Effects of Prophylactic Knee Bracing on Lower Limb Kinematics, Kinetics, and Energetics During Double-Leg Drop Landing at 2 Heights

2016 ◽  
Vol 44 (7) ◽  
pp. 1753-1761 ◽  
Author(s):  
Katie A. Ewing ◽  
Rezaul K. Begg ◽  
Mary P. Galea ◽  
Peter V.S. Lee
Keyword(s):  
Knee Flexion ◽  
Knee Extension ◽  
Flexion Angle ◽  
Initial Contact ◽  
Knee Brace ◽  
Acl Injuries ◽  
Negative Power ◽  
Peak Knee ◽  
Knee Braces ◽  
Biomechanical Factors

Background: Anterior cruciate ligament (ACL) injuries commonly occur during landing maneuvers. Prophylactic knee braces were introduced to reduce the risk of ACL injuries, but their effectiveness is debated. Hypotheses: We hypothesized that bracing would improve biomechanical factors previously related to the risk of ACL injuries, such as increased hip and knee flexion angles at initial contact and at peak vertical ground-reaction force (GRF), increased ankle plantar flexion angles at initial contact, decreased peak GRFs, and decreased peak knee extension moment. We also hypothesized that bracing would increase the negative power and work of the hip joint and would decrease the negative power and work of the knee and ankle joints. Study Design: Controlled laboratory study. Methods: Three-dimensional motion and force plate data were collected from 8 female and 7 male recreational athletes performing double-leg drop landings from 0.30 m and 0.60 m with and without a prophylactic knee brace. GRFs, joint angles, moments, power, and work were calculated for each athlete with and without a knee brace. Results: Prophylactic knee bracing increased the hip flexion angle at peak GRF by 5.56° ( P < .001), knee flexion angle at peak GRF by 4.75° ( P = .001), and peak hip extension moment by 0.44 N·m/kg ( P < .001). Bracing also increased the peak hip negative power by 4.89 W/kg ( P = .002) and hip negative work by 0.14 J/kg ( P = .001) but did not result in significant differences in the energetics of the knee and ankle. No differences in peak GRFs and peak knee extension moment were observed with bracing. Conclusion: The application of a prophylactic knee brace resulted in improvements in important biomechanical factors associated with the risk of ACL injuries. Clinical Relevance: Prophylactic knee braces may help reduce the risk of noncontact knee injuries in recreational and professional athletes while playing sports. Further studies should investigate different types of prophylactic knee braces in conjunction with existing training interventions so that the sports medicine community can better assess the effectiveness of prophylactic knee bracing.

scholarly journals Quadriceps Neuromuscular Function and Jump-Landing Sagittal-Plane Knee Biomechanics After Anterior Cruciate Ligament Reconstruction

2018 ◽  
Vol 53 (2) ◽  
pp. 135-143 ◽  
Author(s):  
Sarah H. Ward ◽  
J. Troy Blackburn ◽  
Darin A. Padua ◽  
Laura E. Stanley ◽  
Matthew S. Harkey ◽  
...  
Keyword(s):  
Knee Flexion ◽  
Sagittal Plane ◽  
Neuromuscular Function ◽  
Knee Extension ◽  
Spinal Reflex ◽  
Flexion Angle ◽  
Voluntary Activation ◽  
Knee Flexion Angle ◽  
Jump Landing ◽  
Peak Knee

