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The purpose of the current investigation was to test the hypothesis that subjects with patellar tendinopathy would demonstrate altered sagittal plane joint moment contributions during hopping tasks. Fourteen subjects (7 patellar tendinopathy, 7 controls) participated. Sagittal net joint moments of the lower extremity, total support moment, and joint contributions to the total support moment were calculated while subjects hopped continuously at a self-selected frequency and at 1.67 Hz. Significant differences were observed for contributions to the total support moment (p = .022). When averaged across hopping frequencies, subjects with patellar tendinopathy demonstrated greater hip contribution (p = .030) and lesser knee contribution (p = .006) compared with the control subjects. Shifting the workload away from the knee and toward the hip may result in a detrimental increase in hip demand and potentially harmful long-term effects on the articular cartilage of the hip. [ABSTRACT FROM AUTHOR]

BACKGROUND: It has been proposed that female athletes who limit knee and hip flexion during athletic tasks rely more on the passive restraints in the frontal plane to deceleration their body center of mass. This biomechanical pattern is thought to increase the risk for anterior cruciate ligament injury. To date, the relationship between sagittal plane kinematics and frontal plane knee motion and moments has not been explored. METHODS: Subjects consisted of 58 female club soccer players (age range: 11-20 years) with no history of knee injury. Kinematics, ground reaction forces, and surface electromyography were collected while each subject performed a drop landing task. Subjects were divided into two groups based on combined sagittal plane knee and hip flexion angles during the deceleration phase of landing (high flexion and low flexion). FINDINGS: Subjects in the low flexion group demonstrated increased knee valgus angles (P=0.02, effect size 0.27), increased knee adductor moments (P=0.03, effect size 0.24), decreased energy absorption at the knee and hip (P=0.02, effect size 0.25; and P<0.001, effect size 0.59), and increased vastus lateralis EMG when compared to subjects in the high flexion group (P=0.005, effect size 0.35). INTERPRETATION: Female athletes with limited sagittal plane motion during landing exhibit a biomechanical profile that may put these individuals at greater risk for anterior cruciate ligament injury. [ABSTRACT FROM AUTHOR]

STUDY DESIGN: Experimental laboratory study. OBJECTIVES: To examine how a change in trunk position influences the kinematics, kinetics, and muscle activity of the lead lower extremity during the forward lunge exercise. BACKGROUND: Altering the position of the trunk during the forward lunge exercise is thought to affect the muscular actions of the lead lower extremity. However, no studies have compared the biomechanical differences between the traditional forward lunge and its variations. METHODS AND MEASURES: Ten healthy adults (5 males, 5 females; mean age ± SD, 26.7 ± 3.2 years) participated. Lower extremity kinematics, kinetics, and surface electromyographic (EMG) data were obtained while subjects performed 3 lunge exercises: normal lunge with the trunk erect (NL), lunge with the trunk forward (LTF), and lunge with trunk extension (LTE). A 1-way analysis of variance with repeated measures was used to compare lower extremity kinematics, joint impulse (area under the moment-time curve), and normalized EMG (highest 1-second window of activity for selected lower extremity muscles) among the 3 lunge conditions. RESULTS: During the LTF condition, significant increases were noted in peak hip flexion angle, hip extensor and ankle plantar flexor impulse, as well as gluteus maximus and biceps femoris EMG (P<.015) when compared to the NL condition. During the LTE condition, a significant increase was noted in peak ankle dorsiflexion and a significant decrease was noted in peak hip flexion angle (P<.015) compared to the NL condition. CONCLUSIONS: Performing a lunge with the trunk forward increased the hip extensor impulse and the recruitment of the hip extensors. In contrast, performing a forward lunge with the trunk extended did not alter joint impulse or activation of the lower extremity musculature. LEVEL OF EVIDENCE: Therapy, level 5. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Based on the recent suggestion that proximal hip control may be related to a predisposition to anterior cruciate ligament injury, our purpose was to identify gender differences in hip mechanics between female athletes who previously demonstrated greater knee valgus moments and their male counterparts. DESIGN: Descriptive laboratory study. SETTING: Testing was conducted in a biomechanics research laboratory. PARTICIPANTS: Thirty collegiate soccer players (15 women and 15 men) participated in this study. All subjects were healthy with no current complaints of lower extremity injury. MAIN OUTCOME MEASUREMENTS: Three-dimensional hip joint kinematics and kinetics were collected while subjects performed a side-step cutting maneuver. Gender differences in hip mechanics were compared using independent sample t tests. RESULTS: Compared with male athletes, female athletes demonstrated significantly greater hip internal rotation and decreased hip flexion. In addition, female athletes demonstrated significantly greater hip adductor moments as well as decreased hip extensor moments. CONCLUSION: Overall, it appeared that female athletes moved into greater hip internal rotation and used less sagittal plane hip motion during the early deceleration phase of the cutting maneuver. The findings of this investigation support the premise that altered hip kinematics and kinetics may influence loading at the knee. Future studies are needed to further explore the impact of these differences on knee loading and to ascertain the underlying causes. [ABSTRACT FROM AUTHOR]

Purpose: The capacity to explosively contract quadriceps within the critical timeframe associated with anterior cruciate ligament (ACL) injury, quantified by the rate of torque development, is potentially essential for safe landing mechanics. This study aimed to investigate the influence of explosive quadriceps strength on ACL-related sagittal-plane landing mechanics in females with and without ACL reconstruction (ACLR)., Methods: Quadriceps explosive strength and landing mechanics were assessed in 19 ACLR and 19 control females during isometric contractions and double- and single-leg jump landings. A stepwise multiple linear regression model determined the variance in each of the landing biomechanics variables for the ACLR limb and nondominant limb of controls that could be explained by the group, rate of torque development and/or their interaction. If peak kinetic variables could be predicted by the rate of torque development or interaction, additional analyses were conducted, accounting for knee flexion as a covariate in the regression model., Results: During single-leg landings, ACLR females exhibited greater knee flexion at initial contact than controls (p = 0.04). Greater quadriceps rate of torque development predicted higher peak posterior ground reaction force and anterior tibial shear force in both groups (p = 0.04). However, after controlling for knee flexion angle at those peak forces, quadriceps rate of torque development was not predictive. In double-leg landings, greater explosive quadriceps strength was associated with quicker attainment of peak knee extension moment and posterior ground reaction force in the ACLR limb (p = 0.03)., Conclusion: Regardless of ACL injury status, females with greater explosive quadriceps strength adopted safer single-leg landings through increased knee flexion, potentially mitigating ACL loading despite encountering higher peak forces. During double-leg landings, a greater explosive quadriceps strength of the ACLR limb is associated with faster achievement of peak force upon landing. Incorporating explosive quadriceps strengthening into post-ACLR rehabilitation and injury prevention programmes may enhance landing mechanics for reducing primary and subsequent ACL injury risks., Level of Evidence: Level II., (© 2024 European Society of Sports Traumatology, Knee Surgery and Arthroscopy.)

