Australas Phys Eng Sci Med DOI 10.1007/s13246-014-0245-1

SCIENTIFIC PAPER

Surface electromyographic analysis of the biceps brachii muscle of cricket bowlers during bowling Nizam Uddin Ahamed • Kenneth Sundaraj Badlishah Ahmad • Matiur Rahman • Md. Asraf Ali • Md. Anamul Islam

•

Received: 24 April 2013 / Accepted: 18 January 2014 Ó Australasian College of Physical Scientists and Engineers in Medicine 2014

Abstract Cricket bowling generates forces with torques on the upper limb muscles and makes the biceps brachii (BB) muscle vulnerable to overuse injury. The aim of this study was to investigate whether there are differences in the amplitude of the EMG signal of the BB muscle during fast and spin delivery, during the seven phases of both types of bowling and the kinesiological interpretation of the bowling arm for muscle contraction mechanisms during bowling. A group of 16 male amateur bowlers participated in this study, among them 8 fast bowlers (FB) and 8 spin bowlers (SB). The root mean square (EMGRMS), the average sEMG (EMGAVG), the maximum peak amplitude (EMGpeak), and the variability of the signal were calculated using the coefficient of variance (EMGCV) from the BB muscle of each bowler (FB and SB) during each bowling phase. The results demonstrate that, (i) the BB muscle is more active during FB than during SB, (ii) the point of ball release and follow-through generated higher signals than the other five movements during both bowling categories, (iii) the BB muscle variability is higher during SB compared with FB, (iv) four statistically significant differences (p \ 0.05) found between the bowling phases in fast bowling and three in spin bowling, and (v) several arm N. U. Ahamed (&)
K. Sundaraj
Md. A. Ali
Md. A. Islam AI-Rehab Research Group, Universiti Malaysia Perlis (UniMAP), Kampus Pauh Putra, 02600 Arau, Perlis, Malaysia e-mail: [email protected] B. Ahmad School of Computer and Communication Engineering, Universiti Malaysia Perlis (UniMAP), Kampus Pauh Putra, 02600 Arau, Perlis, Malaysia M. Rahman College of Computer Science and Information System, Najran University, Najran, Kingdom of Saudi Arabia

mechanics occurred for muscle contraction. There are possible clinical significances from the outcomes; like, recurring dynamic contractions on BB muscle can facilitate to clarify the maximum occurrence of shoulder pain as well as biceps tendonitis those are medically observed in professional cricket bowlers, and treatment methods with specific injury prevention programmes should focus on the different bowling phases with the maximum muscle effect. Finally, these considerations will be of particular importance in assessing different physical therapy on bowler’s muscle which can improve the ball delivery performance and stability of cricket bowlers. Keywords Cricket bowling
Fast and spin bowling
Surface electromyography
Biceps brachii

Introduction Cricket is one of the oldest organized and the world’s second most popular sports. This sport is played in many countries worldwide, particularly British Commonwealth Nations [1, 2]. It is a field-based sport between 2 teams of 11 players, and the players are needed to field and bat throughout the game. Each player assumes different roles throughout the match, and one of these roles is bowling (delivery of the ball) a 156-g cricket ball toward a batsman or his wicket. It typically requires ?1 s for the ball to reach the batsman [3–5]. This bowling step is a complex skill that can be categorized as either fast bowling, which indicates that the ball is delivered at a fast pace (120–160 km/h), or spin bowling, which indicates that the ball is delivered slowly (60–90 km/h) but with some spin such that it bounces at an angle off the bowling pitch [6, 7]. It is notable that, the exact difference between bowlers who

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bowl and bowlers who throw is that those who throw use an action similar to that of softball pitching, volleyball serving and spiking, javelin throwing, and handball throwing [8– 10]. Although a cricket bowler does not throw the ball during delivery and the International Cricket Council (ICC) laws on illegal bowling actions states that a ball is not an illegal delivery if the bowler does not extend his elbow more than 15° from when the upper arm is horizontal (which is not translated to arm reaching shoulder level as it is only the upper arm that needs to reach this level) to when the bowler releases the ball (which is the first frame that the ball is not in contact with any part of the hand) [11]. However, during the delivery of the ball, the most common upper limb active muscles are the biceps brachii (BB), pectoralis major, deltoid, trapezius, latissimus dorsi, infraspinatus, trapezius, serratus anterior, and supraspinatus muscles [9, 12, 13]. Although cricket is a non-contact sport, such as baseball, softball, and volleyball, playing cricket can result in a number of injuries. Furthermore, overuse injuries are frequent and related to the physical demands of high-level cricket. These injuries most likely occur during ball delivery through either fast or spin bowling because the bowling action involves repetitive twisting, extension, contraction, and rotation of the upper limb [1]. Therefore, imperfect too-frequent executions of these movements may lead to overuse damage of the muscles involved. Recently, the Australian Cricket Board (ACB) declared that highlevel fast bowlers (FB) exhibit a significantly enhanced risk of injury if their bowling workload exceeds more than 20–30 bowls during the period of 1 week [14, 15]. Similarly, Stretch [16, 17] reports that 41 % of the injuries that are sustained by cricket bowlers are due to frequent bowling. Although other upper limb muscles are active and affected during cricket bowling, we chose to study only the BB muscle due to the lack of EMG research on this single muscle. The BB muscle is particularly implicated in injuries to FB, because of their repetitive delivery movements [18, 19]. Moreover, BB muscle provides elbow flexion torque during bowling, and therefore this is one of the common areas of upper limb muscle where the biceps tendonitis, strain, fatigue, acute injury and rupture is most frequently occurred in bowler’s muscle [20, 21]. Therefore, it is essential to know when and how much the BB muscles are active during cricket bowling because this information will prove useful to the physicians, physical therapists, bowling trainers, and coaches in the design of proper treatment, training, and rehabilitation protocols for these athletes and will help the cricket bowlers better understand the injury mechanism. Muscle activity can be identified by the EMG sensor since the electrical signals are generated in the human skeletal muscle during muscle fibre contraction, which is always stochastic (random) [22,

