The Youth PhysicalDevelopment Model:A New Approach toLong-Term AthleticDevelopmentRhodri S. Lloyd, PhD, CSCS*D1 and Jon L. Oliver, PhD21Faculty of Applied Sciences, University of Gloucestershire, United Kingdom; and 2Cardiff School of Sport, CardiffMetropolitan University, United Kingdom

S U M M A R Y

THE DEVELOPMENT OF PHYSICAL

FITNESS IN YOUNG ATHLETES IS A

RAPIDLY EXPANDING FIELD OF

INTEREST FOR STRENGTH AND

CONDITIONING COACHES, PHYSI-

CAL EDUCATORS, SPORTS

COACHES, AND PARENTS. PREVI-

OUS LONG-TERM ATHLETE DEVEL-

OPMENT MODELS HAVE CLASSIFIED

YOUTH-BASED TRAINING METHOD-

OLOGIES IN RELATION TO CHRO-

NOLOGIC AGE GROUPS, AN

APPROACH THAT HAS DISTINCT

LIMITATIONS. MORE RECENT MOD-

ELS HAVE ATTEMPTED TO BRIDGE

MATURATION AND PERIODS OF

TRAINABILITY FOR A LIMITED NUM-

BER OF FITNESS QUALITIES,

ALTHOUGH SUCH MODELS APPEAR

TO BE BASED ON SUBJECTIVE

ANALYSIS. THE YOUTH PHYSICAL

DEVELOPMENT MODEL PROVIDES A

LOGICAL AND EVIDENCE-BASED

APPROACH TO THE SYSTEMATIC

DEVELOPMENT OF PHYSICAL PER-

FORMANCE IN YOUNG ATHLETES.

INTRODUCTION

In recent times, scientists and coacheshave shown an increasing interest inthe long-term development of young

athletes (7,23,30,44,63,65,80,100,102).Enhancing the physical abilities of chil-dren throughout childhood and adoles-cence to maximize athletic success at anadult age is not a novel concept, asevidenced by earlier youth-based train-ing programs (20). Researchers havepreviously documented the importanceof not treating children like miniatureadults owing to clear differences inphysical growth and stature (39). There-fore, the content and delivery of youthstrength and conditioning provisionshould be markedly different from thatof fully matured adults.

The long-term athlete development(LTAD) model (7) takes into consider-ation the maturational status of thechild and offers a more strategicapproach to the athletic developmentof youth. The LTAD model suggeststhat there exist critical windowsof opportunity during the develop-mental years, whereby children andadolescents are more sensitive totraining-induced adaptation (7). Themodel also states that a failure to usethese windows will result in thelimitation of future athletic potential(7). However, this concept is largelytheoretical and lacks supporting longi-tudinal empirical evidence (4,44,84).

This article will present a new model,which provides a more considered andevidence-based approach to the long-term development of young athletes.The model will demonstrate that most,if not all, components of fitness aretrainable throughout childhood andwill question some preconceptions ofcurrent LTAD theory.

THE EVOLUTION OF LTAD THEORY

Early attempts at objectifying theprocess of LTAD were based onresearch that highlighted distinctphases of learning that characterizedthe development of elite performers:the early years, the middle years,and the later years (18). This earlywork was extended by Cote (32) who,after interviewing elite junior athletes,identified 3 distinct sport-specificstages of development: the samplingyears (ages 612), the specializingyears (ages 1315), and the invest-ment years (ages 16+). A commonproblem with these models is thatthey are classified in accordance withchronologic age, an approach that haspreviously been deemed flawed (44),

KEY WORDS :

pediatrics; maturation; long-termathlete development

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owing to differential rates of devel-opment of chronologic age andbiologic maturity (57,68,108).

Consequently, a more comprehensiveLTAD model was introduced thatattempted to address the interactionbetween growth, maturation, andtraining (7). The model suggests thatmeasures of height and weight areroutinely collected to be able toidentify peak height velocity (PHV)and peak weight velocity (PWV),which reflect individual maturationrates (68). PHV refers to the maximumvelocity of growth in stature and hasbeen used to characterize develop-ments in performance relative to theadolescent growth spurt (68). PWV isa phase of development characterizedby rapid increases in muscle mass asa result of increasing sex hormoneconcentrations (44). By objectivelymeasuring the rates of change in heightand body mass, it is suggested thatchildren can be trained according tobiologic status as opposed to chrono-logic age (7).

WINDOWS OF OPPORTUNITY

A review article by Viru et al. (110)examined developmental literature andidentified the existence of naturallyoccurring periods of accelerated adap-tation for a range of biomotor qualities.A preadolescent spurt was highlightedfor strength, speed, explosive strength,and endurance, in both boys and girls(110). It was suggested that age-relateddevelopments in neural properties wereresponsible for the prepubertal window,characterized by increased intramuscu-lar and intermuscular coordination andimprovements in motor control pro-grams (110). An adolescent spurt wasalso identified in the review, but thisdifferentiated between biomotor quali-ties (110). Maturity-related adaptationsare typically the result of increasedandrogen concentrations, fiber-type dif-ferentiation, resting adenosine triphos-phate, and creatine phosphate levelsand further architectural developmentof musculotendon units (73).

Viru et al. (110) identified that spurts inspeed and endurance occurred before

and around PHV, respectively,whereas accelerated gains in strengthqualities occurred after PHV (110).Using PHV as a key reference markerof maturation, the LTAD model pro-poses that these periods of acceleratedadaptation offer windows of opportu-nity where training responses will bemaximized (7). In the LTAD model, itis assumed that these periods of rapidnatural development represent a timeof increased sensitivity to training,although empirical evidence support-ing this suggestion is lacking (44).Furthermore, according to the LTADmodel, should a child not engage in theappropriate training during the specificwindow, then their ceiling potentialmay never be reached. This conceptwould appear to be too simplisticand has recently been questionedby researchers (4,44,85). Conversely,research would suggest that mostfitness components are trainablethroughout childhood and should notbe restricted to specific windowsat various stages of development(3,44,94). Another weakness of thecurrent LTAD model (7) is that itsinclusion of stamina, suppleness, speed,strength, and skill presents a somewhatlimited approach to the holisticdevelopment of young athletes.Despite the importance of power,agility, and hypertrophy to humanperformance (56,98,120), no guidanceis offered as to when and why thesequalities should be trained throughoutchildhood and adolescence.

THE YOUTH PHYSICALDEVELOPMENT MODEL

Given the limitations of previousathletic development models, the pres-ent article introduces a new alternativemodel that encompasses athleticdevelopment from early childhood(2 years of age) up to adulthood (21+years of age). The model has beentitled the Youth Physical Development(YPD) model and offers a comprehen-sive approach to the development ofyoung males (Figure 1) and females(Figure 2), respectively. It is expectedthat the new model will providestrength and conditioning coaches,

sports coaches, physical educators,and parents with an overview of totalphysical development, while identify-ing when and why the training ofeach fitness component should beemphasized.

