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Effects of Six Weeks of Medicine Ball Training on Throwing Velocity, Throwing Precision, and Isokinetic Strength of Shoulder Rotators in Female Handball Players

Raeder, Christian1; Fernandez-Fernandez, Jaime2; Ferrauti, Alexander1

The Journal of Strength & Conditioning Research: July 2015 - Volume 29 - Issue 7 - p 1904–1914
doi: 10.1519/JSC.0000000000000847
Original Research
Free

Raeder, C, Fernandez-Fernandez, J, and Ferrauti, A. Effects of six weeks of medicine ball training on throwing velocity, throwing precision, and isokinetic strength of shoulder rotators in female handball players. J Strength Cond Res 29(7): 1904–1914, 2015—The aim of this study was to investigate the effects of 6 weeks of medicine ball training (MBT) on throwing velocity, throwing precision, and isokinetic strength of shoulder rotators in competitive female handball players. Twenty-eight players (mean ± SD; age: 20.8 ± 3.3 years, height: 170.5 ± 5.6 cm, body mass: 65.2 ± 8.0 kg) were randomly assigned to an MBT group (TG; n = 15) and a control group (CG; n = 13). TG performed a supervised MBT program, 3 times a week for a total of 6 weeks, focusing on handball-specific movement patterns. Both groups, TG and CG, also conducted a supervised shoulder injury prevention program with elastic tubes, as part of the warm-up, finishing with regular handball throws. Results showed a significant group × time interaction in throwing velocity (p < 0.001) with the TG posttest results being significantly higher compared with CG (d = 2.1), and also a significant main time effect (p < 0.001), with an increase in throwing velocity of 14% (d = 3.0) and 3.7% (d = 0.3) for both TG and CG, respectively. Throwing precision did not significantly differ between groups and time points. Isokinetic strength measures revealed a significant group × time interaction (p ≤ 0.05) with the TG posttest results being significantly higher compared with CG (d = 0.9) and also a significant main time effect (p < 0.01) with an increase of 15% (d = 0.9) in concentric shoulder internal rotation at 180°·s−1 in the dominant arm in TG, whereas no significant changes occurred in CG. The present results indicate that 6 weeks of MBT elicit significant improvements in functional performance (i.e., throwing velocity) in female handball players, whereas throwing precision remained unaffected. Medicine ball training exercises seem to be a useful and inexpensive strength training strategy in enhancing functional performance by closely mimicking sport-specific movement activities.

1Department of Training and Exercise Science, Faculty of Sports Science, Ruhr-University Bochum, Bochum, Germany; and

2Sports Research Center, Miguel Hernandez University, Elche, Spain

Address correspondence to Christian Raeder, christian.raeder@rub.de.

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Introduction

Handball is an Olympic sport played worldwide, with about 18 million players in more than 150 international federations. From a physical point of view, handball is an intermittent and vigorous contact sports game that requires high-intensity efforts in a short period of time, where players jump, run, and throw the ball at high velocities, followed by low-intensity or rest moments (17). Therefore, it seems that high levels of muscle strength and power during high-intensity movement activities combined with a well-developed aerobic capacity (i.e., a high degree of maximal oxygen uptake) enabling a quick recovery within low-intensity or rest moments are important determinants for successful participation in elite handball (1,19).

As the final aim of the game is to score more times than the opponent, throwing performance seems to be an important key skill for success in competitive handball, with the effectiveness of a shot primarily affected by 2 aspects: throwing velocity and throwing precision (20,23). Overarm throwing is a complex motion and can be considered as a fast discrete movement of high intensity, which can be subdivided into 6 phases: windup, stride, arm cocking, arm acceleration, arm deceleration, and follow through (8,38). Therefore, to achieve maximal throwing velocity, handball players should possess a proper technique characterized by an optimal coordination and timing of consecutive actions of body segments (i.e., intermuscular coordination), together with good levels of muscle strength and power in both, the upper and lower limbs (17,23). Moreover, core strength, as the connecting link between upper and lower extremities, plays also an important role with regard to receiving, adding, and transferring energy from the proximal to the distal body segments (32).

