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Int J Physiother Res 2017;5(3):2133-43. ISSN 2321-1822 2133

Original Research Article

EFFECT OF ISOKINETIC VERSUS PLYOMETRIC TRAINING ONSHOULDER PROPRIOCEPTION AND EXTERNAL TO INTERNALROTATORS STRENGTH RATIO IN SWIMMER CHILDRENSamah Attia El Shemy *1, Kadrya Hosny Battecha 2.

*1 Assistant Professor, Department of Physical Therapy for Growth and Developmental Disordersin Children and Its Surgery, Faculty of Physical Therapy, Cairo University, Egypt.2 Assistant Professor, Department of Basic Science, Faculty of Physical Therapy, Cairo University,Egypt.

Background: Many exercise protocols intended to enhance kinesthetic awareness and muscular performance,however more investigations need to be directed to the restoration of muscular imbalances.

Objective: To compare the impacts of isokinetic training and plyometric training of the rotator cuff muscles onshoulder proprioception and isokinetic strength ratios.

Materials and Methods: Seventy five swimmer boys randomly assigned to three equal-sized groups: controlgroup (A) had no strength training, study group (B) received isokinetic training and study group (C) receivedplyometric training for the rotator cuff muscles. Pre-post testing measurements included: kinesthetic measure-ments at 45° of internal rotation, 45° external rotation and 75° external rotation; and concentric external/internal rotation strength ratios at angular velocities of 60°/s and 180°/s using a Biodex System 3 isokineticdynamometer. The test procedure performed before and after the training period of eight weeks.

Results: Both training groups showed pre-posttest significant differences in all measured variables with non-significant changes in the control group. When comparing the post-treatment results in both training groups, theisokinetic group showed the most significant improvement in the strength ratio. However, no significant differ-ences in kinesthetic awareness found between both training groups.

Conclusion: Isokinetic strengthening is the most effective strategy of adjusting strength ratios of the rotator cuffmuscles. Moreover, both isokinetic and plyometric training enhanced kinesthetic awareness, neither techniquewas superior.

KEY WORDS: Isokinetic Training, Plyometric Training, Rotator Cuff, Proprioception, Strength Ratio, Swimmers.

ABSTRACT

INTRODUCTION

Address for correspondence: Dr. Samah Attia El Shemy, PhD, Assistant Professor, Department ofPhysical Therapy for Growth and Developmental Disorders in Children and Its Surgery, Faculty ofPhysical Therapy, Cairo University, Egypt. E- Mail: [email protected]

International Journal of Physiotherapy and Research,Int J Physiother Res 2017, Vol 5(3):2133-43. ISSN 2321-1822

DOI: https://dx.doi.org/10.16965/ijpr.2017.161

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International Journal of Physiotherapy and Research

ISSN 2321- 1822

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DOI: 10.16965/ijpr.2017.161

Received: 17-04-2017 Peer Review: 18-04-2017 Revised: None

Accepted: 13-05-2017Published (O): 11-06-2017Published (P): 11-06-2017

This regularly connected with an undesirableincrement in joint laxity [1].Besides; it performed in a liquid medium whichoffers more imperviousness to movement thanair. Ordinarily, swimmers start their extraordi-

Swimming is a peculiar sport in that the shoul-ders and upper limbs utilized for velocity, at thesame time requiring shoulder adaptability andscope of movement for maximal productivity.


Samah Attia El Shemy, Kadrya Hosny Battecha. EFFECT OF ISOKINETIC VERSUS PLYOMETRIC TRAINING ON SHOULDER PROPRIOCEPTIONAND EXTERNAL TO INTERNAL ROTATORS STRENGTH RATIO IN SWIMMER CHILDREN.

