Zarei et al. BMC Sports Science, Medicine and 0300-5(2021) 13:71RESEARCH ARTICLEOpen AccessThe effect of a shoulder injury preventionprogramme on proprioception anddynamic stability of young volleyballplayers; a randomized controlled trialMostafa Zarei1*, Saeed Eshghi1 and Mahdi Hosseinzadeh2AbstractBackground: The “FIFA 11 Shoulder” programme has been reported to reduce the incidence of upper extremityinjuries among soccer goalkeepers. It has also been recommended for overhead sports. The purpose of this studywas therefore to investigate the effect of an 8-week “FIFA 11 shoulder” (11 S) programme on shoulder jointposition sense (JPS), threshold to detect passive motion (TTDPM) and upper quarter Y Balance Test in young malevolleyball players.Methods: Thirty-two healthy young elite male volleyball players (17.49 1.47 years) participated in this quasiexperimental study. Participants, recruited from two clubs participating in Iranian premier league, were randomlyassigned into two groups; (1) the intervention group who performed the “FIFA 11 shoulder” programme as theirwarm up protocol, three times per week, and (2) the control group who kept their routine warm up protocolmeanwhile. Proprioception tests including JPS and TTDPM of internal and external rotator muscles of the dominantshoulder were recorded via the isokinetic system pro 4. The upper quarter Y Balance Test determined the shoulderdynamic stability.Results: No statistically significant differences were observed for JPS and TTDPM of shoulder internal and externalrotator muscles; shoulder stability however significantly increased only in the intervention group (p 0.03, ηp2 0.02).Conclusion: Upper quarter dynamic stability improvement due to the 11 S programme leads to volleyball players’performance and may therefore contribute to a reduction in risk of sustaining injury if applied long-term.Trial registration: The trial was retrospectively registered atIranian Registry of Clinical Trials with the number ofIRCT20201030049193N1 at 04/12/2020.Keywords: Proprioception, 11 Shoulder, Injury Prevention, Volleyball* Correspondence: m [email protected] Rehabilitation and Health Department, Faculty of Sports Sciences andHealth, Shahid Beheshti University, Velenjak Square, Evin, 1983963113 Tehran,IranFull list of author information is available at the end of the article The Author(s). 2021 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License,which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you giveappropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate ifchanges were made. The images or other third party material in this article are included in the article's Creative Commonslicence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commonslicence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtainpermission directly from the copyright holder. To view a copy of this licence, visit Creative Commons Public Domain Dedication waiver ) applies to thedata made available in this article, unless otherwise stated in a credit line to the data.

Zarei et al. BMC Sports Science, Medicine and Rehabilitation(2021) 13:71BackgroundRepetitive high-demand throwing activities such asspikes and services put extra pressure on the shoulderjoint of the volleyball players. The ability to performthese movements smoothly requires high coordinationin the muscles around the shoulder. This harmony isachieved through the proprioception [1–3]. Proprioception is a comprehensive word for the sense of motionthat receives sensory input from the spindle, tendon andjoint receptors, which includes our ability to locate ourorgans in space (joint position sense) and our ability todetect motion (kinesthetic) and determines the direction,intensity, and velocity of joint movement [4]. Proprioception plays an important role in providing dynamicstability of the shoulder joint as well as muscle coordination in overhead sports such as volleyball [5]. Dynamicstability is the ability of an athlete to stabilize the centerof mass of the body while rotating the distal extremity.Greater dynamic stability of the joint requires appropriate force applied through the muscle tension. The size ofthese forces must be properly coordinated.Proprioception deficiency can impair muscle nervecontrol, which can lead to muscle imbalance and jointinstability [6]. Contemori et al. [7] stated that proprioception defects can alter the function of the dominantarm of volleyball players exposing them to acute orchronic injury. Moreover, Allegrucci et al. [8] stated thatdefect in dominant shoulders kinesthesia of throwerplayers is a mechanism for sustaining shoulder instability. Identifying effective interventions to enhance proprioception is therefore, important for the prevention ofinjuries and the recovery of function in athletic rehabilitation and musculoskeletal physiotherapy [9].Isokinetic dynamometry is suggested as one of theways to evaluate the proprioception. The isokineticdynamometer is one of the most reliable tools for measuring shoulder proprioception through both the activeand passive protocols [10]. Many researchers have usedthis device to assess proprioception. Lee et al. [11] andSales et al. [12] evaluated the proprioception of shoulderinternal and external rotator cuff muscles using the isokinetic dynamometer.Although the effect of exercise training on proprioception is not clear, exercise