Several studies have been conducted regarding the efficiency of different strength training programs aimed to improve power values (i.e., peak power) and throwing velocity in handball players. Results revealed positive effects after performing heavy strength training (i.e., intensities higher than 80% of 1 repetition maximum) (5,18,20,21). Moreover, specific throw exercise programs including throwing with slightly underweight and overweight balls as regulation balls have also demonstrated beneficial carryover effects on throwing velocity in handball (37) and baseball players (12). However, medicine ball exercises, which are capable to closely mimic the sport-specific actions and movement patterns (i.e., sequential ballistic rotational movements) and are highly recommended in rotational power sports (9), have to date only been shown positive transfer effects on muscle strength and power in female handball players (22) and on torso rotational strength in baseball players (34,35). Its impact on handball throwing velocity remains to be elucidated yet.

Precision or accuracy related to overarm throwing can be defined as freedom from mistake or error and, accordingly, seems to be an important performance variable often associated with sporting success (24). In team sports such as handball, throwing precision could be affected by several variables including anthropometric characteristics (i.e., hand width, grip strength, body size, and proportions), balance ability, visual skills, and also technique (i.e., neuromuscular coordination and timing) to generate an explosive-ballistic throwing motion of high accuracy. Therefore, it represents a relevant measure, besides throwing velocity, which needs to be observed in assessing throwing performance (7,20,23,24,36). Although research reported beneficial effects of different training programs on throwing velocity (5,12,18,20,21,23,37), there is precious little information about their respective influence on throwing precision, particularly in handball. In this regard, previous studies already showed increased throwing velocities with no effect on throwing precision after completion of a 6-week progressive speed-based throw training program in cricket (16), and also after execution of specific strength training methods (i.e., overweight baseball throws, simulated resistive throwing motions by means of a pulley device) over a 8-week period in baseball (12). However, these studies were exclusively conducted with male cricket or baseball players competing at a high level of performance. There is evidence that men have a better throwing accuracy than women (27), and it therefore can be speculated that female handball players throw less accurate compared with their male counterparts. Consequently, there is a need to specifically clarify the impact on throwing precision in amateur female handball players after a medicine ball training (MBT) intervention solely focusing on the improvement of throwing velocity.

Thus, the aims of this study were to determine the effects of a 6-week MBT program on throwing velocity and isokinetic strength of shoulder rotators in competitive female handball players and to evaluate its influence on throwing precision.

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Methods

Experimental Approach to the Problem

A randomized, controlled, and longitudinal (i.e., pretest, posttest) design was used to investigate the outcome effects of 6 weeks of MBT on throwing velocity, throwing precision, and isokinetic strength of shoulder rotators. A total of 28 competitive female handball players were randomly allocated into an MBT group (TG; n = 15) and a control group (CG; n = 13). The training intervention consisted of an MBT program, performed 3 times a week for a total of 6 weeks, focusing on handball-specific movement patterns. Moreover, both groups (TG and CG) also conducted a supervised shoulder injury prevention program with elastic resistance tubes, as part of the warm-up, and a throwing protocol using a regular handball at the end of each training session. Before any baseline testing, all the study participants attended a laboratory familiarization visit to introduce the testing or training procedures and also to ensure that any learning effect was minimal for the baseline measurements. Handball players completed tests for throwing velocity, throwing precision, and isokinetic strength of shoulder rotators 1 week before the training intervention started (pretests) and 1 week after the last training intervention (posttests). During the intervention period, no additional strength, power, or plyometric training was completed, and both groups followed their normal handball training, 3 times per week. In addition, TG and CG also performed 1–2 self-regulated moderate- to low-intensity injury prevention (e.g., core training, shoulder strengthening, and flexibility) sessions. To reduce the interference of uncontrolled variables, all the subjects were instructed to maintain their habitual lifestyle and normal dietary intake before and during the study. Moreover, the subjects were told to refrain from strenuous exercise 24 hours before a test and to consume their last meal at least 3 hours before the scheduled test time. During training and testing, only water was allowed to drink ad libitum.