Context:  Aberrant biomechanics may affect force attenuation at the knee during dynamic activities, potentially increasing the risk of sustaining a knee injury or hastening the development of osteoarthritis after anterior cruciate ligament reconstruction (ACLR). Impaired quadriceps neuromuscular function has been hypothesized to influence the development of aberrant biomechanics. Objective:  To determine the association between quadriceps neuromuscular function (strength, voluntary activation, and spinal-reflex and corticomotor excitability) and sagittal-plane knee biomechanics during jump landings in individuals with ACLR. Design:  Cross-sectional study. Setting:  Research laboratory. Patients or Other Participants:  Twenty-eight individuals with unilateral ACLR (7 men, 21 women; age = 22.4 ± 3.7 years, height = 1.69 ± 0.10 m, mass = 69.4 ± 10.1 kg, time postsurgery = 52 ± 42 months). Main Outcome Measure(s):  We quantified quadriceps spinal-reflex excitability via the Hoffmann reflex normalized to maximal muscle response (H : M ratio), corticomotor excitability via active motor threshold, strength as knee-extension maximal voluntary isometric contraction (MVIC), and voluntary activation using the central activation ratio (CAR). In a separate session, sagittal-plane kinetics (peak vertical ground reaction force [vGRF] and peak internal knee-extension moment) and kinematics (knee-flexion angle at initial contact, peak knee-flexion angle, and knee-flexion excursion) were collected during the loading phase of a jump-landing task. Separate bivariate associations were performed between the neuromuscular and biomechanical variables. Results:  In the ACLR limb, greater MVIC was associated with greater peak knee-flexion angle (r = 0.38, P = .045) and less peak vGRF (r = −0.41, P = .03). Greater CAR was associated with greater peak internal knee-extension moment (ρ = −0.38, P = .045), and greater H : M ratios were associated with greater peak vGRF (r = 0.45, P = .02). Conclusions:  Greater quadriceps MVIC and CAR may provide better energy attenuation during a jump-landing task. Individuals with greater peak vGRF in the ACLR limb possibly require greater spinal-reflex excitability to attenuate greater loading during dynamic movements.

scholarly journals Stiff Landings Are Associated With Increased ACL Injury Risk in Young Female Basketball and Floorball Players

2016 ◽  
Vol 45 (2) ◽  
pp. 386-393 ◽  
Author(s):  
Mari Leppänen ◽  
Kati Pasanen ◽  
Urho M. Kujala ◽  
Tommi Vasankari ◽  
Pekka Kannus ◽  
...  
Keyword(s):  
Knee Flexion ◽  
Injury Risk ◽  
Acl Injury ◽  
Young Female ◽  
Flexion Angle ◽  
Knee Flexion Angle ◽  
Acl Injuries ◽  
Increased Risk ◽  
Peak Knee ◽  
Acl Injury Risk

Background: Few prospective studies have investigated the biomechanical risk factors of anterior cruciate ligament (ACL) injury. Purpose: To investigate the relationship between biomechanical characteristics of vertical drop jump (VDJ) performance and the risk of ACL injury in young female basketball and floorball players. Study Design: Cohort study; Level of evidence, 3. Methods: At baseline, a total of 171 female basketball and floorball players (age range, 12-21 years) participated in a VDJ test using 3-dimensional motion analysis. The following biomechanical variables were analyzed: (1) knee valgus angle at initial contact (IC), (2) peak knee abduction moment, (3) knee flexion angle at IC, (4) peak knee flexion angle, (5) peak vertical ground-reaction force (vGRF), and (6) medial knee displacement. All new ACL injuries, as well as match and training exposure, were then recorded for 1 to 3 years. Cox regression models were used to calculate hazard ratios (HRs) and 95% CIs. Results: Fifteen new ACL injuries occurred during the study period (0.2 injuries/1000 player-hours). Of the 6 factors considered, lower peak knee flexion angle (HR for each 10° increase in knee flexion angle, 0.55; 95% CI, 0.34-0.88) and higher peak vGRF (HR for each 100-N increase in vGRF, 1.26; 95% CI, 1.09-1.45) were the only factors associated with increased risk of ACL injury. A receiver operating characteristic (ROC) curve analysis showed an area under the curve of 0.6 for peak knee flexion and 0.7 for vGRF, indicating a failed-to-fair combined sensitivity and specificity of the test. Conclusions: Stiff landings, with less knee flexion and greater vGRF, in a VDJ test were associated with increased risk of ACL injury among young female basketball and floorball players. However, although 2 factors (decreased peak knee flexion and increased vGRF) had significant associations with ACL injury risk, the ROC curve analyses revealed that these variables cannot be used for screening of athletes.

Does Chronic Ankle Instability Influence Knee Biomechanics of Females during Inverted Surface Landings?

