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Athletes with a history of concussion are at a greater risk for lower extremity musculoskeletal injury. Female athletes may be at an even greater risk than male athletes. Previous researchers on postconcussion landing biomechanics have focused on the lower extremities, but the trunk plays a crucial role as an injury risk factor. To compare lower extremity and trunk biomechanics during jump-landing and cutting maneuvers between female athletes with and those without a concussion history. Cross-sectional study. Biomechanics laboratory. A total of 26 athletes (mean ± SD age = 19.0 ± 1.3 years, height = 1.68 ± 0.07 m, mass = 64.02 ± 6.76 kg, body mass index = 22.58 ± 1.97 kg/m2; median [interquartile range] time since most recent concussion = 37.5 months [25.0 months, 65.8 months]) with a concussion history and 38 athletes (age = 19.0 ± 1.1 years, height = 1.71 ± 0.08 m, mass = 64.72 ± 9.45 kg, body mass index = 22.14 ± 1.80 kg/m2) without a concussion history. Peak kinetics (vertical ground reaction force, vertical loading rate, external knee-abduction moment, and external knee-flexion moment) and kinematics (trunk-flexion angle, trunk lateral-bending angle, ankle-dorsiflexion angle, knee-flexion angle, knee-abduction angle, and hip-flexion angle) were obtained during the eccentric portion of jump-landing and cutting tasks. Separate 2 (group) × 2 (limb) between- and within-factors analyses of covariance were used to compare outcomes between groups. We covaried for time since the most recent concussion and the limb that had a history of musculoskeletal injury. Athletes with a concussion history displayed a greater peak knee-abduction angle in their nondominant limb than their dominant limb (P =.01, ηp2 = 0.107) and the nondominant limb of athletes without a concussion history (P =.02, ηp2 = 0.083) during jump landing. They also had less trunk lateral bending during cutting compared with athletes without a concussion history (P =.005, ηp2 = 0.126). Our results indicated landing biomechanics are different between female athletes with and those without a concussion history. This finding may be due to impairments in neuromuscular control postconcussion that may ultimately increase the risk of subsequent lower extremity injury, although further research is warranted given the cross-sectional nature of our study. [ABSTRACT FROM AUTHOR]

Context: It is unclear if lower-extremity joint cooling alters biomechanics during a functional movement. Objective: To investigate the effects of unilateral lower-extremity cryotherapy on movement alterations during a single-leg drop jump. Design: A crossover design. Setting: Laboratory. Patients: Twenty healthy subjects (10 males and 10 females; 23 y, 169 cm, 66 kg). Intervention(s): Subjects completed a single-leg drop jump before and after a 20-minute ankle or knee joint cooling on the right leg, or control (seated without cooling) on 3 separate days. Main outcome measures: Time to peak knee flexion, vertical ground reaction force, lower-extremity joint angular velocity (sagittal plane only), and angle and moment (sagittal and frontal planes) in the involved leg over the entire ground contact (GC; from initial contact to jump-off) during the first landing. Time to peak knee flexion was compared using an analysis of variance; the rest of the outcome measures were analyzed using functional analyses of variance (P < .05). Results: Neither joint cooling condition changed the time to peak knee flexion (F2,95 = 0.73, P = .49). Ankle joint cooling reduced vertical ground reaction force (55 N at 4% of GC), knee joint angular velocity (44°/s during 5%-9% of GC), and knee varus moment (181 N·m during 18%-20% of GC). Knee joint cooling resulted in a reduction in knee joint angular velocity (24°/s during 37%-40% of GC) and hip adduction moment (151 N·m during 46%-48% of GC), and an increase in hip joint angular velocity (16°/s during 49%-53% of GC) and plantarflexion angle (1.5° during 11%-29% of GC). Conclusion: Resuming activity immediately after lower-extremity joint cooling does not seem to predispose an individual to injury during landing because altered mechanics are neither overlapping with the injury time period nor of sufficient magnitude to lead to an injury. [ABSTRACT FROM AUTHOR]

Recent evidence suggests previously concussed athletes are at greater risk for lower-extremity (LE) injuries than are controls. However, little is known regarding the influence of sports-related concussion (SRC) on landing biomechanics that may provide a mechanistic rationale for LE injury risk. The purpose of this investigation was to examine LE drop-landing biomechanics in adolescent athletes with and without a previous SRC history. Participants included 10 adolescent athletes with an SRC history and 11 controls from multiple sports. Three-dimensional kinematic and kinetic data associated with LE injury risk were analyzed across 5 trials for 30- and 60-cm landing heights. Multivariate analyses indicated group differences in landing patterns from the 30- (P = .041) and 60-cm (P = .015) landing heights. Follow-up analyses indicated that concussed adolescent athletes demonstrated significantly less ankle dorsiflexion and knee flexion versus controls when performing drop landings. Our findings suggest that previously concussed adolescent athletes complete drop-landing maneuvers with ankle and knee joint kinematic patterns that suggest greater risk for LE injury.While limitations such as sport variety and explicit LE injury history are present, the results of this study provide a possible biomechanical rationale for the association between SRC and LE injury risk. [ABSTRACT FROM AUTHOR]