Within the model, training emphasis ishighlighted by increasing font size(i.e., the greater the font size, themore important it is to train for thatfitness quality). For example, the modelshows that a 12- to 13-year-old boyshould primarily focus their trainingon strength, power, speed, agility, andsport-specific skill (SSS) development,with a reduced focus on hypertrophy,mobility, fundamental movement skill(FMS), endurance, and metabolicconditioning. Discussion of how mat-urational status, sex, and initial train-ing level affect the application ofthe model will be discussed later inthe article. Below is a detailed over-view of the rationale behind theemphasis of targeting various fitnesscomponents at different stages ofa childs development.

FUNDAMENTAL MOVEMENTSKILLS AND SPORT-SPECIFICSKILLS

The topic of FMS development hasreceived considerable interest owingto the close association betweenFMS competency, health and well-being, physical activity, and toa lesser degree physical performance(29,38,66,82,83,103). Previous rese-arch has indicated that FMS devel-opment is essential to ensure thatcorrect movement patterns are mas-tered in a safe and fun environmentto ensure safe and effective perfor-mance of more complex sportsmovements at a later stage (85).FMSs have been viewed as thebuilding blocks for sport-specificmovement patterns and should typ-ically be the focus of physical devel-opment programs for children fromearly childhood to develop grossmotor skills (35). From the onset ofpuberty, adolescents can then beintroduced to more SSSs, wherebyFMSs are tested within more com-petitive scenarios.

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However, it must be noted that FMSshould always be present within anystrength and conditioning program, forany athlete, of any age (65). Forexample, the main emphasis of a train-ing session for an inexperienced 7-year-old boy may revolve around a series ofFMS development exercises, whereasa young, elite, 21-year-old man mayintegrate FMS maintenance exerciseswithin a dynamic warm-up. Thislogical approach is reflected in theYPD model (Figures 1 and 2), wherean emphasis is placed on FMS devel-opment up to the onset of puberty, andsubsequently, focus is given to SSSfrom adolescence onward. However,

the YPD model also shows that bothFMS and SSS are present at all timesthroughout childhood and adoles-cence, but the emphasis placed onboth components varies according todevelopmental stage.

STRENGTH

Despite previous concerns, it is nowaccepted that children can safely andeffectively participate in strength train-ing, when prescribed and supervised byappropriately qualified personnel(6,11,39,62,88,105). The LTAD model(7) suggests that a window of oppor-tunity for strength development inyouths occurs 1218 months afterPHV, which is typically commensurate

with PWV (14,15). The rationalebehind this window is that aroundthe time of PWV, adolescents willundergo periods of rapid gains in musclemass resulting from increased circulat-ing androgen concentrations (110).

However, by limiting the period oftrainability to coincide with maturity-related increases in muscle mass wouldsuggest that children can only becomestronger as a consequence of musclefiber hypertrophy and subsequentincreases in muscle cross-sectionalarea. Despite this, it has previouslybeen established that strength devel-opment is multifaceted and resultsfrom a combination of muscular,

Figure 1. The YPD model for males. Font size refers to importance; light blue boxes refer to preadolescent periods of adaptation,dark blue boxes refer to adolescent periods of adaptation. FMS = fundamental movement skills; MC = metabolicconditioning; PHV = peak height velocity; SSS = sport-specific skills; YPD = youth physical development.

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neural, and mechanical factors (1,34).Owing to the neural plasticity associ-ated with the prepubertal years, wheredevelopment of the neuromuscularsystem naturally accelerates (21), it issuggested that strength developmentshould be targeted during childhood inaddition to after the adolescent spurt.This notion is reinforced by researchand meta-analytical reviews that haveproven that both prepubertal childrenand adolescents can achieve training-induced improvements in muscularstrength (12,13,40,42,48).

The YPD model shows that the devel-opment of muscular strength should bea priority at all stages of developmentfor both males and females (Figures 1

and 2). This notion is based onprevious research that has revealedclose associations between muscularstrength and running speed (114),muscular power (104,116), change ofdirection speed (78), plyometric ability(71), and endurance (53). Additionally,it has been speculated that muscularstrength is indeed critical for successfulFMS development (12). Consequently,it is reasonable to suggest that devel-oping levels of muscular strengthshould be a priority of any athletedevelopment program, as strengthwould appear to transcend all otherfitness components. Although not allthese relationships have been validatedin pediatric populations, early research

has indicated that muscular strength(in addition to stature) could accountfor up to 70% of the variability ina range of motor skills includingthrowing, jumping, and sprinting in7- to 12-year-old boys (106).

The development of muscular strengthshould also be viewed as an integralcomponent of youth strength andconditioning programs not only forperformance enhancement but also forreducing the risk of sport-relatedinjuries (39). It has been reported thathigh aerobic fitness and low levels ofmuscle strength heighten the risk offracture in children participating inexercise protocols (26), highlightingthe importance of strength within an

Figure 2. The YPD model for females. Font size refers to importance; light pink boxes refer to preadolescent periods of adaptation,dark pink boxes refer to adolescent periods of adaptation. FMS = fundamental movement skills; MC = metabolicconditioning; PHV = peak height velocity; SSS = sport-specific skills; YPD = youth physical development.

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Youth Physical Development Model

athletic development program. It isnow accepted that the risk of sports-related injuries in youths can bereduced by regularly engaging in anappropriately designed strengthtraining program that is supervisedby appropriately qualified personnel(42,73). In 2011, the NationalAthletic Trainers Association sug-gested that approximately 50% ofoveruse injuries within youth sportscould be preventable in part withappropriate preparatory conditioning(109). However, it must be stressedthat strength development sessionsshould not simply be viewed as anaddition to a young athletes devel-opment program but as a replacementfor another form of training (e.g.,endurance training or skill develop-ment session).

HYPERTROPHY

The YPD model depicts that anemphasis on training for hypertrophymay begin around the ages of 14 yearsin male and 12 years in female athletes.As mentioned previously, these phasesof development will typically occurafter PHV, at a time where levels ofcirculating testosterone and growthhormone rapidly increase in accor-dance with the adolescent growthspurt (68,110). Increases in serum con-centrations of testosterone, estradiol,and progesterone have been directlylinked with the stimulation of proteinsynthesizing pathways (45) and areresponsible for the pubertal growthspurt and adaptations to muscle andskeletal tissue (19). Although notproven with direct evidence, it isreasonable to assume that because ofa lack of circulating androgens, signif-icant training-induced increases inmuscle size before adolescence wouldappear limited. Consequently, withinthe YPD model, it is suggested in termsof resistance training that a focusshould be geared toward strengthdevelopment before adolescence, andafter the adolescent spurt, strengthtraining should be interspersed withbouts of hypertrophy training to makefurther gains in muscular strength andoverall performance.

POWER

The ability to generate high levels ofpower is essential for sporting success(119); however, power is omitted fromthe current LTAD model (7). Verticaljump height is an indirect measure ofmuscular power, and owing to itssimplicity, most developmental litera-ture has used the test modality to assesspediatric lower limb muscular power(50,55).