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23]. Surface EMG is the science and basic technique used for the quantification of muscle activity during movement [24]. In addition, it is a hassle-free procedure that can be used to determine the timing and the amount of muscle activation throughout a given movement and is an essential tool in biomechanical and biomedical investigations [25]. To date, very few researchers have investigated the electromyographic responses of the muscles with bowling arm motion, particularly the BB, of cricket bowlers during cricket bowling. For example, Shorter et al. investigated the EMG consequences in two FB during four bowling delivery stages: the pre-delivery stride, the back foot contact, the ball release (RB), and the follow-through (FT). These researchers briefly evaluated the activities of upper limb muscles and found that the BB and the infraspinatus muscles are more active and inconsistent compared with the other five muscles [12]. Shorter et al. also compared the EMG values between an injured and an uninjured cricket bowler and found that the injured bowler generated greater muscle activity throughout the bowling movement. In another study, the same researchers analysed the EMG signals of the strain of the muscles of FB and discovered that it is influenced by the upper limbs [26]. However, these researchers did not mention the upper limb muscle activity, and the BB was not included. The aims of the two studies performed by Burden et al. were to investigate and determine the sequential and temporal patterns of the muscular activity of cricket bowlers during fast bowling. These researchers found that the deltoid muscles are active throughout the bowling movement; the only exception is the posterior deltoid, which exhibits only a slight contraction. Significant activity was also observed in the latissimus dorsi immediately before the RB. Negligible activity was found in the infraspinatus muscle and BB [13, 27]. Similar to the delivery of the cricket ball, some studies investigated the muscle activity of the upper limb muscles, including the BB muscle, of athletes during an overhead throwing activity, such as baseball pitching, javelin throwing, volleyball serving and spiking, and scoring in basketball. These studies mainly investigated the muscle activity, fatigue, amount of firing patterns, signal variability, and neuromuscular mechanism [10, 28–41]. However, among all of these sports, it has been shown that cricket bowling and baseball pitching exhibit similar characteristics [42, 43]. For example, cricket bowlers bowl with a 156-g cricket ball, and a baseball pitcher throws a 141.74- to 148.84-g ball to generate the BB muscle contraction. Thus, Rojas et al. [10] investigated only the BB activity during pitching and compared it with that observed during the overhead throwing of a ball. In the literature review, the existing studies on the BB muscle were not able to clarify the EMG activity exhibited by the BB muscle of bowlers during spin bowling, did not compare the muscle activities of spin and FB, did not

Australas Phys Eng Sci Med

analyse the EMG signal variability exhibited by the muscle during each of the different bowling phases and obviously EMG signal analysis with motion pictures that synchronize to find the BB muscle activity and arm mechanics. Therefore, based on previous information on the dissimilarities in the variations in the amplitude of the EMG signal during cricket bowling, the rationales of this study were to detect the BB muscle activity during particular phases of a cricket bowling, in addition to compare the overall BB activity between the fast and spin bowlers. Finally, the research hypothesis attributed to the relation between the EMG signal parameters and the muscle contraction mechanisms that underlie each block of the bowling movements.

Materials and methods Participants A group of 16 healthy university cricket male players (amateur bowlers) participated in this study. Of these, eight bowlers performed fast bowling, and the remaining eight performed spin bowling. All of the bowlers had regularly played prior to the study and bowled either in school-, college-, university-, or state-level cricket games. Currently, the participants play in a university cricket team. The mean and the standard deviations (mean ± SD) of the demographics of the two bowling categories were the following: FB, n = 8, age = 25.1 ± 3.1 years, height = 171.1 ± 6.4 cm, and weight = 71.1 ± 3.7 kg; SB, n = 8, age = 24.6 ± 3.3 years, height = 172.4 ± 5.6 cm, and weight = 70.8 ± 3.9 kg. Ethical statement This study was approved by the university research and development review board for human subjects. All of the participants were screened for any musculoskeletal ache or disorder of the BB muscle by an experienced health professional. The entire procedures conformed to the World Medical Association Declaration of Helsinki (Ethical Principles for Medical Research Involving Human Subjects). Additionally, the subjects’ cricket bowling activity and health were assessed with a questionnaire. Familiarization The subjects all participated in an orientation session roughly 1 day prior to testing. This familiarisation session covered the rules of the activity, the testing protocols and process, and a general discussion regarding the EMG data recording and movement analysis during bowling. In addition, the participants were allowed to practice in the

