Official Journal of the American College of Sports Medicine Vol. 52 No. 5 Supplement S1 A-18 Thematic Poster - Athletic Skills Post ACL 71 Board #2 May 27 9:30 AM - 11:30 AM Reconstruction Individualized Training Improves Inter-limb Joint Kinetic Symmetry During Jump Landing After ACL Wednesday, May 27, 2020, 9:30 AM - 11:30 AM Reconstruction Room: CC-2009 Audrey RC Elias, Ryan L. Mizner. University of Montana, Missoula, MT. 68 Chair: Susan M. Sigward. University of Southern California, Email: [email protected] Los Angeles, CA. (No relevant relationships reported) (No relevant relationships reported) Most athletes with unilateral ACL reconstruction present with reduced knee and hip flexion and asymmetrical vertical ground reaction force (VGRF) and internal knee extension moment during two-legged jump landings. This landing movement pattern 69 Board #1 May 27 9:30 AM - 11:30 AM is associated with low scores on self-reported outcome surveys and may contribute to Kinetic Asymmetry During Squatting And Landing the increased risk of re-injury in athletes with ACL reconstruction. The capacity for Are Associated In Anterior Cruciate Ligament correction of inter-limb asymmetries during landing remains understudied. PURPOSE: To determine whether jump training can correct asymmetrical limb Reconstructed Patients loading and whether corrections are retained over time. Robin Queen, FACSM1, Alexander T. Peebles1, DS Blaise METHODS: An 8-camera motion analysis system with dual force plates collected Williams, III, FACSM2. 1Virginia Tech, Blacksburg, VA. 2Nike, kinematic and kinetic data in a 30cm drop vertical jump to screen 48 potential Beaverton, OR. participants with unilateral ACL reconstruction. Twenty-three athletes (14 women, 23 Email: [email protected] ± 5 years old, 20 ± 15 months post-surgical, Tegner score: 7 ± 2) presented with below- WEDNESDAY, MAY 27, 2020 27, MAY WEDNESDAY, Reported Relationships: R. Queen: Industry contracted research; DJO average knee loading symmetry in landing and poor clinical outcomes, and participated Global. in 8 weeks of twice-weekly high-repetition progressive jump landing training. Subjects re-tested at 4 and 8 weeks. Retention testing was performed after 8 weeks post- High kinetic asymmetry during landing is associated with an increased risk for training. Changes in hip and knee kinematics and kinetics including limb symmetry sustaining a second anterior cruciate ligament (ACL) injury in athletes returning to indices (percent of the uninvolved limb) over time were assessed with paired t-tests. sport following ACL reconstruction (ACL-R). While previous literature has found RESULTS: Peak hip and knee flexion angles in the involved limb increased that ACL-R patients have more kinetic asymmetry than healthy controls during significantly in the drop vertical jump after 4 weeks of training (hip: 78±22 to 92±20, both landing and bilateral squatting, it is currently unknown if landing asymmetry p<0.0001; knee: 86±11 to 96±16, p=0.0001). Symmetry in peak VGRF between limbs during landing increased after the full 8-week training period (83%±18% to 91%±16%, and squatting asymmetry are related in ACL-R patients. PURPOSE: Determine the relationship between landing kinetic asymmetry and squatting kinetic asymmetry in p=0.005). Changes in joint flexion and VGRF were retained for at least 8 weeks after the final training session. Symmetry in knee moment between limbs did not reach a ACL-R patients. METHODS: 34 ACL-R patients (19 male; 73 ± 16 kg; 174 ± 10 cm; 6.0 ± 1.5 months post-operative) signed informed consent and participated in the statistical improvement until final retention tests (Pre: 80%±17%, Post: 86%±12%, study. All participants completed one set of 15 bilateral squats and then ten bilateral p=0.47; Retention: 94%±21%, p=0.004). stop jump trials, while 3D lower extremity kinematics and kinetics were recorded at CONCLUSIONS: Individualized jump training results in normalization of limb 240 Hz and 1920 Hz, respectively. Peak knee extension moment (KEM) and vertical loading symmetry during jump landings. Visible kinematic changes occur early in ground reaction force impulse (GRFI) were computed during the descending phase training, but symmetry in loading of the limb and knee specific kinetic measures take of both tasks. The descending phase was defined between squat initiation and the more time to achieve as they integrate into an athlete’s movement pattern. minimum position of the pelvis during each squat and between initial contact and the minimum position of the pelvis for each stop jump. A limb symmetry index (LSI) was 72 Board #3 May 27 9:30 AM - 11:30 AM computed for peak KEM and GRFI as the difference between the surgical and non- Quadriceps Strength And Rate Of Torque