2018 ◽  
Vol 39 (13) ◽  
pp. 1009-1017 ◽  
Author(s):  
Yumeng Li ◽  
Jupil Ko ◽  
Marika Walker ◽  
Cathleen Brown ◽  
Julianne Schmidt ◽  
...  
Keyword(s):  
Internal Rotation ◽  
Knee Flexion ◽  
Sagittal Plane ◽  
Ankle Instability ◽  
Knee Extension ◽  
Chronic Ankle Instability ◽  
Initial Contact ◽  
Knee Biomechanics ◽  
Peak Knee ◽  
Eccentric Work

AbstractThe primary purpose of the study was to determine whether atypical knee biomechanics are exhibited during landing on an inverted surface. A seven-camera motion analysis system and two force plates were used to collect lower extremity biomechanics from two groups of female participants: 21 subjects with chronic ankle instability (CAI) and 21 with pair-matched controls. Subjects performed ten landings onto inverted and flat platforms on the CAI/matched and non-test limbs, respectively. Knee and ankle joint angles, joint angular displacements, joint moments and eccentric work were calculated during the landing phase and/or at the initial contact. Paired t-tests were used to compare between-group differences (p<0.05). We observed that CAI group displayed a significantly increased knee flexion angle, knee flexion displacement, peak knee extension moment and internal rotation moment, and eccentric work in the sagittal plane, possibly due to altered ankle biomechanics. Participants with CAI employed some compensatory strategy to improve their ankle and postural stability during landing onto the tilted surface. The increased knee extension and internal rotation moments of CAI participants could potentially result in a greater ACL loading. In future studies, it may be worthwhile to measure or estimate the ACL loading to confirm whether CAI could relate to the mechanism of ACL injury.

scholarly journals Lower Extremity Muscle Activation and Knee Flexion During a Jump-Landing Task

2012 ◽  
Vol 47 (4) ◽  
pp. 406-413 ◽  
Author(s):  
Meghan Walsh ◽  
Michelle C. Boling ◽  
Melanie McGrath ◽  
J. Troy Blackburn ◽  
Darin A. Padua
Keyword(s):  
Lower Extremity ◽  
Muscle Activity ◽  
Knee Flexion ◽  
Flexion Angle ◽  
Initial Contact ◽  
Knee Flexion Angle ◽  
Jump Landing ◽  
Lower Extremity Muscle ◽  
Peak Knee ◽  
The Relationship

Context: Decreased sagittal-plane motion at the knee during dynamic tasks has been reported to increase impact forces during landing, potentially leading to knee injuries such as anterior cruciate ligament rupture. Objective: To describe the relationship between lower extremity muscle activity and knee-flexion angle during a jump-landing task. Design: Cross-sectional study. Setting: Research laboratory. Patients or Other Participants: Thirty recreationally active volunteers (15 men, 15 women: age = 21.63 ± 2.01 years, height = 173.95 ± 11.88 cm, mass = 72.57 ± 14.25 kg). Intervention(s): Knee-flexion angle and lower extremity muscle activity were collected during 10 trials of a jump-landing task. Main Outcome Measure(s): Simple correlation analyses were performed to determine the relationship between each knee-flexion variable (initial contact, peak, and displacement) and electromyographic amplitude of the gluteus maximus (GMAX), quadriceps (VMO and VL), hamstrings, gastrocnemius, and quadriceps : hamstring (Q : H) ratio. Separate forward stepwise multiple regressions were conducted to determine which combination of muscle activity variables predicted each knee-flexion variable. Results: During preactivation, VMO and GMAX activity and the Q : H ratio were negatively correlated with knee-flexion angle at initial contact (VMO: r = −0.382, P = .045; GMAX: r = −0.385, P = .043; Q : H ratio: r = −0.442, P = .018). The VMO, VL, and GMAX deceleration values were negatively correlated with peak knee-flexion angle (VMO: r = −0.687, P = .001; VL: r = −0.467, P = .011; GMAX: r = −0.386, P = .043). The VMO and VL deceleration values were negatively correlated with knee-flexion displacement (VMO: r = −0.631, P = .001; VL: r = −0.453, P = .014). The Q : H ratio and GM activity predicted 34.7% of the variance in knee-flexion angle at initial contact (P = .006). The VMO activity predicted 47.1% of the variance in peak knee-flexion angle (P = .001). The VMO and VL activity predicted 49.5% of the variance in knee-flexion displacement (P = .001). Conclusions: Greater quadriceps and GMAX activation and less hamstrings and gastrocnemius activation were correlated with smaller knee-flexion angles. This landing strategy may predispose an individual to increased impact forces due to the negative influence on knee-flexion position.

scholarly journals Single-Leg Landings Following a Volleyball Spike May Increase the Risk of Anterior Cruciate Ligament Injury More Than Landing on Both-Legs

