Re training Movement Behavior for ACL Injury Prevention and Rehabilitation: A Matter of Strength or Motor Control?

Transcription

1 Re training Movement Behavior for ACL Injury Prevention and Rehabilitation: A Matter of Strength or Motor Control? Christopher M. Powers, PT, PhD, FACSM, FAPTA Beth Fisher, PT, PhD, FAPTA Division of Biokinesiology & Physical Therapy Session Outline Introduction (Powers) Movement impairments and ACL injury risk (Powers) Retraining movement behavior: Strength or control? (Fisher) The role of practice variables in movement retraining & motor learning (Fisher) Integrating motor learning principles in designing an intervention program to change movement behavior associated with ACL injury risk (Powers) Q & A Movement Behavior Associated With ACL Injury Movement Performance Institute How do ACL injuries occur? 70% of injuries are noncontact Running & cutting Landing from a jump 30% are contact fouls, tackling from behind ACL injured athletes often recall unanticipated event, perturbation, or loss of concentration Mechanism of Injury (Kirkendall and Garrett, 2000) Deceleration/Change in direction Knee flexion 0 30 degrees Tibial rotation and varus/valgus forces

2 Gender Bias Incidence of ACL injury in females is 4 8 times that of males. Arendt et al., 1995 Hutchinson et al., 1995 Malone et al., 1993 High risk group: females years. Each year, one out of 100 high school female athletes and one of 10 college female athletes experiences an ACL injury Adams et al., 2002 Non contact ACL Injury: Categorical Risk Factors I. Structural II. Hormonal III. Biomechanical IV. Neuromuscular Normal Function Injury threshold Movement Impairements & ACL Injury Risk Biomechanical Risk Factors Kinematics hip and knee flexion knee valgus hip internal rotation Kinetics knee valgus moments knee extensor moments hip extensor moments Muscle activation patterns quadriceps activity gluteus max activity Pollard, et al Sigward & Powers, 2007 Pollard, et al., 2009 Neuromuscular Control and Valgus Loading of the Knee Predict ACL Injury Risk in Female Athletes Hewett et al. Am J Sports Med, 2005 Prospective study of 205 female athletes Those who tore their ACL during the course of a season demonstrated knee valgus moments that were 2.5 times greater than those who did not tear their ACL

3 Biomechanical Assessment: Drop Jump Females: Knee Strategy Females Increased Knee Extensor Moments Males: Strategy Increased Quadriceps Activation Decreased Extensor Moments Decreased Glut Max EMG Increased valgus loading at the knee Pollard et al, Clin Biomech, 2010 Knee Strategy Males Decreased Knee Extensor Moments Decreased Quadriceps Activation Greater Utilization of the Extensors is Associated with Decreased Valgus Moments & Angles Increased Extensor Moments Increased Glut Max EMG Decreased valgus loading at the knee Strategy Pollard et al, Clin Biomech, 2010 Pollard et al, Clin Biomech, 2010

4 Extensor Gluteus Maximus: The Tri planar Muscle 3.0 Knee ratios Moments & Energy Absorption Males vs. Females Knee/hip moment ratio 4.0 Knee/hip energy absorption ratio Abductor males females 1.5 males females External Rotator pre -pubertal pubertal post -pubertal young adult pre-pubertal pubertal post-pubertal young adult Sigward et al., Scand J Sports Med Sci Sports (2011) Sex Differences in Behavior What are the Underlying Reasons? Peripheral factors? (muscle performance deficits) and/or Central factors? (motor control deficits) Abnormal Distribution of the and Knee Moments in Females Why? extensor weakness relative to quadriceps Quadriceps overuse Increased ACL loading (anterior shear) Knee Moment Ratios Associated with Knee Strength Ratios Biomechanical Assessment: Side Step Cut Female Knee/ Strength Ratio Male: Knee/ Strength Ratio knee Only extensor17% of the hip extensor variance in movement behavior could be explained by strength knee extensor hip extensor Stearns & Powers, Med Sci Sport Exerc, 2013

5 Causes of Valgus Loading at the Knee Ground reaction force vector moves lateral shifting of COM lateral Medial movement of the knee joint center adduction & internal rotation Female Sigward & Powers, Clin Biomech, 2006 Male Combination of both Female Male Trunk Lean & Knee Valgus Torque average hip internal rotation angle ER IR ( ) males females Pollard, Sigward & Powers, Am J Sports Med, 2006

6 Gluteus Maximus: The Tri planar Muscle Extensor Abductor External Rotator Impaired Gluteus Maximus Muscle Performance & ACL Injury Sagittal Plane Gluteus Maximus Activity Frontal/Transverse Plane Adduction & Int. Rotation Quadriceps Activity Knee Joint Anterior Shear Knee Valgus Angle External Knee Valgus Moment Prospective study of 501 Soccer athletes Risk of ACL injury? Those who tore their ACL during the course of a season had weaker hip abductors than those who did not tear their ACL. Behavioral Changes Following ACL Injury Prevention Training PEP Program Prevent injury and Enhance Performance 1. Agilities 2. Flexibility 3. Strengthening 4. Plyometrics 5. Technique

7 PEP Program Series of warm up, stretching, strengthening, plyometric and sports specific agility drills. 2 3 times a week prior to soccer practice 20 minutes/session (12 week season) Results: Year 1 Mandelbaum et al. Am J Sports Med, 2005 Control: 32 ACL s in 1901 athletes Enrolled: 2 ACL s in 1041 athletes 88% reduction in ACL tears Results: Year 2 Mandelbaum et al. Am J Sports Med, 2005 Control: 35 ACL s in 1913 athletes Enrolled: 4 ACL s in 844 athletes 74% reduction in ACL tears Pre-training biomechanical analysis ACL injury prevention program Post-training biomechanical analysis Improved Kinematics Following PEP Training Decreased hip internal rotation Decreased hip adduction Knee/ Extensor Moment Ratio Drop Jump * Pre- training Post-training *Decreased knee extensor moment Pollard et al., Clin J Sports Med, 2006 Pollard et al. (In review)

8 ACL Injury Prevention: Less Dependence on a Knee Strategy Evaluating & Changing Movement Behavior Ready to Return to Sport?? Ready to Return to Sport?? Strengthening or Movement Re education? Movement Training to Minimize Re Injury Risk

9 Shock Absorption Strategy Pelvis Trunk Total Score out of 10 total Adequate = 2 ; Borderline = 1 Inadequate = 0 Shock Absorption Strategy Pelvis Trunk Total Score out of 10 total Adequate = 2 ; Borderline = 1 Inadequate = 0 Performance or Learning?? And now a word from Beth Performance or Learning?? Concurrent Feedback (Manual)

10 Concurrent Feedback (Visual) Concurrent Feedback (Visual) Post Response Feedback Knowledge of Results Observation & Modeling Motivation Motivation Shock Absorption Strategy Pelvis Trunk Total Score out of 10 total Adequate = 2 ; Borderline = 1 Inadequate = 0

11 Motivation Variability in Practice Shock Absorption Strategy Pelvis Trunk Total Score out of 10 total Adequate = 2 ; Borderline = 1 Inadequate = 0 Variability in Practice Internal vs. External Focus of Attention What feedback would you Give? Keep knees apart Bend knees Lean trunk forward Don t let your knees come forward of your toes External Focused Cues Avoid reference to body parts Spread the floor apart when you land Land softly Lean forward Sit back in the chair

12 External Focus of Attention Put your shoe between the lines External Focus of Attention Stretch the band Land Softly Contextual Interference Transfer of Training Technique Part vs. Whole Training