carried out using the MS Excel Analysis ToolPak. The mean and standard deviation of MVC% were determined for each muscle during the different movement types. The time broadness among peak muscle activities in percent of total time of a movement cycle was calculated separately at each subject [22]. The mean and standard deviation of time broadness were determined by groups. Comparisons of MVC% and the time broadness among peak muscle activities between the two groups were made by unpaired t-test with a set at 0.05. 3. Results The mean values of MVC%, standard deviation (SD), grading of activity of each muscle group and significant
During push the anterior deltoid was maximally active while pectoralis major, middle deltoid, infraspinatus, biceps brachii and triceps brachii were moderately active in the comparison group. On the other hand, the anterior and middle deltoid, the pectoralis major, infraspinatus and the biceps brachii demonstrated moderate activity, all other muscles were minimally active in javelin throwers. In the comparison group, the pectoralis major, the anterior and middle deltoid, the infraspinatus, and the triceps brachii were achieving their maximal activity level in the pushing phase, whereas the posterior deltoid, the supraspinatus, and the biceps brachii were active in the deference phase. In the push phase at the javelin throwers, the pectoralis major, the anterior and middle deltoid, the infraspinatus, and biceps brachii were taking part, while in the deference phase the supraspinatus and the biceps brachii achieved maximum level of activity. Significant difference could be observed between the two groups in the MVC% of the posterior deltoid and supraspinatus (Table 1).
99.80 (0.63), +++
3.3. Elevation In the comparison group all three parts of the deltoid and the supraspinatus demonstrated maximum activity while infraspinatus, biceps brachii and triceps brachii were moderately active and pectoralis major minimally active. In javelin throwers, the anterior and middle deltoid and the supraspinatus were maximally active and the posterior head of deltoid, the infraspinatus and biceps brachii demonstrated moderate activity. All muscles achieved the maximum level of their activity in the elevation phase. Significant differences between the two groups could only be observed in the MVC% of the posterior deltoid. The activity level of the muscle was maximum in the comparison group, while in javelin throwers it was moderate (Table 1). 3.4. Slow overhead throw (as goal oriented movement) All muscles of the subjects in both groups were moderately active except for the biceps brachii, which was minimally active in the comparison group. No significant differences were observed within the group of subjects (Table 1). The mean maximum time broadness among peak muscle activities was 24.5% in the comparison group, while it was 21.9% at javelin throwers if we consider the total time of a throw to be 100%. No significant differences were observed within the group of subjects (p = 0.73) (Table 1).
Activity level: +, minimal; ++, moderate; +++, maximal.
94.7 (8.81), +++ 93.40 (9.86), +++ 100.00 (0.00), +++ 84.10 (17.30), +++ 92.50 (15.30), +++
93.50 (15.17), +++
86.6 (21.45), +++
96.87 (10.36), +++
53.40 (18.15), ++
87.27 (17.89), +++ 89.33 (16.68), +++ 81.27 (17.23), +++
87.73 (22.51), +++
57.20 (18.55), ++ 65.00 (21.66), ++ 41.20 (22.88), ++ 66.60 (18.89), ++ 69.20 (20.36), ++
76.93 (19.40), +++
51.20 (25.10), ++
Comparison group, n = 16 Javelin throwers, n = 9 Fast overhead throw
87.07 (23.34), +++
82.80 (15.73), +++
43.20 (19.84), ++
53.07 (15.72), ++
29.10 (19.24), + 71.10 (35.30), ++ 71.70 (30.78), ++
54.20 (24.10), ++
79.60 (24.67), +++
68.27 (21.40), ++
95.90 (6.17), +++
46.00 (25.97), ++
Comparison group, n = 16 Javelin throwers, n = 9 Slow overhead throw
28.20 (24.36), +
51.60 (21.79), ++
52.9 (26.77), ++
40.67 (27.30), ++
83. 90 (19.95), +++
52.93 (24.82), ++
33.20 (21.65), +
32.30 (28.53), + 53.20 (23.40), ++ 44.80 (20.51), ++
68.60 (26.08), ++ 80.13 (19.44), +++ 89.67 (21.22), +++
19.30 (16.09), + 14.70 (11.11), + 40.30 (27.09), ++
90.00 (14.64), +++
65.50 (26.06), ++
31.93 (26.68), +
47.60 (33.44), ++
Comparison group, n = 16 Javelin throwers, n = 9 Elevation
75.13 (19.35), +++
Comparison group, n = 16 Javelin throwers, n = 9 Push
58.67 (30.85), ++
80.73 (28.50), +++
27.53 (17.28), + 53.87 (27.36), ++
58.47 (23.43), ++
50.67 (28.70), ++ 55.53 (29.95), ++ 50.27 (23.21), ++ 34.13 (16.57), +
44.30 (30.31), ++ 50.90 (23.97), ++ 24.30 (14.20), + 19.20 (6.12), +
32.60 (26.67), +
28.40 (20.63), + 39.60 (16.26), ++ 22.00 (10.42), +
