ACL Injury Prevention in the Female Athlete: WHO, WHAT , and HOW?

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ACL Injury Prevention in the Female Athlete WHO,
WHAT , and HOW?

• Jill Thein-Nissenbaum, PT, DSc, SCS, ATC
• Assistant Professor, UW-Madison
• Staff PT, Badger Athletics
• thein_at_pt.wisc.edu

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Objectives

• WHO determine the age at which ACL prevention
  programs can be successfully implemented
• WHAT Identify the content of a successful ACL
  prevention program, including frequency and
  duration
• HOW identify the best verbal and visual motor
  learning strategies to deliver the information

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Brief History

• Injury to the anterior cruciate ligament (ACL)
  occurs 4-6x more frequently in female athletes
  vs. males in similar sports
• 125,000 ACL reconstruction surgeries performed
  in the US/year
• gt10,000 articles related to ACL on Medline
• Do ACL prevention programs work?

Myer, Am J Sports Med, 2013
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The Good News

• Strong evidence for a significant, positive
  effect of prevention programs 62 reduction
  (meta-analysis with 8 studies)
• Training interventions have a preventive effect
  on ACL tears (systematic review with 9 studies)
• ACL tear reduction by approximately 50, lots of
  variance (meta-analysis with 14 studies, n
  27,000)

Sadoghi, JBJS, 2012
Stojanovic, Res Sports Med, 2012
Gagnier, Am J Sports Med, 2013
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ACL reduction expectation

• On average, intervention programs can drop risk
  by about 50 (risk is cut approximately in half)
  which is a huge effect on relative risk provided
  by neuromuscular training

Hewett, IJSPT, 2010
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The Challenge

• No conclusive evidence supporting any one
  specific type of intervention
• Various types of neuromuscular and educational
  interventions
• The concern At the end of the day, individuals
  who have torn their ACL-regardless of how it is
  managed-have knee OA at a rate 10x those without
  an ACL injury

Sadoghi, JBJS, 2012
Stojanovic, Res Sports Med, 2012
Gagnier, Am J Sports Med, 2013
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Objectives

• WHO determine the age at which ACL prevention
  programs can be successfully implemented
• WHAT Identify the contents of a successful ACL
  prevention program, including frequency and
  duration
• HOW identify the best verbal and visual motor
  learning strategies to deliver the information

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The Active Youth

• Youth sport participation has significantly
  increased over the past decade and children are
  starting sport at an earlier age
• The 2008 Physical Activity Guidelines for
  Americans recommends youth (ages 6 to 17)
  include muscle and bone strengthening
  exercises in their exercise regimens.
• When are children capable of understanding the
  fundamentals of movement and performance?

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The Window of Opportunity

• Meta-analysis of timing of initiation of
  prevention programs on ACL reduction (14 clinical
  trials)
• ACL injuries reported
• NMT intervention that aimed at decreasing ACL
  tears
• A control group
• Prospective controlled trial study design
• Females
• RESULTS Significantly greater knee injury
  reduction in female athletes in prevention
  programs vs. controls (OR 0.54 95 CI 0.35,
  0.83)

Myer, Am J Sports Med, 2013
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The Window of Opportunity

• Reduction rankings
• 1Mid-teens (14-18y), 72 reduction rate
• 2 Late teens (18-20y), 52 reduction rate
• 3 Early adults (gt20y), 16 reduction rate
• May be optimal to implement NMTprograms during
  pre or early adolescence.

Myer, Am J Sports Med, 2013
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How Young is TOO Young?

• Compare the effects of traditional and
  age-specific pediatric ACL prevention programs on
  lower extremity biomechanics during a cutting
  task in youth athletes
• 65 youth soccer athletes (38 boys, 27 girls) age
  9-11, participated in the 9-week program (12-14
  minutes, 2-3x/week)
• Teams were clustered (1) pediatric injury
  prevention program, (2) a traditional injury
  prevention program, or (3) a control group and
  performed the program as part of warm-up

DiStefano, Am J Sports Med, 2011
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How Young is TOO Young?

• The Pediatric Program
• High repetitions of BW strengthening exercises,
  gradual increase in training sessions per week.
  Slowly implemented plyometric exercises
• Provided constant verbal feedback and cues such
  as bend your knees and keep your toes
  straight ahead
• Progressions included a lot of variety, which may
  improve motivation and compliance

DiStefano, Am J Sports Med, 2011
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How Young is TOO Young?

