optimizing performance by improving

7/28/2019 Optimizing Performance by Improving

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A.*.! SpOftsMea2008.38(l2):W5-1VIEW ARTICLE Oll2-li>d2/O8/OO12W5/M8

2008 AcitsData inlormatlon SVAilights e m v e d .

Optimizing Performance by ImprovingCore Stability and Core Strength

ngela E. Hibbs,^'^ Kevin G . Thompson,^'"^ D uncanFrench,^ Allan Wrigley^an d lain Spears'

English Institute of Sport, Gatesh ead, UKCan adian Sport Cen tre Pacific, Vancouver, British Colum bia, Can adaUniversity of Teesside, Middlesb roug h, UKSchool of Psychology and Sports Science, No rthum bria University, New castle, UK

ontentsAbstract 9951. Definition of Perform anc e, Core Stability an d Core S trength 9962. Functionai A nato m y of the "Core' as it Reiates to A thletic Perform anc e 9973. Types of Core Training 9984. Eviden ce of Core Training Benefits 1000

4.1 Rehabilitation Sec tor 1001

4.2 Athietic Sector 10025. Measuring the Core an d its Relation to Perform ance 10046. Conciusions 1006

ract core stability and core strength have been subjectto research since theearly 1980s. Research has highlighted benefits of training these processes forpeople with back pain and for carrying out everyday activities. However, lessresearch has been performed on the benefits of core training for elite athletesand how this training should be carried out to optimize sporting perfor-mance. M any elite athletes undertak e core stability and core strength trainingas part of their training prog ramm e, despite contradictory findingsandconclusions as to their efiicacy. This is mainly due to the lack of a goldstandard method for measuring core stability and strength when performingeveryday tasks and sporting movem ents. A further confounding factor is thatbecause of the differing demands on the core musculature during everydayactivities (low load, slow movements) and sporting activities (high load,resisted, dynamic movements), research performed in the rehabilitation sec-tor cannot be applied to the sporting environment and, subsequently, dataregarding core training programmesand their effectiveness on sportingperformance are lacking.

There are many articles in the literature that promote core training pro-grammes and exercises for performance enhancement without providinga


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improvements in core stability and core strength following a core traiprogramme. A clearer understanding of the roles that specific muscles during core stability and core strength exercises would enable more ftional training programmes to be implemented, which may result in a efiective transfer of these skills to actual sporting activities.

1. Definition of Performance, CoreStability and Core Strength

Core stability and core strength have beensubject to research since the early 1980s.1'"^'What is referred to as the core varies betweenstudies, with many studies including upper andlower sections of the body including the should-ers, trunk, hips and upper leg.f"*""' Fur thermore,many studies also fail to distinguish between corestability and core strength, two concepts that arefundamentally very different. The confusion overthe precise definition of core stability and core

strength is largely because what is included inthese definitions differs greatly depending on thecontext in which they are viewed. F or exam ple, inthe rehabilitation sector, the focus is on rehabi-litation following injuries causing lower backpain (LBP). arm and leg pain and enabling thegeneral population to perform everyday (lowload) tasks using exercises that emphasize thecontrol of spinal loading. This requires less corestability and core strength than elite and highlytrained athletes in the sporting sector who have tomaintain stability during highly dynamic and, inmany cases, highly loaded movements.^'^' Theanatomy involved during sporting tasks includesmuch more of the body, i.e. shoulders and knees,which contribute to the transfer of forces throughthe body to produce effective sporting techniquesresulting in a different definition of core stabilityand core strength. Therefore, although the pro-cess of core stability and core strength can bedefined, what is anatomically included in thesedefinitions varies.