Context: Noncontact anterior cruciate ligament injury often occurs during rapid deceleration and change-of-direction maneuvers. These activities require an athlete to generate braking forces to slow down the center of mass and change direction in a dynamic environment. During preplanned cutting, athletes can use the penultimate step for braking before changing direction, resulting in less braking demand during the final step. During reactive cutting, athletes use different preparatory movement strategies during the penultimate step when planning time is limited. However, possible differences in the deceleration profile between the penultimate and final steps of preplanned and reactive side-step cuts remain unknown., Objective: To comprehensively evaluate deceleration during the penultimate and final steps of preplanned and reactive cutting., Design: Cross-sectional study., Setting: Laboratory., Patients or Other Participants: Thirty-six women (age = 20.9 ± 1.7 years, height = 1.66 ± 0.07 m, mass = 62.4 ± 8.7 kg)., Intervention: Participants completed 90° side-step cutting maneuvers under preplanned and reactive conditions., Main Outcome Measure(s): Approach velocity, velocity at initial contact, and cutting angle were compared between conditions. Stance time, deceleration time, and biomechanical indicators of deceleration were assessed during the penultimate and final steps of preplanned and reactive 90° cuts. Separate repeated-measures analysis-of-variance models were used to assess the influence of step, condition, and their interaction on the biomechanical indicators of deceleration., Results: Approach velocity (P = .69) and velocity at initial contact of the penultimate step (P = .33) did not differ between conditions. During reactive cutting, participants achieved a smaller cutting angle (P < .001). We identified a significant step-by-condition interaction for all biomechanical indicators of deceleration (P values < .05)., Conclusions: A lack of planning time resulted in less penultimate step braking and greater final step braking during reactive cutting. As a result, participants exhibited a decreased cutting angle and longer stance time during the final step of reactive cutting. Improving an athlete's ability to respond to an external stimulus may facilitate a more effective penultimate step braking strategy that decreases the braking demand during the final step of reactive cutting., (© by the National Athletic Trainers’ Association, Inc.)

Background: The relationship of running biomechanics, footwear, and injury has been studied extensively in adults. There has been little research on the effects of footwear on running biomechanics in youth., Hypothesis: Running biomechanics of youth will be significantly affected by changes in footwear. Minimal shoe running will demonstrate similarities to barefoot., Study Design: Crossover study design: randomized trial., Level of Evidence: Level 2., Methods: A total of 14 active male youth (8-12 years old) participants with no previous exposure to minimalist shoes or barefoot running had running biomechanics (lower extremity sagittal plane kinematics and vertical ground reaction forces [vGRFs]) collected and analyzed in 3 footwear conditions (barefoot, traditional, and minimal shoe)., Results: The average vertical loading rate (AVLR) was significantly greater running barefoot (173.86 bodyweights per second [BW/s]) and in the minimal shoe (138.71 BW/s) compared with the traditional shoe (78.06 BW/s), ( P < 0.01). There were significant differences between shoe conditions for knee flexion at initial contact ( P < 0.01), knee sagittal plane excursion ( P < 0.01), peak dorsiflexion ( P < 0.01), and dorsiflexion at initial contact ( P = 0.03). No participants displayed a forefoot-strike during this study., Conclusion: The introduction of barefoot and minimalist running in habitually shod youth significantly affected the running biomechanics of youth and caused immediate alterations in both lower extremity kinematics and vGRFs. Running barefoot or in minimal shoes dramatically increased the AVLR, which has been associated with injury, compared with a traditional shoe., Clinical Relevance: This study evaluated the effects of footwear on overground running biomechanics, including AVLR, in pre- and early-adolescent youth males. Based on our findings, clinicians should exercise caution in barefoot or minimal shoe transition among young, habitually shod, runners due to the immediate and dramatic increases in AVLRs., Competing Interests: The authors report no potential conflicts of interest in the development and publication of this article.

Background: Tailored, challenging and progressed exercise programs addressing risk factors are recommended for preventing falls in community-dwelling older adults. Knowing the biomechanical demands of exercises commonly performed in efficacious falls prevention programs provides evidence for exercise prescription., Methods: Twenty-one non-sedentary older adults (10 men, 11 women, mean age 69 [SD 5] years) performed five standing exercises (hip abduction, side-step, squat, forward lunge, and side lunge). A biomechanical analysis of the dominant limb was performed to calculate peak joint angles and net joint moments at the ankle, knee and hip in multiple planes. Repeated-measures one-way analyses of variance followed by post-hoc comparisons were performed to identify differences in the calculated variables between exercises., Findings: Peak hip abduction moments during hip abduction were greater than during the forward lunge and squat (P < 0.001). During the side-step, peak plantar flexion moments were greater than the squat and peak hip abduction moments were greater than the squat and forward lunge (P < 0.001). During the squat, peak hip flexion was greatest (P < 0.001) while peak plantar flexion (P < 0.001) and hip abduction moments (P ≤ 0.002) were less than all other exercises. During the forward lunge, peak hip extension moments (P < 0.001) were greatest. During the side lunge, peak knee extension moments were greater than all other exercises (P < 0.001)., Interpretation: These biomechanical data will allow clinicians to tailor exercises for falls prevention to efficiently challenge but not overload muscle groups and minimize exercise prescription redundancies., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Achilles tendinopathy (AT) and medial tibial stress syndrome (MTSS) are two of the most common running-related injuries. In a previous study investigating running biomechanics before and after a six-week transition to maximal running shoes, two runners dropped out of this study due to Achilles pain and shin pain, respectively. The purpose of this case series was to investigate running biomechanics in those two runners, identifying potential causes for injury in relation to maximal shoe use. Running biomechanics were collected in a laboratory setting for these two runners wearing both a maximal running shoe and traditional running shoe before the six-week transition using an 8-camera motion capture system and two embedded force plates. Both runners displayed prolonged eversion in the maximal shoe, which has been previously cited as a potential risk factor for developing Achilles tendinopathy and medial tibial stress syndrome. Relatively high loading rates and impact forces were also observed in the runner with shin pain in the maximal shoe, which may have contributed to their pain. More prospective research on injury rates in individuals running in maximal shoes is needed.