The YPD model shows that the keyperiod of power development starts atthe onset of adolescence and continuesthroughout adulthood, largely becauseof rapid improvements in musclepower during adolescence being attrib-uted to maturational influences (15).However, although power develop-ment is emphasized primarily afterthe onset of puberty, the YPD modeldoes suggest that some training focusshould also be given to developingpower during the prepubertalphase. This is in response toresearch that shows that both chil-dren and adolescents can makeworthwhile training-induced impro-vements in measures of muscularpower (25,41,64,69,92,97,118). As isthe case with muscular strength, theresearch would therefore suggestthat muscular power is trainablethroughout childhood, although themagnitude and rate of developmentmay differ before and after the onsetof puberty.

SPEED

Currently, the LTAD model advocatesthat windows of opportunity for speeddevelopment are entirely age related(7). According to the model, anytraining effects will therefore resultfrom neural adaptations, which havepreviously been highlighted as signifi-cant factors in speed gains (21).However, alternative research hasindicated that speed development inyoung athletes might also be influencedby maturation (94), which suggests thatas is the case with many fitnesscomponents, speed is indeed trainablethroughout childhood and adolescence.Interestingly, the review of Rumpf et al.(94) revealed that prepubescents

benefited most from training requiringhigh levels of neural activation (plyo-metrics and sprint training), whereasadolescents responded more favorablyto training modes that targeted bothneural and structural development(strength and plyometrics). This mightsupport the concept of windows whendifferent training adaptations predomi-nate reflecting natural development;however, trainability per se remainsthroughout childhood. From a practicalperspective, this would suggest thatprepubescent children should focustheir speed development around plyo-metrics, technical competency, andsprint work to develop existing physicalqualities, whereas adolescents shouldfocus more on strength training, plyo-metrics, and sprint training, to maximizeoverall speed gains.

AGILITY

Agility is arguably one of the mostunderresearched fitness componentswithin the pediatric literature, despitethe acknowledgment that a highdegree of agility is required for optimalperformance in the majority of sports(56). Furthermore, a window of oppor-tunity is not present within the currentLTAD model (7). Consequently, it isdifficult to determine whether age,maturation, or both are determinantsof agility performance. There is a lackof research that identifies appropriatetime frames to target agility-specifictraining. Therefore, the YPD modelmakes inferences in relation to thedevelopment of the subcomponents ofagility, as defined previously (99,120):change of direction speed (inclusive oftechnique, straight sprinting speed,lower limb strength, and anthropom-etry) and cognitive function (perceptualand decision-making processes).

Change of direction speed. Whenexamining the literature surroundingthese components, the YPD modelsuggests that agility should be targetedduring both prepubescence and ado-lescence. As lower limb strengthand straight running speed are compo-nents of agility (120), it is logical tolook to develop agility and reinforce

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coordination and movement patternaccuracy during the early years. Theprepubertal years have already beenshown to represent an opportunity forchildren to enhance strength (12,48)and speed (94), resulting fromenhanced neural contribution to rateof force development (110). Oncea child reaches adolescence, they willtypically experience further gains instrength through continued neuralmaturation and also significant in-creases in lean muscle mass, owing toincreased serum androgen concentra-tions (110). It is reasonable to suggestthat adolescence will therefore serve asan opportune time to further developagility, as peak force and peak rateof force development are likely toincrease because of the adaptation inmuscle structure. Prepubescence hasalso been identified as a period thatsees children undergo rapid develop-ments in the neuromuscular system(21), with the rates of brain maturationpeaking between 6 and 8 and 10 and12 years (90). Naturally, owing to theneural plasticity associated with pre-pubescence, this would seem an idealopportunity to develop motor controlprograms inclusive of basic changeof direction techniques in the firstinstance and then progressing to moresport-specific agility movements as thechild approaches adolescence.

Cognitive function. According toSheppard and Young (99), a numberof perceptual variables influence agility.Specifically, the authors state thatvisual scanning, knowledge of situa-tions, pattern recognition, and antici-patory qualities influence individualagility performance (99). Minimal lit-erature exists examining the influence ofgrowth and maturation on these com-ponents and their subsequent effectson agility performance. Outside sport-ing situations, research suggests thatcognitive capacities increase duringlate childhood and adolescence andthat throughout these phases ofdevelopment, repeated exposure toa given stimulus will result in fasterresponse times because of an apparent

strengthening of existing synaptic path-ways (24). Whether these theoriestranslate to actual sporting situations,in which athletes will need to reactrapidly to fluctuating stimuli (e.g. bodyposition, bounce of ball, oppositionmovement), remains to be seen.

It is expected that the locomotivevocabulary developed during the pre-pubertal phase will continuously beenhanced as the child progressesthrough adolescence and into adult-hood, through an increase in experientiallearning opportunities within sports-specific environments. Given the lackof existing developmental literature, it issuggested that the training focus ofagility should be made more challengingas the individual progresses throughchildhood and into adulthood, withthe use of more open and unplannedtraining methods to continually overloadthe training stimulus. Additionally, withan increase in training demands withinan overall athletic schedule, it is expectedthat agility development (and mainte-nance) will be garnered from specificsports skill-based sessions, where move-ment demands replicate the exact loco-motive demands of the sport.

As per speed development, a caveatshould be noted for agility developmentduring adolescence, as children learn tomove with longer limbs. The rapidgains in limb length during the adoles-cent growth spurt can lead to decre-ments in motor control performance,a concept commonly referred to asadolescent awkwardness (87). Duringthis stage of development, researchershave suggested that many of the pre-viously acquired movement patternswill need to be reperfected (37).Through regular monitoring of growthrates, periods of adolescent awkward-ness can potentially be identified andstrength and conditioning coachesshould be aware of the underlyingprocesses attributable to such disrup-tions in motor control and adjust thecontent of training sessions accordingly.

MOBILITY

Despite highlighting suppleness asone of the key components to develop

through training (7), the LTAD modelfails to suggest an appropriate windowof opportunity for its development.The YPD model purports that at nostage is mobility the main emphasis ofa training program during childhood oradolescence. However, it should benoted that as authors, we recommendthat mobility development and main-tenance should be an essential part ofany athletic program to ensure athletesare capable of reaching the requisiteranges of motion required for theirsports.

Specifically, the YPD model proposesthat middle childhood (ages 511)serves as the most important timeframe for an individual to incorporateflexibility and mobility training. Therationale for this selection is that itincorporates a period that has pre-viously been termed a critical period ofdevelopment for flexibility (67,96). Sexdifferences are apparent within theresearch, suggesting that boys showa reduction in trunk forward flexibilitybetween 9 and 12 years (16), whereasgirls demonstrate accelerated improve-ment beginning at 11 years of age (22).It is therefore suggested that pre-pubescence serves as an opportunityto develop mobility, whereas main-tenance of the acquired levelsshould be the focus for adolescentsand adults.

ENDURANCE AND METABOLICCONDITIONING

Early research produced conflictingresults with respect to the trainabilityof youths, with studies suggesting thatchildren who were circa-PHV pos-sessed greater training responsiveness(113) or, conversely, that large traininggains were possible for children whowere pre-PHV (93). It is suggested thatinconsistencies in research design havebeen attributable to these confoundingresults and that a lack of longitudinalempirical evidence refutes the claims ofthe existence of a window of opportu-nity as defined in the LTAD model (44).Regardless of the lack of evidence,growth-related changes in central andperipheral cardiovascular systems, neu-romuscular function, and metabolic

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capacities are expected to influenceendurance and metabolic conditioningdevelopment throughout childhood(93). As physiological components arecontinuingly developed throughoutchildhood and adolescence, it is not sur-prising that prepubertal, circumpuber-tal, and postpubertal children have allbeen reported as being able to makeworthwhile improvements in endur-ance performance as indicated by_VO2max responses (3).