external rotators is of crucial significance wheninterpreting upper limb strength tests [7].As indicated by Myers et al. [8] objective datawith respect to the multifaceted balance ofagonist-antagonist muscular quality encompass-ing the glenohumeral joint is a fundamentalasset in the restoration and prophylactic treat-ment of the shoulder joint. Anomalous externalto internal rotator torque proportion is anunavoidable outcome of swimming. Therefore,the key figure preparing programs proposed toimprove shoulder ER muscle quality in overheadcompetitors is the adjustment in ER to IR qual-ity proportion particularly to begin swimmers tolimit the danger of future damage [9].In spite of advances in restoration and surgicalmethods, the best “treatment” remainscounteractive action. So as to fulfill this, coachesand swimmers need to get comfortable withpro-per training methods, mechanics and havethe capacity to perceive the normal changes instroke mechanics designs related with shoulderdysfunction. With a specific end goal to dimin-ish the risk of swimmer’s shoulder, an injuryprevention program must address strengthimbalances and impeded range of motion tolessen the danger of shoulder impingement [10].Isokinetic strength assessment of shoulderrotation is a profitable method in shoulderinjury appraisal, especially aggravations in theagonist-antagonist balance. It is a referencetechnique for assessing shoulder musclequality and distinguishing shortfalls in particu-lar muscle groups found in certain shoulderdisorders. Such measurement is a profitableapparatus for situating rehabilitation towards theaffected muscle groups [11]. Isokinetic resis-tance training is powerful in improving muscu-lar strength coming about because of highstrengths delivered by muscles contracting at aconsistent speed through the whole scope ofjoint movement. Isokinetic activities might beperformed concentrically or eccentrically asexternal forces are applied to the limb [12].Plyometric activities defined as eccentricloading instantly took after by a concentriccontraction. Plyometric practice alludes to thoseexercises that empower a muscle to achievemaximal drive in the most limited conceivabletime. A plyometric action is isolated into three

nary preparing at an early age of 8 to 11 yearsof age. The high recurrence and preparing ofswimming can regularly prompt to shoulderoveruse injuries, or what is called “swimmer’sshoulder” [2].Proprioception is fundamental to the centralsensory system to direct neuromuscular controlwith a specific end goal to keep up functionaljoint strength, particularly in the shouldercomplex, which depends vigorously on muscu-lar contractions for stability. Subjects with shoul-der instability have demonstrated propriocep-tion deficits. It is conceivable that injured orloose ligaments, capsules, and muscles influ-ence proprioception afferent information.Proprioception deficits may bring about impededneuromuscular control, which could prompt tomuscle imbalance and joint instability [3].Joint position sense (JPS) has recorded as anindividual’s capacity to reproduce a predeter-mined joint angle either actively or passively.Both sorts of measurement commonly carriedout in the open kinetic chain. Joint position sensetesting instruments have extended from themost essential standard goniometer to the moreadvanced isokinetic dynamometers furnishedwith their own internal electrogoniometers [4].Various reviews have documented that theinternal rotator (IR) musculature is stronger inswimmers as a result of the repetitive concen-tric contractions required during the propulsiveperiod of the swim stroke. Conversely, externalrotator (ER) strength is reliably weaker in swim-mers and high eccentric requests put on theexternal rotator muscles cause chronic fatigue,making it hard to control glenohumeral-jointtranslation and muscular imbalances in theshoulder rotators of youthful swimmers. As aresult of increased levels of IR strength and en-durance that are proportionally larger than thoseof their antagonists. A compensatory strengthtraining program should be considered [5, 6].Typical strength ratios for the ER and IR of theshoulder have accounted for to be 2:3 roughly66% in ordinary. Keeping up a balance of qualitybetween the external and internal rotators ofthe shoulder is basic for typical muscular forcecouple activity and, along these lines, fundamen-tal for glenohumeral steadiness. Assessing themuscular strength balance of the internal and



stages including, the eccentric preload stage,the amortization stage and the concentriccontraction. Arrangement of the three stagesidentified as the stretch shortening cycle [13].Plyometric exercises considered as a vitalsegment of rehabilitation, which underpins thehypothetical ideas for utilizing these sorts ofexercises for the upper limbs. This kind of prac-tice performed for shoulder strength training.However, on account of the different levels offorce related with plyometrics, and additionallythe critical impacts these activities have onproprioception and muscle execution, it issensible that plyometrics could likewise beadvantageous if actualized in the before phasesof shoulder restoration[14].Therefore, the purpose of this study was tocompare the outcomes of isokinetic training andplyometric training in terms of: 1) shoulderproprioceptive sense 2) shoulder external tointernal rotators strength ratio (ER concentric/IR concentric ratio).