Panjabi^'-^' suggested that core stability is the

activities to be carried out during daily Kibler et al. ' '"' summarized core stabilitsporting environment as "the ability to the position and motion of the trunk overpelvis to allow optimum production, transfcontrol of force and motion to the terminment in integrated athletic activities." Akand Nadlert'*^! defined core strength as thcular control required arou nd the lum bar sm ainta in fun ctional stability . Th is is diffethe traditional concept of strength in the spsector, which has been suggested by Lehmanthe maximal foree that can be generatedspecific velocity by a muscle or muscle Faries and Greenwood''*' ' provide clearer tions as to the difference between eore stand core strength for the rehabilitation secsuggesting that core stability refers to the to stabilize the spine as a result of muscle awith core strength referring to the ability musculature to then produce force througtractile forces and intra-abdominal pressur

Due to the different demands placed o

body during sporting activities, more cocore exercises are trained (usually highly dymovements with added resistance) comwith those used for training the general ption (mostly static in nature). As a resuresearch findings performed in patients witand the general population cannot be extto the athletic and elite sports performerinability to generalize findings along with sistent definitions makes the collection andcation of meaningful data difficult anarguably lead to the inconclusive and contradfindings reported to date. It has been sugg


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ability and strength, athletic performance couldenhancedJ"*'To establish whether training core stabilityd/or core strength are important in everydayd sporting activity, research needs to establish

hat impact training in these areas can have onsulting performance. What is termed as per-rmance, as with the definitions of core abilityore stability and core stren gth), differs betweene rehabilitation and athletic sectors. In the re-bilitation sector, an improved performance for

patient w ith LB P would be the ability to performeryday tasks pain free;[^'*^J whereas in theorting sector, an improved performance may bearacterized by not necessarily being pain free,t by improving technique in order to run faster,

ro w further or ju m p higher J'' althou gh it couldo include the reporting of fewer injuries, which

hances performance in training.^''^-^'^^Research performed to date has highlighted

nefits of training core stability and core stren-h for patients with LBP and for carrying outeryday activities. However, less research hasen performed on the benefits of core trainingr elite athletes and how this training should berried out to optimize sporting performance.though many studies have reported contra-

ctory findings and conclusionsj-^-^**'^-''^^!any elite athletes continue to undertake coreability and core strength training as part of theiraining programme.

2. Functional Anatom y of the 'Co re' as itRelates to Athletic Performance

A number of models have been published thaty to describe the core musculature and themplex integration of the separate processesat work together to bring about core stabi-y. Physiologically, what is included as "there' varies from study to studyt-''^ depending on

e context (rehabilitation or athletic) that it isewed in. The core has been described as a box

d bl ll d li d H ^1 ith th bd

bottom.f **' Meanwhile, other researchers focus-ing on sports performance define the core asincluding all of the anatomy between the sternumand the knees with a focus on the abdominalregion, low back and hips.t^' Other researchersconclude that the core musculature should in-clude the muscles in the shoulder and pelvis asthey are critical for the transfer of energy fromthe larger torso to the smaller extremities, whichmay be more involved in sporting movementsrather than everyday tasks.'^^^^^^^"^ Leetun

et al. ' ' - ' supp orts this by reporting that hip m uscleactivation significantly infiuences the ability togenerate force in the upper leg muscles and ithas been identified that hip muscle activation isimportant when looking at core stability andtrying to improve core strength.I-*' ' Elphinston' ' ' 'and Wilson'-*^' consider the gluteus maximus tohave an essential role in core stability and hipcontrol. A weak gluteus maximus muscle has aninfluence on the alignment of the lower knee and

ankle, resulting in greater medial and rotationalmovement, which leads to an increase in strain onthe join ts, predispo sing to a greater injury risk.

Panjabi' '-*' summarized the contributors tospinal stability into three groups: passive (e.g.vertebrae., ligaments and intervertebral discs),active (muscles and tendons around the joints)and neural (CNS and other contributing nerves).Bergmark'-'- ' ' developed a model to summarizethe role of the trunk muscles and their contribu-tion to core stability. Bergmark's model labelsmuscles as 'local' (those with attachments to thelumbar vertebrae and which therefore infiuenceinter-segmental control) and 'global ' (those withattachments to the hips and pelvis and whichtherefore infiuence spinal orientation and controlthe external forces on the spine). It is importantthat both systems are integrated to establishnormal movement function, for example, if onlythe global mobilizer muscles are trained, a mus-cular imbalance occurs because they "take over'the role of the stabilizer muscles, resulting inrestricted and compensatory movement patterns


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force and power'^-'l because of their multi-jointpositioning and large momenl arms. All of theseabove processes are important to train, whetherin the rehabilitation or sporting sector, as they allcontribute to performing movements safely andcorrectly.