cricket net. The subjects received information on the trials and the objectives of the experiment and provided signed informed consent. Experimental overview Cricket bowling Bowling is the action in a cricket game during which the ball is pushed toward the wicket that is defended by a batsman (opposite side), and a cricket player that is an expert at bowling is called a bowler [44]. Although no batsman was present in this experiment, the bowlers delivered the ball toward the wicket, and each bowler performed 3 overs, i.e., 18 ball deliveries, during the trials (a set of 6 ball deliveries is called an over). There was a 5-min gap between each over and a 1-min gap between each delivery. One-hundred and forty-four trials (ball deliveries) of each bowling category were performed (from the SB and FB, e.g., 8 SB delivered 18 balls to obtain 18 9 8 = 144 total trials), and the corresponding motion direction of the upper extremity and EMG data from BB muscle were recorded during each trial. Only the valid deliveries according to the law of ICC were considered [45]. Thus, an expert and officially recognized cricket coach was present throughout the trials for the bowling validation [he is currently a Level I coach in the Asia region and is a recognized Asian Cricket Coach (ACC)]. Some exclusion criteria (did not consider for EMG data analysis) during bowling were the following: ball delivered outside the pitch, extremely full-touched (over the head), no-ball (cross the line of the bowling popping crease), and throwing (the bowling delivery rules and legalities were not maintained). If such case happened, that particular ball delivery was cancelled for EMG measurement process. Finally, EMG data from all 144 trials per bowling style were chosen for analysis. Also, during the bowling action, the velocity of each bowling delivery was measured using a handheld ProSpeed Professional radar gun (Bushnell Speedster Series 2, Radar Gun, Model No. 101900), which was placed in back of the stamps. The average speed of the ball bowled through fast bowling was 128.73 ± 0.34 km/h, and the average speed of the ball bowled through spin bowling was 83.4 ± 0.67 km/h. These speeds fulfilled the bowling speed classification according the ICC and other definitions from cricket researchers [6, 7]. Motion analysis All the experiments were carried out in the university biomechanics and human motion analysis laboratory. Three high-speed digital cameras [Qualisys Track Manager (QTM) software; Qualisys AB, Gothenburg, Sweden]

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Fig. 1 Phases during cricket fast bowling (see text for further information), a RU run-up, b PS pre-delivery stride, c MB mid bound, d BC backfoot contact, e FC front-foot contact, f RB release of the ball, and g FT follow-through

sampling at 400 Hz were placed next to the bowling crease and relative to the bowler to assist in the definition of the different phases of the delivery stride. The camera was used to quantify the synchronisation between the bowling phases, EMG data processing and for the analysis of the bowling arm motion. Also, it was used to determine the trimmings of each of the phases using frame-by-frame assessment of the video. Three anatomically aligned, passive and retro-reflective markers were placed on the subject’s muscle according to the following specifications: shoulder, elbow and wrist. Both of the bowling deliveries (FB and SB) were broken down into seven stages: (a) runup (RU), (b) pre-delivery stride (PS), (c) mid bound (MB), (d) back-foot contact (BC), (e) front-foot contact (FC), (f) release of the ball (RB), and (g) follow-through (FT) [27, 46, 47]. Figure 1 depicts these 7 stages in the delivery of a ball from a FB. Three types of dynamic contractions of the bowling phases (eccentric, concentric and isokinetic) were identified by examining the muscle fascicle lengths (muscle shortening and lengthening) and pennation angle (at a constant joint angle) during manual muscle test. EMG measurement The electromyographic activity at the BB muscle skin surface was recorded using two channels of single differential wireless EMG with an inter-electrode space of 10 mm (DE-02, Delsys Inc., Bagnoli-4, Boston, MA, USA). The Delsys EMG system also included a portable myomonitor, which was fixed to the bowler’s waist (Fig. 2). Before recording the raw signal, the skin of the BB muscle was set up by shaving and removing any oil and dust from the skin surface with an abrasive alcohol swab (as suggested by the manufacturer). The skin was then prepared, and the electrodes were placed in accordance with the method described by Hermens et al., Zipp, and Delagi and Perotto [48–50]. The studied bowling movements were extremely fast and dynamic, thus a particular care in electrode positioning was took place during each