can enhance proprioception bymodifying the sensitivity of muscle spindles as well as increasing subject attention to the joint position [13, 14].Inconsistent results are however reported [15, 16]. Salleset al. [17] state that strength training directly affects thefunctional capacity of dynamic stabilizers, which resultsin increased joint stability and consequently, reduced injury rates. They then concluded that strength training atthe same intensity improves JPS compared to differentintensity training, which improves muscle spindle sensitivity and hence improves neuromuscular control in thePage 2 of 9shoulder; furthermore they demonstrated that closedkinetic chain (CKC) exercises increase and/or restorethe dynamic stability of the shoulder by facilitating theco-activation of the shoulder muscles caused by the jointapproximation [18, 19]. Open kinetic chain (OKC) exercises but increase the proprioception by emphasizingawareness of the joint position [20]. Padua et al. [21]however, stated that CKC exercise, OKC exercise andProprioceptive Neuromuscular Facilitation (PNF) are notable to improve shoulder proprioception and neuromuscular control in young men and women.FIFA has already developed a shoulder preventionprogramme called the “FIFA 11 shoulder” (11 S)programme for goalkeepers [22]. The programme consists of three sections: general warm-up, exercises to improve the strength and balance of shoulder muscles,elbows, wrists and fingers; and advanced exercises forcore stability and muscle control. The 11 S programmewas initially intended for soccer goalkeepers, theprogramme however could be recommended for playersof other overhead sports as well [22, 23], and since volleyball is also one of the overhead sports, although withdifferent movement pattern comparing to goalkeepersbut still volleyball players have some similarity usingtheir shoulder over their head [24, 25], and also the defect of shoulder proprioception and dynamic stability involleyball players increase the need of the sensory-motorsystem for neuromuscular control and the feed forwardand feedback mechanisms are considered as criticalpoints of the kinetic chain, making their training extremely impor thelevels, the test was performed twice before the start. Alltests were performed between 9 am and 2 pm. For eachindividual, pre and post tests were taken approximatelyat the same time of the day with the same manner andorder.To determine the JPS, shoulder internal/external rotation were measured at 2 degrees per second in passivemode. The rationale for choosing these velocities wasbased on previous studies in which comparable velocitieswere used [11].The dominant shoulder was positioned at 90 degreesof abduction and 0 degrees of external rotation (ER) inthe scapula plane (30 degrees ahead of the frontal plane),as the measurement of the proprioception of internaland external rotators at this angle has high validity [10].The elbow flexed 90 degrees. The forearm was in internal rotation (IR); see Fig. 1. The target angle was 45degrees of IR (from neutral to 45 degrees of IR) and 75Ethical considerationsThis study was approved by research ethics committeeof sport science research institute of Iran. Written consent was obtained from the participants before participation at the study. Participants had the right to withdrawfrom the study at any time without any consequences.ProceduresDemographic dataAll the participants filled into the questionnaires on theage, height and weight, previous shoulder injuries, theirspecific game post, game level and training hours.Proprioception measurementThe Biodex System 4 dynamometer (Biodex MedicalSystems, New York, USA) was used to measure theFig. 1 Setup for assessing proprioception of shoulder external andinternal rotation using the isokinetic dynamometer

Zarei et al. BMC Sports Science, Medicine and Rehabilitation(2021) 13:71degrees of ER (from neutral to 75 degrees of ER). Thelimb moved up to 45 degrees of IR by the device and theshoulder was kept in this position for 10 s and the participant was then asked to focus on the position. Thenthe manual key was given to the participant and the device information on the motion was inactivated by 45degrees of IR and 75 degrees of ER, and the participantwas asked to press the key at any angle he felt that hereached to the target angle. Three repetitions for IR andthree repetitions for ER were performed and the magnitude of the difference between the reconstructed anglesand the target angle was calculated and considered asthe angle reconstruction error [11].To determine the TTDPM, shoulder internal/externalrotators muscles were measured at 0.25 degrees per second in passive mode. The dominant shoulder positionwas similar to the JPS test (Fig. 1). Then the manual keywas given to the participant and the shoulder passivelystarted from 0 degree to the IR direction and the personwas asked to press the key as soon as the movement wasdetected. Then the onset test and the mean motion detection threshold were recorded 3 times in the test [31].The same protocol was then repeated for ER.Page 4 of 9supero-lateral and infero-lateral directions[34] as far aspossible with his free hand (Fig. 2). In order to be ableto compare the results of this study with others, Theplayer’s upper limb length reach values (the seventh cervical vertebra to the end of the longest finger at 90 