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REVIEW ARTICLE
Year : 2019  |  Volume : 19  |  Issue : 2  |  Page : 31-37

Core stability and its impact on upper extremity function in racket sports: A narrative review


1 Department of Physiotherapy and Neuro-Rehabilitation Center, Mount Adora Hospital, Sylhet, Bangladesh
2 Department of Neuro Physiotherapy, Maharishi Markandeshwar Institute of Physiotherapy and Rehabilitation, Maharishi Markandeshwar (Deemed-to-Be) University, Ambala, Haryana, India
3 Abhinav Bindra Targeting Performance, Mohali, Punjab, India
4 Department of Sports Physiotherapy, Maharishi Markandeshwar Institute of Physiotherapy and Rehabilitation, Maharishi Markandeshwar (Deemed-to-Be) University, Ambala, Haryana, India

Date of Submission19-Sep-2019
Date of Decision29-Apr-2020
Date of Acceptance23-May-2020
Date of Web Publication07-Jul-2020

Correspondence Address:
Dr. Sohel Ahmed
Department of Physiotherapy and Neuro-Rehabilitation Center, Mount Adora Hospital, Sylhet-3100
Bangladesh
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DOI: 10.4103/sjsm.sjsm_15_19

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  Abstract 

Over the past decade, core stability exercise has become popular for injury prevention and performance enhancement. Although there is scarcity of literature, core stability has become a well-recognized component in athletic performance and injury prevention. This study aimed to report about the current evidence for the impact of core stability on upper extremity function in racket sports. A structured literature search was conducted in various electronic database including PubMed, Scopus, PEDro, Directory of Research Journals Indexing, Google Scholar, and Embase till April 2019 for this narrative review. We selected studies related to racket sports that measure core stability and upper extremity function published in peer-reviewed journal. A total of 17 studies were shortlisted; however, following the application of exclusion and inclusion criteria, finally five were reviewed. Majority of the studies reported that core stability exercise can enhance upper extremity performance in racket sports. Core stability training is very important for athletic performance enhancement, especially it gives benefits to enhance upper extremity function in racket sports. However, there is still limited evidence regarding this issue; hence, further well-designed research required in this field.

Keywords: Athletic performance, core, muscle strength, racket sports


How to cite this article:
Ahmed S, Akter R, Saraswat A, Esht V. Core stability and its impact on upper extremity function in racket sports: A narrative review. Saudi J Sports Med 2019;19:31-7

How to cite this URL:
Ahmed S, Akter R, Saraswat A, Esht V. Core stability and its impact on upper extremity function in racket sports: A narrative review. Saudi J Sports Med [serial online] 2019 [cited 2020 Sep 20];19:31-7. Available from: http://www.sjosm.org/text.asp?2019/19/2/31/289157




  Introduction Top


Nowadays, core stability has become popular for the prevention of injury and enhancement of sports performances.[1] Substandard core stability increases the risk of athletes' upper limb injury.[2] The incidence of injury in racket sports varies: in tennis, the incidence rate is about 0.05–2.9 injuries per player per year. The occurrence rate of injury in badminton that has been reported in every 1000 h of badminton playing is 2.9 injuries per player. In squash, the rate of injuries reported as 18 injuries per 1000 h of participation.[3] Most of the injuries in racket sports that occurred in the upper extremity are chronic and most likely fragments to injuries are the shoulder girdle (17.2%), wrist (12.23%), and elbow.[4]

Core stability is the capability to maintain the pelvic in the neutral position, ideal force production, control, and transfer of force to the extremity during movements.[5] Core muscles work as stabilizers and mobilizers and they assist in transferring a load from the center to the extremities. Evidence support that core strengthening exercises prevent and alter the injury risk.[2],[6] Several authors have proposed that the core is the fundamental foundation for most of the kinetic chain in the human body and it helps to facilitate the torque and momentum between the upper and lower extremities.[7],[8],[9]

Over a decade ago, it was hypothesized that core stability plays a cardinal role in athletic injury and performance. Substandard core stability increases the risk of athletes' upper limb injury and performance.[2],[10],[11] However, the limited body of evidence supports this hypothesis regarding the role of core stability and its impact on upper extremity performance in racket sports. The purpose of this study was to give an overview of current evidence for the influence of core stability on upper extremity performance in racket sports.