The YPD model proposes that moreattention is given to endurance andmetabolic conditioning as the childapproaches adulthood, and at no stage,it is seen as the main focus of anindividuals training. Although this mayappear controversial, the rationale isbased on the assumption that anindividual will be exposed to sport-specific endurance development whileparticipating in organized matches orcompetitions and potentially withina technical skill session of their givensport. Additionally, remarkable levels ofendurance are not necessarily requiredin the majority of sports, and enduranceappears to remain trainable in adult-hood. Within the education sector,cardiovascular endurance is inadver-tently the most commonly developedfitness component, as asking a child toperform some form of submaximallocomotion would appear safer toteachers than asking them to participatein some form of resistance training. Thisis especially the case within the primaryschool setting in the United Kingdom,where not only have strength levels inchildren diminished in the last decade(31) but also it is recognized thatteachers are inappropriately preparedthrough their teacher training to teachphysical education and that statutoryrequirements for physical education areroutinely not achieved (59).

THE NEED TO INDIVIDUALIZELONG-TERM ATHLETICDEVELOPMENT PROGRAMS

The YPD model is presented for bothmales (Figure 1) and females (Figure 2)displaying what would be classified asan average maturing child (i.e., not anearly or late maturer). However,

strength and conditioning coaches willhabitually come into contact withathletes of varying stages of matura-tion, age, sex, and training history.Although previous models havealluded to these variables (7), it is notapparent that the impact of theindividual variables on training pre-scription has been addressed. Conse-quently, the following section willexamine how the YPD model shouldbe manipulated when considering sex-dependent factors, timing and rates ofmaturation, and the training historyassociated with different athletes.

SEX DIFFERENCES

Despite more boys engaging in youthsports than girls, there has been anincrease in the overall number ofchildren and adolescents actively par-ticipating in organized youth sportsover the past decade (77). Withparticipation numbers increasing, it isimperative that any strength andconditioning coach is aware of thephysiological and maturational differ-ences that exist between males andfemales and design-specific programsaccordingly.

During the prepubertal years, boys andgirls will follow similar rates of devel-opment in growth and maturation, anddespite consistent sex differences,strength, speed, power, endurance,and coordination will develop at sim-ilar rates for both sexes throughoutchildhood (14). Consequently, froma training perspective, both boys andgirls can follow similar training pro-grams during the prepubertal years.The YPD model advocates a prepuber-tal focus of training for both boys andgirls that centers on FMS, strengthspeed, and agility development.

The prepubertal years are a periodwhere children will experience rapidgains in bone mass because of model-ing and remodeling (9). Exposure toappropriately designed weight-bearingexercise of moderate- to high-loadintensity (with appropriate technicalcompetency) is an osteogenic stimulus(60,61,111,115). Such training can resultin large increases in bone mass and

density (5,10,17,46,117), and researchhas suggested that this adaptive res-ponse is most sensitive during theprepubertal years (8). Due to womenpossessing a greater risk of osteoporosisin later life (58) and that strengthtraining has previously been deemedto offer the potential of reducingosteoporotic fractures in older women(79), the importance of strength trainingfor women at all stages of developmentshould not be underestimated.

Upon the onset of the adolescentgrowth spurt, clear maturational differ-ences are apparent for nearly allcomponents of fitness, with menmaking greater improvements in mostphysical qualities, with the exception offlexibility (14,68). Typically, the onsetof the adolescent growth spurt occursaround 2 years earlier in girls (about10 years of age) than in boys (approx-imately 12 years of age) (14), and in themajority of instances, girls experiencePHV at an earlier age than boys(12 years versus 14 years) (15). Despitean earlier attainment of PHV in girls,the magnitude of the growth spurt isgreater in boys (15).

During the adolescent spurt, femaleathletes will undergo sex-specificphysiological processes that mayaffect performance: increased fatmass, differential rates of develop-ment of neuromuscular strength, andheight and weight; commencement ofmenstrual cycle, increased joint laxity,increased knee valgus angle; andincreased reliance on quadriceps-dominant landing strategies, all ofwhich have been associated withan increased risk of noncontactanterior cruciate ligament injury(2,43,51,52,72,75,86,89).

Consequently, the YPD model sug-gests that training strategies designedto reduce the risk of noncontactanterior cruciate ligament injuries,such as plyometrics, core strength-ening, strength training, and balanceand perturbation training (74),should be implemented within thestrength and conditioning program

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of female athletes and maintainedinto adulthood.

EARLY VERSUS LATE MATURINGINDIVIDUALS

Because of the highly individual timingof maturation, it is imperative that anyLTAD model contains a degree offlexibility (65). An early maturing childhas previously been defined as a girlor boy who starts their adolescentgrowth spurt approximately 1.5 or2 years earlier than a late maturingchild (47).

Although research has indicatedthat eventual adult height is notaffected by early or late maturation(49), strength and conditioningcoaches must appreciate that an earlyor late maturing child will need tobe treated somewhat differently thanan average maturing child, whenprescribing long-term athletic develop-ment programs. For example, if a childis routinely monitored for stature andbody mass every 36 months through-out childhood, growth rates, percent-age of adult height, and predictions ofage from PHV can be calculated (70).Using these measurements, the matu-rational status of a child can beapproximated, thus providing a more r-obust estimate of their biological age.

In relation to the YPD model, ifa child is deemed to be an earlymaturer, then the components ofthe model will need to be moved tothe left, thus enabling the child tocommence more advanced trainingtechniques at an earlier chronologicage. In contrast, a strength andconditioning coach must allow thecomponents of the YPD model tobe moved to the right for a childwho is deemed a late maturer, therebyintroducing them to more advancedtraining at a later chronologic age,when they are physiologically readyto cope with the increased trainingstimulus. In either of these instances,although training prescription willvary according to chronological age,it should allow greater consistencyand more accuracy in terms of thechilds biological age.

INITIAL TRAINING STATUS

Irrespective of chronological or biolog-ical age, a strength and conditioningcoach must give thought to the trainingage of any athlete that they startworking with. Training age can bedefined as the number of years anathlete has been participating in formal-ized training and is an important factorto consider when designing long-termathletic development programs. Such anapproach is particularly pertinent whena strength and conditioning coachbegins to work with an athlete who isapproaching adulthood that has missedthe initial stages of the YPD model.

In such an instance, the athletes shouldbegin with early development of FMSand muscular strength before embark-ing on the training content that iscommensurate with their chronologi-cal age. Conversely, should a strengthand conditioning coach begin workingwith an early maturing 10-year-old boywho can display exceptional strength,speed, and power while maintainingthe requisite technical competency,then they should not be restricted tothe introductory training methodsmore akin to his chronological age.This concept has previously beendiscussed in relation to both plyomet-ric (63) and weightlifting (65) devel-opment models.