degrees shoulder abduction and extension of the elbow,wrist, and toe) were normalized [35]. While maintainingthe push up position the ability to reach all three directions was measured without rest and without touchingthe ground. The participant was allowed, after eachround of reaching all 3 directions, to place the free handon the ground and rest [33]. Before the test, each participant was allowed to perform two practice trials. Threeconsecutive trials in all three directions were performedon the dominant arm. In each direction, the highestreach was recorded and was calculated in the followingformula to calculate the overall composite score [35]:Combined score ¼ ðmiddle access þ lower external access þ upper external accessÞ ðupper limb length 3ÞDynamic stability measurementThe Upper Quarter Y Balance Test (UQYBT) was usedto measure the dynamic stability of the dominant shoulder. The UQYBT is a valid and reliable test (with ICCcoefficients ranging from 0.80 to 1.0 for test-retest aswell as intra-rater reliability) [32, 33] for measuring unilateral (dominant hand) upper extremity performanceand stability in a closed-chain position. It can identifyupper extremity motor limitations and asymmetry andtherefore can be used to predict injury in athletes [33].To perform this test, the participant was asked toplace the thumbs on the palms of the fingers and elbowsopen, keeping the spine and lower limbs in one position.The location of the thumb was indicated by a line andthe legs were about the shoulder-width apart (the legswere not more than 30 cm apart). In this situation, theparticipant was asked to maintain the position of thesupport arm, trunk, and lower limb, to reach the medial,Intervention programmeThe 11 S programme was developed by an international group of experts, including orthopedics, physiotherapists, and sports rehabilitation specialists. Theprogramme focuses on core stability, neuromuscularcontrol, eccentric rotators’ strength, and shoulder agility.It consists of three parts: general warm-up (part I);strength and balance training for the shoulders, elbows,wrists, and fingers (part II); core stability and musclecontrol exercises (part III). The second part of theprogramme has three levels of difficulty and to achievethat elastic bands at three resistance levels (blue [low],black [medium], and gold [high]) are used. Prior to theimplementation of the 11 S programme by the participants of intervention group, several educational sessionswere organized for the coaches by the researcher tofamiliarize the coaches with the exercises and how theyFig. 2 Upper Quarter Y-Balance Test - Direction of reach is named relative to the stationary upper extremity (A. Medial Reach Direction, B.Superior Lateral Reach Direction, and C. Inferior Lateral Reach Direction)

Zarei et al. BMC Sports Science, Medicine and Rehabilitation(2021) 13:71are implemented, this was done in order to ensure thatthe programme would be properly implemented by thecoaches, Informative posters were also provided. The researcher supervised the training at intervention group ateach session to validate the implementation of the 11 Sinjury prevention programme. The content of the training and participants’ progress was monitored by the researcher every two weeks during the intervention period.All players started training from level one and movedon to the next level if they were able to do error-freetraining determined by coaches under standard conditions. The participants at the intervention group performed 11 S exercises three times per week as theirwarm-up protocol. The 11 S programme was usuallytaken about 20–25 min.The control group also performed their normal warmup for 25 min, including 5 min of stretching exercisesfor the whole body, then dynamic warm-up exercises for10 min, including running and jumping movements, andfinally 10 min of exercises with the ball, including spiking, etc.In order to avoid the effect of fatigue on the proprioception due to increased intramuscular concentrationsof lactic acid, bradykinin, arachidonic acid, and serotoninafter fatiguing contractions which may affect the musclespindle system, and, thus, proprioceptive acuity [28],players performed JPS and TDDPM tests with an isokinetic dynamometer before the UQYBT test. Before thepre-test and post-test, the players performed a standardized 5-minute warm-up on an arm-cycle ergometer(Monarch Model 894E, Sweden) at a self-determined cadence (between 80 and 110 rpm) with the workload setto 75 W. Participants then familiarized with the dominant shoulder test to learn how to perform a proprioception test with an isokinetic device. They tried to do theUQYBT test, did the test twice in three directions. Theproprioception and UQYBT tests for the dominantshoulder were conducted in standard conditions. Alltests were conducted three days before and three daysafter the intervention programme at the Shahid BeheshtiUniversity Sport Laboratory.Statistical analysisAll statistical analyses were performed by SPSS 24.0 software (IBM corp. Amork, NY). Descriptive data are provided as mean and standard deviation. The demographiccharacteristics of the participants of two groups at baseline were analyzed using the independent samples Ttest. Measurements of proprioception in internal and external shoulder movement (for JPS and TTDPM) havebeen reported. Two-factor ANOVA test (condition