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Subjects

Twenty-eight competitive amateur female handball players (mean ± SD; age: 20.8 ± 3.3 years, range: 18–30; height: 170.5 ± 5.6 cm, weight: 65.2 ± 8.0 kg) of the fourth national division volunteered to participate in the study. The mean training background of the players was ∼6 years, which focused on handball-specific training (i.e., technical and tactical skills), aerobic and anaerobic training (i.e., on- and off-court exercises), and some basic strength training (i.e., core strength and machines). In accordance with the Declaration of Helsinki, before any participation, experimental procedures and potential risks were explained fully to the subjects, and the study was approved by the local Ethics Committee. The subjects were free to withdraw from this study without penalty at any time, and they all provided written informed consent.

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Procedures

Throwing Velocity and Precision Measurements

To analyze both, throwing velocity and precision, the dimensions of a regular handball goal (i.e., 2 × 3 m) were fixed at a wall using tape. A 6-cm red-colored and circular target mark, which was visible for all the players, was fixed in the upper right corner of the goal, separated 15 cm from the upper bar and side post (Figure 1). This point was considered as a precise placement for the handball throw by experts. A radar gun (Stalker Professional Sports Radar; Radar Sales, Plymouth, MN, USA) was used to measure throwing velocity. The radar gun was set on “peak mode” to detect maximal ball velocity, between the range of 40 and225 km·h−1. Before each experimental session, the radar gun was calibrated in accordance with the manufacturer's specifications. The radar gun was positioned 4 m behind the free-throw line, aligned with the approximate height of ball throw release (∼2 m) and pointed down straightforward to the target mark in the upper right corner of the goal to eliminate any angle errors in throwing velocity measurement. A pre-investigation identified the mean throwing velocity variable of the sixth to tenth attempt (V6–10) as the most reliable value (intraclass correlation (ICC) (95% confidence interval [CI]) = 0.98 (0.89–0.99); SEM = 0.87 km·h−1; systematic bias = 0.88 ± 1.23 km·h−1).

Figure 1

Figure 1

Throwing precision was assessed by recording every throw with a high-speed video camera recorder (Casio Exilim EX-FH25; Tokyo, Japan). The distance between the predefined target mark and the recorded impact point was calculated through video (Kinovea 0.8.15) and computer analysis (OpenOffice, version 3.2.1; Oracle, Redwood City, California). Thus, ball precision was calculated by determining the x- and y-axis in its centre at the real impact point. For video calibration, an L-shaped calibration mark was fixed in the near of the target mark to provide a scale on the video images and to determine the position of the handball in the X-Y plane at real point of impact (Figure 1). The accuracy of the detection of the x- and y-axis by Kinovea amounted to ±1 cm. Further on, a pre-investigation assessing handball throwing precision by means of Kinovea video analysis showed high levels of intrarater reliability (ICC [95% CI] = 0.997 [0.99–0.995], SEM = 0.61 cm) and interrater reliability (ICC [95% CI] = 0.997 [0.991–0.99], SEM = 0.62 cm), respectively, but moderate values of test-retest reliability (ICC [95% CI] = 0.88 [0.30–0.98], SEM = 3.76 cm, systematic bias = −3.16 ± 5.32 cm).

In addition to accurate assessment of throwing precision by video measurement, the goal success (sum of points for 15 throws) by every throw was determined by allocating points ranging from 0 to 2 to subjects' handball throws. Therefore, at the time of video analysis, a target area (70 × 50 cm) was digitally placed in the upper right corner of the goal. A throw inside the precision target area was scored with 2 points. A throw inside goal but outside precision target area was scored with 1 point, whereas throws outside the goal (and hitting post or bar) were scored with zero points. Test-retest reliability for goal success was found to be moderate (ICC [95% CI] = 0.77 [−0.36 to 0.96], SEM = 2.85 points, systematic bias = −0.6 ± 0.27 points).

After completion of a standardized dynamic warm-up routine and moderate (5 × 50%), submaximal (3 × 80%), and maximal throws (2 × 100%), the subjects were asked to perform 15 maximum throws interspersed by 5- to 10-second rest within the throws, which is based on specific competitive throwing demands in team handball (4,30). The participants were instructed to stand on both feet at the 7-m free-throw line (i.e., penalty throw) and to throw in an overhead motion with maximum effort aiming at the predefined target mark. The given instruction to the subjects was as follows: “Throw as fast and hard as you can on the predefined target mark!”