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Fig. 2 Photograph depicting a cricket bowler performing spin bowling. The right photograph illustrates the position of the arm (and the BB muscle) during a spin delivery at the end of the run up phase and prior to the delivery of the ball. a EMG electrodes with a double-sided adhesive skin interface, b reference electrode, c 156-g cricket ball with a circumference of 224–229 mm, d the myomonitor system connected to the EMG electrodes and connected wirelessly with the Bagnoli Desktop EMG System, and e high-speed digital camera

ball delivery. For example, an elastic bandage was wrapped around the EMG electrodes to secure the devices from extraneous movement while not impeding muscular function or movement about the shoulder and elbow joints, because it produces relatively dynamic movement between muscle and skin. Also, the entire protocol was designed to minimize movement artifact (e.g. cross talk) and make sure a tolerable level of electrode impedance (inter-electrode impedance was \2,000 X) [51]. In addition, the raw EMG signals were visually analysed before the recording to ensure that the background noises and artifacts from the appliances in the testing area were minimized. Prior to the bowling action, 2 electrodes were attached to the mid-belly of the contracted BB muscle of the bowlers, and the exact point was instantly marked with semi-permanent ink to ensure constant placement throughout the testing period. The electrodes were silver bar electrodes (10 mm 9 1 mm) and were placed at a fixed inter-electrode distance of 10 mm. The reference electrode (2 cm 9 2 cm) was attached to the lateral epicondyle of the humerus of the bowling arm (*1 inch on the olecranon of the elbow).

Australas Phys Eng Sci Med

Figure 2 illustrates the complete experimental process of the EMG data recording of the activity of the BB muscle of a cricket bowler. (It was a demo photo, so the elastic bandage was not used to show the electrodes placement.)

(EMGpeak), the RMS (EMGRMS), the CVs (EMGCV), and the significant differences between each bowling phase are summarized in Table 1. Additionally, the statistical comparisons (absolute value) between the two bowling categories and the seven phases are presented in Table 2.

EMG data analysis Muscle activity during the seven bowling phases One of the main aims of this study was to quantitatively evaluate the amplitude variations of the EMG signal from the bowler’s BB muscle activation levels. For this reason, the raw signals were recorded and digitized at a sampling rate of 2 kHz before their A–D conversion and stored on a compatible computer for subsequent analysis. The raw EMG signals were sampled with a 10–500 Hz band pass filter (4th order Butterworth; CMRR [92 dB, input noise \1.2 l V, impedance of 1,012 X in parallel with 5 pF), and the gain was fixed at 1,000 for all of the channels. The total configuration is in accordance with the earlier suggestions provided by De Luca [52]. The raw EMG signal was performed off-line using MATLAB with the Signal processing toolbox (The Math-works, USA). The EMG amplitude measurements (in mV) from the bowler’s BB muscle during each of the seven bowling phases during the two bowling categories were obtained. Maximum EMG reference values were calculated for the BB muscle by using the maximum peaks (from six deliveries) EMG signals to represent 100 % MVC. Then the normalized signal amplitude [root mean square (RMS [mV])], were computed from the EMG signal for 7 phases of the 2 bowling categories. The time window (sequence lengths) for the RMS calculation for each phases are presented in Table 3, where the average segments are presented with ±milliseconds (ms). Statistical analysis Descriptive statistics, including the mean and standard deviation, the RMS, and the peak amplitude (average maximum peak) of the normalized EMG data, for each phase and bowling type were examined. The coefficient of variation (CV, the standard deviation expressed as a percentage of the mean) was calculated for the normalized data for both bowling types. A two-way repeated measures ANOVA (2 techniques of bowling delivery 9 7 bowling phases) was used to compare the normalized EMG. All of the statistical tests were performed using the MedCalc statistical software (MedCalcÒ Version 11.3.0.0). Statistical significance was defined at p \ 0.05 (95 %).

Results The EMG data obtained for the 16 bowlers were pooled for the analysis. The mean ± SD, the the maximum peak

Fast bowling The maximum BB activity was found during the RB (release of ball) phase, and the outcomes were measured by the mean ± SD, the EMGpeak, and the EMGRMS (1.93 ± 0.05, 1.97, and 1.39 mV, respectively). During the FT phase, the BB exhibited slightly lower activity than during the RB phase but higher activity than that observed during the other 5 phases (the mean ± SD, the EMGpeak, and the EMGRMS during this phase were 1.42 ± 0.04, 1.47, and 1.03 mV, respectively). In contrast, the BB generated lower signals during the RU, PS, and MB phases (the mean ± SD were 0.42 ± 0.01, 0.65 ± 0.02, and 0.75 ± 0.02, respectively; the EMGpeak values were 0.44, 0.68, and 0.79, respectively; the EMGRMS values were 0.31, 0.48, and 0.55 mV, respectively). Moreover, the EMG values were moderate during the BC and FC phases (the mean ± SD were 0.91 ± 0.03 and 0.98 ± 0.08, respectively; the EMGpeak values were 0.96 and 1.16, respectively; the EMGRMS values were 0.68 and 0.82 mV, respectively). The EMG signal variability on the BB was higher during the FC phase (7.84 %). However, the signal was more constant during the RB, FT, and MB phases (within 1–3 %). Subsequently, the BB was slightly steady during remaining 3 movements: RU, PS and BC (within 3–4 %). In addition, in this bowling category, the EMG amplitude analysis revealed significant differences (p \ 0.05) between the RU and the MB phases, between the PS and the FC phases, between the BC and the FT phases, and between the RB and the FT phases (see Fig. 3; Table 1). On the other hand, the remaining phases did not significantly differ from each other (p [ 0.05). Spin bowling During this bowling movement, the BB muscle was active during the RB and the FT phases (the mean ± SD were 1.21 ± 0.04 and 1.11 ± 0.12, respectively; the EMGpeak values were 1.31 and 1.39, respectively; the EMGRMS values were 0.92 and 0.98 mV, respectively). The running with the ball (RU) phase generated a lower EMG activity compared with all of the other stages (the mean ± SD, the EMGpeak, and the EMGRMS were 0.31 ± 0.02, 0.35, and 0.24 mV, respectively). There were less signal differences found between the PS and the MB phases and between the