THE YPD MODEL AS A VEHICLEFOR ATHLETE WELL-BEING

Well-being has been defined as a pos-itive and sustainable state that allowsindividuals, groups, or nations to thriveand flourish (54). The philosophy ofthe YPD model is that it permitsindividualization, is athlete centered,and promotes the development of thechild over performance outcomes. Thismay sacrifice short-term performancesuccess but should maximize theopportunity to foster a sense of well-being and provide long-term gains.This philosophy will help the child toappreciate the benefits of training anddevelop intrinsic motivation for par-ticipating in training, which is a strongpredictor of well-being (95) and isassociated with positive behaviors(112). Additionally, provided the coach

can deliver the content of the model ina positive manner the child shouldrecognize the gains they are achieving(e.g., technical, physical, developmen-tal), leading to increased perceivedcompetence, which is a primarydeterminant of a sense of well-beingin child athletes (91). This will increasethe likelihood of the child being ableto persist in the face of adversity andto sustain continued interest in sport(4,36).

The YPD model advocates the devel-opment of FMS from a young age,which are associated with physical andpsychologic health benefits in children(66). Furthermore, the progressionprovided throughout the YPD modelwill enable the children to experiencecontinued mastery of new tasksthroughout their developmental years.

Task mastery is associated with incre-ased enjoyment, perceived competence,satisfaction, and beliefs that effort causessuccess (81,101,107). Such positiveexperiences should also provide valu-able and highly transferable life skills(33). The continued and overlappingdevelopment of a number of fitnesscomponents in the YPD model shouldalso provide the strength and condi-tioning coach with the ability todevelop training programs containinga high degree of variation, somethingthat has been suggested to be importantin maintaining the interest of andpromoting the well-being of childathletes (85).

DESIRED CREDENTIALS FORSTRENGTH AND CONDITIONINGCOACHES WORKING WITH YOUTHATHLETES

It is important to realize that thesuccess of any long-term developmentprogram will be dependent largely onthe level of education and quality ofinstruction received by the athlete fromthe responsible coach (73). Within theliterature, cases of training-inducedinjury in children and adolescents arereported only in instances wherea young athlete has been exposed toexcessive, unfamiliar, and poorly pre-scribed training, which in both caseshave led to exertional rhabdomyolysis

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and hospitalization (27,28). Researchsuggests that outside these isolatedcases, most incidences of resistancetraining-related injuries tend to beaccidental in nature, with the numberof accidental injuries decreasing with age(76). However, to minimize the chancesof such isolated instances occurring, it isimperative that those coaches whoactively coach young athletes possessthe appropriate credentials.

First, a coach must hold a relevantstrength and conditioning qualification(e.g., Certified Strength and Condition-ing Specialist in the United States orAccredited Strength and ConditioningCoach in the United Kingdom). Sec-ond, a coach must have a sound un-derpinning knowledge of pediatricexercise science, ideally at an under-graduate or postgraduate level. Finally,a coach should have a strong peda-gogical background to ensure theyhave an appreciation of the differentstyles of communication and interac-tion that they will need to adopt withathletes, who might range from earlyprepubescent to late adolescent. Satis-faction of these criteria will hopefullyensure that young athlete developmentmodels are delivered in a safe andeffective manner, underpinnedby appropriate individual programdesign (inclusive of exercise selectionand progressions, volume loads, rest,and recovery), realistic goal setting, anda coaching philosophy that is tailoredtoward the holistic development of theyoung athlete.

SUMMARY

The present article has provided a soundrationale for the YPD model. Thisapproach to the development of youngathletes appears to be more realistic interms of acknowledging that mostfitness components are trainablethroughout childhood. Central to theYPD model is that during prepubes-cence, strength, FMS, speed, and agilityshould be the main physical qualitiestargeted and that adaptive responses tothe appropriate training methods will beneural in nature. Once the child reachesadolescence, additional components(SSS, power, and hypertrophy) become

more important owing to the increasedandrogenic internal environment asso-ciated with this stage of development.The need for individualization of themodel should not be underestimatedwhen dealing with athletes of differentsex, maturity status, and training history.Crucially, appropriately qualified per-sonnel should always be responsible forthe implementation of the YPD model,to ensure the holistic development ofchildren and adolescents.

Rhodri S. Lloydis the programdirector for theSport Strength andConditioningdegrees at theUniversity ofGloucestershire.

Jon L. Oliveris a lecturer inSport and ExercisePhysiology atCardiff Metropoli-tan University.

REFERENCES1. Aagaard P. Training-induced changes in

neural function. Sports Med 31: 6167,

2003.

2. Arendt E and Dick R. Knee injury patterns

among men and women in collegiate

basketball and soccer: NCAA data and

review of the literature. Am J Sports Med

23: 694701, 1995.

3. Bacquet G, van Praagh E, and Berthoin S.

Endurance training and aerobic fitness

in young people. Sports Med 33:

11271143, 2003.

4. Bailey R, Collins D, Ford P, MacNamara A,

Toms M, and Pearce G. Participant

development in sport: An academic

review. Sports Coach UK 4: 1134,

2010.

5. Bailey DA, Faulkner RA, and McKay HA.

Growth, physical activity and bone

mineral acquisition. In: Exercise and

Sports Science Review. American

College of Sports Medicine Series.

Holloszy JO, ed. Vol. 24. Baltimore,

MD: Williams & Wilkins, 1996. pp.

233266.

6. Baker D, Mitchell J, Boyle D, Currell S,

Wilson G, Bird SP, OConnor D, and

Jones J. Resistance training for children

and youth: A position stand from the

Australian Strength and Conditioning

Association (ASCA). 2007. Available at:

http://www.strengthandconditioning.org.

Accessed July 13, 2011.

7. Balyi I and Hamilton A. Long-Term Athlete

Development: Trainability in Childhood

and AdolescenceWindows of

OpportunityOptimal Trainability.

Victoria, Canada: National Coaching

Institute British Columbia & Advanced

Training and Performance Ltd, 2004.

8. Bass SL. The prepubertal yearsA unique

opportune stage of growth when the

skeleton is most responsive to exercise?

Sports Med 30: 7378, 2000.

9. Bass S, Delmas PD, Pearce G, Hendrich E,

Tabensky A, and Seeman E. The differing

tempo of growth in bone size, mass and

density in girls is region-specific. J Clin

Invest 104: 795804, 1999.

10. Bass SL and Myburg K. The effect of

exercise on peak bone mass and bone

strength. In: Sports Endocrinology.

Warren M and Constantini N, eds.

Totowa, NJ: Humana Press Inc, 2000. pp.

253280.

11. Behm DG, Faigenbaum AD, Flak B, and

Klentrou P. Canadian Society for

Exercise Physiology position paper:

Resistance training in children and

adolescents. Appl Physiol Nutr Metab

33: 547561, 2008.

12. Behringer M, vom Heede A, Matthews M,

and Mester J. Effects of strength training

on motor performance skills in children

and adolescents: A meta-analysis. Pediatr

Exerc Sci 23: 186206, 2011.

13. Behringer M, vom Heede A, Yue Z, and

Mester J. Effects of resistance training in

children and adolescents: A meta-analysis.