Background: The ankle is prone to injury during drop landing with usual residual symptoms, and functional ankle instability (FAI) is the most common. Vision guarantees the postural stability of patients with FAI, and visual deprivation (VD) increases their risk of injury when completing various movements. This study explored injury risk during drop landing in patients with FAI under VD through the kinetics of lower extremities. Methods: A total of 12 males with FAI participated in the study (age, 23.0 ± 0.8 years; height, 1.68 ± 0.06 m; weight, and 62.2 ± 10.4 kg) completed singleleg drop landings under visual presence (VP) and VD conditions. Ground reaction force (GRF), time to peak GRF, joint torque, and vertical length variation (ΔL) were measured. Results: Significant effects were detected in the group for time to peak lateral GRF (p = 0.004), hip extensor torque (p = 0.022), ankle plantarflexion torque (p < 0.001), ankle varus torque (p = 0.021), lower extremity stiffness (p = 0.035), and ankle stiffness (p < 0.001). Significant effects of conditions were detected for vertical GRF, time to peak vertical and lateral GRF, loading rate, hip extensor torque, knee extensor torque, hip varus torque, knee varus torque, lower extremity stiffness, and ankle stiffness (p < 0.05). ΔL was affected by VD with a significant difference (p < 0.001). Conclusion: In patients with FAI, an unstable extremity has a higher injury risk than a stable extremity, and VD increases such risk. However, because the influence of the central nervous system on hip strategy is also affected, the effect on the unstable extremity is more significant and more likely to result in injury. Deepening the squat range may be an effective preventive measure for reducing injury risk of unstable extremities during drop landing. [ABSTRACT FROM AUTHOR]

BACKGROUND Lower limb asymmetries may be associated with increased injury risk in an active female population. However, an appropriate method for determining these asymmetries has not been established. HYPOTHESIS/PURPOSE The purpose of the present study was to examine the single leg drop landing (SLD) kinematic waveforms of female recreational athletes for the pelvis, hip, and knee using statistical parametric mapping (SPM). It was hypothesized that individual bilateral differences would be masked by the group analysis. STUDY DESIGN Descriptive Laboratory Study. METHODS The current study examined the sagittal and frontal plane pelvis, hip, and knee kinematics of nine physically active females during a SLD. To better elucidate whether asymmetries were present between right and left limbs throughout the landing phase, data were analyzed with SPM. The time-series data were comprised from initial contact to the bottom of the landing. A single subject design was also included to account for potential interindividual variability. RESULTS At the group level there were no statistical differences between the right and left limbs of participants for all variables. The single subject design yielded at least two significant asymmetries for all participants. Six out of the nine participants had bilateral differences for all six kinematic time-series. CONCLUSIONS The lack of significant differences at the group level may have been masked by movement variability amongst participants. For example, when considering participants with significant differences for hip flexion, four participants had greater values on the left limb and three on the right. A similar observation was made for knee flexion where three participants had significantly greater kinematic values on the left versus four on the right. Until a method is developed to adequately dichotomize lower extremities during the SLD task, a single subject design strategy be used with group analysis when making bilateral comparisons. [ABSTRACT FROM AUTHOR]

Purpose: Individuals with mechanical ankle instability (MAI) and functional ankle instability (FAI) present with residual movement dysfunctions after an initial lateral ankle sprain. This study investigated leg stiffness control to determine how behavioural characteristics between MAI and FAI differ during single-leg drop landing movement. Methods: Thirty individuals (10 with MAI, 10 with FAI, and 10 healthy controls) participated in this study. During single-leg drop landing movement, we estimated dimensionless leg stiffness, peak vertical force (PVF), change in the displacement of leg movement, loading rate, angular joint movement, and internal joint moment for impaired and unimpaired legs, respectively. Univariate one-way analysis of variance was used for each dependent variable across leg conditions. Results: The MAI group had lower dimensionless leg stiffness with greater change in the displacement of leg movement for the impaired leg than the FAI and control groups. Moreover, reduced leg stiffness was associated with greater hip joint flexion movement in the MAI group, whereas ankle dorsiflexion movement increased to decrease the leg stiffness in the FAI and control groups. Conclusion: These findings indicate that lower leg stiffness in the MAI group than in the FAI group may be attributed to compensatory actions to minimise reliance on their ankle movement after landing. [ABSTRACT FROM AUTHOR]