2020 ◽  
Vol 11 (1) ◽  
pp. 130
Author(s):  
Datao Xu ◽  
Xinyan Jiang ◽  
Xuanzhen Cen ◽  
Julien S. Baker ◽  
Yaodong Gu
Keyword(s):  
Anterior Cruciate Ligament ◽  
Knee Flexion ◽  
Sagittal Plane ◽  
Cruciate Ligament ◽  
Flexion Angle ◽  
Ligament Injury ◽  
Time Range ◽  
Acl Injuries ◽  
Volleyball Players ◽  
Anterior Cruciate

Volleyball players often land on a single leg following a spike shot due to a shift in the center of gravity and loss of balance. Landing on a single leg following a spike may increase the probability of non-contact anterior cruciate ligament (ACL) injuries. The purpose of this study was to compare and analyze the kinematics and kinetics differences during the landing phase of volleyball players using a single leg (SL) and double-leg landing (DL) following a spike shot. The data for vertical ground reaction forces (VGRF) and sagittal plane were collected. SPM analysis revealed that SL depicted a smaller knee flexion angle (about 13.8°) and hip flexion angle (about 10.8°) during the whole landing phase, a greater knee and hip power during the 16.83–20.45% (p = 0.006) and 13.01–16.26% (p = 0.008) landing phase, a greater ankle plantarflexion angle and moment during the 0–41.07% (p < 0.001) and 2.76–79.45% (p < 0.001) landing phase, a greater VGRF during the 5.87–8.25% (p = 0.029), 19.75–24.14% (p = 0.003) landing phase when compared to DL. Most of these differences fall within the time range of ACL injury (30–50 milliseconds after landing). To reduce non-contact ACL injuries, a landing strategy of consciously increasing the hip and knee flexion, and plantarflexion of the ankle should be considered by volleyball players.

scholarly journals Kinematic Comparison between Medially Congruent and Posterior-Stabilized Third-Generation TKA Designs

2021 ◽  
Vol 6 (1) ◽  
pp. 27
Author(s):  
Stefano Ghirardelli ◽  
Jessica L. Asay ◽  
Erika A. Leonardi ◽  
Tommaso Amoroso ◽  
Thomas P. Andriacchi ◽  
...  
Keyword(s):  
Knee Flexion ◽  
Knee Kinematics ◽  
Primary Total Knee Arthroplasty ◽  
Flexion Angle ◽  
Heel Strike ◽  
Third Generation ◽  
Knee Flexion Angle ◽  
Posterior Stabilized ◽  
Rotational Angle ◽  
Peak Knee

Background: This study compares knee kinematics in two groups of patients who have undergone primary total knee arthroplasty (TKA) using two different modern designs: medially congruent (MC) and posterior-stabilized (PS). The aim of the study is to demonstrate only minimal differences between the groups. Methods: Ten TKA patients (4 PS, 6 MC) with successful clinical outcomes were evaluated through 3D knee kinematics analysis performed using a multicamera optoelectronic system and a force platform. Extracted kinematic data included knee flexion angle at heel-strike (KFH), peak midstance knee flexion angle (MSKFA), maximum and minimum knee adduction angle (KAA), and knee rotational angle at heel-strike. Data were compared with a group of healthy controls. Results: There were no differences in preferred walking speed between MC and PS groups, but we found consistent differences in knee function. At heel-strike, the knee tended to be more flexed in the PS group compared to the MC group; the MSKFA tended to be higher in the PS group compared to the MC group. There was a significant fluctuation in KAA during the swing phase in the PS group compared to the MC group, PS patients showed a higher peak knee flexion moment compared to MC patients, and the PS group had significantly less peak internal rotation moments than the MC group. Conclusions: Modern, third-generation TKA designs failed to reproduce normal knee kinematics. MC knees tended to reproduce a more natural kinematic pattern at heel-strike and during axial rotation, while PS knees showed better kinematics during mid-flexion.

scholarly journals Quadriceps Strength Symmetry Does Not Modify Gait Mechanics After Anterior Cruciate Ligament Reconstruction, Rehabilitation, and Return-to-Sport Training

2020 ◽  
pp. 036354652098007
Author(s):  
Elanna K. Arhos ◽  
Jacob J. Capin ◽  
Thomas S. Buchanan ◽  
Lynn Snyder-Mackler
Keyword(s):  
Knee Flexion ◽  
Cruciate Ligament ◽  
Return To Sport ◽  
Quadriceps Muscle ◽  
Quadriceps Strength ◽  
Flexion Angle ◽  
Knee Flexion Angle ◽  
Sport Training ◽  
Gait Biomechanics ◽  
Peak Knee