Background: Knee osteoarthritis (OA) is a degenerative joint disease that affects millions of individuals each year. Several biomechanical variables during walking have been identified as risk factors for developing knee OA, including the peak external knee adduction moment (KAM) and the knee flexion angle at initial contact. Many interventions have been studied to help mitigate these risk factors, including footwear. However, it is largely unknown how varying shoe cushioning may affect walking biomechanics related to knee OA risk., Research Question: What is the effect of maximally and minimally cushioned shoes on walking biomechanics compared to a traditionally cushioned shoe in older females?, Methods: Walking biomechanics in three shoes (maximal, traditional, minimal) were collected on 16 healthy females ages 50-70 using an 8-camera 3D motion capture system and two embedded force plates. Key biomechanical variables related to knee OA disease risk were compared between shoes using repeated measures ANOVAs., Results: The KAM was significantly larger in the maximal shoe (p = 0.005), while the knee flexion angle at initial contact was significantly larger in both the maximal and minimal shoe compared to the traditional shoe (p = .000). Additionally, the peak knee flexion angle (p = .000) and the loading rates of the vertical ground reaction force were (instantaneous: p = 0.001; average: p = .010) were significantly higher in the minimal shoe., Significance: While these results are specific to the shoes used in this study, clinicians should exercise caution in prescribing maximal or minimal shoes to females in this age group who may be at risk of knee OA given these results. Research is needed on the effect of these shoes in patients with knee OA., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Lower explosive quadriceps strength, quantified as rate of torque development (RTD), may contribute to landing mechanics associated with anterior cruciate ligament (ACL) injury risk. However, the association between quadriceps RTD and landing mechanics during high demand tasks remains unclear. Therefore, this study investigated the influence of quadriceps RTD on sagittal plane landing mechanics during double-leg jump landings (DLJL) and single-leg jump cuts (SLJC) in females with and without ACL reconstruction (ACLR). Quadriceps RTD was measured during isometric muscle contractions. Landing mechanics were collected during DLJL and SLJC tasks. Separate stepwise multiple linear regression models determined the amount of variance in sagittal plane landing mechanics that could be explained by quadriceps RTD, group (ACLR or Control), and their interaction. The results indicate that greater quadriceps RTD is associated with lower loading rate ( p = 0.02) and longer time to peak vertical ground reaction force ( p = 0.001) during SLJC, regardless of ACLR status. As greater loading rate may lead to higher risk of ACL injuries and post-traumatic knee osteoarthritis post-ACLR, explosive muscle strength interventions might be useful for individuals with and without ACLR to facilitate the use of safer landing mechanics.

Purpose: A functional test battery (FTB) has been proposed to evaluate the readiness of return to activity after ACLR. However, there is limited evidence documenting the usefulness of an FTB. Therefore, the purpose of the current investigation was to compare knee joint landing biomechanics asymmetry during double-leg jump landing (DLJL) and single-leg jump cutting (SLJC) between healthy females and ACLR females who pass (ACLR-pass) or fail (ACLR-fail) an FTB before and after the completion of a sustained exercise protocol., Method: Eighteen ACLR females (ten ACLR-pass and eight ACLR-fail) and twelve healthy females performed an FTB including The 2000 International Knee Documentation Committee Subjective Knee Evaluation Form, the Knee Outcome Survey Activities of Daily Living Scale, quadriceps strength, and single-leg hop tests. DLJL and SLJC knee joint biomechanics asymmetry were measured before and after exercise., Results: During DLJL, there were significant main effects of group on peak anterior tibial shear force (ATSF) asymmetry [F (2,27)  = 3.86, p < 0.05, [Formula: see text] = 0.214] and peak vertical ground reaction force (vGRF) asymmetry [F (2,27)  = 3.34, p = 0.05, [Formula: see text] = 0.198]. During SLJC, there was a significant group main effect for peak ATSF asymmetry [F (2,27)  = 3.494, p = 0.04, [Formula: see text] = 0.206]., Conclusion: ACLR-fail exhibited greater asymmetry in peak ATSF during DLJL and SLJC compared to healthy females. In addition, ACLR-pass exhibited greater asymmetry in peak ATSF and peak vGRF during DLJL and SLJC, respectively, compared to healthy females. However, ACLR-fail did not exhibit any significant differences in landing biomechanics asymmetry during either task compared with ACLR-pass. Furthermore, the completion of a sustained exercise protocol did not affect knee joint landing biomechanics asymmetry across groups., Level of Evidence: II.