injury for which they have sought medicalattention and/or had kept them from practicing.In addition, any child skipped three successivetimes from the exercise program excluded fromthe study. The recruitment process and the flowchart of participants illustrated in figure 1.Demographic characteristics of participantspresented in Table 1.Instructions about the purpose and methods oftesting provided for each child before each test-ing session to make every child familiar with thedevice. All children’s parents gave their informedconsent to have their children participated in thestudy. The work carried out in accordance withthe code of Ethics of the World Medical Asso-ciation (Declaration of Helsinki) for experimentsinvolving humans. The study approved by theEthics Review Committee of Faculty of PhysicalTherapy, Cairo University, Egypt (P.T.REC/012/001583).Randomization: Following the baseline mea-surements, randomization performed simply byadding a specific identification number for eachchild. Consequently, the recruited children allo-cated randomly on a computerized base usingStatistical Package for the Social Sciences (SPSS)into three equal groups of 25 children each.These three groups named as control group (A)continued to participate in regularly scheduledswim practice. Study group (B) received shoul-der isokinetic training as well as regularly sched-uled swim practice similar to group A. Studygroup (C) received shoulder plyometric trainingin addition to regularly scheduled swim prac-tice given to group A.

MATERIALS AND METHODS

αSubjects: A preliminary power analysis appliedwith effect size = 0.40, = 0.05, power = 0.80,groups= 3 and evaluation times = 2 with a re-sult of sample size of total 66 children at leastfor this study.Through the following procedure, eighty swim-mer children assessed for eligibility of this studyrecruited from Wadi Degla Sporting Club. Threechildren did not meet the inclusion criteria whileanother two refused to engage in this study. Thestudy conducted on seventy-five swimmer boys,their age ranged from 13-15 years. Each childassessed after 24-48 hours from the last train-ing to minimize the difference of training loadeither over training or unloading of muscles.Moreover, all participants belonged to the sameswimming team, which is engaged in a 4 hoursof training per week. All children submitted to acomplete medical examination prior to thebeginning of the study. Children who met thefollowing inclusion criteria enrolled in thecurrent study. They had good style swimmingand free from rheumatoid arthritis or otherinflammatory joint diseases. Accordingly,participants excluded from the study if they hadsuffered a recent shoulder, cervical or thoracic Fig. 1: Flow chart of the study.


Active joint repositioning sense and ER concen-tric /IR concentric strength ratio of the domi-nant shoulder assessed for each child of thethree groups before and after 8 weeks oftraining program by using the Biodex III isokineticdynamometer.Instrumentations

For evaluation: Biodex III isokinetic dynamom-eter (Biodex Medical System, Inc, Shirley, NY,USA) is one of the most comprehensivecomputer devices provided with attachmentsand isolation straps for every part of the body. Itprovides testing data, graph recording andprinted results for torque, work, power andproprioception [15].For treatmentBiodex III isokinetic dynamometer: It utilizedfor the training of different muscle groups so asto enhance the muscular performance indynamic conditions and consistent preselectedspeed of movement. These elements give safetyin the recovery of patients with muscular andligamentous injuries. The movement speed ofvarious exercises recreated during training toenhance the training impact. Data acquisitionand analysis improved by utilizing computersystems interfaced to isokinetic dynamometers[16].The equipments utilized in plyometric trainingincluded medicine balls (1 kg for the single armexercises and 1.36 kg for the 2-handed exercises)and Theraband latex tubing (The Hygenic Corp.,Akron, OH).Procedures for evaluationActive repositioning test procedure: Activejoint reposition senses determined by measur-ing the subject ability to actively reproduce apassively placed joint position. Active reposi-tioning accuracy test of dominant shoulder wasmeasured by Biodex III Isokinetic Dynamometer.Dominant arm dictated by asking swimmerswhich arm they would use to write. All partici-pated children were right handed. Each childpositioned sitting on the related seat andsecured with belts around the trunk and pelvisso as to avoid compensatory movements withhis shoulder situated in 90° of shoulderabduction, 90° of elbow flexion, and neutral pr-onation /supination [17].