Triceps brachii
49.80 (27.82), ++ 45.60 (25.00), ++ 59.60 (28.03), ++ 52.07 (25.71), ++ 95.60 (7.23), +++ 65.47 (27.81), ++
Biceps brachii Infraspinatus Supraspinatus Posterior deltoid Middle deltoid
37.67 (24.16), ++
Anterior deltoid Pectoralis major
30.47 (22.86), +
Comparison group, n = 16 Javelin throwers, n = 9 Pull
Table 1 Average MVC% (standard deviation) of the muscles examined of the comparison group and javelin throwers; grading of activity level of muscles during: (a) pull, (b) push, (c) elevation, (d) slow overhead throw, (e) maximal speed overhead throw
47.33 (26.94), ++
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289
286
3.4.1. Fast overhead throw (as goal oriented movement with maximum speed) All muscles of the subjects of both groups were maximally active. Significant differences could be observed in the activity of the posterior deltoid (Table 1). Longer time broadness among peak muscle activities could be observed in the comparison group comparing to the javelin throwers (Fig. 3). In javelin throwers the difference was minimal (Fig. 3(b)). The mean of time broadness among peak muscle activities was 13.1% in the comparisons and 10.6% in javelin throwers if we considered the total time of a throw to be 100%. The difference was not significant (p = 0.44).
4. Discussion The presumable selective use of certain muscles to throw a ball determines the quality of a thrower. Throw is a complex act that uses the muscles of the lower extremities, the trunk, the shoulder, the elbow, the wrist and the fingers. The skilled thrower throws a ball accurately, quickly and repetitively because
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289
Fastoverhead throw -Comparisongroup 100 Pectoralis major
90
Infraspinatus
MVC%
80
Anterior deltoid
70
Middle deltoid
60
Posterior deltoid Supraspinatus
50
Biceps brachii
40
Ttriceps brachii
30 20 10 0 0
20
(a)
40
60
80
100
Percent of movement cycle[%]
Fast overhead throw -Javelin throwers 100 Pectorolalis major
90
Infraspinatus
80
Anterior deltoid Middle deltoid
70
Posterior deltoid
MVC%
60
Supraspinatus Biceps brachii
50
Triceps brachii
40 30 20 10 0 0
(b)
20
40
60
80
100
Percent of movement cycle [%]
Fig. 3. Normalized EMG curve of the muscles examined, during maximal speed overhead throw: (a) comparison group, (b) javelin throwers.
these muscles are well-coordinated and well-conditioned. In our study only the muscle activity of the shoulder is investigated. The goal of our study was to examine how the muscle activity pattern depends on the quality of throwers. The muscle activity pattern was characterized by maximal value of contraction and by time broadness in the percent of the movement cycle. Surface EMG electrodes were used, neither of them caused pain or restricted subjectsÕ movements. The amplifiersÕ bandwidth was sufficient for both type of motion (isokinetic and dynamic). Processing the data, we used the MVC% of each muscle to compare various muscle activities of different subjects during several movements. The advantage of this type of normalizing method is that it belongs to a dynamic condition and a second set is not needed for determining the RVC. Average activity period of mus-
287
cles during the movement cycle and mean time broadness in the percent of the movement cycle were calculated by analyzing all cycles. These two parameters should be considered in evaluating muscle activity pattern. The pattern is different in case there is a difference in any of the parameters above. The rationale for using EMG to study muscle activation during elementary motion and during throwing movement is to provide a better understanding of muscle firing patterns during these shoulder movements. The movements of pull, push and elevation were isokinetic as the same speed during various movements at different subjects was ensured with metronome. The overhead throw was dynamic motion. Two different types of movements gave us an opportunity to analyze the effect of speed on muscle activity. In our experience, professional javelin throwers and recreational athletes were examined and compared to each other. Gowan et al. [7] and Kelly et al. [13] have defined two groups of muscles. Infraspinatus, supraspinatus, three part of deltoid defined as stabilizers. Subscapularis, pectoralis major, latissimus dorsi and triceps brachii defined as accelerators. On the basis of our study this definition could be use not only for throw, but it could be used for pull, push and elevation as well. During pull and push, the activity of all muscles of recreational athletes is higher than that of professional athletesÕ (Table 