Development surgical leg divided by their average during each squat and each stop jump, and then Are Associated With Countermovement Jump Knee the LSI was averaged across trials. Peak KEM LSI and GRFI LSI were then compared Kinetics Post-aclr between the stop jump and squat trials using Pearson’s correlations. RESULTS: There was a significant relationship between both stop jump kinetic asymmetry outcomes Daniel G. Cobian, Matthew D. Bjork, Sarah A. Gamillo, and both squat kinetic asymmetry outcomes (Table 1). CONCLUSION: Kinetic Mikel R. Stiffler-Joachim, Jennifer L. Sanfilippo, Bryan C. asymmetry during squatting and bilateral landing are associated in ACL-R patients, Heiderscheit. University of Wisconsin-Madison, Madison, WI. which indicates that biofeedback retraining during bilateral squatting could result in Email: [email protected] improvements in bilateral landing symmetry. (No relevant relationships reported) Quadriceps neuromuscular dysfunction is ubiquitous after anterior cruciate ligament reconstruction (ACLR) and can impair knee function during athletic activities. While peak quadriceps strength is often measured, time-dependent metrics such as rate of torque development may be important to sports performance. PURPOSE: To determine the relationships between quadriceps strength, rate of torque development, time since surgery, and knee joint kinetics during jumping in collegiate athletes up to 2 years post-ACLR. METHODS: 31 Division I athletes (age 20.3±1.3, BMI 26.1±3.9 kg/m2, 17 female) performed countermovement jumps (CMJ) on force plates while whole body kinematics were recorded and completed maximal and rapid voluntary isometric knee extension (KE) contractions. Sagittal plane KE impulses were computed for concentric (CON) and landing (LAND) CMJ phases; KE peak torque (PT) and rate of torque development from 20-80% of peak torque (RTD) were extracted from isometric KE efforts. Limb symmetry indices (LSI) were computed and clinically relevant cutoffs of 90% LSI were investigated. A mixed effects model accounted for repeated measurements and assessed the relationships of PT, RTD, and time from surgery with CON and LAND. All possible pairwise interactions were tested. RESULTS: Among 31 athletes, 81 tests were completed 4-24 months post-surgery. PT and RTD were significantly correlated with CON (PT: p=.001, RTD: p=.044) and LAND (PT: p=.009, RTD: p=.008). No significant pairwise interactions between PT, RTD, and time from surgery were detected. Among 24 instances of PT LSI ≥ 90%, mean CON and LAND LSI were 87.3% and 94.2%, respectively. In comparison, among 15 occurrences of RTD LSI ≥ 90%, mean CON and LAND LSI were 93.0% and 102.2%. Among the 22 assessments completed ≥ 1 year post-surgery, mean CON and LAND LSI were 82.4%, and 83.3%, respectively. However, when CON and LAND LSI were ≥ 90%, mean PT was 94.5-94.7% and mean RTD was 85.1-85.3%. CONCLUSIONS: Both peak and rapid knee extensor torque development are strongly associated with symmetrical sagittal plane CMJ knee mechanics. CMJ knee Abstracts were prepared by the authors and printed as submitted. S2 Vol. 52 No. 5 Supplement MEDICINE & SCIENCE IN SPORTS & EXERCISE® kinetic asymmetries did not resolve over time, independent from quadriceps function. Subjective limb confidence demonstrated a strong relationship with limb symmetry of Restoring maximal and rapid quadriceps torque capacity appears to be an important sagittal plane mechanics with a 1% difference in LSI of GRFz corresponding to a 0.4% step in recovering symmetrical CMJ mechanics post-ACLR. difference in IKDC scores during a DL and not SLHOP task. Symmetry in mechanics during a bilateral task may be more reflective of patient confidence in utilizing the 73 Board #4 May 27 9:30 AM - 11:30 AM affected limb prior to return to sport after ACLR. Biomechanical Determinants Of Return To Sport Board #6 May 27 9:30 AM - 11:30 AM Following Anterior Cruciate Ligament Reconstruction 75 Quantifying The Relationship Between Quadriceps Ashley Holzer, Chelsey Roe, Gregory Hawk, Leon Su, Katherine Thompson, Darren Johnson, Cale Jacobs, Brian Noehren, Strength And Aerobic Fitness Following Acl FACSM. University of Kentucky, Lexington, KY. Reconstruction (No relevant relationships reported) Lindsay V. Slater1, Levi J. Hargrove1, Joseph M. Hart, FACSM2. 1Shirley Ryan AbilityLab, Chicago, IL. 2University of Virginia, The ability to return to sport (RTS) after an anterior cruciate ligament reconstruction Charlottesville, VA. (Sponsor: Joe Hart, FACSM) (ACLR) return to sport is due to many factors. To date, few studies have considered (No relevant relationships reported) the role of poor biomechanics to predict RTS status. Potentially, higher ground reaction forces (GRF) and better frontal plane knee alignment