The lever arm attachment length and seat backadjusted so that the rotational axis of thedynamometer situated to be co-axial with theshoulder axis during the testing procedures. Theforearm secured to the lever arm, constrainingshoulder movement to internal and externalrotation. The positioning of the subjects and thejoint alignment done by the directions set out inthe device’s operations manual [18].Preceding being tested, each child received apractice session followed by a 30-second restperiod, and subsequently began the activereposition test. Three positions tested accord-ing to Blasier et al. [19] The reference angleswere 45° of internal rotation (from 90° at thestart to the 45° internal position), 45° of exter-nal rotation (from 90° at the start to the 45°external position), and 75°of external rotation(from 30° at the start to the 75° externalposition). During the test session for the activereposition test, all children were blindfolded inan effort to eliminate the commitment of visualcues to joint repositioning [4]. Participants askedto focus on the presented angle and activelymove their shoulder to each of the pre-chosentest positions within 60 sec.The angular speed for the active reposition testset at 30°/sec. Three trials recorded for everyreference angle, each starting from the startingposition/angle. There was a period of rest, oneminute between each trial and the other. Jointreposition sense assessments recorded inabsolute degrees of error between thepreselected angle and the repositioned angle[20]. The mean angular differences of the threetrials recorded and utilized in the statisticalanalysis.Isokinetic testing procedure: Biodex IIIIsokinetic Dynamometer used to determineisokinetic peak torque values for concentric ER/IR strength ratio of the dominant shoulder. Fromthe previous described position, range ofmotion set from 0°-90° ER/IR rotation of theshoulder joint. Concentric strength testingmeasured at angular velocities of 60, and 180°/s. The same sequence followed for all thesubjects to increase reliability of data acquisi-tion. Before data collection, all subjects in thethree groups completed a 5 minute warm up onan upper body ergometer before starting their



of 20 repetitions were completed [25] with 90seconds of rest between each set for rebuildingof muscles stored energy [26].According to Carter et al. [25] and Davies et al.[27], plyometric training program includes walldribbling exercises, plyometric ball throws andTheraband exercises focused on strengtheningthe external rotators of the shoulder.The plyometric training program includes thefollowing exercises:Plyometric push-ups against wall each childinstructed to stand against wall leaning towardswall then pushing his body away from the wall.Plyometric push-ups on the ground each childstarted by getting into a push-up position on theground lowering himself to the ground and thenexplosively pushing up so that his hands leavethe ground. Each child instructed to catch hisfall with his hands and immediately lowerhimself into push-up again.Theraband 90/90 external rotation of shoul-der each child should start this exercise withhis shoulder abducted 90° and elbow flexed 90°.Theraband taut and positioned to oppose theexternal rotators of the shoulder.Theraband external rotation of shoulder eachchild instructed to perform the same previousexercise, but from adducted shoulder with histrunk facing sideways throughout the exerciseas he tucks his elbow into his side.Two hands chest pass with plyometric balleach child instructed to stand holding plyometricball throwing it forward pushing it off his chest.He should try to anticipate the catch and returnthe ball as quickly as possible keeping the catchtime as short as possible.Slams with plyometric ball from standingposition, each child instructed to pull plyometricball back overhead and forcefully throw balldown on the ground as hard as possible. Thechild then catches the ball on the bounce fromthe ground and repeat.Overhead throws each child instructed toperform the same previous exercise, but heforcefully throws the ball forward as far aspossible into the wall. The child then catchesthe ball on the bounce from the wall and repeat.Single arm overhead throws from standing

testing or training protocol [21].The testing protocol consisted of three sub-maximal warm up repetitions at each angularvelocity to be familiar with the isokineticexercise. A two minute rest provided at the endof the practice session. Five maximal concen-tric test repetitions completed through the rangeof motion from 0° to 90° at each angular veloc-ity [22]. Children instructed to provide maximaleffort throughout the entire repetition and givenboth verbal and visual feedback and encourage-ment to facilitate maximum performance. Oneminute rest period allowed between tests of eachvelocity. At the end of testing, ER/IR peak torqueratio ascertained.Procedures for treatmentIsokinetic training program: The isokineticgroup followed an isokinetic strengtheningprogram utilizing the isokinetic testing positiondepicted previously. The training protocolcomprised of 8 weeks of isokinetic exercise work-outs, two times each week. Every individualworkout consisted of ten sets of ten repetitionsusing the velocity spectrum 90, 120, 180, 210,240, 240, 210, 180, 120, and 90°/s. A velocityspectrum rehabilitation protocol used toenhance a training response at various angularvelocities. Ten repetitions at each angularvelocity with 10-second rest between angularvelocities were optimal to increase isokineticpeak torque across a velocity spectrum [23]. Atotal of 16 workout sessions were completed byevery child in the allotted 8 weeks period.Plyometric training protocol: The trainingprotocol comprised of 8 weeks of plyometrictraining, two sessions per week. Childreninstructed to utilize maximal exertion and toperform exercises in a ballistic manner depictedby Pretz [24] in order to decrease the amortiza-tion phase and to boost the training effects. Athorough warm-up is essential prior to plyometrictraining in the form of general mobility, particu-larly about the joints involved in the arrangedplyometric session. A cool-down should followeach session. Exercises performed using 3 setsof 10–20 repetitions. The progression of thetraining protocol was 1st and 2nd week theparticipants completed 3 sets of 10 repetitions,from 3rd to 5th week they completed 3 sets of 15repetitions and finally from 6th to 8th week 3 sets