Pediatrics 126: 11991210, 2010.

14. Beunen GP and Malina RM. Growth and

biological maturation: Relevance to

athletic performance. In: The Child and

Adolescent Athlete. Bar-Or O, ed. Oxford,

United Kingdom: Blackwell Publishing,

2005. pp. 317.

15. Beunen GP and Malina RM. Growth and

physical performance relative to the timing

of the adolescent spurt. Exerc Sport Sci

Rev 16: 503540, 1988.

16. Beunen GP, Malina RM, Vant Hof MA,

Simons J, Ostyn M, Renson R, and

Strength and Conditioning Journal | www.nsca-scj.com 69

Van Gerven D. Adolescent Growth and

Motor Performance. Champaign, IL:

Human Kinetics, 1988. pp. 69.

17. Blimkie CJ, Rice S, Webber CE, Martin J,

Levy D, and Gordon CL. Effects of

resistance training on bone mineral

content and density in adolescent

females. Can J Physiol Pharmacol 74:

10251033, 1996.

18. Bloom BS. Developing Talent in Young

People. New York, NY: Ballentine Books,

1985. pp. 139211.

19. Boisseau N and Delamarche P. Metabolic

and hormonal responses to exercise in

children and adolescents. Sports Med 30:

405422, 2000.

20. Bompa TO. Total Training for Young

Champions. Champaign, IL: Human

Kinetics, 2000. pp. 2131.

21. Borms J. The child and exercise: An

overview. J Sports Sci 4: 420, 1986.

22. Branta C, Haubenstricker J, and Seefeldt V.

Age changes in motor skills during

childhood and adolescence. Exerc Sport

Sci Rev 12: 467520, 1984.

23. Burgess DJ and Naughton GA. Talent

development in adolescent team sports: A

review. Int J Sports Physiol Perform 5:

103116, 2010.

24. Casey BJ, Giedd JN, and Thomas KM.

Structural and functional brain

development and its relation to cognitive

development. Biol Psychol 54: 241257,

2000.

25. Chiodera P, Volta E, Gobbi G, Milioli MA,

Mirandola P, Bonetti A, Deisignore R,

Bernasconi S, Anedda A, and Vitale M.

Specifically designed physical exercise

programs improve childrens motor

abilities. Scand J Med Sci Sports 18:

179187, 2008.

26. Clark EM, Tobias JH, Murray L, and

Boreham C. Children with low muscle

strength are at an increased risk of

fracture with exposure to exercise.

J Musculoskelet Neuronal Interact 11:

196202, 2011.

27. Clarkson PM. Case report of exertional

rhabdomyolysis in a 12-year-old boy.

Med Sci Sports Exerc 38: 197200,

2006.

28. Cleary MA, Sadowski KA, Lee SY, Miller GL,

and Nichols AW. Exertional

rhabdomyolysis in an adolescent athlete

during preseason conditioning: A perfect

storm. J Strength Cond Res 25:

35063513, 2011.

29. Cliff DP, Okely AD, Smith LM, and

McKeen K. Relationships between

fundamental movement skills and

objectively measured physical activity in

preschool children. Pediatr Exerc Sci 21:

436449, 2009.

30. Cobley S, Baker J, Wattie N, and

McKenna J. Annual age-grouping and

athlete development: A meta-analytical

review of relative age effects in sport.

Sports Med 39: 235256, 2009.

31. Cohen DD, Voss C, Taylor MJ, Delextrat A,

Ogunleye AA, and Sandercock GR. Ten-

year secular changes in muscular fitness

in English children. Acta Paediatr 100:

e175e177, 2011.

32. Cote J. The influence of the family in the

development of talent in sport. Sport

Psychol 13: 395417, 1999.

33. Danish S, Forneris T, Hodge K, and Heke I.

Enhancing youth development through

sport. World Leisure J 46: 3849, 2004.

34. De Ste Croix M. Advances in paediatric

strength assessment: Changing our

perspective on strength development.

J Sports Sci Med 6: 292304, 2007.

35. Deli E, Bakle I, and Zachopoulou E.

Implementing intervention movement

programs for kindergarten children.

J Early Child Res 4: 518, 2006.

36. Donaldson SJ and Ronan KR. The effects

of sports participation on young

adolescents emotional wellbeing.

Adolescence 41: 369388, 2006.

37. Drabik J. Children & Sports Training: How

Your Future Champions Should Exercise

to be Healthy, Fit, and Happy. Island

Pond, VT: Stadion Publishing Co, 1996.

38. Faigenbaum AD, Farrell A, Fabiano M,

Radler T, Nacierio F, Ratamess NA,

Kang J, and Myer GD. Effects of

integrative neuromuscular training on

fitness performance in children. Pediatr

Exerc Sci 23: 573584, 2011.

39. Faigenbaum AD, Kraemer WJ, Blimkie CJ,

Jeffreys I, Micheli LJ, Nitka M, and

Rowland TW. Youth resistance training:

Updated position statement paper from

the National Strength and Conditioning

Association. J Strength Cond Res 23:

S60S79, 2009.

40. Faigenbaum AD, Loud RL, OConnell J,

Glover S, OConnell J, and Westcott W.

Effects of different resistance training

protocols on upper-body strength and

endurance development in children.

J Strength Cond Res 15: 459465,

2001.

41. Faigenbaum A and Mediate P. Medicine

ball for all: A novel program that enhances

physical fitness in school-age youths.

J Phys Educ Recreation Dance 77:

2530, 2006.

42. Faigenbaum AD and Myer GD.

Resistance training among young

athletes: Safety, efficacy and injury

prevention effects. Br J Sports Med 44:

5663, 2010.

43. Fischer DV. Neuromuscular training to

prevent anterior cruciate ligament injury in

the female athlete. Strength Cond J 28:

4454, 2006.

44. Ford PA, De Ste Croix MBA, Lloyd RS,

Meyers R, Moosavi M, Oliver J, Till K, and

Williams CA. The long-term athlete

development model: Physiological

evidence and application. J Sports Sci 29:

389402, 2011.

45. Fragala MS, Kraemer WJ, Denegar CR,

Maresh CM, Mastro AM, and Volek JS.

Neuroendocrine-immune interactions and

responses to exercise. Sports Med 41:

621639, 2011.

46. Fuchs RK, Bauer JJ, and Snow CM.

Jumping improves hip and lumbar spine

bone mass in prepubescent children: A

randomized controlled trial. J Bone Miner

Res 16: 148156, 2001.

47. Gasser T, Sheehy A, Molinari L, and

Largo RH. Growth of early and late maturers.

Ann Hum Biol 28: 328336, 2001.

48. Granacher U, Goesele A, Roggo K,

Wischer T, Fischer S, Zuerny C, Gollhofer A,

and Kriemler S. Effects and mechanisms

of strength training in children. Int J Sports

Med 32: 357364, 2011.

49. Hagg U and Taranger J. Height and

height velocity in early, average and late

maturers followed to the age of 25: A

prospective longitudinal study of

Swedish urban children from birth to

adulthood. Ann Hum Biol 18: 4756,

1991.