Numerous studies have investigated anterior cruciate ligament (ACL) injury risk by examining gender differences in knee and hip biomechanics during a side-step cutting manoeuvre since it is known that ACL injury often occurs during such a task. Recent investigations have also examined lower extremity (LE) biomechanics during side-step cutting in individuals following ACL reconstruction (ACLR). Common research practice is to compare knee and hip biomechanics of the dominant limb between groups but this can add considerable complexity for clinicians and researchers. At this time, it is not known if there is a difference in LE biomechanics between the dominant and non-dominant limb during side-step cutting. Three-dimensional kinematics and kinetics were collected while 31 healthy participants performed five, side-step cutting manoeuvres with the dominant and non-dominant limbs. Knee and hip variables examined are those commonly investigated in ACL injury literature. There were no differences between limbs in all but one variable (knee internal rotation). These results demonstrate that healthy individuals exhibit little side-to-side differences in certain LE biomechanics when performing a side-step cutting manoeuvre. These findings can be utilised by clinicians when conducting dynamic evaluations of their ACLR patients and when developing injury prevention and rehabilitation programmes.

Objectives: Previous studies comparing shoes based on the amount of midsole cushioning have generally used shoes from multiple manufacturers, where factors outside of stack height may contribute to observed biomechanical differences in running mechanics between shoes. Therefore, the purpose of this study was to compare ground reaction forces and ankle kinematics during running between three shoes (maximal, traditional, and minimal) from the same manufacturer that only varied in stack height., Design: Within-participant repeated measures METHODS: Twenty recreational runners ran overground in the laboratory in three shoe conditions (maximal, traditional, minimal) while three-dimensional kinematic and kinetic data were collected using a 3D motion capture system and two embedded force plates. Repeated measures ANOVAs (α=.05) compared biomechanical data between shoes., Results: While the loading rate was significantly greater in the minimal shoe compared to the maximal shoe, no other differences were seen for the ground reaction force variables. Peak eversion was greater in the maximal and minimal shoe compared to the traditional shoe, while eversion duration and eversion at toe-off were greater in the maximal shoe., Conclusions: Previously cited differences in ground reaction force parameters between maximal and traditional footwear may be due to factors outside of midsole stack height. The eversion mechanics in the maximal shoes from this study may place runners at a greater risk of injury. Disagreement between previous studies indicates that more research on maximal running shoes is needed., (Copyright © 2019 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

Background: A recent study suggested that maximal running shoes may increase the impact force and loading rate of the vertical ground-reaction force during running. It is currently unknown whether runners will adapt to decrease the impact force and loading rate over time., Purpose: To compare the vertical ground-reaction force and ankle kinematics between maximal and traditional shoes before and after a 6-week acclimation period to the maximal shoe., Study Design: Controlled laboratory study., Methods: Participants ran in a traditional running shoe and a maximal running shoe during 2 testing sessions 6 weeks apart. During each session, 3-dimensional kinematics and kinetics were collected during overground running. Variables of interest included the loading rate, impact peak, and active peak of the vertical ground-reaction force, as well as eversion and dorsiflexion kinematics. Two-way repeated measures analyses of variance compared data within participants., Results: No significant differences were observed in any biomechanical variable between time points. The loading rate and impact peak were higher in the maximal shoe. Runners were still everted at toe-off and landed with less dorsiflexion, on average, in the maximal shoe., Conclusion: Greater loading rates and impact forces were previously found in maximal running shoes, which may indicate an increased risk of injury. The eversion mechanics observed in the maximal shoes may also increase the risk of injury. A 6-week transition to maximal shoes did not significantly change any of these measures., Clinical Relevance: Maximal running shoes are becoming very popular and may be considered a treatment option for some injuries. The biomechanical results of this study do not support the use of maximal running shoes. However, the effect of these shoes on pain and injury rates is unknown.

Background: Lower extremity injuries are common among runners. Recent trends in footwear have included minimal and maximal running shoe types. Maximal running shoes are unique because they provide the runner with a highly cushioned midsole in both the rearfoot and forefoot. However, little is known about how maximal shoes influence running biomechanics., Purpose: To examine the influence of maximal running shoes on biomechanics before and after a 5-km (5K) run as compared with neutral running shoes., Study Design: Controlled laboratory study., Methods: Fifteen female runners participated in 2 testing sessions (neutral shoe session and maximal shoe session), with 7 to 10 days between sessions. Three-dimensional kinematic and kinetic data were collected while participants ran along a 10-m runway. After 5 running trials, participants completed a 5K treadmill run, followed by 5 additional running trials. Variables of interest included impact peak of the vertical ground-reaction force, loading rate, and peak eversion. Differences were determined by use of a series of 2-way repeated-measures analysis of variance models (shoe × time)., Results: A significant main effect was found for shoe type for impact peak and loading rate. When the maximal shoe was compared with the neutral shoe before and after the 5K run, participants exhibited an increased loading rate (mean ± SE: pre-maximal shoe, 81.15 body weights/second [BW/s] and pre-neutral shoe, 60.83 BW/s [ P < .001]; post-maximal shoe, 79.10 BW/s and post-neutral shoe, 61.22 BW/s [ P = .008]) and increased impact peak (pre-maximal shoe, 1.76 BW and pre-neutral shoe, 1.58 BW [ P = .004]; post-maximal shoe, 1.79 BW and post-neutral shoe, 1.55 BW [ P = .003]). There were no shoe × time interactions and no significant findings for peak eversion., Conclusion: Runners exhibited increased impact forces and loading rate when running in a maximal versus neutral shoe. Because increases in these variables have been associated with an increased risk of running-related injuries, runners who are new to running in a maximal shoe may be at an increased risk of injury., Clinical Relevance: Understanding the influence of running footwear as an intervention that affects running biomechanics is important for clinicians so as to reduce patient injury., Competing Interests: The authors declared that they have no conflicts of interest in the authorship and publication of this contribution.