position, the child instructed to grasp plyometricball and throw the ball up into the air as high aspossible then catches the ball on the bounceand repeat.Side throws with plyometric ball the childinstructed to hold plyometric ball with both handswith arms slightly bent. He swings the ball overto right and/or left hip and forcefully underhandtoss ball towards the wall, and then he catchesthe ball on the bounce from the wall and repeat.90/90 external rotation side throw withplyometric ball the same as previous exercise,but one hand side arm throw with ball from 90°shoulder abduction and 90° elbow flexion.Plyometric arch chops the child instructed toraise the plyometric ball up with his armsextended over his right shoulder. In one continu-ous motion he brings the ball down towards hisleft foot. He stands back up and raises the ballstraight up over his left shoulder and then bringsthe ball down towards his right foot. Return tothe starting position and repeat.Catch and throw backhand from standingposition the participant instructed to bend hiselbow to 90 degrees and tucks his elbow intohis side. The child rotates his arm out to catchthe plyometric ball. The child throws the ballback to the therapist and focuses the effort onexternal rotators.Reverse catch external rotation plyometricThe same as previous exercise while the arm in90° of abduction and 90° of elbow flexion.Prone 90/90 external rotation plyometricThe child positioned prone on a standard treat-ment table with 90° of shoulder abduction and90° of elbow flexion. The plyometric ball usedto alternately catch and drop.Control group participated only in regular swim-ming training practice. Three groups swam forfour hours per week in the eight weeks through-out the study. The swimming training wasidentical for the three groups and conducted bythe same coach to ensure consistency in coach-ing techniques and programming [28].Statistical analysis: Descriptive statistics ofmean and standard deviation calculated for allmeasured variables. Parametric tests (pairedt-test and ANOVA) used to analyze the pre andpost treatment mean values of shoulder prop-

rioception within group and among groups. Non-parametric tests (Wilcoxon-Signed Rank,Kruskal-Wallis and Mann-Whitney Signed Rank)used to analyze the pre- and post-treatmentmean values of ER/IR concentric ratio withingroup and among groups. Statistical analysisperformed using the software package SPSS forWindows, version 20. A p-value of less than 0.05considered significant (95% CI).

RESULT

There were no significant differences among thethree groups with respect to demographiccharacteristics as shown in Table 1 as well as inthe baseline mean values of active reposition-ing senses and ER/IR concentric strength ratiosat two angular velocity 60°/s, 180°/s as shownin Table 2.Tables 2 and 3 show the results of within groupcomparison as there were significant reductionsin absolute degrees of error at 45° IR, 45° ERand 75° ER as well as ER/ IR concentric ratios at60°/s, 180°/s post treatment in isokinetic train-ing and plyometric training groups with non-sig-nificant changes in the control group as com-pared with baseline values. In addition, table 2and 3 summarize the results of among group’scomparisons of proprioception and ER/ IR con-centric ratios for the three groups. There weresignificant differences among the three groupsregarding the measured variables after treat-ment.Table 1: Demographic characteristics of participatedchildren.

Control group Isokinetic group Plyometric group p- value

Age (years) 14.12 ±0.78 13.96 ± 0.84 13.84±0.74 0.45

Weight (kg) 43.20±2.04 44.36±2.73 44.28 ±3.57 0.28

Height (cm) 146.68± 3.77 148.00±4.09 147.96±2.90 0.34

BMI (kg/m2) 20.10±1.13 20.25±1.03 20.24±1.82 0.9 Values are mean ± SD; BMI: Body Mass Index; p-value:Level of significance *p <0.05It is evident from Table 4, that there weresignificant differences between groups in allmeasured variables when multiple comparisonsperformed after eight weeks of treatment (p<0.05). There were significant differences in allmeasured variables between control group A andisokinetic group B in favor of group B. Compari-son between group A and plyometric group Crevealed significant differences in all measured



variables in favor of group C. Moreover, comparison between group B and C showed significantdifferences in ER/ IR concentric ratios at both angular velocities in favor of group B while nonsignificant differences observed between both groups in shoulder proprioception.