• Results
• The Pediatric Group lower peak internal knee
  rotation at initial contact of a cutting
  maneuver, but no sagittal or frontal plane
  changes were observed
• The Traditional Training Group no changes
• These findings suggest limited effectiveness of
  both programs for athletes younger than 12 years
  of age in terms of biomechanics during a cutting
  task.

DiStefano, Am J Sports Med, 2011
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Objectives

• WHO determine the age at which ACL prevention
  programs can be successfully implemented
• WHAT Identify the contents of a successful ACL
  prevention program, including frequency and
  duration
• HOW identify the best verbal and visual motor
  learning strategies to deliver the information

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Meta-analyses of prevention programs

• No conclusive evidence supporting any one type of
  intervention
• No superiority of balance board exercises, new
  protocols over older ones
• Moderate evidence to support the use of
  stretching, proprioception, strength, plyometric
  and agility drills with additional verbal and/or
  visual feedback on proper landing technique
• Unable to determine which program components were
  most or least effective.

Sadoghi, JBJS, 2012
Stojanovic, Res Sports Med, 2012
Gagnier, Am J Sports Med, 2013
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PEP Program

• Prevent injury and Enhance Performance (PEP)
  Program
• Warm-up, stretching, strengthening, plyometrics,
  and sport specific agility exercises for soccer
• Performed on the field before practice no extra
  specialized equipment
• 19 components
• 20 minutes
• 3x/week

Gilchrist, Am J Sports Med, 2008
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PEP in 14-18 yo females

• gt1000 female athletes in the intervention group
  (education, stretching, strengthening,
  plyometrics, and sports-specific agility drills)
• gt1900 female athletes in the control group
  (traditional warm-up)
• Year 1 88 decrease in ACL injury rate in the
  intervention group as compared to the control
  group
• Year 2 74 reduction

Mandelbaum, Am J Sports Med, 2005
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PEP in NCAA DI females

• 61 female soccer teams consisting of 1435
  athletes(852 control athletes 583 intervention)
• ACL rate in the intervention group was 1.7 x less
  than in the control athletes (41 decrease)
• Intervention athletes with a history of ACL
  injury were significantly less likely to suffer
  another ACL tear compared to controls with
  previous ACL tears
• Santa Monica Sports Medicine Foundation and the
  PEP (Prevent Injury and Enhance Performance)
  Program http//smsmf.org/smsf-programs/pep-program
  

Gilchrist, Am J Sports Med, 2008
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11

• 125 soccer clubs in Norway followed for one
  league season (eight months)
• Participants were 1892 female players aged 13-17
  
• Intervention Comprehensive warm-up program to
  improve strength, awareness, and neuromuscular
  control during static and dynamic movements

Soligard, BMJ, 2008
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Soligard, BMJ, 2008
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• In the intervention group, there was a
  significantly lower risk of severe injuries,
  overuse injuries, and injuries overall

Soligard, BMJ, 2008
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HarmoKnee Program

• Goals
• Increase awareness of injury risk
• To provide a structured warm-up program
• To provide strengthening exercises that produces
  less strain to the knee joint
• Swedish female soccer players age 13-19

Kiani, Arch Intern Med, 2012
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HarmoKnee Program

• The training program implemented at a practice
  session athletes and coaches were trained in the
  correct way to perform and teach the exercises
• 5 parts warm-up, muscle activation, balance,
  strength, and core stability
• Integrated into the regular soccer practice
  sessions with no additional equipment

Kiani, Arch Intern Med, 2012
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HarmoKnee Program

• 94 of intervention teams reported gt75
  compliance
• Control group 13 knee injuries (5 ACL tears)
• Intervention group 3 knee injuries (NO ACL
  tears)
• A 77 reduction in knee injury incidence and a
  90 reduction in noncontact knee injury incidence

Kiani, Arch Intern Med, 2012
26
Programs Summarized

• PEP (RR 0.18, CI 0.08 to 0.42) 82 reduction
• The PEP also significantly reduced the risk of
  recurrence in those with previous non-contact ACL
  injuries (P 0.046)
• HarmoKnee (RR 0.22, CI 0.06 to 0.76) 78
  reduction
• The 11 program (RR 0.48, CI 0.32 to 0.72) 52
  reduction

Herman, BMC Medicine, 2012
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Rankings Systematic Review

• Effectiveness of neuromuscular warm-ups
• PEP most effective in reducing ACL injuries
• 11 and HarmoKnee significant reduction of knee
  injury risk

Herman, BMC Med, 2012
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ACL prevention programs are successful

• Especially adolescent female soccer players
• Mostly done as warm-up
• Little to no equipment
• Some strength training, some plyometric activity
  and some balance