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0.75 ± 0.02

0.91 ± 0.03*c

0.98 ± 0.08

1.93 ± 0.05*

1.42 ± 0.04

MB

BC

FC

RB

FT

1.47

1.97

1.16

0.68

1.69

Ave

1.03

1.39

0.82

0.68

0.55

0.48

0.31

EMGRMS 0.76

Ave

2.55

1.89

7.84

3.76

2.32

3.05

3.61

EMGCV (%) 3.58 %

Ave

1.11 ± 0.12

1.21 ± 0.04

1.39

1.31

0.87

0.83 ± 0.02*g

0.63

0.58

0.35

EMGpeak

0.85

0.78 ± 0.04

Ave

0.82 ± 0.01*f

0.58 ± 0.04

0.52 ± 0.03*e

0.31 ± 0.02

Mean ± SD

Spin bowlers (SB)

g

f

e

d

c

b

a

Significant difference compared to RB

Significant difference compared to FT

Significant difference compared to BC

Significant difference compared to FT

Significant difference compared to FT

Significant difference compared to FC

Significant difference compared to MB

* Denotes p \ 0.05

RU run-up, PS pre-delivery stride, MB mid bound, BC back-foot contact, FC front-foot contact, RB release of the ball, FT follow-through

d

0.79 0.96

0.65 ± 0.02*b

PS

0.44

1.02 ± 0.03

0.42 ± 0.01*a

RU

EMGpeak

Ave

Fast bowlers (FB)

Mean ± SD

Phase

Table 1 Summary of the EMG activity of the BB muscle during the seven different phases of fast bowling and spin bowling

0.86

Ave

0.98

0.92

0.61

0.60

0.44

0.41

0.24

EMGRMS

0.61

Ave

10.94

4.41

2.13

1.56

6.93

5.08

5.48

EMGCV (%)

4.23 %

Ave

Australas Phys Eng Sci Med

Australas Phys Eng Sci Med Table 2 Statistical comparison between each bowling stages (absolute value) Phase

DMean

DSD

DCV (%)

DPeak

DRMS

RU

0.11

0.01

1.87

0.09

0.06

PS

0.13

0.01

2.04

0.11

0.07

MB

0.17

0.02

4.61

0.16

0.11

BC

0.09

0.02

2.19

0.12

0.08

FC

0.15

0.06

5.71

0.29

0.21

RB

0.72

0.01

2.52

0.67

0.47

FT

0.31

0.08

8.39

0.08

0.06

RU run-up, PS pre-delivery stride, MB mid bound, BC back-foot contact, FC front-foot contact, RB release of the ball, FT followthrough Fig. 4 Mean and SD (error bar) of the muscle activation during SB (from eight bowlers)

Fig. 3 Mean and SD (error bar) of the muscle activation during FB (from eight bowlers)

BC and the FC phases during this bowling movement. The variability of the FT phase generated the maximal muscle inconsistency (10.94 %) compared with the other phases. The RU, PS, RB, and MB phases exhibited slightly lower inconsistency in the signal generation (within 4–6 %). However, the BB muscle of SB was constant during the BC and FC phases (1.56 and 2.13 %, respectively). In addition, in this bowling category, the EMG amplitude analysis revealed significant differences (p \ 0.05) between the PS and the BC phases, between the BC and the FT phases, and between the RB and the FC phases (see Fig. 4; Table 1). On the other hand, the remaining phases did not significantly differ from each other (p [ 0.05). EMG comparison between FB versus SB The line graph on Fig. 5 shows the average (mean) EMG signal difference between two bowling deliveries. The sum

Fig. 5 Activity of the BB muscle during fast (eight participants) and spin (eight participants) bowling (based on the EMGAVG)

of all of the bowling phases revealed that the BB muscle was more active during FB (1.02 ± 0.03 mV) than during SB (0.78 ± 0.04; Table 1). Additionally, large differences (0.83 mV) were found in the EMGpeak value between the two bowling categories. The EMGRMS results show that a higher force on the BB muscle was generated during FB compared with SB (0.76 and 0.61 mV, respectively). However, the signal variability during FB (3.58 %) was qualitatively less than that during SB (4.23 %), as reflected in Fig. 6. Table 2 illustrates some of the high and low differences between the seven bowling phases during FB and SB. For example, the RU and BC phases exhibit lower signal (mean values) differences (0.1 and 0.08 mV, respectively) during both bowling deliveries. In contrast, a large dissimilarity was found in the muscle variability during the FT and the FC phases (8.39 and 5.7 %, respectively). Similarly, the EMGRMS and EMGpeak results show a large difference during the RB stage (0.471 and 0.665 mV, respectively).