50. Harrison AJ and Gaffney S. Motor

development and gender effects on SSC

performance. J Sci Med Sport 4:

406415, 2001.

51. Hewett TE, Myer GD, and Ford KR.

Decrease in neuromuscular control about

the knee with maturation in female

athletes. J Bone Joint Surg Am 86:

16011608, 2004.

52. Hewett TE, Zazulak BT, and Myer GD.

Effects of the menstrual cycle on anterior

cruciate ligament injury risk: A systematic

review. Am J Sports Med 35: 659668,

2007.

53. Hoff J, Helgerud J, and Wisloff U. Maximal

strength training improves work economy

in trained female cross-country skiers.

VOLUME 34 | NUMBER 3 | JUNE 201270

Youth Physical Development Model

Med Sci Sports Exerc 31: 870877,

1999.

54. Huppert FA, Baylis N, and Keverne B.

Introduction: Why do we need a science

of well-being? Philos Trans R Soc Lond B

Biol Sci 359: 13311332, 2004.

55. Isaacs LD. Comparison of the vertec and

just jump systems for measuring height of

vertical jump by young children. Percept

Mot Skills 86: 659663, 1998.

56. Jeffreys I. Motor learningApplications for

agility, part 1. Strength Cond J 28:

7276, 2006.

57. Katzmarzyk PT, Malina RM, and Beunen GP.

The contribution of biological maturation

to the strength and motor fitness of

children. Ann Hum Biol 24: 493505,

1997.

58. Kelly PJ, Twomey L, Sambrook PN, and

Eisman JA. Sex differences in peak adult

bone mineral density. J Bone Miner Res

5: 11691175, 1990.

59. Kirk D. Physical education, youth sport

and lifelong participation: The importance

of early learning experiences. Eur Phys

Edu Rev 11: 239255, 2005.

60. Lanyon LE. Functional strain in bone

tissue as the objective and controlling

stimulus for adaptive bone remodeling.

J Biomech 20: 10831095, 1987.

61. Lanyon LE and Rubin CT. Static versus

dynamic loads as an influence on bone

remodeling. J Biomech 12: 897907,

1984.

62. Lloyd RS, Brewer C, Faigenbaum AD,

Jeffreys I, Moody J, Myer GD, Oliver JL,

Pierce K, and Stone MH. United Kingdom

Strength and Conditioning Association

position statement on youth resistance

training. Prof Strength Cond J In press.

63. Lloyd RS, Meyers RW, and Oliver JL. The

natural development and trainability of

plyometric ability during childhood.

Strength Cond J 33: 2332, 2011.

64. Lloyd RS, Oliver JL, Hughes MG, and

Williams CA. Effects of 4-weeks

plyometric training on reactive strength

index and leg stiffness in male youths.

J Strength Cond Res 2012, in press.

DOI: 10.1519/JSC.0b013e318242d-

2ec.

65. Lloyd RS, Oliver JL, Meyers RW, Moody J,

and Stone MH. Long-term athletic

development and its application to

youth weightlifting. Strength Cond J

2012, in press. DOI: 10.1519/

SSC.0b013e31825ab4bb.

66. Lubans DR, Morgan PJ, Cliff DP, Barnett LM,

and Okely AD. Fundamental movement

skills in children and adolescents. Sports

Med 40: 10191035, 2010.

67. Malina RM. Growth, maturation and

development: Applications to young

athletes and in particular to divers. In:

USA Diving Coach Development

Reference Manual. Malina RM and

Gabriel JL, eds. Indianapolis, IN: USA

Diving, 2007. pp. 329.

68. Malina RM, Bouchard C, and Bar-Or O.

Growth, Maturation, and Physical Activity.

Champaign, IL: Human Kinetics, 2004.

pp. 4177.

69. McGuigan MR, Tatasciore M, Newton RU,

and Pettigre S. Eight weeks of resistance

training can significantly alter body

composition in children who are

overweight or obese. J Strength Cond

Res 23: 8085, 2009.

70. Mirwald RL, Baxter-Jones AD, Bailey DA,

and Beunen GP. An assessment of

maturity from anthropometric

measurements. Med Sci Sports Exerc 33:

689694, 2002.

71. Miyaguchi K and Demura S. Relationships

between muscle power output using the

stretch-shortening cycle eccentric

maximum strength. J Strength Cond Res

22: 17351741, 2008.

72. Murphy DF, Connolly DAJ, and Beynnon BD.

Risk factors for lower extremity injury: A

review of the literature. Br J Sports Med

37: 1329, 2003.

73. Myer GD, Faigenbaum AD, Ford KR,

Best TM, Bergeron MF, and Hewett TE.

When to initiate integrative neuromuscular

training to reduce sport-related injuries and

enhance health in youth. Curr Sports Med

Rep 10: 157166, 2011.

74. Myer GD, Ford KR, Palum-Bo JP, and

Hewett TE. Neuromuscular training

improves performance and lower-

extremity biomechanics in female athletes.

J Strength Cond Res 19: 5160, 2005.

75. Myer GD, Ford KR, Paterno MV, Nick TG,

and Hewett TE. The effects of generalized

joint laxity on risk of anterior cruciate

ligament injury in young female athletes.

Am J Sports Med 36: 10731080, 2008.

76. Myer GD, Quatman C, Khoury J, Wall E,

and Hewett T. Youth vs. adult

weightlifting injuries presenting to

United States emergency rooms:

Accidental vs. non-accidental injury

mechanisms. J Strength Cond Res 23:

20542060, 2009.

77. National Council on Youth Sports. NCYS

report on trends and participation in

organized youth sports (2008 Edition).

Available at: http://www.ncys.org/pdfs/

2008/2008-ncys-market-research-

report.pdf. Accessed December 23, 2011.

78. Negrete R and Brophy J. The relationship

between isokinetic open and closed

kinetic chain lower extremity strength and

functional performance. J Sports Rehab

9: 4661, 2000.

79. Nelson ME, Fiatarone MA, Morganti CM,

Trice I, Greenberg RA, and Evans WJ.

Effects of high-intensity strength training

on multiple risk factors for osteoporotic

fractures. J Am Med Assoc 272:

19091914, 1994.

80. Norris SR. Long-term athlete

development Canada: Attempting system

change and multi-agency cooperation.

Curr Sports Med Rep 9: 379382, 2010.

81. Ntoumanis N and Biddle SJH. A review of

motivational climate in physical activity.

J Sports Sci 17: 643665, 1999.

82. Okely AD, Booth ML, and Patterson JW.

Relationship of physical activity to

fundamental movement skills among

adolescents. Med Sci Sports Exerc 33:

18991904, 2001.

83. Okely AD, Booth ML, and Patterson JW.

Relationship of cardiorespiratory

endurance to fundamental movement skill

proficiency among adolescents. Pediatr

Exerc Sci 13: 380391, 2001.

84. Oliver JL and Lloyd RS. Long-term athlete

development and trainability during

childhood. Prof Strength Cond J. In press.

85. Oliver JL, Lloyd RS, and Meyers RW.

Training elite child athletes: Welfare and

well-being. Strength Cond J 33: 7379,

2011.

86. Padua DA, Arnold BL, Perrin DH,

Gansneder BM, Carcia CR, and Granata KP.