Lee^-''*'suggested that stability is not about the'quantity of motion' and the "quality of the endfeel', but about the control of systems that allowload to be transferred and movements to besmooth and effortless. This may be true for spor-ting movements where the individual is lookingsolely to optimize their technique and not neces-sarily worry about pain, but for patients withLBP and the general population, the range ofmovement and 'quality of the end feel' (i.e. nopain) are more important. Brown^--' suggests thatcore stability is achieved by the muscular systemof the trunk providing the majority of the dyna-mic restraint along with passive stiffness from thevertebrae, fascia and ligaments of the spine.Akuthota and Nadler ' '*' provide a detailed sum-mary of the anatom y of the lumbar spine and thecontribution of these parts to core stability andthey draw attention to the contributions of theihoracolumbar fascia, osseous and ligamentousstructures, paraspinals, quadratus lumborummuscle, abdominal muscles, '"-^^^ hip girdle mus-culature, diaph ragm and the pelvic floor m uscles.

Lehman'^l identified certain muscles that are

essential to monitor when analysing core stabilityand core strength. These include the transverseabd om inis (TrA)., rectus abdo m inis (RA ), externaloblique (EO), internal oblique (IO), erector spi-nae, quadratus lumborum and latissimus dorsi.The contribution of these abdominal muscles tostability is related to their ability to produce flex-ion., lateral flexion and rotation movements andcontrol external forces that cause extension, ilex-ion and rotation to the spine.'"''''^ Comerford andMottram'^^l emphasise the importance of the RAmuscle and believe that this muscle has a highrecruitment threshold and is important in bracing

precise roles of these muscles in core stabitcore strength is not clear and future researcto be performed to establish these links.Eexample, McGill'^' found that the psoas (the largest muscle in the lower lumbar spdoes not provide much stability, wGibbonst"] reported that this muscle does stability role through axial compressiosuggested that it was involved with lateral frotation and extension as well as hip fDespite the apparent confusion and com

outlined here, it would seem reasonable to that when training the core, it is essential tostand the contribution to stability and sthat all of the musculature, neural andstructures have, and subsequently to traisection depending on the requirements findividual (i,e. whether they are an athlete nhigher stability and strength or from the population and require the ability to mstability at lower loads).

3. Types of C ore Training

Core training programmes include prothat target muscular strengthening and con trol of the core musculature.f^' Co re stening exercises are very popular in rehabilpro gram m es despite little scientific evidencting as to their eTicacy on improving subsperformance,''''' 'I aUhough some researsuggested that a number of methods can eneurom uscular contro l. These include joinlity exercises,'^^^ contraction exercises {coneccentric and isometric),'^^' balance traiperturbation (proprioceptive) training,''*"'''-^metric (jump) exercises (plyometric temphasises loading of joints and muscles trically before the unloading concentric actiand sport-specific skill training.'**] In the fphysiotherapy, proprioceptive training is be

to be important and, consequently, progruse methods and exercises that challengprioception using equipment such as w


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rformance, Core Stability and Core Strength 999

rform both low- and high-load threshold train-g .'' ' ' ' Com er ford'"^^ identified the followingb-areas of core training that all need to be in-uded when training core stability and strength:

Motor control stability: low-threshold stabiHtyhere the CNS modulates the efficient integra-on and low-threshold recruitment of local andobal muscle systems.

Core strength training: high-threshold andverload training of the global stabilizer musclestem and leads to hypertrop hy as an ada ptatio noverload training.!*^'Systematic strength training: traditional high-

reshold or overload strength training of theobal mobilizer muscle system.Comerford'"^' argues that it is essential for

cal muscles to be targeted and for low-loadreshold training to be performed to avoid anyuscle recruitment imbalanc e, which may lead too vem ent dysfunction and injuries. It is pr o-osed that initial core strengthening programmesould enable people to become aware of motor

atterns and allow them to learn to recruit mus-es in isolation (it is possible to use biofeedbackvices or verbal cues). Programmes can thenogress to functional positions and activities. ' '^1kuthota and Nadler"^^ stated that re-learninge motor control of inhibited muscles may beore important than strengthening in patientsith LBP. In this case, it may be that improve-ents in performance are a result of improved