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Fig. 6 The bar graph shows the EMG variability between the two bowling types and the seven bowling phases

Arm mechanics Table 3 presents the type of motion patterns of the cricket bowler’s upper extremity during seven phases of bowling. This relates to BB muscle’s activation in concert with surrounding muscles. The length of analyzed EMG signal epochs was considered according to the subject’s motions which are mentioned in the following table. Also, the types of dynamic contractions are given according to the manual test performed prior to the final experiment. Finally, some references are given as the evidence of similar contortions during such movement during pitching, volleyball serving and other throwing activities. The arm mechanics and the timing activity (duration) of the bowlers during two types of bowling delivery was almost similar, except the duration of running (RU) phase, because it differed between two bowling style.

Discussion Three primary activities are observed during a cricket game: bowling, fielding, and batting [42]. Among these movements, bowling exhibits the highest chance of muscle injury, and both types of bowlers (fast and spin) are at risk, especially if they bowl frequently [16, 17]. Consequently, the different bowling phases in cricket require the stressful use of the upper limb muscles, and the BB muscle is one of the most common muscles that are injured during bowling. Indubitably, BB considered as the most important muscle from the superior limb because it helps to control movements in the shoulder, elbow and proximal radioulnar joints. Therefore, it is important to know the exact characteristic of the BB muscle during cricket bowling. The main aim of this experiment was to examine the

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electromyographic role of the BB muscle during the 7 bowling phases in fast and spin bowling. The experimental data showed that FB generated higher EMG signals than SB, and that the muscles are more active during ball delivery and follow-though phases on both the bowling categories. In addition, these variables have a significant influence on the level of EMG activity and may account for the high amount of variability detected between some phases of the bowling action. Another important finding of this research is, as BB muscle is most commonly injured during bowling, this study examined the upper extremity recruitment during arm movements of seven phases, which include all planes of motion (see Table 3). This relates to BB muscle’s activation in concert with surrounding muscles. The effect of EMG on the upper limb muscles during cricket bowling has been extensively reported in earlier studies. Also, they have mentioned that most of the movements in bowling seems to be performed by the shoulder joint (flexion, extension and hyperextension), which are mobilized mainly by deltoideus and latissimus dorsalis muscles. However, the exact activity of the BB muscle during each phase of the bowling action and the differences between the two types of bowlers are not completely and clearly understood [12, 13, 26, 27]. It is commonly thought that the BB muscle is more active during the last two stages (RB and FT) overhead throwing compared with the other five stages, as was shown by Rojas et al. [10] in a windmill ball pitching (throwing) experiment. One study on cricket bowling by Shorter et al. [12] analysed and compared the activities of the infraspinatus, supraspinatus, deltoid, BB, and triceps brachii muscles between injured and uninjured bowlers during five phases of fast bowling. These researchers also showed that the BB is more active during the last phases and that the BB muscle generates the third highest EMG activity of the upper limb muscles. Our findings demonstrate that the BB muscle has significantly higher EMG activity during the last 2 phases, which supports the initial hypothesis. Comparison of Figs. 3 and 4 illustrates that the BB muscle of a FB running (RU-phase) with a 156-g ball exhibits a slightly higher signal than that exhibited by a SB with a slow movement. In addition, the isokinetic submaximal contraction was produced when the speed of the arm movement was constant until the PS stage. The next phase, which is the pre-delivery stride, occurs when the elbow is extended, the BB is slightly contracted, and the shoulder is rotated. This low contraction generates a better EMG signal than the previous phase for both bowling categories. During the third phase, the elbow was fully bent and the arm positioned behind the head where the BB muscle was concentrically contracted. Conversely, the next phase (BC) generates an eccentric contraction when the arm is straightened toward the ground. During these 2 phases, the EMG activities were moderate during both bowling

Australas Phys Eng Sci Med Table 3 Definitions of motions were examined during bowling (only from the bowling arm)

BP

RU Fig. 1(a)

PS Fig. 1(b)

MB Fig. 1(c)

BC & FC Fig. 1(d) & (e)

RB Fig. 1(f)

FT Fig. 1(g)