1). Significant differences could be observed between the two groups of the middle and posteror deltoid, supra- and infraspinatus (Table 1). The difference is best visible during elevation, as in the comparison group the activity of all three parts of the deltoid and the supraspinatus is maximum while in javelin throwers the anterior and middle deltoid and the supraspinatus demonstrate maximal activity (Table 1). This indicates that coordination in muscle contraction plays a significant role in stabilizing the shoulder joint, and the role of the muscles mentioned above is higher in recreational athletes during pull, push and elevation than in qualifier throwers. During overhead throw in the comparison group, the activity level of one head of the deltoid is much higher than that of the other muscles while in javelin throwers besides the deltoid the activity level of one of the rotator cuff muscles is higher than the othersÕ (Table 1). During slow overhead throw, there was no significant difference in the maximum contraction of the muscles between the two groups (Table 1). We suppose that this type of motion was equally unknown for both groups and this is the reason why the supposedly more developed neuromuscular comparison of the athletes was not obvious. During maximum speed overhead throw, there was significant difference between the two groups in the activity of the posterior deltoid (Table 1). This indicates that during overhead throw
288
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289
of professional athletes an additional muscle (posterior deltoid) has to be involved to ensure proper stability of the shoulder joint as forces generated during fast speed throw requires this. On basis of the results it could be determined the peak muscle activity is significantly higher during the dynamic motion, as the overhead throw than during the isokinetic motion. Peak muscle activity depends on force, on speed and on proprioception level of muscles. In the comparison group, 3–4 muscles achieve nearly 100% MVC value, while in javelin throwers 5–8 muscles achieve nearly 100% MVC value. In javelin throwers, the standard deviation of MVC values of the muscles is significantly higher than that of the comparison group (p = 0.007) (Table 1). These findings are correlated by results of Hintermeister et al. [10]. The other parameter for the characteristics of muscle activity pattern is the time broadness in the percent of the movement cycle. In javelin throwers that of the agonist and antagonist muscles are minimal, while in the comparison subjects the time broadness is wider; however, the difference between the groups is not significant (Table 1). This can be well observed during fast overhead throw (Fig. 3). This suggests that different neuromuscular control and proprioception of javelin throwers cause different muscle coordination during throwing. The comparison of results of MVC% and time broadness in the percent of the movement cycle may strengthen our belief that the different motion patterns could be characterized by MVC and by time broadness in the percent of the movement cycle. The observations above resulted from different motion patterns in the two groups that may refer to the learned character of overhead throw, which is correlated by findings of earlier studies [5–8,12,13]. Muscle activity patterns have clinical implications for both the training and rehabilitation protocol: 1. By knowing the manner in which different muscles fire during various motions (pull, push, elevation and throw), muscle-specified conditioning protocols could be provided. The demonstration of distinct patterns of muscle activation may have further implications for changes in training and rehabilitation protocols. 2. The maximal activation documented during the different movement in all muscles tested suggests the mechanism of muscle injury. Movements execute with low peak amplitudes may minimize the risk of damage for initial muscular training. This is useful in the first part of rehabilitation and for strengthening stabilizer muscles. Large peak amplitudes may exceed the maximal load that repaired and injured muscles can withstand. Exercises with
large peak amplitudes can be used in the last period of rehabilitation and the strengthening of accelerator muscles. The data collected in this study enhance the knowledge of the muscle activity used during pull, push, elevation and throw.
Acknowledgements This work was supported in part by the Hungarian Scientific Found T034150 by Stipendium Istva´n Sze´chenyi (Rita Kiss,) and by the Research Group of Hungarian Academy of Sciences.