eural co-ordination and recruitment rather thanecific improvements in core strength or stabi-

ty. Careful performance measures are requiredstudies to identify which of these is ultimately

rgeted following intervention programmes,

The choice of exercise is important as theagnitude of the muscle activation and the re-uitment pattern of the motor units deter-ines whether core stability or core strength is

eveloped. Vezina and Hubley-Kozey'' '^' suggestat an activation of >60% maximal voluntary

ontraction (MVC) is required to result inh b fi '**^' i h bili d l

abdo mina l and two trunk extensor muscle sites andperformed three low-load core exercises; pelvictilt, abdominal hollowing and level1 of the trunkstability test' '*' ' ' to compare muscle activation.They identified that the three exercises recruitedthe five muscles differently, with the externaloblique muscle showing the highest activationlevels during the pelvic tilt (25% MVC). Theyconcluded that the activation during theseexercises would not elicit any strength benefits,but these exercises could be used to form an as-

sessment of an individual's core stability to for-mulate a more demanding training programme.Similarly. Davidson and Hubley-Kozey''*^^ ob-served muscle electromyog ram (EM G ) activity of3-7% MVC during a progressive leg extensionexercise test, which suggests that this exercise isnot sufficient to result in muscle strength im-provements, but would be sufficient to establishand maintain trunk stability.'^-^^

Comerford'-' ' ' suggests that core stability

training should range from isolated activation ofthe deep abdominal muscles to lifting weights onuneven su rfaces. Th is is due to the different functional roles of the muscles during exercises andtherefore it is advised'^^' that a range of exer-cises be performed to challenge the core muscu-lature in all three planes and ranges of movementto develop total core stability. For example, flex-ion (targeting hip flexors, back extensors, ab-dominal and glutei muscles, e.g. curl-ups, legraising and squats with rotation), extension (e.gtargets hip extensors and hamstrings) and rota-tional exercises''*^' shou ld be include d. Steph enso nand Swank'^*"' believe that a core strength devel-opment programme should include: flexibility ofthe abdominal and lower back, hip extensor andtlexor muscles; exercises in an unstable environ-ment; as well as isometric and dynamic exercises.

Lehman'^' believes that because only a mini-mal level of muscle contraction is required tostabilize the spine (1-3% MVC). muscle en-durance may be more important than musclestrength. Lehman'*^' identified exercises such as


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the muscle, but do not exceed the thresholdsfor cotnpression and shear loading, which maypredispose the body to injuries. This is suppor-ted by McGillJ''-'^"] who suggests that mus-cular endurance is more important to stabilitythan muscle strength, and by Faries andGreenwood.I"^1 who suggest that enduranceshould be trained before strength while focusingon establishing the correct m otor c ontrol systemsprior to increasing the bodies stabilizationstrength. Faries and Greenwood'"'^ suggest that

endurance training focuses on low load. longer(30-45 seconds), less demanding exercises, whilestrength exercises are based on high-load, low-repetition exercises.

Speed, direction and order of hmb movementduring exercise are seen as critical factors whentraining. For example, the speed at which anexercise is performed will affect the gravitationaland mechanical resistance experienced on thebody. This is due to fast movements recruiting

the fast motor units in the muscles when perfor-ming a movement optimally. Slow motor unitsof the muscle are utilized during low-thresholdrecruitment in postural sway and movementsinvolved with unloaded limbs. It is importantfor optimum motor control to train both thefast and slow motor units in a muscle to optimizecore stability an d core strength.[-"1 Th e directionand order of limb movements also has a pro-found effect on muscle activation. Cresswell'^' '

found that the abd om inal m uscles, the RA. EOand IO were only active during acceleration,when they generated the movement, and decel-eration, when they opposed the movement. Themagnitude of movement has also been in-vestigated; for example, feed-forward responsein these muscles was identified when movementsof the elbow and shoulder were performed, butnot when the wrist and thumb were moved.'^' '1Furthermore, when the arm is moved, the onsetof TrA activation precedes the deltoid by30 ms.f"' when the leg is also move d, activa tion ofthe TrA precedes the deltoid by more than

delayed in tasks where the postural demincreasedl-^"*- ! du e to the ex tra tim e neeprepare the body for the resultant forcResearch on the optimum speed and orloading on the muscles is limited: theit remains unclear what speed and directmovement should be used, only that it shofunctional and sport-specific for the indivneeds.I**-'-' Future research should try tblish these characteristics to enable theeffective training programme to be implem

and to maximize the potential for the and training benefits to be transferredperformance.i*^^"^**'