Table 2: Comparison of the mean values of joint position sense within and among groups.

Table 3: Comparison of the mean values of external to internal rotators concentric ratios within and amonggroups.

Pre Post Pre Post± SD ± SD ± SD ± SD

Control group 74.96± 2.90 74.64± 2.17 -0.397 0.691 76.04±2.55 75.72±3.07 -0.471 0.638

Plyometric group 75.16± 2.82 68.12±2.14 -4.208 0.0001* 76.24±3.08 69.36±2.54 -4.25 0.0001*

K-value 1.205 52.63 0.286 48.04p- value 0.548 0.0001* 0.867 0.0001*

Isokinetic group 75.68± 1.67 66.12± 2.18 -4.419 0.0001*

ER/IR concentric ratios at 60˚/s ER/IR concentric ratios at 180˚/sZ-value p- value Z-value p- value

76.44±3.37 67.16± 2.56 -4.293 0.0001*

: Mean; SD: Standard deviation; Z: Wilcoxon signed-rank test value; K- value: Kruskal-Wallis test value; ER/IR:External/ Internal rotators; p-value: Level of significance *p <0.05 (95% CI)

Table 4: Comparison of post-treatment mean values of joint position sense and external to internal rotatorsconcentric ratios between groups.

Control group vs isokinetic group

1.12 0.000a 1.23 0.000a 1.49 0.000a 8.52 0.000b 8.56 0.000b

Control group vs plyometric group

1 0.000a 1.17 0.000a 1.56 0.000a 6.52 0.000b 6.36 0.000b

Isokinetic group vs plyometric group

0.12 0.176 0.05 0.683 0.07 0.376 2 0.002b 2.2 0.002b

p- value

JPS 45˚ IR JPS 45˚ ER JPS 75˚ ER ER/IR ratios at 60˚/s ER/IR ratios at 180˚/s

MD MD MD MD MDp- value p- value p- value p- value

MD: Mean difference; JPS: Joint position sense; ER/IR: External/ Internal rotators; a: Significant difference betweenboth groups (post hoc least significant difference test); b: Significant difference between both groups (Mann-Whitney signed-rank test); p-value: Level of significance p <0.05 (95% CI)

Selection of the high intensity of both trainingprograms comes in agreement with Lin andKarduna [30] who stated that activities, particu-larly focusing on individual muscles with lowintensity may not be adequate to enhance ashoulder joint position sense. Future workexpected to additionally investigate which typesof exercise are more effective in enhancing the

DISCUSSION

Rehabilitation programs incorporate activities toreestablish muscle imbalances and sensorimo-tor control are essential for patients with shoul-der injuries [29]. The aim of this study was toinvestigate the impact of two types of shoulderexercise training programs over 8-weeks periodon active reproduction joint position sense andER/IR strength ratio in swimmer children.


Pre Post Pre Post Pre Post

± SD ± SD ± SD ± SD ± SD ± SD

F-value 1.5 93.13 2.238 51.91 0.216 239.06

p- value 0.22 0.0001* 0.114 0.0001* 0.805 0.0001*

JPS 45 ̊IR JPS 45˚ ER JPS 75˚ ER

Control group 1.66 0.109 3.92 ± 0.31 3.87 ± 0.32 0.91

Isokinetic group 12.86 0.0001* 4.08 ± 0.24 2.64 ± 0.55

Plyometric group 21.64 0.0001* 4.01 ± 0.19 2.69 ± 0.53

p- value

0.0001*

38.86 0.0001*

16.16 0.0001* 34

0.37 0.3 0.76

19.84 0.0001*

t-value p- value t-value p- value t-value

3.26±0.283.25± 0.313.04±0.223.1± 0.27

1.77±0.223.2±0.273.16±0.31 1.91±0.38

1.7±0.343.21±0.272.04±0.333.25± 0.34

: Mean; SD: Standard deviation; t- value: Paired t -test; F- value: Analysis of variance value; JPS: Joint position

sense; p- value: Level of significance *p <0.05 (95% CI)