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Frequency

• Agreement that an ACL prevention program should
  include at least 10 minutes of exercises 3x/week,
  as a bare minimum
• Most studies report performing 15-20 minutes
  of activity
• Determined that the estimated protective effect
  was relatively stronger in studies involving more
  training time each week and in those studies with
  better compliance

Sadoghi, JBJS, 2012
Gagnier, Am J Sports Med, 2013
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Duration

• Programs should begin prior to season, at least 6
  weeks pre-season
• Most studies recommend 8 or more weeks in
  duration to allow sufficient neuromuscular
  changes and performance training effects
• Ideally, the program can be continued throughout
  the season, at a lower frequency or duration
  (i.e.-cut the warm-up to 10-15 minutes if
  necessary)

Sadoghi, JBJS, 2012
Voskanian, Curr Rev Musculoskelet Med, 2013
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Numbers Needed to Treat

• Determine overall ACL injury risk in female
  athletes through relative risk reduction (RRR)
  and numbers needed to treat (NNT)
• 12 studies, Systematic review (ish)
• To prevent one ACL in one competitive season
  108
• PEP (82 reduction) 70
• HarmoKnee (78 reduction) 72
• The 11 program (52 reduction) 28 (?)

Sugimoto, BR J Sports Med, 2012
Herman, BMC Medicine, 2012
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Components of an Injury Prevention Program

• Muscle strengthening
• Plyometrics
• Neuromuscular training / control / balance
• Education and feedback regarding body mechanics
  and proper landing patterns in a dynamic
  atmosphere (HOW)

Voskanian, Curr Rev Musculoskelet Med , 2013
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Weeks 1-3
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Weeks 4-6
Sagittal plane plyometrics get bigger, start
introducing single leg impact and light
plyometrics
Impact and landing still stressed, add frontal
and transverse planes movements, progress balance
Combined movements that incorporate multiple
muscles, start sagittal, then progress to frontal
and transverse planes, less isolated
strengthening
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Weeks 7
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Objectives

• WHO determine the age at which ACL prevention
  programs can be successfully implemented
• WHAT Identify the contents of a successful ACL
  prevention program, including frequency and
  duration
• HOW identify the best verbal and visual motor
  learning strategies to deliver the information

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Motor Learning

• Prevention programs most likely address the
  impairments that need to be addressed.
• Laboratory data show improvements in jumping and
  landing techniques.
• However, ACL tears are still happening at a
  fairly high rate.
• Is something lost in transition from conscious
  awareness during training / rehabilitation
  sessions to automatic movements during practice /
  competition?

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3 Stages of Motor Learning

• Cognitive conscious attempt to determine what
  exactly needs to be done, step by step. This
  requires considerable attentional capacity.
• Associative basic movement pattern is acquired
  the movement outcome is more reliable, movements
  are more consistent, automatic, and economical.
• Autonomous fluent and seemingly effortless
  motions that are accurate, consistent, and
  efficient. The skill is performed largely
  automatically and requires little or no attention.

Benjaminse, JOSPT, 2015
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Explicit Motor Learning

• Explicit motor learning acquiring motor skills
  with an internal focus on their movement pattern
• Focus is on HOW the individual is moving
• Land with your knees flexed
• Land with your feet shoulder-width apart
• Focus on the quality of movement
• Land in the knee-over-toe position
• http//youtu.be/ctFmp_TQqkI

Benjaminse, Knee Surg Sports Traumatol Arthrosc ,
2011
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Explicit Motor Learning

• Less resilient under psychological and
  physiological fatigue
• Less durable when a fast response is required
• Less efficient, attention demanding, and slow
• May be affected to by an individuals
  intelligence
• Extensively repeating the ideal movement that is
  explained and demonstrated might be too
  cognitive.

Benjaminse, JOSPT, 2015
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Explicit Motor Learning

• Results in an increase of co-contraction,
  resulting in a stiff landing and recruiting
  unnecessary motor units
• In a lab setting, using explicit cues, jump
  forces and landing techniques immediately
  improved one week later, retention was POOR
• Clinicians provide explicit feedback 95 of the
  time.