Fatigue, vertical leg stiffness, and stiffness

control strategies in males and females.

J Athl Train 41: 294304, 2006.

87. Philippaerts RM, Vaeyens R, Janssens M,

Van Renterghem B, Matthys D, Craen R,

Bourgois J, Vrijens J, Beunen GP, and

Malina RM. The relationship between

peak height velocity and physical

performance in youth soccer players.

J Sports Sci 24: 221230, 2006.

88. Pierce KC, Brewer C, Ramsey MW, Byrd R,

Sands WA, Stone ME, and Stone MH.

Youth resistance training. Prof Strength

Cond J 10: 923, 2008.

89. Quatman CE, Ford KR, Myer GD, and

Hewett TE. Maturation leads to gender

differences in landing force and vertical

jump performance: A longitudinal study.

Am J Sports Med 34: 806813, 2006.

Strength and Conditioning Journal | www.nsca-scj.com 71

90. Rabinowickz T. The differentiated

maturation of the cerebral cortex. In:

Human Growth: A Comprehensive

Treatise, Postnatal Growth:

Neurobiology. Falkner F and Tanner J,

eds. Vol. 2. New York, NY: Plenum, 1986.

91. Reinboth M, Duda JL, and Ntoumanis N.

Dimensions of coaching behavior, need

satisfaction, and the psychological and

physical welfare of young athletes. Motiv

Emot 28: 297313, 2004.

92. Rhea MR, Peterson MD, Lunt KT, and

Ayllon FN. The effectiveness of resisted

jump training on the VertiMax in high

school athletes. J Strength Cond Res 22:

731734, 2008.

93. Rowland TW. Aerobic response to

endurance training in prepubescent

children: A critical analysis. Med Sci

Sports Exerc 17: 493497, 1985.

94. Rumpf MC, Cronin JB, Oliver JL, and

Hughes MG. Effect of different training

methods on running sprint times in male

youth. Pediatr Exerc Sci In press.

95. Ryan RM and Deci EL. Self-determination

theory and the facilitation of intrinsic

motivation, social development, and

wellbeing. Am Psychol 55: 6878, 2000.

96. Sands WA. Physiology. In: Scientific

Aspects of Womens Gymnastics. Sands

WA, Caine DJ, and Borms J, eds. Basel,

Switzerland: Karger, 2002. pp. 128161.

97. Santos E and Janeira MA. Effects of

complex training on explosive strength in

adolescent male basketball players.

J Strength Cond Res 22: 903909,

2008.

98. Schoenfeld BJ. The mechanisms of

muscle hypertrophy and their application

to resistance training. J Strength Cond

Res 24: 28572872, 2010.

99. Sheppard JM and Young WB. Agility

literature review: Classifications, training

and testing. J Sports Sci 24: 919932,

2006.

100. Smith DJ. A framework for understanding the

training process leading to elite performance.

Sports Med 33: 11031126, 2003.

101. Smith RE, Smoll FL, and Cumming SP.

Motivational climate and changes in young

athletes achievement goal orientations.

Motiv Emot 33: 173183, 2009.

102. Stafford I. Coaching for Long-Term

Athlete Development: To Improve

Participation and Performance in Sport.

Leeds, United Kingdom: Sports Coach

UK, 2005.

103. Stodden DF, Goodway JD, Langendorfer SJ,

Roberton MA, Rudisill ME, Garcia C,

and Garcia LE. A developmental

perspective on the role of motor skill

competence in physical activity: An

emergent relationship. Quest 60:

290306, 2008.

104. Stone MH, Sanborn K, OBryant HS,

Hartman M, Stone ME, Proulx C, Ward B,

and Hruby J. Maximum strength-power-

performance relationships in collegiate

throwers. J Strength Cond Res 17:

739745, 2003.

105. Stratton G, Jones M, Fox KR, Tolfrey K,

Harris J, Maffulli N, Lee M, and Frsotick

SP. BASES position statement on

guidelines for resistance exercise in

young people. J Sports Sci 22: 383390,

2004.

106. Teeple JB, Lohman TG, Misner JE,

Boileau RA, and Massey BH. Contribution

of physical development and muscular

strength to the motor performance

capacity of 7 to 12 year old boys. Br J

Sports Med 9: 122129, 1975.

107. Theeboom M, De Knop P, and Weiss MR.

Motivational climate, psychological

responses, and motor skill development in

childrens sport: A field-based

intervention study. J Sport Exerc Psychol

17: 294311, 1995.

108. Vaeyens R, Lenoir M, Williams MA, and

Philippaerts RM. Talent identification and

development programmes in sport.

Sports Med 38: 703714, 2008.

109. Valovich-McLeod TC, Decoster LC, Loud

KJ, Micheli L, Parker JT, Sandrey MA, and

White C. National Athletic Trainers

Association position statement:

Prevention of pediatric overuse injuries.

J Athl Train 46: 206220, 2011.

110. Viru A, Loko J, Harro M, Volver A,

Laaneaots L, and Viru M. Critical periods

in the development of performance

capacity during childhood and

adolescence. Eur J Phys Educ 4:

75119, 1999.

111. Vuori I, Heinonen A, Sievanen H, Kannus

P, Pasanen M, and Oja P. Effects of

unilateral strength training and detraining

on BMD and content in young women: A

study of mechanical loading and

deloading in human bones. Calcif Tissue

Int 55: 5967, 1994.

112. Wang CKJ and Biddle SJH.

Understanding young peoples motivation

towards exercise. In: Intrinsic Motivation

and Self-Determination in Exercise and

Sport. Hagger MS and Chatzisarantis

NLD, eds. Champaign, IL: Human

Kinetics, 2007. pp. 193208.

113. Weber G, Kartodiharjo W, and Klissouras V.

Growth and physical training with

reference to heredity. J Appl Physiol 40:

211215, 1976.

114. Weyand PG, Sternlight DB, Bellizzi MJ,

and Wright S. Faster top running speeds

are achieved with greater ground forces

not more rapid leg movements. J Appl

Physiol 89: 19911999, 2000.

115. Whalen RT and Carter DR. Influence of

physical activity on the regulation of bone

density. J Biomech 21: 825837, 1988.

116. Wisloff U, Castagna C, Helgerud J, Jones R,

and Hoff J. Strong correlations of maximal

squat strength with sprint performance

and vertical jump height in elite soccer

players. Br J Sports Med 38: 285288,

2004.

117. Witzke KA and Snow CM. Effects of

plyometric jump training on bone mass in

adolescent girls. Med Sci Sports Exerc

32: 10511057, 2000.

118. Wong P, Chamari K, and Wisloff U.

Effects of 12-week on-filed combined

strength and power training on physical

performance among U-14 young soccer

players. J Strength Cond Res 24:

644652, 2010.

119. Young WB. Transfer of strength and

power training to sports performance. Int

J Sports Physiol Perform 1: 7478,

2006.

120. Young WB, James R, and Montgomery I.

Is muscle power related to running

speed with changes of direction?

J Sports Med Phys Fitness 43:

282288, 2002.

VOLUME 34 | NUMBER 3 | JUNE 201272

Youth Physical Development Model