joint position sense and the mechanisms asso-ciated with those progressions.In the current study the pre treatment meanvalues of the measured variables showed thatthe swimmer groups have a more prominentmuscle imbalance of the shoulder joint and,consequently, higher risk for injury. This comesin agreement with West et al. [31] who reportedthat decrease in the value of concentric strengthof the ER, consolidated with an increase of thestrength of the IR is a feature of athletes whopresent with instability of the glenohumeraljoint contributing to an increased risk for jointinjury. Accordingly, this fact reinforces thesignificance of performing particular compen-satory exercises, which should concentratemainly on the ER.Selection of the reference angles in JPS comesin consistent with Blasier et al. [19] who distin-guished larger deficiencies in angular reproduc-tion in the middle range of rotation (at a setangle of 30°) than that at other set angles lessthan 30°. In this study, the reference angles 45°and 75° in the middle ranges of internal andexternal rotations were set in active JPS test.The larger angular changes can detect speci-fied mechanoreceptors more precisely.The findings of this study support the use of bothupper extremity isokinetic and plyometricstrength training for reducing commonly identi-fied upper extremity injury risk factors andimproving upper extremity performance. Theprimary findings of the current study demon-strated that plyometric and isokinetic groups hadsignificantly improved JPS from pretests toposttests as well as ER/IR concentric strengthratio when compared with the control group. Theexercise groups were better able to reproduceangles and had a better awareness of thelocation of their upper extremity in space incomparison with the control group. Moreover,isokinetic group showed the greatest improve-ments in agonist antagonist ratio whencompared with control and plyometric groups.In the current study strength-ratio values atbaseline were already close to 76% optimalvalues. Furthermore, these values reached 66%to 68% following treatment program. This indi-cates that both training programs allowed theshoulder rotator muscles to remain balanced.

This comes in agreement with Hurd et al. [32]who reported that a proper balance between IRand ER musculature thought to provide dynamicstabilization to the inherently unstable shoul-der joint.In the present study, isokinetic muscular train-ing has a distinct advantage over other methodof strength training as maximal torque can becreated throughout the entire range of motion.Improvement of ER/IR strength ratio in theisokinetic group could clarify by the work ofWernbom et al. [33] who reported that inisokinetic training, muscle activities performedat a constant angular velocity. This feature givessafety in the rehabilitation of patients with mus-cular and ligamentous injuries. Since the sub-ject can freely differ the level of exertion in thewhole movement to accommodate for pain orweakness in certain regions of the range ofmotion. The isokinetic mode is very helpful inrestoration and enhances the muscular perfor-mance in dynamic conditions.This finding supported by the work of Baltzop-oulos and Brodie [34] who exhibited thatisokinetic training has a predominant impactupon different modes of training for swimmingperformance. This recommends isokinetic train-ing resembling the functional activity of the sportcan effectively enhance muscular force devel-opment. Furthermore, Beneka et al. [35] distin-guished more prominent changes in muscleperformance after isokinetic strengthening. Theycompared the effectiveness of different train-ing modes in altering shoulder strength ratios.They concluded that isokinetic strengthening isthe best strategy for changing strength propor-tions of the rotator cuff muscles.With respect to this study, using isokinetic train-ing considered more compelling in enhancingER/IR ratio. This finding highlights the signifi-cance of the principle of contraction specificityduring isokinetic training. This principle basedon research supporting the concept that resis-tance training impacts are most robust whenperformed at the velocity in which the actualactivity happens [36] Comparing the mean ratioof the two angular velocities tested, it seemsthat, at greater velocity the ratios are somewhatincreased. This outcome is in accordance withHinton [37] who reported that the proportions



articular mechanoreceptors close to the endscope of movement in the shoulder during theseexercises. Moreover, rapid length/tensionchanges put on the tendomuscular structuresduring eccentric loading may have encouragedadjustments to muscle spindles and Golgitendon organs. Heightening the sensitivity of themuscle spindle system may increase theirafferent contributions to the central nervoussystem with respect to joint position. Theseadaptations may likewise be responsible for theimproved proprioception [42].Central adaptations resulting from plyometrictraining may also improve proprioception. Thenovelty of this task required preliminary muscleactivation in anticipation of catching the ball andinvoluntary muscle activity for concentric forceproduction while throwing the ball. Jointposition sense essentially enhanced whenmuscles stimulated; hence, this activity mayhave reinforced or enhanced conscious aware-ness of joint position. Consequently, incorporat-ing these activities into upper extremity reha-bilitation can help with restoring proprioceptionand neuromuscular control through peripheraland/or central adaptations [43].The findings in this study revealed that externalto internal strength ratio decreased after 8weeks of functional training as a result of im-provements in the external rotation mean peaktorque values. For this reason, exceptionalaccentuation sets on strengthening the exter-nal rotators in young swimmers. Upper extrem-ity sports require a most extreme amount ofmuscle force delivered in a minimal amount oftime. These specific demands can successfullyreproduced by performing shoulder plyometricexercises, and if a diminishing in amortizationtime enhances involuntary muscle activity, it willallow for greater muscle recruitment and usageof stored elastic energy. Increased neuromus-cular proficiency and coordinated muscle firingmay diminish the onset of exhaustion and helpwith dynamic restraint and functional stability[14].The plyometric group’s improvement in torquedecrement may attribute to the relatively highrepetitions performed during training thatincreased muscle coordination and productivity,resulting in the maintenance of torque production