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Isokinetic Strength Measurements

The use of isokinetic testing enables an isolated and specific strength assessment of certain muscle groups of the upper extremity (e.g., shoulder internal and external rotation) at more functional speeds with regard to the throwing motion. Furthermore, there has been reported a significant relationship between shoulder internal rotation and throwing velocity (38). Therefore, the collection of isokinetic data can provide valuable information for the strength development of the upper extremity (10,28). Isokinetic strength testing of shoulder rotators was arranged 2 days later after the assessment of throwing velocity and throwing precision to allow subjects a 48-hour recovery period. Before any isokinetic testing, a 5-minute warm-up was performed on an arm-cycle ergometer (Cybex Inc., Ronkonkoma, NY, USA) at a resistance level of 25 W followed by light dynamic stretching exercises. After the warm-up, subjects were placed on the isokinetic dynamometer (Cybex—division of Lumex, Cybex 6000; Cybex Inc., ) to evaluate concentric-eccentric internal and external shoulder rotation strength measures (for a total of 5 repetitions at angular speeds of 90°·s−1 and 180°·s−1) for both the dominant and nondominant arm. These angular speeds have been previously used to determine isokinetic strength of shoulder rotators (2,3,28). Subjects assumed the supine position, and standard stabilization strapping was placed across their chest and hips. The upper extremity was positioned with the shoulder abducted to 90° and the elbow flexed to 90°, according to the manufacturer's specification. Strength of internal and external rotators was tested through 120° of range of motion (between 60° of internal rotation and 60° of external rotation) to prevent excessive range of motion of the shoulder joint according to previous research (2). Subjects performed 3 submaximal trials to familiarize themselves with the range of motion and the accommodating resistance of the dynamometer. The subjects were then tested with a maximum of 5 repetitions carried out at angular speeds of 90°·s−1 and 180°·s−1, and the best of 5 isokinetic peak torques obtained was used for later analysis. This method of isokinetic testing was reported highly reliable according to previous research (2). A 60-second rest period was used between sets for all subjects to prevent fatigue buildup. Consistent verbal commands were given during test. All subjects were tested by 1 examiner who was trained and experienced in the use of isokinetic testing devices. Before testing, the dynamometer was calibrated according to the manufacturer's specifications and was checked before testing each subject.

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Training and Exercise Prescription

Training Protocol

The MBT was conducted 3 times per week on nonconsecutive days for a total of 6 weeks, before the handball training sessions. Subjects performed different medicine ball throws that all illustrate handball-specific movement patterns (35) (e.g., 2-arm overhead diagonal throws, 2-arm side rotational throws, single-hand shot put throws). Before MBT, players conducted a standardized dynamic warm-up routine for the upper extremity that consisted of general mobilization exercises (i.e., arm circles, leg kicks), a general activation of shoulder muscles to prevent shoulder joint injuries using elastic resistance tubes (Thera-Band) (2 sets of 15 repetitions of front and side lifts, reverse flies, upper rowing, bilateral external rotation [0° of shoulder abduction], and unilateral external rotation [90° of shoulder abduction]). The degree of elastic resistance was carefully selected (red or green) to enable a proper movement execution over the full range of motion and to sufficiently cause fatigue at the end of each set. If necessary, elastic resistance was increased by changing the band grade. The MBT program consisted of different throwing exercises using 2 different ball weights (2 and 1 kg), followed by a throwing protocol using a regular handball. Training sessions included a stepwise increase of the training load throughout the study period (2 repetitions more every 2 weeks). A detailed description of the MBT program is shown in Table 1.

Table 1

Table 1

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Two-arm Overhead Throw

The subjects were informed to stand with the feet shoulder width apart and facing the wall to which the ball is to be thrown, holding a medicine ball at belly button in both hands. Then, the ball was reached deep behind the head by slightly bending the knees and leaning back followed by an immediate and vigorous throw forward against the wall using the whole body to generate an explosive throwing movement.

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Two-Arm Overhead Backward Throw

The subjects were asked to stand with the feet shoulder width apart, with their back directed to the wall to which the ball is to be thrown, holding a medicine ball overhead in both hands. The ball was brought down at knee level and then violently thrown by explosively extending hips, knees, and ankles releasing the ball overhead backwards.