Background: Injury prevention training has been shown to be effective in reducing the incidence of noncontact anterior cruciate ligament (ACL) injury; however, the underlying reason for the success of these training programs is unclear., Purpose: To investigate whether an ACL injury prevention program that has been shown to reduce the incidence of ACL injury alters sagittal plane hip and knee biomechanics during a drop-landing task., Study Design: Descriptive laboratory study., Methods: Thirty female club soccer players (age range, 11-17 years) with no history of knee injury participated in this study. Kinematics and ground-reaction forces were collected while each participant performed a drop-landing task prior to and immediately after participation in a 12-week ACL injury prevention training program., Results: After ACL injury prevention training, participants demonstrated decreased knee extensor moments ( P = .03), increased energy absorption at the hip ( P = .04), decreased knee-to-hip extensor moment ratios ( P = .05), and decreased knee-to-hip energy absorption ratios ( P = .03)., Conclusion: Participation in an ACL injury prevention training program decreased reliance on the knee extensor muscles and improved use of the hip extensor muscles, which may explain the protective effect of this type of training program on ACL injury., Clinical Relevance: Based on these findings, clinicians can better understand how ACL injury prevention training, such as the Prevent Injury and Enhance Performance (PEP) Program, may change movement behavior at both the hip and knee. Furthermore, the study findings may support the implementation of the PEP Program, or a similar program, for clinicians aiming to improve use of the hip in an effort to reduce knee loading and consequent injuries., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: This study was funded by the National Institutes of Health (R01 AR053073-02).

Objectives: Normalization of joint moments to reduce anthropometric influences prior to making group comparisons is a widely-accepted practice. However, a seminal prospective study reported greater non-normalized knee abduction moment (KAM) in nine females who subsequently sustained an ACL injury. It is not clear if this finding may have been influenced by the fact that the ACL-injured females were on average 3.6cm taller and 2.4kg heavier than uninjured females., Design: Cross-sectional., Methods: Peak KAM was identified in thirty-six females completing jump landings. A custom software program randomly divided participants into two groups that were compared on: (1) non-normalized KAM, (2) KAM normalized to body mass, and (3) KAM normalized to body height times weight a total of 500,000 times and the results categorically coded for statistical significance (α≤0.05). For the 10,591 iterations in which one group was 3-4cm taller and 2-3kg heavier, the agreement between results obtained using non-normalized versus normalized data were assessed using non-parametric analyses., Results: Despite moderate-strong agreement between the results obtained using non-normalized and normalized data (Κ=0.614-0.744), a significant effect of normalization on the interpretation of group differences in peak KAM was identified (p<0.001). In 30.4-41.9% of the cases in which non-normalized KAM was deemed significantly different between groups, no group differences were identified when using normalized KAM., Conclusions: While it is unlikely the magnitude of the difference in non-normalized KAM identified prospectively in ACL-injured females was attributable solely to anthropometric differences, caution should be exercised when evaluating research findings reporting non-normalized KAM., (Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

Background: The relationships between hip abductor and extensor strength and frontal plane hip and knee motions that are associated with anterior cruciate ligament injury risk are equivocal. However, previous research on these relationships has evaluated relatively low-level movement tasks and peak torque rather than a time-critical strength measure such as the rate of torque development (RTD)., Hypothesis: Females with greater hip abduction and extension RTD would exhibit lesser frontal plane hip and knee motion during a single-leg jump-cutting task., Study Design: Descriptive laboratory study., Methods: Forty recreationally active females performed maximal isometric contractions and single-leg jump-cuts. From recorded torque data, hip extension and abduction RTD was calculated from torque onset to 200 ms after onset. Three-dimensional motion analysis was used to quantify frontal plane hip and knee kinematics during the movement task. For each RTD measure, jump-cut biomechanics were compared between participants in the highest (high) and lowest (low) RTD tertiles., Results: No differences in frontal plane hip and knee kinematics were identified between high and low hip abduction RTD groups. However, those in the high hip extension RTD group exhibited lower hip adduction (high, 3.8° ± 3.0°; low, 6.5° ± 3.0°; P = .019) and knee valgus (high, -2.5° ± 2.3°; low, -4.4° ± 3.2°; P = .046) displacements during the jump-cut., Conclusion: In movements such as cutting that are performed with the hip in a relatively abducted and flexed position, the ability of the gluteus medius to control hip adduction may be compromised. However, the gluteus maximus, functioning as a hip abductor, may take on a pivotal role in controlling hip adduction and knee valgus motion during these types of tasks., Clinical Relevance: Training with a specific emphasis on increasing explosive strength of the hip extensors may be a means through which to improve frontal plane hip and knee control during high-risk maneuvers such as cutting.

Background: Lower extremity injuries are common in athletes. Valid tests to assess for risk of injury that are easily performed during a preparticipation sports physical examination are lacking. Two-dimensional (2D) analysis of the drop-jump test can identify athletes at risk, but it is too expensive and cumbersome to use in this setting., Objective: To identify if those who perform a "positive"(abnormal postures) single leg squat (SLS) test also exhibit greater "dynamic valgus" on the 2D drop-jump test. Our secondary purpose was to assess whether group differences in gender, age, or body mass index are evident between those who exhibit a positive SLS test result versus a negative SLS test result. Also, we wanted to determine any gender differences with the 2D drop-jump test., Design: A cross-sectional study., Setting: Private practice, preparticipation sports physical examinations., Participants: A total of 142 middle school and high school athletes., Methods: Participants performed a SLS test and a drop-jump test during their preparticipation sports physical examination. Individuals were partitioned into groups based on the outcome of their SLS test (positive SLS group versus negative SLS group). Independent sample t-tests were used to evaluate SLS group differences in the drop-jump test, age, and body mass index, and the χ(2) test was used to evaluate SLS group differences in gender (P ≤ .05)., Main Outcome Measurements: The SLS test and drop-jump test., Results: Seventy-three of the 142 athletes (51%) had a positive SLS test result, whereas 69 athletes (49%) had a negative SLS test result. Individuals in the positive SLS group had a significantly lower knee-hip ratio), indicative of greater dynamic knee valgus, than did those in the negative SLS group (P = .02). Individual characteristics between SLS groups including gender, age, and body mass index were similar., Conclusion: The SLS test is a reasonable tool to use in preparticipation sports physical examinations to assess for dynamic knee valgus and the potential risk of lower extremity injury., (Copyright © 2015 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.)