Due to the many factors mentioned abthe paragraph above, the ability to train thcles to imp rove core stability a nd/o r strengton the training being functional and specificeveryday or sporting movement that is to bformed. Any improvements in training can ttranslated into improvements in perfor

Therefore, whether the targeted movementsbe low or high lo ad will have a significant efthe type of training prog ramm e implementeapparent contradiction between the traddynamic approach of the strength and coning coach compared with the more modest men ts prescribed by physiotherap ists has tyled to confusion as to which method is mfective. Prior to any training programmeinitiated, the exercises included and intensity

prog ram me shou ld be carefully e valuatepending on the individual involved and thei(i.e. to be pain free to improve sporting pman ce). Therefore, future research shouldon establishing which exercises are sufficieimproving each part of core stability (i.e. passive and active systems) and core strengtneural adaptations) to be able to target thesformance goals more eTectively.

4. Evidence of C ore Training Benefits


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formance,Co re Stabilityand Core S trength 1001

nk-Stabilizing muscles and inappropriate re-uitm ent of the trunk and abd om inal m uscles. '''^^is important that any trunk-stabilizing muscleakness is identified and corrected as this sig-icantly increases an individual 's muscle andn t injury risk.'**^! Ne ura l ad ap ta tio ns from co reining inelude: more efficient neural recruit-nt patterns, faster nervous system activation.,proved synchronization of motor units and a

wering of neural inhibitory refiexes.'^*^^ High-reshold strength training results in hype rtroph y

the muscles (structural change) and neuralaptat ions (e.g. of the motor units in the mus-es) of the niuscles, which benefits performance

increasing the possible force generation, CNScilitation, improved intrinsic muscle stiffnessd improved tissue mobilization. ' '^!Research stat ing whether there are any bene-s of specific core stability or core strengthercises in activating muscles is limited andnfiicting because of the wide variety of data

llection methods, exercise techniques and sub-ts used for analysis. There is not one singleercise that activates and challenges all of there muscles; therefore, a combination of exer-es is required to result in core stability andength enhancements in an individual. '-^^^ture research needs to identify which of theseercises are most effective in resulting in benefitspending on the performance goal .

4.1 Rehab ilitation SectorMost research in the rehabilitation sector fo-

ses on how core stability influencesLBP, ' ' ' '^ ' ' '^^^^th many condit ioning programmes being basedound training the abdominal mtiscles to im-ove their strength and subsequently the stability

the spine. '^ ' This is based on the know-dge that strong abdominal muscles providepport tor the lumbar spine during day to daytivities.'' "^1 Jeng'''-''J re po rt ed th a t the oc cu rren ce

LBP may be decreased by strengthening theck, legs and abdomen to improve muscular

therefore reduce the risk of LBP. One of the mainmuscles associated with ' the core" is the TrA , T hisis the deepest abdominal muscle and providesspecific support to the lumbar spine and has beenshown to be impaired in those withLBP.P4.36.52.53.61,66-68] Hodges and Richard-g^jj^[53.69] observed that TrA activity in healthyindividuals precedes that of arm and leg move-ment by approximately 30 and 100 ms, respec-tively, suggesting that this muscle has apreparatory stabilizing effect and assists in sta-

bilizing the trunk, thereby enabling force productio n at the extrem ities. The Tr A m uscle is alsofound to be act ive regardless of body movementdirection, unlike other core muscles such as theRA, EO and lO. '-^l Therefore, theoretically,training the abdominal muscles and improvingtheir strength should have beneficial effects onresultant stabil i ty and performance.