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Two-Arm Overhead Diagonal Throw

The subjects were instructed to stand sideways (i.e., alternating both, the left and the right foot and shoulder pulled forward), and facing the wall to which the ball is to be thrown, holding a medicine ball at belly button in both hands. The ball was reached deep behind the head by an inversely directed diagonal rotation and then the ball was vigorously slammed to the ground over the forward placed foot.

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Two-Arm Side Rotational Throw

The subjects were informed to stand sideways (i.e., alternating both, the left and the right foot and shoulder pulled forward), and facing the wall to which the ball is to be thrown, holding a medicine ball at belly button in both hands. To begin, the subjects performed a countermovement at height of the waist and then the ball was forcefully thrown straight path by an explosively executed hip and trunk rotation.

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Vertical Squat Chest Throw

The subjects were asked to stand with the feet shoulder width apart, holding a medicine ball at chest level in both hands. It was lowered into a squat position and then immediately exploded upward off the ground, delivering the ball into the air.

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Single-Arm Shot Put Throw

The subjects were instructed to stand sideways (i.e., alternating both, the left and the right foot and shoulder pulled forward), and facing the wall to which the ball is to be thrown, holding a medicine ball behind the face on top of the anterior shoulder part in both hands. Then, the back hip and the back foot were twisted forward releasing the ball straight path with 1 hand and maximum effort against the wall (i.e., throwing such as a straight right- or left-handed punch).

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Statistical Analyses

Data are presented as mean ± SD. An independent sample t-test was conducted for matching study participants and for eliminating any significant differences in throwing velocity between experimental and control group at the onset of the intervention study. Before performing parametric tests, the assumption of normality was verified. A 2-factor analysis of variance for repeated measurements was calculated to determine differences between the measurement points (main effect for time), between the groups (main effect for group), and for the changeover in time in response to the different training interventions (group × time interaction). The Bonferroni correction was used to perform multiple comparisons between groups and time points as well as to control for type I errors. If sphericity was found, p values were adjusted by the Greenhouse-Geisser correction. To enable a better interpretation of the results, effect sizes as Cohen's d were also calculated following the recommendations described elsewhere (14), and values of 0–0.2, 0.2–0.6, 0.6–1.2, 1.2–2.0, and >2.0 were considered trivial, small, moderate, large, and very large, respectively. The p ≤ 0.05 criterion was used to constitute statistical significance. Data analyses were performed with SPSS statistical package (version 18; SPSS Inc., Chicago, IL, USA) and OpenOffice (version 3.2.1; Oracle).

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Results

The results of throwing velocity are shown in Figure 2. Results showed a significant group × time interaction (p < 0.001) with the TG posttest results being significantly higher compared with CG (d = 2.1) and a significant main time effect (p < 0.001) in throwing velocity, with an increase in throwing velocity of 14% (d = 3.0) and 3.7% (d = 0.3) for both, TG and CG, respectively.

Figure 2

Figure 2

Table 2 shows the results for throwing precision and goal success. There were no significant group × time interactions and no significant main time effects. Moreover, no significant differences were found between groups in both parameters, throwing precision and goal success.

Table 2

Table 2

The results of isokinetic strength measures of shoulder internal and external of the dominant and nondominant arm are presented in Tables 3 and 4, respectively. Results showed a significant group × time interaction (p ≤ 0.05) with the TG posttest results being significantly higher compared with CG (d = 0.9) and also a significant main time effect (p < 0.01) for concentric internal rotation at 180°·s−1 (IR180) in the dominant arm in TG, with an increase in concentric IR180 of 15% (d = 0.9) in TG, whereas no significant changes occurred in CG. There was a significant main time effect (p ≤ 0.05) but no significant group × time interaction for eccentric IR180 of the nondominant arm in TG, with an increase in eccentric IR180 of 10% (d = 0.4) in TG. A significant main group effect (p ≤ 0.05) was found in concentric external rotation at 180°·s−1 (ER180) of the dominant arm, with the TG pretest results being significantly higher compared with CG (d = 0.2). No statistical significance could be detected in any of the remaining isokinetic variables analyzed, as shown in Tables 3 and 4, respectively.