Background: Anterior cruciate ligament (ACL) reconstruction (ACLR) is common after an ACL tear and is thought to restore functional stability to the knee. A recent investigation demonstrated that individuals who have undergone ACLR exhibited increased lower extremity coupling variability during gait, suggestive of altered dynamic stability. However, little is known about whether they exhibit alterations in lower extremity variability during dynamic sport-specific tasks., Purpose: To determine if female soccer players who have had an ACLR demonstrate differences in lower extremity coupling variability as compared with athletes with no history of knee injury during a side-step cutting maneuver., Study Design: Controlled laboratory study., Methods: Ten female soccer players who had undergone ACLR served as the experimental group, and 10 female soccer players with no history of knee ligament injury composed the control group (CON). Three-dimensional kinematics and ground-reaction forces were collected while each participant performed a side-step cutting maneuver. Based on known ACL loading patterns, 7 lower extremity intralimb couplings were created. With use of a vector-coding technique, the coordination variability was calculated for each coupling. Independent t tests were used to determine group differences in variability for each coupling (P ≤ .05)., Results: Individuals who had undergone ACLR exhibited increased lower extremity variability during side-step cutting as compared with control subjects in the following couplings: hip rotation/knee abduction-adduction (27.2° ± 11.5° [ACLR] vs 19.7° ± 6.8° [CON]; P = .04), hip flexion-extension/knee abduction-adduction (26.0° ± 13.3° [ACLR] vs 18.6° ± 5.3° [CON]; P = .05), knee abduction-adduction/knee flexion-extension (13.5° ± 5.7° [ACLR] vs 7.3° ± 2.7° [CON]; P < .01), and knee abduction-adduction/knee rotation (26.4° ± 10.8° [ACLR] vs 19.3° ± 4.5° [CON]; P = .03). In addition, there was a trend toward increased variability in the hip rotation/ankle inversion-eversion coupling (22.9° ± 9.3° [ACLR] vs 18.0° ± 6.7° [CON]; P = .09) and knee abduction-adduction/ankle inversion-eversion coupling (25.9° ± 10.0° [ACLR] vs 20.2° ± 9.7° [CON]; P = .10)., Conclusion: Female soccer players who have undergone ACLR and returned to sports participation exhibit altered lower extremity coupling variability during side-step cutting., Clinical Relevance: While individuals who have had an ACLR exhibit mechanical knee stability before returning to sports, the observed increased movement variability during side-step cutting is likely reflective of altered neuromuscular control and may contribute to the known increased risk for ACL reinjury and knee osteoarthritis after return to sports participation. Improving the understanding of altered lower extremity coupling variability after ACLR will aid in the development of more effective rehabilitation programs., (© 2014 The Author(s).)

Background: Athletes who have undergone anterior cruciate ligament reconstruction (ACLR) have a high risk of reinjury upon the return to sports participation. While the mechanisms behind this increased risk of reinjury are unknown, it has been suggested that altered knee biomechanics during sports-specific activities may be a contributing factor. Purpose/, Hypothesis: To compare frontal plane knee joint angles and moments during a sidestep cutting maneuver in female soccer athletes who have undergone ACLR with those in athletes with no history of knee injury. It was hypothesized that athletes with a history of ACLR would exhibit increased knee abduction angles and knee adductor moments compared with those with no history of injury., Study Design: Controlled laboratory study., Methods: Twelve female soccer players with a history of ACLR served as the experimental group, and 12 female soccer players with no history of knee injury constituted the control group. Three-dimensional kinematics and ground-reaction forces were collected while each participant performed a sidestep cutting maneuver. Variables of interest included the knee abduction angle and knee adductor moment during the early deceleration phase of the cutting maneuver. Independent-samples t tests were used to evaluate differences between groups (P ≤ .05)., Results: Participants in the ACLR group exhibited increased average knee abduction angles (ACLR: 3.8° vs control: 1.8°; P = .03) and peak knee adductor moments (ACLR: 1.33 N·m/kg vs control: 0.80 N·m/kg; P = .004) compared with the control group., Conclusion: Female soccer players who have undergone ACLR and returned to sports participation exhibited increased knee abduction angles and knee adductor moments during the early deceleration phase of cutting compared with their healthy counterparts with no history of knee injury., Clinical Relevance: Even though athletes are able to return to sport after ACLR, they are at an increased risk for reinjury. It may be the case that the increased frontal plane knee angles and moments exhibited by these athletes after ACLR could be contributing to this risk for reinjury. Therefore, it is important that rehabilitation programs after ACLR include the restoration of frontal plane knee mechanics.

Introduction: Females have been reported to have a three to five times greater incidence of noncontact anterior cruciate ligament injury when compared with their male counterparts. Previous research suggests that physical maturation is one factor that is associated with the development of potentially injurious lower extremity biomechanics in female athletes., Purpose: The study's purpose was to determine whether lower extremity biomechanics differ between male and female soccer athletes during a cutting maneuver across different stages of maturational development., Methods: One hundred fifty-six soccer players (76 males and 80 females) between the ages of 9 and 23 yr participated. Subjects were classified on the basis of maturation as prepubertal, pubertal, postpubertal, or young adult. Lower extremity kinematics, kinetics, and ground reaction forces (GRFs) were obtained during a 45° side-step cutting maneuver. Differences between sex and maturation were assessed for peak knee valgus angle, knee adductor moments, and GRFs (vertical, posterior, and lateral) during weight acceptance using a two-factor ANCOVA (controlling for approach velocity)., Results: No sex × maturation interactions were found for any variable of interest. On average, females exhibited greater knee abduction and adductor moments than males. Prepubertal athletes demonstrated greater knee adductor moments and GRFs than all other groups., Conclusions: Biomechanical differences between males and females were evident across all stages of maturation. On average, less mature athletes exhibit biomechanical patterns during cutting that may place them at greater risk for injury than their more mature counterparts.