Functional anatomy of core muscles and core stability

The core is a box-shaped group of muscles surrounding the lower back and pelvis.[12],[13],[14] Core stability is the active ability to maintain the trunk in position, permit motion during movements, and control and transfer of force during the period of functional activities.[11] The theory of core stability has been described by Panjabi's model. The model explains the mechanism of core stabilization in three different ways that are active, passive, and neural controls.[15] The passive structure includes the joints, ligaments, capsules, intervertebral disc as well as the passive properties of muscles. It gives stabilization at the terminal range of motion and provides a message to the neural control system through the mechanoreceptor, while tensile force and mechanical resistance increase during movement.[15] The dynamic subsystem of core muscle gives dynamic stabilization to the spine and proximal appendicular skeleton and also provides information of movement to the neural control system. The focal point for all the three subsystems is the neural control system that provides efferent and afferent signals from the brain that ultimately maintains the core stability.[15],[16]

The core muscles are categorized into stabilizers and mobilizers. The local stabilizers are attached near the vertebrae, work eccentrically to limit movement, and provide static stability. Elsewhere, global mobilizers are skin deep muscles that work concentrically to generate large torques for power and movements. The local stabilizers and global mobilizers act together and attach to the axial–appendicular skeleton that transfers force and momentum between the extremities and core.[17],[18]

How to assess core stability

There is a variety of valid and reliable tests to measure core stability and strength. The assessment of core stability is interrelated with muscle recruitment, postural control, muscle strength, endurance, balance, and movement control.[2],[19],[20],[21],[22] Three tests are used widely that include flexor and extensor endurance test and side bridge test.[21],[23],[24] The flexion endurance test is implemented in a sitting position with the hips, knees, and ankle flexed at 90° [Figure 1]. The foot should be stabilized with a strap or stabilizer. The participant tries to hold the position of a 60° angle relative to the table as long as he/she can.[19] The extensor endurance test is executed with the participants in a prone position [Figure 2]. The participant is asked to place the lower body up to pelvic over the couch and upper body outside the couch. The participant maintains this position as long as possible. Side bridge tests performed inside-lying position [Figure 3]. The participants raise the hips on the feet to support the body on feet and flexed elbow. The mean times are used for interpreting the results.[19]
Figure 1: Flexion endurance test

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Figure 2: Extension endurance test

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Figure 3: Side bridge test

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Now days, functional assessment of core stability has become an important component to assess core endurance and strength. By screening movement patterns, components of core stability can be assessed including joint stability, proprioception, balance, mobility, strength, and neuromuscular control. It was developed as a screening tool for injury risk assessment.[10] Core stability can be evaluated in functional position at multiple planes by close or open kinetic chain testing or eccentric versus concentric contraction (single-leg standing balance and squat).[2]

Core stability can also be measured using the stabilizer pressure biofeedback unit. A pressure biofeedback unit [Figure 4] positioned beneath the lumbar spine inflated to 40 mmHg in subject with the supine lying position. An air-filled reservoir detects the lumbar spine movements. While performing subsequent testing, participants are instructed to do abdominal hollowing manoeuver. Pressure changes while performing the subsequent test reflect the uncontrolled movement of the lumbar spine. The highest level achieved[1],[2],[3],[4],[5] without pressure change >10 mmHg should be calculated as the level of core stability.[25],[26]
Figure 4:Core stability testing with pressure biofeedback

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Kinetic interaction between core and upper extremities