Motion

Subject grab the ball cylindrically within their palm, the wrist was with mid-supination through to the fully pronated position (the forearm volar side was parallel to the ground), the arm was hanging straight down with a straight elbow and the shoulder was neutral position (0º abduction neutral rotation) and the arm was swinging almost at same movement speed and generates pendular motion. 90° abduction of the shoulder with maximum active sidelyng external rotation, elbow movements in the presence of the external torque (which tended to lengthen the elbow joint) provided by a low-load weighted ball and BB muscle was slightly contracted. Shoulder provided forward elevation, lift their arm dynamically to >90° (90° to 150°), placed their hand actively behind their head (at ear level) and concentric contractions were made with the active arm. The shoulder moved with complete overhead elevation where the clavicle elevates at 35º, the clavicle relocates with anteriorly and posteriorly in an arc of 35º, the clavicle rotates on its long axis at 45º while the arm is elevated to the complete overhead position. Likewise, the shoulder continued its internal rotation with straight elbow angle (flexors) and horizontal flexion. The eccentric contractions were made against gravity with the active arm. The elbow extension strength demonstrates its peak at from 100° to 120° of the elbow joint angle, maximal abduction and external rotation occurred at the shoulder and continues until the ball release. Final interval of arm motion where it dissipates some of the deceleration forces. The shoulder continued its internal rotation and minimum elbow horizontal flexion.

Cont (BB) References (Ave time: ±ms) (according to similar movement)

Isk

[55,56]

FB: 2870 SB: 1945

Conc

[57,58]

570

Conc

[59,60]

659

[61,62] Ecn 450 (d) 549 (e)

Ecn [63,58] 360 Ecn [37,64] 1400

BP bowling phases, Cont contraction, Isk isokinetic, Conc concentric, Ecn eccentric, Shoulder angles in the coronal plane measured with a goniometer, the arrow symbol represents the immediate changes of the certain motion from one to another

deliveries. During the fifth phase, the arm reaches its highest external rotation and maximal elbow flexion. As a result, the generated EMG signals on the BB muscle were higher than those observed during the previous phases. The maximal forces were generated during ball delivery and followthrough during both bowling types. Therefore, the produced EMG signals were higher during these last 2 stages.

We must emphasise that the bowling movement is quite complex and happens at high velocities of execution. Hence, one can point out that angular joints accelerations and decelerations provided by BB muscle, mainly in shoulder and elbow joints, must happen under significant variations of the EMG signal energy. It happens because there is no homogeneity in the spatial motor unit recruitment (including

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nearby the surface electrodes), even in a fusiform muscle such as BB, and also due to the length and torque and moment of inertia variations. All these variables will lead to very complex and non stationarity content in the temporal and frequency domains in the EMG signal and so resulting in different CVs for the parameters calculated. Moreover, the amplitude normalization performances in the stretch shortening cycle have a variable consequence on the CV. As a result, issues of signal variability and consistency need to be considered when the temporal EMG signal characteristics are used for the classification of movement strategies [53]. According to the CV results, the BB muscles are more variable during spin bowling (4.23 %) than during fast bowling (3.58 %) due to the increased interval rotation, horizontal adduction, and elbow extension and flexion that are generated during spin bowling. Therefore, a twisting force is generated on the muscle that tends to cause rotation, i.e., torque. As illustrated in Fig. 6, most of the SB phases exhibit high signal variability compared to the corresponding FB phases. Moreover, the BB muscle exhibits high signal variation after ball delivery (FT) in SB and during the front-foot contact phase in FB. One study by Shorter et al. [12] described the muscle variability during cricket bowling and demonstrated the inconsistency of the upper limb muscles during fast bowling between 2 subjects. However, the BB muscle variability during the different phases of FB and SB has not been investigated. In addition, previous researchers who have investigated cricket bowling have not reported any significant differences between the bowling phases. In contrast, our results proved that significant differences (p \ 0.05) are found between the RU and the MB phases, between the PS and the FC phases, between the BC and the FT phases, and between the RB and the FT phases in fast bowling. Additionally, significant differences (p \ 0.05) were observed during spin bowling between the PS and the BC phases, between the BC and the FT phases, and between the RB and the FC phases. We hope that the EMG data recorded and analysed in this study may progress the body of knowledge on the activity of the BB muscle during both types of cricket bowling, which is a topic that is still under discussion in the sports medicine community. Based on the findings, some precise training of rehabilitation programs can be developed for the bowlers. Additionally, bowlers can enhance their strength and muscle power during bowling to obtain the highest execution to defeat the batsman. Practical applications Both professional and amateur cricket bowlers deliver a large number of balls throughout their sports career, and these frequent bowling deliveries enhance their risk of