Table 3

Table 3

Table 4

Table 4

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Discussion

The aims of this study were to determine the effects of an MBT program on shoulder rotational strength and throwing velocity in amateur female handball players and to evaluate its influence on throwing precision. Results showed that 6 weeks of periodized MBT can elicit significant improvements in the performance variables analyzed (throwing velocity, isokinetic strength of the shoulder rotators) in amateur female handball players, whereas throwing precision remained unaffected which is in line with the previous research (12,16).

To the best of our knowledge, this is the first study conducted with competitive female handball players examining the effects of MBT combined with elastic resistance tubing and regular handball throws on functional performance (i.e., throwing velocity and throwing precision). Results showed an increase in throwing velocity after 6 weeks of intervention training of 14 and 3.7% associated with very large (d = 3.0) and small (d = 0.3) effect sizes in TG and CG, respectively, whereas there were no significant changes in both groups regarding throwing precision (Table 2). However, given the large significant difference in throwing velocity between both groups at the time of the posttest amplified by a very large effect size (d = 2.1), it can be concluded that the MBT exercises were the main determining factor for the improvement of throwing velocity in TG.

Comparisons are difficult because we are not aware of similar studies. Only Ignjatovic et al. (22) and Szymanski et al. (35) analyzed the effects of MBT on the strength and power in young female handball athletes and high school baseball players, respectively, showing that the athletes participating in the MBT program made significantly greater gains in different performance tests (i.e., medicine ball throw tests, torso rotational strength) compared with a control group. However, the effects of the aforementioned MBT programs on throwing velocity were not assessed. The present results showed increases in throwing velocity (ranging from ∼4 to 14%) similar to previous research analyzing the effects of different strength training interventions (6–12 weeks) using moderate to heavy loads (5,20,21,23). Moreover, results are in line with the conclusions of a review analyzing the effects of training with underweight and overweight balls and the combination of both on overarm throwing velocity in different sports (i.e., handball, baseball), suggesting improvements in handball throwing velocities ranging between 2 and 18% (12,37).

Although overarm throwing is a complex motion, which depends on several components (i.e., technique, strength and power, and a proper kinetic chain) (5,23,38), the present MBT (i.e., sport-specific explosive movements in either the transverse or oblique planes) allows exercises to be performed at relatively high speeds, compared with classical strength training using free weights or machines, but with greater force than those performed during normal sport competition (9,33,34), eliciting movement-specific adaptations with an increased amount of specific angular velocity from the proximal to the distal body segments until the release of the ball (9,25). This is supported by previous research reporting significant improvements (10–20%) on strength and power variables of the upper body (i.e., shoulders) and on rotational strength of the trunk and hip muscles after performing MBT in female handball and male baseball players, respectively (22,34). Moreover, it can be speculated that the relatively high coordinative closeness of MBT exercises (i.e., angular specificity, complex sport-specific movement patterns of high velocity and explosiveness) to target movements relevant in team handball (i.e., throwing) is of considerable importance in enhancing functional performance (9).

Isokinetic strength results of the shoulder rotators obtained here showed a significant improvement in concentric IR180 of the dominant arm of ∼15% in TG after the training intervention, whereas there were no changes in CG. Additionally, there was a significant main group difference in concentric ER180 of the dominant arm before the intervention (pretests), but no significant main time effect or a group × time interaction, which may be related to the subjects' inconsistent performance levels at the time of pretesting, as players were matched based on throwing velocity results, but not on the isokinetic shoulder rotational strength values. Moreover, it was observed a significant increase in eccentric IR180 of the nondominant arm of ∼10% in TG but no significant main group effect or a group × time interaction for the same variable, which probably may be attributed to improved neuromuscular coordination patterns in this analyzed muscle action. Insofar, it can be speculated that repetitive medicine ball throwing in an explosive forceful fashion predominantly concentrically activates internal shoulder rotator muscles causing an increase in strength (29), and that the combination of MBT exercises with regular handball throws may elicit a velocity-specific training adaptation in the dominant arm (6). Moreover, the gradual reduction of the medicine ball weight (from 2 to 1 kg) in every training session enabling throwing at higher velocities to better resemble game speeds may also contribute to a velocity-specific training adaptation because it is well known that training at a given velocity enhances strength capabilities mainly at the performed exercise velocity (6). However, comparing the present findings to previous research is difficult because large methodological differences were observed (i.e., test equipment, different arm and body positions during the tests, the degree of arm abduction and horizontal adduction, and the different angular speeds used) (2,26,39). Indeed, former research analyzed the effects of different volumes of upper-extremity plyometric training on isokinetic shoulder strength in male baseball players (3,31), reporting significant improvements of shoulder IR and ER. However, these studies failed to indicate the percentage increases of isokinetic shoulder strength and to determine statistical significant differences between training and control groups.