The upper extremity dynamic movement depends on the interaction of structural and functional elements of the neuromuscular system that is gained by a stabilization force from the lumbopelvic-hip complex and scapula.[6] The pelvis gives a stable base of support for the scapula and scapula for the shoulder to initiate shoulder movement.[27] Proximal stability is important for distal mobility. Kinetic chain theory defines the mechanism, generation, and transfer based on biomechanical forces and motor control theories from one body segment to another. The theory describes the combined working mechanism during functional and sports activities.[28],[29] The ideal performance of upper extremity does not only depend on shoulder girdle force control but also stabilizing force from the trunk and pelvis.[30] The optimum core stability is achieved through local and global stabilizers. The large global stabilizers including the abdominal muscles, erector spinae, latissimus dorsi, and hip abductors generate necessary power and stability for upper extremity function.[31] The trunk muscles are active during upper and lower extremity movements.[27] If the trunk and pelvic complex is unstable, the shoulder and elbow musculature have to work more to generate energy. It has been suggested that kinetic and kinematic interaction of the pelvis and trunk altered the action of the shoulder, elbow, and wrist during overhead motion.[6] Studies have been reported that gluteal muscle activation allows shoulder and elbow mobility efficiently, and the lumbopelvic-hip complex plays a major role in instability and energy production and transfer to the upper extremity.


  Methodology Top


Study selection

A systematic literature search was conducted by each researcher independently from March 2018 to June 2019. We have included a randomized control trial that focused on the effect of core stability training on upper extremity performance in racket sports. We also included observational studies that investigate the relationship between core stability and upper limb performance in racket spots. The other selection criteria for this study were full-text article in the English language and published peer-reviewed journals till June 2019. Studies were omitted those who did not execute a target intervention, outcome measures, and within the scope of the athletic performance. The eligibility criteria were evaluated by four independent reviewers, who did an initial filter by title, a second filter by abstract, and finally in result. The full texted article was read by all the listed authors to verify the selection criteria. The quality of the experimental studies was assessed using the Physiotherapy Evidence Database (PEDro) scale.[32] The quality of the correlational studies was screened using a tools named “Quality Assessment and Validity Tool for Correlational studies” adapted from the previous literature.[33]

Search strategy

Our literature search aimed to identify the available literature (experimental and nonexperimental studies) regarding core stability and upper extremity function in racket sports. Available articles were searched from the electronic searches of PubMed, Scopus, PEDro, DRJI, Google Scholar, and Embase. The search was projected by MeSH keywords to identify studies that measured core stability, serve velocity, tennis, badminton, squash, racket sports, upper extremity, and performance with the Boolean terms “AND,” “OR.” A total number of 86 studies were identified for initial review; among them, 17 were shortlisted; however, this reduced to five when we followed our subject population criteria, variables, and study design. We used the PEDro checklist to ensure the quality of the randomized controlled trial.


  Results Top


After the Boolean search, 17 studies were shortlisted, after the removal of duplication, matching with inclusion and exclusion criteria 5 articles were selected for the final review. Two randomized controlled trials and three observational studies were selected and reviewed. [Table 1] briefs out the available observational studies and [Table 2] briefs out about the randomized controlled trial studies related to core stability and upper extremity function.
Table 1: Observational studies related to core stability and upper extremity function in racket sports

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Table 2: Randomized controlled trials that measure core stability and upper extremity function in racket sports

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  Discussion Top


The purpose of this study was to give a summary of current evidence for the impact of core stability on upper extremity function in racket sports. A strong core is important for peak performance in sports.[28],[29] It is important to recapitulate briefly the association between core stability and upper extremity function in racket sports, as kinetic chain theory describes the force generation and transfer is interlinked with core stability. It is also suggested that upper extremity injuries are caused by abnormal force generation.[6] Athletic performance is built by the demand of whole body muscles where core acts as a bridge, providing a stable base of support[12] and transferring force from pelvis to the upper extremity.[37] Core muscles sustain the pelvis in a neutral station and protect the lumbar spine from injuries.[38] If the core muscles are producing the maximal power, but the generated power cannot be transferred, the sport performance will negatively be impacted on performance.

Hassan IHI reported that that core stability training increases the smash velocity and accuracy in badminton players.[12] In this study, 20 under 19 badminton players were divided into experimental and control groups. The investigational group received 8 weeks of core stability training program, while the control group received only badminton training. The methodology of this study is not satisfactory based on the Pedro scale as there is no statement regarding allocation concealment, blinding of the participants, therapist, and assessor.