References [1] J.V. Basmajian, C.J. DeLuca, Muscles Alive: Their Functions Revealed by Electromyography, fifth ed., Williams & Wilkins, Baltimore, 1985. [2] J.P. Bradley, J.E. Tibone, Electromyographic analysis of muscles action about the shoulder, Clin. Sports Med. 10 (1991) 789–805. [3] C.R. Constant, A.H.G. Murley, A clinical method of functional assessment of the shoulder, Clin. Orthop. 214 (1987) 160–164. [4] C.R. Constant, Assessment of the shoulder function, in: D.F. Gazielly, P. Gleyze, P. Thomas (Eds.), The Cuff, Elsevier, Paris, 1997, pp. 39–44. [5] G. David, M.E. Magarey, M.A. Jones, Z. Dvir, K.S. Tu¨rker, M. Sharpe, EMG and strength correlates of selected shoulder muscles during rotations of the glenohumeral joint, Clin. Biomech. 15 (2000) 95–102. [6] M.J. Decker, J.M. Tokish, H.B. Ellis, M.R. Torry, R.J. Hawkins, Subscapularis muscle activity during selected rehabilitation exercises, Am. J. Sports Med. 31 (2003) 126–134. [7] I.D. Gowan, F.W. Jobe, J.E. Tibone, J. Perry, D.R. Moynes, A comparative electromyographic analysis of the shoulder during pitching, Am. J. Sports Med. 15 (1987) 586– 590. [8] G.D. Heise, EMG changes in agonist muscles during practice of a multijoint throwing skill, J. Electromyogr. Kinesiol. 5 (1995) 81– 94. [9] H.J. Hermes, B. Freriks, R. Merletti, D. Stegemann, J. Blok, G. Rau, C. Disselhorst-Klug, G. Hagg, European Recommendations for Surface Electromyography, Results of the SENIAM project Roessingh Research and Development b.v., Enschede, The Netherlands, 1999. [10] R.A. Hintermeister, G.W. Lange, J.M. Schulteis, M.J. Bey, R.J. Hawkins, Electromyographic activity and applied load during shoulder rehabilitation exercises using elastic resistance, Am. J. Sports Med. 26 (1998) 210–219. [11] L. Hovelius, Anterior dislocation of the shoulder. PhD thesis. Linko¨ping University No. 139, Linko¨ping, Sweden, 1982. [12] F.V. Jobe, D.R. Moynes, Tibone, J. Perry, An EMG analysis of the shoulder in pitching. A second report, Am. J. Sports Med. 12 (1984) 218–220. [13] B.T. Kelly, S.I. Backus, R.D. Warren, R.J. Williems, Electromyographic analysis and phase definition of the overhead football throw, Am. J. Sports Med. 30 (2002) 837–847.
A´. Illye´s, R.M. Kiss / Journal of Electromyography and Kinesiology 15 (2005) 282–289 [14] M. Kronberg, G. Ne´meth, L.A. Brostro¨m, Muscle activity and coordination in the normal shoulder, Clin. Orthop. Rel. Res. 257 (1990) 76–85. [15] J.B. Moseley Jr., F.W. Jobe, M. Pink, J. Perry, J. Tibone, EMG analysis of the scapular muscles during a shoulder rehabilitation program, Am. J. Sports Med. 20 (1992) 128– 134. [16] J. Ovensen, S. Nielsen, Posterior instability of the shoulder joint, Acta Othop. Scand. 57 (1986) 436. [17] J. Ovensen, S. Nielsen, Stability of the shoulder joint, Acta Othop. Scand. 56 (1985) 149. [18] A.K. Saha, Dynamic stability of the glenohumeral joint, Acta Othop. Scand. 42 (1971) 491. [19] K. Schu¨ldt, J. Ekholm, K. Harms-Ringdahl, U.P. Arborelius, G. Ne´meth, Influence of sitting postures on neck and shoulder emg during arm-hand work movement, Clin. Biomech. 2 (1987) 126. [20] G.L. Soderberg, T.M. Cook, An electromyographic analysis of quadriceps femoris muscle setting and straight leg rising, Phys. Ther. 63 (1983) 1434. [21] H. Townsend, F.W. Jobe, M. Pink, J. Perry, Electromyographic analysis of the glenohumeral muscles during a baseball rehabilitation program, Am. J. Sports Med. 19 (1991) 264– 272. [22] D.A. Winter, Biomechanics and motor control of human movement, second ed., Wiley, New York, 1990.
289
Kiss, Rita PhD, senior research fellow, member of HAS-BUTE Research Group of Structures, working at Biomechanical Lab. Graduated from the Faculty of Civil Engineering of the Technical University of Budapest as qualified civil engineer in 1991. Main research area: analysis of human motion mechanics. From 2001: Sze´che´nyi grant holder. Member of several – domestic and international – scientific and educational bodies/committees. Published a number of special articles, methodology guides, and conference lectures in the past years. ´ rpa´d MD, orthopaedic surgeon, Illye´s, A traumatologist. Graduated from the Faculty of General Medicine of Debrecen University of Medical Sciences in 1992; passed special examination of traumatology in 1998 and of orthopaedy in 2001. Main research areas: conservative and operative treatment/rehabilitation of injuries, sports surgery analysis of sports movements. Published a number of special articles, methodology guides, and conference lectures in the past years.