The throwing motion consists of a summation of forces with powerful concentric and eccentric contractions on the shoulder rotator cuff muscles (i.e., the internal and external rotators) (13). The fast transition between the acceleration phase, characterized by a maximal external rotation followed by a subsequent explosive shoulder internal rotation, and the deceleration phase, with a high eccentric antagonist muscle action of the external rotators for stabilizing the shoulder joint (15), makes the throwing motion as one of the most potential injury risk actions, especially for the shoulder rotator cuff muscles (11,29). Given the prevalence of shoulder joint injury in the modern professional game, strengthening the rotator cuff is considered as a fundamental component of any strength training program focused on throwing athletes (11,29). Thus, in this study, it was regarded necessary to implement a shoulder injury prevention program during the intervention period. At the end of the study, none of the subjects suffered from a shoulder joint injury or reported serious complaints with the shoulder joint during the intervention period.

In conclusion, the present results showed that 6 weeks of periodized MBT elicit significant improvements in functional performance (i.e., throwing velocity) and isokinetic strength of the shoulder rotators, whereas throwing precision remained unaffected. In addition, an “injury-preventive” warm-up for the shoulder complex using elastic resistance bands before MBT and regular handball throws as a coordinative transfer after MBT can be highly recommended. Future research is warranted to examine the effectiveness of these plyometric exercises, as several methodological limitations can be found in this study. For example, the present test design used just 1 measurement for throwing performance (e.g., standing straight throw), and it remains unclear if MBT leads to further improvements on throwing velocity in other throwing techniques (e.g., standing jump shot, 3-step straight throw, or 3-step jump shot). Moreover, upper-body and rotational trunk strength variables were not evaluated. In this regard, rotation of the trunk is an integral part of the development of power and transfer of energy up to the kinetic chain from the lower to the upper extremities (9), with previous studies reporting significant improvements in trunk strength after MBT (22,34). Finally, isokinetic measurements enable testing at more functional speeds (velocity spectrum of 1°·s−1 to approximately 600°·s−1) related to the throwing motion. The fact that most functional activities have angular velocities (8) far exceeding the capabilities of isokinetic dynamometers suggests that isokinetic assessment techniques are only 1 part of the evaluation and, if necessary, rehabilitation process (10).

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Practical Applications

The present results highly recommend the use of MBT exercises combined with regular handball throws preceded by elastic resistance tubing, as part of a shoulder injury prevention warm-up, for the enhancement of functional performance (i.e., throwing velocity) in female handball players. Because throwing performance is one of the most relevant key skills in competitive handball players (20), an MBT intervention based on handball-specific movement patterns conducted 3 times per week, for a minimum of 6 weeks, may be helpful in improving functional performance levels. The MBT allows complex sport-specific movements to be performed explosively with greater resistance than that seen during regular sports competition in a specific manner (i.e., using specific range of motions, angular velocities, and varying limb positions closely mimicking sport-specific movement executions) (9). Moreover, the use of MBT exercises represents an inexpensive strength training strategy with high practicability. As to that, the implementation of an effective and beneficial MBT program merely needs a couple of bouncy medicine balls (no weight room, no machines or free weights) of different weights (ranging from 1 to 2 kg for females, whereas for males even more medicine ball weight is certainly needed) as well as just the regular handball court enabling adequate space to throw the medicine balls. In this regard, as the present results indicate, it is recommended to use both single-handed and 2-handed medicine ball throws in preferably all planes and axes of movement (i.e., sagittal, frontal, and transverse plane).

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Keywords:

speed; accuracy; medicine ball exercises; specific strength training; team sport

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