This study reported that 6 weeks of core stability training improves the serve velocity and accuracy of a tennis player.[36] Thirty nationally ranked junior tennis players were randomly allocated into two groups. Both groups performed 6 weeks supervised stretching routine all besides the experimental group received elastic resistance, core strength, and medicine ball exercise for 60-70 min per se ssion, 3 sessions per week. The result showed a significant improvement in the experimental group. In this study, we cannot say that core strength training is directly attributed to the results as it is also associated with elastic resistance exercise and upper body plyometric exercises.

Smart et al.[39] conducted a study to investigate the effects of core training on the tennis serve velocity. A total number of 35 men and women who were intermediate-level tennis players were participated in this study. After the baseline assessment, the control group returned to their tennis practice and competitive play, while the investigational group completed 8 weeks of a core training program. The core training program concentrated on core stability, endurance, and strength. The training session lasts for 8 weeks, 2–3 days per week. The result showed that 8 weeks of core training alone cannot improve the serve velocity. The study recommended upper and lower body strength and conditioning along with core training.

The effectiveness of the core stability training program also investigates in other games such as soccer,[13] football,[40] lacrosse,[41] and baseball[42] players. Lust et al. testified that 6 weeks of core stability training can improve the throwing precision, proprioception, and core stability in baseball.[42] Willson et al.[8] reported that trunk muscle activity and lower limb movement are interlinked with each other. Appropriate core stability training can diminish the chance of injury. On the other hand, Nesser et al. stated that core stability is moderately related to performance and core strength is not directly contributed significantly to strength and conditioning. Ozmen investigate the association between balance, jumping performance, and core stability in a soccer player. Core stability was evaluated with different test variables and found that trunk flexion is associated with squat jump height. The result suggests that there is no association between core stability and dynamic balance.[13]

Söǧüt,[14] examine the relationship between core stability and performance parameter in tennis. Twenty-nine tennis players (14 male and 15 female) were participated in this study. The result reported nonsignificant correlation between core stability and other variables. Another study found a strong negative correlation between core stability and medicine ball throw.[34] Baiget et al. reported that back extension and shoulder external rotation are associated with average serve velocity in tennis.[35]

Core strength is important for the upper body and trunk rotation during smashing movements of racket sports. The kinetic chain play a key role in transferring energy to the upper body which comes from core muscles. The possible reason for the improvement of upper extremity function may be due to routine core stability exercises that include crunch ball, hip thrust, and Russian ball which increases the endurance of core muscle and core muscle allows them to use during upper extremity movements while performing smash stroke.

Gaps in the literature

Core stability is an important factor for the performance of racket sports, but the role of core stability for the improvement of upper extremity performance is still controversial. Limited studies are available in the field of core stability and upper extremity function in racket sports. Our literature search addressed a small number of high-quality studies that find the relationship between core stability and upper extremity function in racket sports. Those articles evaluating the effects of core stability on upper extremity function and performance in racket sports do not solely on competitive athletic population. There are also few questions remain that how core transmit force to the upper extremity, how good core stability prevent injury, and how core stability enhances performance? However, till the date to the best of our knowledge, there is no literature available that addressed how core stability prevents injuries of the upper extremity in racket sports. Comprehensive assessment and training require a multifaceted approach to address how core stability enhances upper extremity function and prevents injuries in racket sports. In future, more and more research are required in this field of core stability and upper extremity function in racket sports.


  Conclusion Top


Core stability training is very important for athletic performance enhancement, especially it gives benefits to enhance upper extremity function in racquet sports. However, there is still limited evidence regarding this issue; hence, further well-designed research required in this field.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Acknowledgment

The authors would like to extend special thanks Dr. Asir John Samuel, Associate professor, Department of Pediatric and Neonatal Physiotherapy, Maharishi Markandeshwar Institute of Physiotherapy and Rehabilitation, Maharishi Markandeshwar University, Mullana-133207, Haryana, India, for his valuable support and encouragement for this study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

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