rise as the angular velocity increments. Con-versely, Ivey et al. [38] found that the ratiosdiminished with faster velocities.The mechanism for the improvement of shoul-der joint reposition sense in both isokinetic andplyometric groups is most likely related to theextra stimulation of the joint and muscle recep-tors realized by the resistance exercise. In thismanner, the physiologic reason behind theenhanced performance is that the propriocep-tive spindles became more delicate afterstrength training, bringing about better positiondetection. Receptors in charge of detecting jointposition include the Pacinian corpuscles andRuffini end-organs found in the joint capsule andthe Golgi tendon organs and muscle spindlesfound in the muscle. Consequently, all thesereceptors are delicate to changes in tensionwithin the muscle or noncontractile tissues [39].Moreover, strengthening exercises of rotator cuffand scapulothoracic muscles categorized asopen-chain and closed-chain exercises and aretypically part of the shoulder proprioceptionrehabilitation protocol [40].In the present study, improvement of proprio-ceptive acuity in both training group mayattribute to the impact of training intensity whichcomes in agreement with Salles et al. [41] whodemonstrated that the group trained with higherintensity showed more improvement, comparedto the group trained with lower intensity.Considering the results of the present study,open-chain exercise involving multiple joints andlarge muscle groups with high intensity mightbe more effective in enhancing JPS.Specifically, the control group maintained thesame absolute degrees of error and did notimprove proprioceptive acuity. Therefore, thefindings of this study support the current clini-cal practice of strength training to address prop-rioception shortages in JPS. Accordingly,strength-training activities used to increase musculardevelopment and enhance proprioception andneuromuscular control [4].The findings of this study support the use ofplyometric training for improving kinestheticawareness and agonist antagonist strengthratio, which could credit to the impact of plyom-etric training on peripheral adaptations that mayresult from the repetitive stimulation of the



during prolonged episodes of exercise.Plyometric exercises promote endurance adap-tations in the shoulder rotator cuff musculature,which is basic for reestablishing functionalstability. Consequently, utilized appropriately,plyometric-ball, and Theraband activities caneffectively accomplish sport-specific strengthand capacity of the musculature around theshoulder [44].The results of this study support the rationalethat plyometric training may not be the mosteffective activity to improve torque advance-ment, especially in highly trained competitors.Also, in light of the fact that plyometric exer-cises performed at different levels of intensity,it is suitable to utilize them in conjunction withstrengthening exercises [45].The results of this study contradict withHeiderscheit et al. [46] who stated that neitherisokinetic group, nor plyometric group showedsignificant changes in the kinesthetic awarenessof the shoulder. Furthermore, they found thatplyometric training was not effective for increas-ing power output while isokinetic trainingimproves power output.

From the obtained results, it concluded thatathletes who particularly use the shoulder toperform their sport can help them be moreproficient and limit the risk of injury by applyingsimple strength training protocols. Bothexercise training programs studied weresuccessful in modifying the joint position senseand the strength ratios, but isokinetic trainingappeared to be significantly more effective. Ifisokinetic equipment is not accessible, plyom-etric training is a practical alternative to adjustshoulder rotator strength ratio to reestablish anymuscle imbalances and to enhance kinestheticawareness.

CONCLUSION

ACKNOWLEDGEMENTS

The authors would like to express their appre-ciation to all the children and their parents fortheir co-operation and participation in this study.

Conflicts of interest: None

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Source of Funding: This research received no specificgrants from any funding organization in the public,commercial, or non- profit sectors.


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