Prapavessis, JOSPT, 2003
Durham, Physiother Research Inter, 2009
Lohse, Acta Psychologica, 2012
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Implicit Motor Learning

• Implicit motor learning acquisition of a motor
  skill without the concurrent acquisition about
  the performance of a skill
• Implicit learning has an external focus, directed
  at the outcome of movements (end result, such as
  Imagine sitting down on a chair when landing)

Benjaminse, Knee Surg Sports Traumatol Arthrosc ,
2011
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Implicit Motor Learning

• Implicit learning includes observation and
  imitation of a drill or activity this
  observation plays an important role
• Copying of observed body movements

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Implicit Motor Learning

• Shortens the cognitive and associative stages of
  motor learning
• Enhances skill acquisition more efficiently and
  increases the potential to transfer to sport with
  its complex motor skills
• Example with jumping and landing, implicit
  learning results in more efficient EMG activity,
  greater knee flexion, and reduced vertical ground
  reaction forces

Benjaminse, Phys Ther in Sport, 2014
Benjaminse, JOSPT, 2015
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Research Supports Implicit Learning

• Jump height with Vertec was better with
  instruction to concentrate on the rungs of the
  Vertec vs. the tips of their fingers
• Instructing subjects to jump towards a target
  resulted in superior jump distance vs.
  instructing subjects to extend their knees as
  rapidly as possible
• Land more softly by listening to the sound of the
  landing resulted in significant lower GRF
  compared to the control group.

McNair, Br J Sports Med, 2000
Wu, J Strength Cond Res, 2012
Bredin, Applied Phys Nutr Metab, 2013
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How does Implicit Learning work?

• The premotor cortex has a role in preparation and
  execution of movements utilization of the
  premotor cortex may reduce brain resources needed
  for movement control, allowing more free space
  to focus on other game factors (i.e., other
  athletes, field conditions, and position of the
  ball).

Benjaminse, JOSPT, 2015
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Implicit Learning and Mirror Neurons

• Mirror neurons are housed in the premotor / motor
  areas. They fire both when an action is performed
  AND when a similar or identical action is
  passively observed
• A KEY aspect of mirror neurons is their ability
  to link visual and motor properties.

Benjaminse, Knee Surg Sports Traumatol Arthrosc ,
2011
48
Mirror Neurons

• Mirror neurons map observed movements onto a
  motor program and your brain develops a template
  of the movement
• This motor map of the observed action corresponds
  to that which is spontaneously generated during
  active action.

Benjaminse, Knee Surg Sports Traumatol Arthrosc ,
2011
Rizzolatti, Annu Rev Neurosci, 2004
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Mirror neurons were discovered in the 1990s, when
researchers found neurons in the brains of
macaque monkeys that fired both when the monkeys
grabbed an object and also when the monkeys
watched another primate grab the same object.
(Rizzolatti)
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Mirror Neurons

• Amount of mirror neuron activation correlates
  positively when the athletes are already
  proficient in performing that skill
• Stronger mirror neuron activation is found when
  observing the same gender

Benjaminse, Knee Surg Sports Traumatol Arthrosc ,
2011
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SO.

• Is the solution to injury prevention hidden in
  the brains of the subjects themselves?
• Maybe it IS all in their head (mirror neurons)
  AND what we say (external focus / implicit
  learning)!!!

Benjaminse, Knee Surg Sports Traumatol Arthrosc ,
2011
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Example Learning and Single Leg Hop

• Implicit learning vs. explicit learning on single
  leg hop jump distance and knee kinematics in
  patients after ACLR. (N16)
• Internal focus (explicit learning) Jump as far
  as you can. While you are jumping, I want you to
  think about extending your knees as rapidly as
  possible.
• External focus (implicit learning) Jump as far
  as you can. While you are jumping, I want you to
  think about pushing yourself off as hard as
  possible from the floor.
• Measured numerous variables related to landing

Gokeler, PT in Sport, 2014
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Example Learning and Single Leg Hop

• External focus (implicit learning) group had
• larger knee flexion angles at initial contact
• greater peak knee flexion
• greater total ROM
• Concluded hopped farther with less valgus, more
  knee flexion with external focus (implicit
  learning)

Gokeler, PT in Sport, 2014
56
Example Plyometrics

• External focus (implicit learning) resulted in
  higher jump-and-reach heights, greater force and
  more knee flexion vs. using an internal focus of
  attention
• Focusing on an external object, such as a Vertec
  or hanging ball, is considered positive feedback,
  which increases motivation

Wulf, J Mot Behav, 2009
Makaruk, J Sports Med Phys Fitness, 2012
57
Implicit Learning Method Dyad Training

• Fancy way of saying Watch your partner
• A visual example (dyad) of a teammate performing
  the task can increase the effectiveness of
  feedback and training methods without an
  excessive cost of time
• A combination of observation and practice can
  result in more effective and cumulative learning
  than either type alone.

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Example Dyad Training

• Balance on a stabilometer in healthy college
  students goal was to keep the platform
  horizontal for as long as possible during a
  90-second trial. Success was the time horizontal.
  