Background: After anterior cruciate ligament (ACL) reconstruction (ACLR), biomechanical asymmetries during gait are highly prevalent, persistent, and linked to posttraumatic knee osteoarthritis. Quadriceps strength is an important clinical measure associated with preoperative gait asymmetries and postoperative function and is a primary criterion for return-to-sport clearance. Evidence relating symmetry in quadriceps strength with gait biomechanics is limited to preoperative and early rehabilitation time points before return-to-sport training. Purpose/Hypothesis: The purpose was to determine the relationship between symmetry in isometric quadriceps strength and gait biomechanics after return-to-sport training in athletes after ACLR. We hypothesized that as quadriceps strength symmetry increases, athletes will demonstrate more symmetric knee joint biomechanics, including tibiofemoral joint loading during gait. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Of 79 athletes enrolled in the ACL-SPORTS Trial, 76 were participants in this study after completing postoperative rehabilitation and 10 return-to-sport training sessions (mean ± SD, 7.1 ± 2.0 months after ACLR). All participants completed biomechanical walking gait analysis and isometric quadriceps strength assessment using an electromechanical dynamometer. Quadriceps strength was calculated using a limb symmetry index (involved limb value / uninvolved limb value × 100). The biomechanical variables of interest included peak knee flexion angle, peak knee internal extension moment, sagittal plane knee excursion at weight acceptance and midstance, quadriceps muscle force at peak knee flexion angle, and peak medial compartment contact force. Spearman rank correlation (ρ) coefficients were used to determine the relationship between limb symmetry indexes in quadriceps strength and each biomechanical variable; alpha was set to .05. Results: Of the 76 participants, 27 (35%) demonstrated asymmetries in quadriceps strength, defined by quadriceps strength symmetry <90% (n = 23) or >110% (n = 4) (range, 56.9%-131.7%). For the biomechanical variables of interest, 67% demonstrated asymmetry in peak knee flexion angle; 68% and 83% in knee excursion during weight acceptance and midstance, respectively; 74% in internal peak knee extension moment; 57% in medial compartment contact force; and 74% in quadriceps muscle force. There were no significant correlations between quadriceps strength index and limb symmetry indexes for any biomechanical variable after return-to-sport training ( P > .129). Conclusion: Among those who completed return-to-sport training after ACLR, subsequent quadriceps strength symmetry was not correlated with the persistent asymmetries in gait biomechanics. After a threshold of quadriceps strength is reached, restoring strength alone may not ameliorate gait asymmetries, and current clinical interventions and return-to-sport training may not adequately target gait.

Comparison of Biomechanical Factors between the Kicking and Stance Limbs

2004 ◽  
Vol 13 (2) ◽  
pp. 135-150 ◽  
Author(s):  
Scott Ross ◽  
Kevin Guskiewicz ◽  
William Prentice ◽  
Robert Schneider ◽  
Bing Yu
Keyword(s):  
Knee Flexion ◽  
Reaction Force ◽  
Knee Extension ◽  
Knee Kinematic ◽  
Vertical Ground Reaction Force ◽  
Time To Peak ◽  
Balance Task ◽  
Vertical Ground ◽  
Biomechanical Factors ◽  
Anterior Posterior

Objective:T o determine differences between contralateral limbs’ strength, proprio-ception, and kinetic and knee-kinematic variables during single-limb landing.Setting:Laboratory.Subjects:30.Measurements:Hip, knee, and foot isokinetic peak torques; anterior/posterior (AP) and medial/lateral (ML) sway displacements during a balance task; and stabilization times, vertical ground-reaction force (VGRF), time to peak VGRF, and knee-flexion range of motion (ROM) from initial foot contact to peak VGRF during single-limb landing.Results:The kicking limb had significantly greater values for knee-extension (P= .008) and -flexion (P= .047) peak torques, AP sway displacement (P= .010), knee-flexion ROM from initial foot contact to peak VGRF (P< .001), and time to peak VGRF (P= .004). No other dependent measures were significantly different between limbs (P> .05).Conclusion:The kicking limb had superior thigh strength, better proprioception, and greater knee-flexion ROM than the stance limb.