During landing and cutting, females exhibit greater frontal plane moments at the knee (internal knee adductor moments or external knee abduction moments) and favor the use of the knee extensors over the hip extensors to attenuate impact forces when compared with males. However, it is not known when this biomechanical profile emerges. The purpose of this study was to compare landing biomechanics between sexes across maturation levels. One hundred and nineteen male and female soccer players (9-22 years) participated. Subjects were grouped based on maturational development. Lower extremity kinematics and kinetics were obtained during a drop-land task. Dependent variables included the average internal knee adductor moment and sagittal plane knee/hip moment and energy absorption ratios during the deceleration phase of landing. When averaged across maturation levels, females demonstrated greater internal knee adductor moments (0.06±0.03 vs 0.01±0.02 N m/kg m; P<0.005), knee/hip extensor moment ratios (2.0±0.1 vs 1.4±0.1 N m/kg m; P<0.001) and knee/hip energy absorption ratios (2.9±0.1 vs 1.96±0.1 N m/kg m; P<0.001) compared with males. Higher knee adductor moments combined with disproportionate use of knee extensors relative to hip extensors observed in females reflect a biomechanical pattern that increases anterior cruciate ligament loading. This biomechanical strategy already was established in pre-pubertal female athletes., (© 2011 John Wiley & Sons A/S.)

Purpose: The purpose of this study was to compare kicking biomechanics between young female soccer players at two different stages of physical maturation and to identify biomechanical predictors of peak foot velocity., Methods: Swing and stance limb kinematics and kinetics were recorded from 20 female soccer players (10 prepubertal, 10 postpubertal) while kicking a soccer ball using an angled two-step approach. Peak foot velocity as well as hip and knee kinematics and kinetics were compared between groups using independent-samples t-tests. Pearson correlation coefficients and stepwise multiple regression were used to identify predictors of peak foot velocity., Results: Peak foot velocity and the peak swing limb net hip flexor moment was significantly greater in the postpubertal group when compared with the prepubertal group (13.4 vs 11.6 m·s(-1), P = 0.003; 1.22 vs 1.07 N·m·kg(-1)·m(-1), P = 0.03). Peak stance limb hip and knee extensor moments were not different between groups. Although the peak swing limb hip and knee flexion angles were similar between groups, the postpubertal group demonstrated significantly less peak stance limb hip and knee flexion angles when compared with the prepubertal group (P < 0.001 and P = 0.045). Using a linear regression model, swing limb peak hip flexor moment and peak swing limb hip extension range of motion combined to explain 65% of the variance in peak foot velocity., Conclusions: Despite a difference in stance limb kinematics, similar swing limb kinematics between groups indicates that the prepubertal female athletes kicked with a mature swing limb kick pattern. The ability to generate a large hip flexor moment of the swing limb seems to be an important factor for improving kicking performance in young female soccer players.

Study Design: Controlled laboratory study using a cross-sectional design., Objectives: To analyze lower extremity kinematics during takeoff of a "saut de chat" (leap) in dancers with and without a history of Achilles tendinopathy (AT). We hypothesized that dancers with AT would demonstrate different kinematic strategies compared to dancers without pathology, and that these differences would be prominent in the transverse and frontal planes., Background: AT is a common injury experienced by dancers. Dance leaps such as the saut de chat place a large demand on the Achilles tendon., Methods: Sixteen female dancers with and without a history of AT (mean ± SD age, 18.8 ± 1.2 years) participated. Three-dimensional kinematics at the hip, knee, and ankle were quantified for the takeoff of the saut de chat, using a motion analysis system. A force platform was used to determine braking and push-off phases of takeoff. Peak sagittal, frontal, and transverse plane joint positions during the braking and push-off phases of the takeoff were examined statistically. Independent samples t tests were used to evaluate group differences (α = .05)., Results: The dancers in the tendinopathy group demonstrated significantly higher peak hip adduction during the braking phase of takeoff (mean ± SD, 13.5° ± 6.1° versus 7.7° ± 4.2°; P = .046). During the push-off phase, dancers with AT demonstrated significantly more internal rotation at the knee (13.2° ± 5.2° versus 6.9° ± 4.9°; P = .024)., Conclusion: Dancers with AT demonstrate increased peak transverse and frontal plane kinematics when performing the takeoff of a saut de chat. These larger displacements may be either causative or compensatory factors in the development of AT.

Study Design: Controlled laboratory study using a cross-sectional design., Objectives: To evaluate knee joint dynamics in elite volleyball players with and without a history of patellar tendinopathy, focusing on mechanical energy absorption and generation. We hypothesized that tendinopathy would be associated withreduced net joint work and net joint power., Background: Patellar tendinopathy is a common, debilitating injury affecting competitive volleyball players., Methods: Thirteen elite male players with and without a history of patellar tendinopathy (mean ± SD age, 27 ± 7 years) performed maximum-effort volleyball approach jumps. Sagittal plane knee joint kinematics, kinetics, and energetics were quantified in the lead limb, using data obtained from a force platform and an 8-camera motion analysis system. Vertical ground reaction forces and pelvis vertical velocity at takeoff were examined. Independent sample t tests were used to evaluate group differences (α = .05)., Results: The tendinopathy group, compared to controls, demonstrated significant reductions (approximately 30%) in net joint work and net joint power during the eccentric phase of the jump, with no differences in the concentric phase. Positive to-negative net joint work and net joint power ratios were significantly higher in the tendinopathy group, which had a net joint work ratio of 1.00 (95% CI: 0.77, 1.24) versus 0.76 (95% CI: 0.64, 0.88) for controls, and a net joint power ratio of 1.62 (95% CI: 1.15, 2.10) versus 1.00 (95% CI: 0.80, 1.21) for controls. There were no significant differences in net joint moment, angular velocity, or range of motion. Peak vertical ground reaction forces were lower for the tendinopathy group, while average vertical ground reaction forces and pelvis vertical velocity were similar., Conclusion: Patellar tendinopathy is associated with differences in sagittal plane mechanical energy absorption at the knee during maximum-effort volleyball approach jumps. Net joint work and net joint power may help define underlying mechanisms, adaptive effects, or rehabilitative strategies for individuals with patellar tendinopathy.