• RESULTS Alternating between practice forms
  (physical, observational, and dialog with a
  partner) was more effective in retention than
  individual, isolated practice.
• BONUS The benefits of dyad training transfer to
  situations where participants have to perform the
  movement individually.

Shea, J Mot Behav, 1999
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Benefits of Dyad Training

• Athletes may set goals at a higher level of
  difficulty, after seeing what their peer can do.
  (Motivational)
• Training with a partner and sharing learning
  strategies might increase the athletes feeling
  of responsibility and they may take ownership of
  the task.

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Video Feedback

• Imitation activates the mirror neurons, which
  link visual input with motor output.
• Can observe skilled or unskilled athlete.
  (Observing lower skill can positively affect
  learning.)
• Viewing either a correct model or learning model
  was equally effective in learning correct squat
  form.
• Observation of lower skill level helps identify
  movement deficits and assists the athlete to
  develop strategies to correct their own errors.
• Ubersense, Dartfish, Coachs Eye, or BaM Video
  Delay

Benjaminse, JOSPT, 2015
McCullagh, Exerc Sport Sci Rev, 1989
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Frequency of Feedback

• A high frequency of feedback that promotes an
  external focus (implicit learning) is superior to
  a low feedback frequency in athletes.
• In contrast, a high frequency of feedback that
  promotes an internal focus (explicit learning),
  was shown to be detrimental to learning.
• Research supports giving the athlete some control
  over frequency of feedback in a practice session
  (may enhance motor learning)
• Athletes are fairly good at self-assessing

Chiviacowsky, Front Psychol, 2012
62
Summary Motor Learning
Cognitive Associative Autonomous

• The transition from conscious awareness to
  automatic movements involves complicated motor
  learning this might not fit in explicit learning
  strategies
• An external focus (implicit learning) may get an
  athlete to the autonomous stage of motor control
  faster and improve performance.
• A focus on the movement outcome promotes the
  utilization of unconscious or automatic processes

Benjaminse, Knee Surg Sports Traumatol Arthrosc ,
2011
63
Implicit Learning Applications

• The ability for individuals to view themselves
  performing correctly or making mistakes and
  responding to the corrections is of greater value
  to individuals than is viewing an expert model
  performing the task correctly
• Learning is a problem-solving process the more
  involved the individual is in analyzing his or
  her own performance, the greater the learning
  value

Benjaminse, Knee Surg Sports Traumatol Arthrosc ,
2011
64
Implicit Learning Applications

• Provide opportunities for the athlete to watch /
  observe the expected movement patterns
• Team Practice!! (Re-think what the athlete is
  doing during team practice, perhaps they should
  be intently WATCHING!)
• Provide opportunities for athlete to watch
  themselves, self-assess, and re-try the movement
  
• Video works well (iPad, phone)
• Mirrors
• Watch your words!
• Focus is on the GOAL, not the process. Jump out
  as far as you can towards the cone

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Put it all together 3 objectives
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Recommendations WHO

• Although there are limitations, implementation of
  an ACL injury prevention is advisable No study
  has demonstrated any significant detrimental
  effects
• Age at or prior to the onset of puberty (12
  1, start by 14, and not lt 10)
• Consider pre-season risk assessment by a
  qualified healthcare provider to identify those
  at greatest risk of large benefit (I would argue
  to avoid singling out individuals)

Dai, Res Sports Med, 2012
67
Key Elements WHAT

• Duration 6-8 weeks prior to the sport and during
  season
• Frequency 3x/week pre-season and 2x/week
  mid-season
• Length at least 15 minutes

Voskanian, Curr Rev Musculoskelet Med, 2013
68
Recommendations WHAT

• Dynamic warm-up is a strong option can use
  throughout pre- and in-season practice
• Strengthening exercises and FUNDAMENTAL MOVEMENT
  PATTERNS (with body weight) should be considered
  with younger athletes in particular
• Add impact, landing and plyometrics as a
  progression
• Balance training has also shown some positive
  results, but it may require additional equipment

Dai, Res Sports Med, 2012
69
Recommendations HOW

• Challenges with cueing and feedback!
• Implicit motor learning with an external focus is
  best
• Delivery Demonstration (does not have to be
  expert). Consider partner drills (watch each
  other), use of mirror or videotaping.
• Use cues like land quietly on your feet, sit
  back as if you were sitting in a chair, jump
  towards the farthest cone

Dai, Res Sports Med, 2012
70
Thanks!
I hear and I forget I see and I remember I do and
I understand Confucius