1. 3-Dimensional Motion Analysis 8-cameraVicon system (sampling: 200Hz, filtered:12 Hz) 14 mm reflective markers positioned as shown Force Plates 2 force plates (sampling:1200 Hz, low pass filter: 50 Hz) Measuring Vertical Ground Reaction Force (VGRF) Kin-Com Isokinetic Dynamometer Maximum Voluntary Isometric Contraction (MVIC) Both hamstring and quadriceps Adaptation of Quadriceps and Hamstring Activation Patterns Following Landing Instruction in Patients with ACL Reconstruction Audrey RC Elias, DPT, OCS; Curt D Hammill, MS; Ryan L Mizner, PT, PhD School of Physical Therapy and Rehabilitation Science, The University of Montana, Missoula, MT Introduction Introduction Purpose Subjects Methods Discussion Results To explore changes in activity patterns of the muscles surrounding the knee during and after instruction for improved knee performance in landing More than 200,000 people undergo anterior cruciate ligament (ACL) reconstruction (ACLR) of the knee yearly Risk of re-injury is 1 in 4 to 1 in 7 1 ; healthy athlete injury rate is 1 in 100 (female) and 1 in 500 (male) > 50% show evidence of early onset osteoarthritis within 10 – 15 years 1 The ACLR knee is unable to accept weight and attenuate force normally during high demand activities Fortunately, these movement patterns respond well to training 2 Well-established “optimal” landing strategies Controversy over how optimal landing helps Two Common Alternatives: o Train for “co-contraction” 3 o Train for selective contraction 4 Use hamstrings at the same time as quadriceps “Brace” the joint  responsiveness of the joint Use quadriceps more than hamstrings What changes during training for optimal performance? N = 36 (15 male, 21 female) Mean age = 22.1 ± 4.45 years Tegner Activity Scale = 7.03 ± 1.48 Surgery 26.4 ± 15.7 months prior Inclusion Criteria Unilateral ACLR within 6 – 48 mos Exclusion Criteria ≥ 3 ACL surgeries or bilateral ACLR Medical conditions that could limit function in last 6 months <4 Tegner physical activity scale Dynamic Task Performance 5 minute treadmill walking warmup Single leg landing from 20 cm step 3-5 warm up trials 5 recorded trials before and after training session Motion Analysis, Force Plate, and EMG data collected with focus on weight acceptance phase (contact to peak knee flexion) Standard Training and Instruction 5 – 10 minutes of instruction and practice to adapt landing Visual demonstration and explanation of undesirable landing Followed by instruction and demonstration of desired landing Blocked practice with positive feedback for successful landing “Try to land softly and quietly” “Increase the bending in your knee and use your knee to absorb impact” “Stay balanced over your feet and look straight ahead when you land” Kinematic and Kinetic Analysis Muscle Activation Analysis Delsys Electromyography (EMG) System Surface EMG hamstrings and qudriceps (sampling: 1200 Hz) Bandpass filtered: 20 – 350 Hz Full-wave rectified Low-pass filtered: 12 Hz Linear envelope normalized to MVIC Co-activation index (CI) between hamstrings and quadriceps integrated over interval 50 ms pre-land to peak knee bending CI = (EMG less / EMG more ) + (EMG less + EMG more ) 5 EMG less = activation level of less active muscle EMG more = activation level of more active muscle Performance Improvement with Training Knee Muscle Activation Patterning Muscle CI  significantly Pre-training: 30.4 ± 17.5 Post-training: 22.6 ± 14.6 Paired t -test: p -value < 0.001 Change in patterning primarily correlated to  hamstring activation No change in quadriceps Hamstrings Pre: 22.18 ± 11.27 Post: 17.56 ± 9.39 r = 0.889 Significant improvement in all measures of performance Standard cues tend to train selective recruitment of the knee musculature, rather than bracing Athletes are frequently warned away from “quadriceps-dominance” but: Optimal landing is quadriceps dominant behavior May abnormally increase joint compression during high loading 6 Selective recruitment more adaptive for high intensity tasks References 1.Oiestad BL, Holm I, Aune AK, Gunderson R, Myklebust G, Engebretsen L, Fosdahl MA, Risberg MA. (2010). Knee function and prevalence of knee osteoarthritis after anterior cruciate ligament reconstruction: A prospective study with 10 to 15 years of follow-up. American Journal of Sports Medicine, 38(11): 2201-2210 2.Milner CE, Fairbrother JT, Srivatsan A, Zhang S. (2011). Simple verbal instruction improves knee biomechanics during landing in female athletes. The Knee, 19(4):399-403 3.Hewett TE, DiStasi SL, Myer GD. (2012). Current concepts for injury prevention in athletes after anterior cruciate ligament reconstruction. American Journal of Sports Medicine DOI: 10.1177/0363546512459638 4.Adams D, Logerstedt D, Hunter-Giordano A, Axe MJ, Snyder-Mackler L. (2012). Current concepts for anterior cruciate ligament reconstruction: A criterion-based rehabilitation progression. Journal of Orthopaedic and Sports Physical Therapy, 42(7):601-614 5.Rudolph KS, Axe MJ, Buchanan TS, Scholz JP, Snyder-Mackler L. (2001). Dynamic stability in the anterior cruciate ligament deficient knee. Knee Surg, Sports Traumatol, Arthrosc. 9:62-71 6.Tsai L-C, McLean S, Colletti PM, Powers CM. (2012) Greater muscle co-contraction results in increased tibiofemoral compressive forces in females who have undergone anterior cruciate ligament reconstruction. Journal of Orthopaedic Research, 30:2007-2014 PREPOST Average ± St.Dev; All Comparisons are significantly different p < 0.001 VGRF 3.5 ± 0.39 BW Knee Angle 55° ± 11° VGRF 3.07 ± 0.31 BW Knee Angle 78° ± 11° Representative Single Leg Land EMG Activity 50 ms pre-land to peak knee bending Black: Pre-training; Green: Post-training