Background: Researchers have theorized that the disproportionate number of anterior cruciate ligament injuries in females, as compared to males, may be related to knee laxity, which in turn may be influenced by hormones. The purpose of this study was to investigate the collective effects of gender, estrogen and exercise on knee laxity., Methods: Subjects consisted of 12 females and 12 males with no history of lower extremity injury. Serum estrogen levels and knee laxity were measured for the female subjects at specific times to represent three menstrual cycle phases while knee laxity of the male subjects was measured on three different days. For each data collection session, knee laxity was measured just prior to and immediately following an exercise protocol. Separate repeated measures ANOVAs were used to compare estrogen levels across the phases and analyze the laxity data., Findings: Females exhibited greater knee laxity than males both pre- and post-exercise across all phases of the menstrual cycle. Estrogen fluctuations across the menstrual cycle did not modify knee laxity in females. Prior exercise induced equivalent increases in knee laxity in males and females across the data collection periods and irrespective of estrogen concentration., Interpretation: If the anterior cruciate ligament is more distensible during athletic activities, it may be less capable of providing the necessary stability in order to prevent injury. This decreased stability may be contributing to the female athlete's increased incidence of anterior cruciate ligament injury. Overall, if females experience greater knee laxity during athletic activities, specific training strategies to compensate for these differences are warranted.

Objective: To examine the influence of in-season injury prevention training on hip and knee kinematics during a landing task., Design: Longitudinal pre-post intervention study., Setting: Testing sessions were conducted in a biomechanics research laboratory., Participants: Eighteen female soccer players between the ages of 14 and 17 participated in this study. All subjects were healthy with no current complaints of lower extremity injury., Interventions: Testing sessions were conducted prior to and following a season of soccer practice combined with injury prevention training., Main Outcome Measurements: During each testing session three-dimensional kinematics were collected while each subject performed a drop landing task. Peak hip and knee joint angles were measured during the early deceleration phase of landing and compared between pre- and post-training using paired t-tests., Results: Following a season of soccer practice combined with injury prevention training, females demonstrated significantly less hip internal rotation (7.1 degrees vs. 1.9 degrees; P = 0.01) and significantly greater hip abduction (-4.9 degrees vs. -7.7 degrees; P = 0.02). No differences in knee valgus or knee flexion angles were found post-season., Conclusions: Female soccer players exhibited significant changes in hip kinematics during a landing task following in-season injury prevention training. Our results support the premise that a season of soccer practice combined with injury prevention training is effective in altering lower extremity motions that may play a role in predisposing females to ACL injury.

Purpose: Tibial stress fractures (TSF) are among the most serious running injuries, typically requiring 6-8 wk for recovery. This cross-sectional study was conducted to determine whether differences in structure and running mechanics exist between trained distance runners with a history of prior TSF and those who have never sustained a fracture., Methods: Female runners with a rearfoot strike pattern, aged between 18 and 45 yr and running at least 32 km.wk(-1), were recruited for this study. Participants in the study were 20 subjects with a history of TSF and 20 age- and mileage-matched control subjects with no previous lower extremity bony injuries. Kinematic and kinetic data were collected during overground running at 3.7 m.s(-1) using a six-camera motion capture system, force platform, and accelerometer. Variables of interest were vertical impact peak, instantaneous and average vertical loading rates, instantaneous and average loading rates during braking, knee flexion excursion, ankle and knee stiffness, and peak tibial shock. Tibial varum was measured in standing. Tibial area moment of inertia was calculated from tibial x-ray studies for a subset of runners., Results: The TSF group had significantly greater instantaneous and average vertical loading rates and tibial shock than the control group. The magnitude of tibial shock predicted group membership successfully in 70% of cases., Conclusion: These data indicate that a history of TSF in runners is associated with increases in dynamic loading-related variables.

The purpose of this study was to determine if gender differences exist in the variability of various lower extremity (LE) segment and joint couplings during an unanticipated cutting maneuver. 3-D kinematics were collected on 24 college soccer players (12 M, 12 F) while each performed the cutting maneuver. The following intralimb couplings were studied: thigh rotation (rot)/leg rot; thigh abduction-adduction/leg abd-add; hip abd-add/knee rot; hip rot/knee abd-add; knee flexion-extension/knee rot; knee flx-ext/hip rot. A vector-coding technique applied to angle-angle plots was used to quantify the coordination of each coupling. The average between-trial standard deviation of the coordination pattern during the initial 40 % of stance was used to indicate the coordination variability. One-tailed t-tests were used to determine differences between genders in coordination variability for each coupling. Women had decreased variability in four couplings: 32 % less thigh rot/leg rot variability; 40 % less thigh abd-add/leg abd-add variability; 46 % less knee flx-ext/knee rot variability; and 44 % less knee flx-ext/hip rot variability. These gender differences in LE coordination variability may be associated with the increased incidence of ACL injury in women. If women exhibit less flexible coordination patterns during competition, they may be less able to adapt to the environmental perturbations experienced during sports. These perturbations applied to a less flexible system may result in ligament injury.

Objective: To investigate gender differences in three-dimensional hip and knee joint mechanics in collegiate athletes during a randomly cued cutting maneuver., Design: Three-dimensional kinematics and kinetics were collected on 24 collegiate soccer players (12 females and 12 males) while each performed the cutting maneuver. In order to create a randomly cued condition, subjects were signaled by a lighted target board that directed them to perform one of three tasks. Hip and knee joint mechanics were compared between genders using one-tailed t-tests., Background: Female athletes have an anterior cruciate ligament injury rate that is larger than their male counterparts. Gender differences in hip and knee joint mechanics during a randomly cued cutting maneuver have not been previously reported., Methods: Five randomly cued cutting trials were included in the analysis. Selected peak hip and knee joint angles and moments were measured during the first 40 degrees of knee flexion across the stance phase., Results: Females demonstrated significantly less peak hip abduction than did males. Otherwise, there were no gender differences in selected peak hip and knee joint kinematics and moments., Conclusions: Male and female collegiate soccer players demonstrate similar hip and knee joint mechanics while performing a randomly cued cutting maneuver., Relevance: Because it is known that females incur a greater number of anterior cruciate ligament injuries than males, it is of interest to identify gender differences in lower extremity mechanics when performing sport specific tasks. Understanding of these differences will contribute to the development of prevention training programs.