scholarly journals Military Protein Intake Related to Strength and Fat Mass Independent of Energy Intake

2020 ◽  
Vol 185 (9-10) ◽  
pp. e1671-e1678
Author(s):  
Jeremy A Ross ◽  
D Travis Thomas ◽  
Joshua D Winters ◽  
Scott D Royer ◽  
Christopher J Halagarda ◽  
...  
Keyword(s):  
Energy Intake ◽  
Body Mass ◽  
Knee Flexion ◽  
Protein Intake ◽  
Performance Metrics ◽  
Knee Extension ◽  
Special Operations ◽  
Knee Extension Strength ◽  
Peak Knee ◽  
Flexion Strength

ABSTRACT Introduction Kinetic military units operate in austere training environments and deprivation not commonly experienced by competitive athletes. Nutritional strategies to protect against decrements in performance and potential injury risk may differ for these two groups. A cross sectional analysis was conducted to determine energy and macronutrient characteristics associated with performance metrics. Materials and Methods 78 male subjects (age: 28.4 ± 6.0 years, height: 178.3 ± 6.7 cm, mass: 84.3 ± 9.4 kg, 8.5 ± 5.8 years of service) assigned to Marine Corps Forces Special Operations Command completed a 1-day performance assessment. Body mass, lean body mass, fat mass (FM), aerobic capacity (VO2max), lactate inflection point (LT), anaerobic power, anaerobic capacity, knee flexion strength, knee extension strength, peak knee flexion strength, and peak knee extension strength outcome values were recorded. Dietary intake was collected using automated self-administered 24-hour dietary recall (ASA24). Performance assessment scores were compared with macronutrient intake and controlled for energy intake using analysis of covariance. Results Differences in knee flexion strength, knee extension strength, peak knee flexion strength, and peak knee extension strength were significant across low (LPRO), medium (MPRO), and high (HPRO) protein intake groups (p &lt; 0.05) with LPRO performance metrics significantly lower than both MPRO and HPRO and MPRO significantly lower than HPRO. FM was significantly higher in LPRO than MPRO or HPRO (p &lt; 0.05). Low carbohydrate intake (LCHO) was associated with greater body mass and FM compared with high (HCHO) (p &lt; 0.05). There was no association between fat intake and any variable. Conclusions Increases in protein intake may have beneficial performance effects independent of total energy intake, while moderate increases in carbohydrate intake may not be sufficient to enhance physical performance in a special operations population.

scholarly journals The Kinematics and Kinetics Analysis of the Lower Extremity in the Landing Phase of a Stop-jump Task

2015 ◽  
Vol 9 (1) ◽  
pp. 103-107 ◽  
Author(s):  
L Yin ◽  
D Sun ◽  
Q.C Mei ◽  
Y.D Gu ◽  
J.S Baker ◽  
...  
Keyword(s):  
Lower Extremity ◽  
Ground Reaction Force ◽  
Knee Flexion ◽  
Reaction Force ◽  
Flexion Angle ◽  
Contact Phase ◽  
Peak Knee ◽  
Significant Difference ◽  
The Impact ◽  
Kinematics And Kinetics

Large number of studies showed that landing with great impact forces may be a risk factor for knee injuries. The purpose of this study was to illustrate the different landing loads to lower extremity of both genders and examine the relationships among selected lower extremity kinematics and kinetics during the landing of a stop-jump task. A total of 35 male and 35 female healthy subjects were recruited in this study. Each subject executed five experiment actions. Lower extremity kinematics and kinetics were synchronously acquired. The comparison of lower extremity kinematics for different genders showed significant difference. The knee and hip maximum flexion angle, peak ground reaction force and peak knee extension moment have significantly decreased during the landing of the stop-jump task among the female subjects. The hip flexion angle at the initial foot contact phase showed significant correlation with peak ground reaction force during landing of the stop-jump task (r=-0.927, p<0.001). The knee flexion angle at the initial foot contact phase had significant correlation with peak ground reaction force and vertical ground reaction forces during landing of the stop-jump task (r=-0.908, p<0.001; r=0.812, P=0.002). A large hip and knee flexion angles at the initial foot contact with the ground did not necessarily reduce the impact force during landing, but active hip and knee flexion motions did. The hip and knee flexion motion of landing was an important technical factor that affects anterior cruciate ligament (ACL) loading during the landing of the stop-jump task.

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