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sustaining an overuse injury in the upper limb extremities, especially on the BB muscle. Therefore, damage to the BB muscle can affect and reduce the bowler’s performance. It is notable that bowling trainers, physical therapists and cricket coaches have a qualitative depiction of the BB muscle activation patterns required to deliver the ball to the batsman. Indeed, extensive knowledge of the activation and variability of the BB muscle during the cricket bowling action provides the physicians, clinicians and researchers working with cricket athletes a hypothesis for the design of preventative and rehabilitative programs. Additionally, clinicians should integrate strengthening exercises that imitate the timing of the activation and foundation of the maximal muscle activation observed throughout the different bowling phases. For example, if the BB muscle on the dominant arm is most active during the RB and the FT phases, rehabilitation exercises should be developed in these two phase positions. Similarly, the BB muscle activity and consistency observed in fast and SB are different; thus, different rehabilitation protocols or exercises need to be developed for both bowling categories. Alternatively, during the rehabilitation of a cricket bowler with biceps tendonitis (an inflammation of the biceps tendon), attention should paid to the activity from just before the RB and throughout the FT phase. Moreover, interior strengthening is required to properly assist the transmission of energy to reduce the stress placed on the BB muscle during a successful ball delivery on the cricket pitch. Strengths of this study To the best of our knowledge, this is the first study that has objectively analyzed the BB muscle activity during fast and spin (slow) cricket bowling and during each phase of these two bowling categories with arm mechanics. We did not find any comparable studies in the literature that explained these physiological measurements on the BB muscle during cricket bowling. Another key strength of the current study was the analysis of the electromyographic signal variability during each phase and bowling type. The signal consistency of the BB muscle has not been examined in previous EMG studies, and this feature is a significant prospective confounder based on the inconsistency observed in some of the EMG characteristics between bowlers. Another strong point of this research is that the limitations of earlier studies on cricket bowling were considered during the design of the study. The EMG normalisation techniques, the protocols, and the sample size were cautiously assessed before the data recording was commenced. We hope that the findings of this study will aid the cricket medicine community because the proper prevention of BB muscle damage is essential for the rehabilitation of cricket bowlers.

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Limitations of the study It is essential to note that there are a number of limitations in this study. Although other upper limb muscles are influenced and active during cricket bowling, our main focus was on the activity of the BB muscle on the bowling arm. Thus, this study only investigated the performance of the BB muscle on the right arm of male cricket players. Next, all of the subjects were amateur bowlers. We overestimated the entire EMG data results and not taking any advantage from the kinematic data to estimate kinetic parameters (for example, moments of inertia, flexion/ extension cycles, movement velocities in contractions), which would surely help to flesh them out.

Conclusions Although the analysis of the muscle activity during cricket bowling is important due to the high rate of injury of the upper limb muscles, very few studies have analyzed the muscle activity, especially the activity of the BB muscle, based on an electromyographic investigation. To address this research gap, the current study evaluated EMG data to determine the BB activity and the peak activity areas during each phase of fast and spin bowling. In summary, the present research showed that, (i) the BB muscle is active during fast bowling, (ii) the EMG signal is inconsistent during spin bowling, (iii) the BB muscle is active during the last two phases (RB and FT) of both bowling categories, and (iv) four significant differences between the phases of fast bowling and three significant differences between the phases of spin bowling were found. Finally, the entire results support our hypothesis and provide a basic understanding of the BB muscle activation patterns, which may help elucidate the patterns of muscle injury and improve the rehabilitation protocols used in the treatment of cricket bowling athletes. Additionally, these outcomes might encourage cricket bowlers and coaches to design resistance training protocols from a performance and prophylactic perspective. This scientific investigation could be applied to formulate muscle-specific instructions, exercises, and treatment protocols to reduce injuries, support rehabilitation, and improve the performance and durability of cricket bowlers. Recommendations for future research Further investigations on the BB muscle during cricket batting and fielding (over head and under arm ball throw) are needed. Additionally, other upper limb muscles, such as the deltoids, pectoralis, latissimus dorsi, trapezius, teres major and minor, triceps brachii, wrist flexors, and rotator cuff

muscles, are involved during the cricket bowling action [1, 12, 13, 27, 54]. Future studies need to investigate the effect and coordination of these muscles and the EMG effect through motion analysis (kinematic data) to obtain a clearer understanding of the bowling phases. Furthermore, there is a clear need for fundamental research on the electromyographic differences between professional and amateur bowlers using a large sample size. Another important topic on EMG analysis is muscle fatigue or failure, which includes a group of discriminating effects that damage and weaken the motor performance of human muscle. This is particularly important in the muscles of bowlers due to the frequency of ball delivery during a test or one-day game, i.e., during a game, bowlers typically deliver the ball six times, which may reduce the muscle performance. Researchers should investigate the different EMG results that are obtained for the BB muscle of individuals with different anthropometric characteristics, such as age, height, weight, gender, fat thickness, and other demographic characteristics, and with variations in the inter-electrode distance. Moreover, studies on how the different bowling deliveries influence the BB and other muscles should be conducted. For example, there are several types of spin bowling deliveries: arm-ball, doosra, teesra, flipper, googly, carrom ball, leg break, off break, slider, and top-spinner. As a result, different torques may be generated during this bowling action, and these may produce different muscle activities. Acknowledgments The authors would like to thank all the bowlers for their participation in this study. The authors would also like to thank Mr. Moganraj Palianysamy, a Level I Asian Cricket Coach (ACC), for his assistance and full-time presence during the bowling and data recording process.

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