factor: “pre” and “post” and group factor: intervention vs.control) with a group x condition interaction was usedto analyze the within and between group evaluation overPage 5 of 9the eight-week intervention period at 95 % significancelevel with alpha equal or less than 0.05. To limit the possibility of getting a statistically significant result, Bonferroni adjustment for multiple comparisons was used forpost hoc test. To analyze the effect of the interventionon the different proprioception measures, we calculatedthe mean differences and the Δ%between the intervention group and the control group. The effect size wascalculated using Cohen’s d value. An effect size between0.2 and 0.5 was considered a small effect, between 0.5and 0.8 a medium effect, and greater than 0.8 a large effect [36].ResultsFour out of the 32 young male volleyball players, twoout of each group, dropped out of the study because ofleaving their teams and not attending the training sessions (see the flow of participants, Fig. 3). The data related to 28 players were analyzed (intervention group(INT), n 14 and the control group (CON), n 14). Theparticipants did not suffer any physical complaints priorto the tests. No injuries induced-time-loss occurred during the period of conducting the study in any of the twogroups. All players reached level three in the intervention group. The demographic characteristics e.g. age,body height and weight, Body Mass Index and volleyballexperience of the two groups were not significantly different (p .05) (Table 1). The participant’ maturity wasdetermined via Tanner scales while all of the kept positions four (IV) and five (V).Between subject repeated measures ANOVA showedno significant interaction effect between the time groups in none of the proprioception (JPS and TTDPM)variables (Table 2). However, there was a main effect oftime in the JPS of the shoulder IR motion at -45 degree(F1, 26 21.31, p 0.05) and the JPS of the shoulder ERmotion at 75 degree (F1, 26 23.11, p 0.05) and theTTDPM of the shoulder ER motion at 75 degree (F1,26 5.35, p 0.05).There was a statistically significant interaction effect oftime group on the dynamic stability (F1, 26 5.11, P 0.03, ηp2 0.16). Dynamic stability was found to improve from pre- to post-test in the intervention group(0.77 0.04, 0.85 0.06 respectively).DiscussionAlthough 11 S was useful for soccer goalkeepers, andgiven that this program is also recommended for playersin other overhead sports, our hypothesis was that the11 shoulder program has an effect on shoulder proprioception and shoulder stability of volleyball players aswell.The most important finding of this study was that following an eight-week 11 S warm-up programme, the

Zarei et al. BMC Sports Science, Medicine and Rehabilitation(2021) 13:71Page 6 of 9Fig. 3 Flow of the studydynamic stability of shoulder increased in young malevolleyball athletes. Based on the findings of this studyour hypothesis was therefore confirmed.Since this is the first study to investigate the effects ofthe 11 S programme on the proprioception and dynamic stability of shoulder in young male volleyballplayers, no other similar study is available to comparethe results with.Regarding to the findings related to Y-Balance test inline with our study, Amirkolahi et al. (2019) in the studyof the effect of Swiss ball training on the integration offunctional movement ies may improve their JPS,however such effect is not expected in healthy peopleand it will not have much effect on the JPS.Another interpretation attributed to the controversybetween previous studies investigating the effect of exercise training on proprioception would be the differencebetween the type and mode of the exercise training andthe test applied in these studies. Conducting active testing techniques for assessing proprioception can lead todifferent results; Swanik et al. [16] who used an activetechnique to assess shoulder proprioception concludedthat plyometric exercise training increases the proprioception of the shoulder joint. Salles et al. [17] who applied 4 types of strength training including chest press,lat pull, shoulder press, and rowing and assessed shoulder JPS via the Joint-Position Reproduction Test reported similar results. Finally, the 11 S trainingprotocol includes OKC and CKC exercises (e.g. push-upand walking on the hands), the efficiency of these exercises on proprioception is reported inconsistent in different studies. Salles et al. [17] and Rogol et al. [43]reported that these exercises are effective for improvingthe shoulder proprioception. However, Padua et al. [21]who examined the effect of five weeks of CKC and OKCexercises on shoulder JPS found that these exercises didnot have any significant effect on proprioception andneuromuscular control of the shoulder; they thereforesuggested that CKC exercises should not be consideredas an effective approach to facilitate proprioception andneuromuscular control.ConclusionsResults of this study suggested that 11 S injury prevention programme can improve the dynamic stability ofthe volleyball player

vention programme on shoulder proprioception and stability in Iranian young male volleyball players. Methods Design This study was a Pre-test – post-test quasi-experimental cohort design with a control group aiming to investigate the effect of an eight-week 11 S programme on shoul-der proprioception and sta