Rehabil i tat ion programmes have used Swissballs to improve core stability with some benefit

being documented.''^' ' ' Behm et al. '^"' suggestthat using a Swiss ball provides an unstable sur-face, which challenges the core muscles to agreater extent and improves trunk stability andbalance. Cosio-Lima et al. '^l tested two groups osubjects, one tra ining on the fioor and one using Swiss ball and found that the Swiss-ball grouphad a significantly greater change in muscleEMG activity during fiexion and extension andgreater balance scores than the oor-exerciseg ro up . Behm et al.' **! sugg ested th at the S wiss

ball can be used to increase stability, balanceand proprioceptive ability, but not musclestrength.'-^' '! As a result, many researchers advocate using a Swiss ball only as a low-thresholdrehabil i tat ion tool to improve joint posi tionsense, balance, posture and proprioception.'"'"'"-'*''This has led to modern day rehabilitation programmes using a mixed conditioning approachwhich includes a range of metho ds to improve co rstability and core strength. Saal and Saal'^^' investigated the effectiveness of an exercise trainingprog ram m e on pa tients with LB P. which consistedof a fiexibility programme, joint mobilization o


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au tho rs rep orted successful recoveries for 50 of the52 subjects (96%). However, it is not possible toconclude how much of this improvement was di-rectly due to the core stability work (other factorssuch as medication, injections and healing overtime would all have had an additional effect).

Whether a training programme results in animproved performance or not depends on the ef-fectiveness of the core exercise performed. Thismay explain why some research has resulted incontradictory research on the efficacy of somerehabilitation programmes to strengthen coremuscles.f ''- ' ^ The effectiveness of an exercise isdetermined by factors such as functionali-ty/specificity of the movement, intensity/thres-hold, familiarization and frequency. Differentcore exercises that challenge the core m uscu latureat different intensities of muscle activation arerequired to result in stability or strength enhance-ments,'**! bu t the se mu st be specific to th e perfor -mance goals to result in any enhancement. In

summary, research in the rehabilitation sectorhas been conducted, which has begun to assesshow core muscles respond to low-load corestability exercises and their effect on LBP, andsuggests that by performing core training ex-ercises, performance relating to injury risk andrecovery can be improved (table I). How coremuscles respond to higher threshold exercises andmovements/demands, seen regularly in sportingenvironments, however, cannot be elucidated by

such methodologies.

4.2 Athletic Sector

There is a lack of research looking at the effectof core stability on athletic performance.'^-'Although some studies have implied that there isan advantageous effect on performance by im-proving core stability and strength, these con-clusions are largely assumptions based on basictesting.['^-^^-^**l Roetertt'^1 reported that corestability and balance are critical for good per-

trunk muscles to provide cfTective core stSome sports require good balance, somproduction, and others body symmetry, require good core stability in all three plmotion.il A lack of core strength and stathought to result in an inefficient tecwhich predisposes the athlete to injury.t**example, LBP is a common problem in anthat requires significant rotatory or twistitions, repetitive llexion and/or extension.'"'"^swimming, the maintenance of posture,

and alignment is thought to be critical iimizing propulsion and minimizing drag, ynot common practice for core musclestrained, with most strength programmes ing arm exercises.f''' Leetun ct al. ' ' - ' foun41 (28 women , 13 men) of 139 athletes (basand track) sustained 48 back or lower exinjuries du ring the season (35% of the w22% of the men). They identified that the who sustained an injury generally had po

stability (i,e. weaker hip abduction and erotation strength, which decreased their abmaintain stability) and also concluded thawere greater dem ands on the female lumbomusculature, which resulted in a greaterrisk to the lower back for females (this ported by previous research).''^^"''*'*'*''' quently, core training could play an imrole in injury prevention, especially in fem

Physiologically, core strength and s

training is believed to lead to a greater mpower and more efTicient use of the musthe shoulders, arms and legs.'**' This theorresults in a lower risk of injury and peffects on athletic performance, in terspeed, agility, power and aerobic enduranTraining programmes at tempting to weak links in an individual's core ability strategies that regain control of the site rection of the deficiency at the appropriat

hold of training. Typically, programmdesigned to:


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formance, Core Stability and Core Strength 1003

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Many sport-specific training programmes failto include low-load motor control training, whichhas been identified as an essential part of corestrength training and improving core stability.'^"^'By neglecting the local muscles, the force producedby the global muscles will be too great for thelocal muscles to control and leads to greaterinjury risk.'"*' It is believed that high-load trainingchanges the muscle structure, whereas low-loadtraining improves the ability of the CNS to controlmuscle coordination and hence the efficiency of

the movement.'"^' Therefore, by performing awell structured and functional programme usingboth low- and high-load training, improvementsshould be attained in all the processes contributingto core stability and core strength, which, it isreasoned, will in turn, impact on sporting perfor-mance. Low- and high-load training involves diffe-rent types of movements; for example, low-loadtraining involves less demanding, posture-relatedexercises that focus on muscle recruitment,

whereas high-load training can involve exercisessuch as overhead weighted squats and hangingleg raises, which places a greater stress on thecore musculature and also promotes core strengthdevelopment.'^^

Many questions remain regarding what typeof core training programme is most effectivefor improving core ability, but if future researchcan establish (i) clear defmitions; (ii) reliablemethods for summarizing the effectiveness ofdifferent core exercises; and (iii) the extent towhich these muscles need to be active to bringabout sufficient core stability and strength im-provements, these training programmes would bemore effective and we should expect to see fewerinjuries and subsequently to observe improvedsporting performances.

5. Measuring the C ore and itsReiation to Performance

Tse etal.'-^"'evalua ted th e effect of a core end u-rance programme (2 days a week for 30-40 min-

40-m sprint, overhead medicine-baa 2000-m maximum rowing test. revealed significant improvements inion tests of the core group; however, differences were observed in the perbetween the two groups. The authothis may have been due to the marprovement in the subjects being relatthis highly conditioned group of athhomogenous group of athletes, howeable a high level of sensitivity in th

statistic should any improvements following an intervention programmof significant differences in the study may also be due to the exercises pbeing functional enough to significaperformance. The length of interventmay also have not been sufficient tofonnance enhancement (see figure 1)

Stan ton et al.'"' investigated the efterm Swiss-ball training on stature,

EMG activity of abdominal and batreadmill maximal oxygen uptakeconomy and running posture. Eachfamiharization sessions on the coreminimize the learning effect and thtwo sessions per week for 6 weeks.used the Sahrmann core stability testabilizer pressure biofeedback unit pad that the subject lies supine on)EMG from the RA, EO and ere

muscles. Stanton et al.,"' Scibek et CUSet al.'**''' all observed significanSwiss-bail stability; however, no sigferences in EMG activity or performeters were observed. Stanton et al.that the training may have had an efmuscles that were not analysed (e.latissimus dorsi). Swiss-ball trainingfore, may not elicit the same perfvantage as explosive or high-intentraining. The lack of effect on perfserved in many studies may be duetraining programmes not being funct


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6. Conclusions

The definitions of core stability and corestrength are yet to be clearly established in therehabilitation and sporting sectors, and as a re-sult, this has led to many contradictory and con-fusing findings in the area. These definitions needto be established before a clear conclusion as towhich exercises and what type of training pro-gramme will most effectively result in perfor-mance enhancements, such as recovering from or

lowering the risk of injury and improving theability to perform everyday activities or enhan-cing sporting perform ance. If future research canestablish clear definitions for core stability andcore strength and reliable methods for summa-rizing the effectiveness of different core exercises,fewer injuries and subsequently improved per-formances in the rehabilitation and athletic sec-tors should be expected.

There are many articles in the literature thatpromote core training programmes and exer-eises for performance enhancement withoutproviding a strong scientific rationale of theireffectiveness, especially in the sporting sector.In the rehabilitation sector, it has been reportedthat improving core stability leads to improve-ments in lower back injury. Few studies haveobserved any performance enhancement insporting activities despite observing improve-ments in core stability and core strength follow-

ing a core training programme. It might be thatimprovements made in stability and strengthonly impact indirectly on sporting performanceby allowing athletes to train injury free moreoften. A clearer understanding of the roles thatspecific muscles have during core stability andcore strength exercises would enable more func-tional training programmes to be implemented,which may result in a more effective translationof core training into improvements in sporting

performance.

sources offunding were received in the prep aratioarticle and the authors have no conflicts of interestrelevant to its conte nts.

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Correspondence: Angela E. Hibbs, English Institu

Sport, Gateshead International Stadium, NeilsonGateshead, NEIOOEF, UK.E-mail: [email protected]


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