We quantified the effect of lead leg selection on landing force–time characteristics during a vertical drop landing (VDL) initiated with a step‐off. Plyometric‐trained subjects (male: n = 8; female: n = 5; age =23 ± 3.3 years; body mass =74.4 ± 11.2 kg) performed 6 step‐off‐initiated VDLs from a 45‐cm box (n = 3/lead leg). Pooled and lead leg stratified between‐limb comparisons of limb‐specific initial ground contact timing, peak vertical ground reaction force (Fzpeak), and early landing‐phase impulse (Impulse100ms) were assessed by a two‐factor, within‐subject ANOVA, and limb symmetry indexes were calculated (α = 0.05). Pooled data showed that the lead leg made contact prior to the trail leg and contributed a greater fraction to Fzpeak compared with the trail leg. Stratifying trials by lead leg selection led to significant between‐limb differences in Fzpeak (p < 0.05) and Impulse100ms (p < 0.01) with the right leg leading but not with the left leg leading. Lead leg selection in step‐off‐initiated VDLs influenced landing performance and limb symmetry indexes of variables associated with lower limb injury risk, suggesting the need to control for lead leg selection in these tasks. A step‐off may not be a suitable technique to initiate landing tasks when assessing limb symmetry. [ABSTRACT FROM AUTHOR]

Background: When landing from a jump or a drop, muscles contract before touchdown to anticipate imminent collision with the ground, soften ground contact and allow to return to a stable standing position without stepping or rebounding.Research Question: This study assesses the effect of the unsteadiness of the environment on the motor control of landing. The 'unsteady environment' was induced by asking participants to perform drop landings inside an aircraft that underwent trajectories parallel to Earth's surface. The participants also performed the same task in a 'steady environment' in our laboratory.Methods: Ground reaction forces, lower limb joints' movements and the activity of lower limb muscles were recorded. The stability of the landing was assessed by the vertical and anterior-posterior stability indexes, center of pressure measures and by the coefficient of variation of kinetic and kinematic parameters.Results: On one hand, participants slowdown their joint movements and reduce the knee joint excursion during landing, probably to avoid excessive movements that may induce imbalance. On the other hand, the stability of the landing is reduced while the variability of the movement is increased, illustrating a less stable and less consistent landing. In addition, whatever the environment, landing parameters associated with increased stiffness (i.e., increased impact forces and decreased joint range of motion) are correlated with decreased landing stability.Significance: Overall, landings in the'unsteady environment' appear to be more cautious but less stable and less finely tuned. Since the stability of the landing is not directly influenced by the steadiness of the environment, this more cautious behavior could be, at least in part, related to the fear/apprehension induced by sudden acceleration variations of the frame of the aircraft. [ABSTRACT FROM AUTHOR]

BACKGROUND: It remains unclear if plyometric training as a single component could improve landing mechanics that are potentially associated with lower risk of ACL injury in the long term OBJECTIVE: The purpose of this study was to investigate the influence of experience undertaking plyometrics on landing biomechanics in female athletes. METHODS: Non-jumpers with little experience in plyometric training (12 female college swimmers) and jumpers with five years of experience in plyometric training (12 female college long jumpers and high jumpers) were recruited to participate in two testing sessions: an isokinetic muscle force test for the dominant leg at 120 ∘ /s and a 40-cm drop landing test. An independent t test was applied to detect any significant effects between cohorts for selected muscle force, kinematic, kinetic, and electromyography variables. RESULTS: While female jumpers exhibited greater quadriceps eccentric strength (P = 0.013) and hamstring concentric strength (P = 0.023) during isokinetic testing than female swimmers, no significant differences were observed in kinematics, kinetics, and muscle activities during both drop landing and drop jumping. CONCLUSIONS: The results suggest that the female jumpers did not present any training-induced modification in landing mechanics regarding reducing injury risks compared with the swimmers. The current study revealed that plyometric training as a single component may not guarantee the development of low-risk landing mechanics for young female athletes. [ABSTRACT FROM AUTHOR]

This article looks into the effects of the initial knee flexion angle at the contact time on the peak of the impulsive lower limb forces during landing, and how these effects are related to muscular activities. The impact dynamics of drop landing is studied via a musculoskeletal model with eight Hill-type lower-limb muscles. A method is proposed for the representation of two landing strategies: landing with high and low joint stiffness. Then, in each landing strategy, the effect of the initial knee flexion angle on the peak ground reaction force (GRF), the peak knee ligaments force and the peak tibiofemoral contact force is investigated by considering different initial contact postures. It is observed that while landing with a flexed knee decreases the peak GRF in both landing strategies, it decreases the peak tibiofemoral and knee ligaments forces only in landing with low joint stiffness. Specifically, by increasing the initial knee flexion from 0° to 70°, the peak tibiofemoral and knee ligaments forces decrease monotonically by 54% and 82%, in landing with low joint stiffness. For high joint stiffness, however, as the initial knee flexion increases from 10° to 70°, the peak tibiofemoral force is seen to increase monotonically by 42% and the peak knee ligaments force is seen to have a non-monotonic behavior, first decreasing by 42%, and then, increasing by 250%. These results can be considered in training landing strategies to reduce the risk of knee injury. [ABSTRACT FROM AUTHOR]

Few studies have focused on the effect of fatigue severity on landing strategy. This study aimed to investigate the effect of fatigue progression on ground reaction force during landing. Eighteen participants performed a fatigue exercise protocol. Then participants performed drop landings at three levels of fatigue: no fatigue, medium fatigue, and severe fatigue. Multiple linear regression was conducted to identify the predictors of the peak vertical ground reaction force at each level of fatigue. Two-way ANOVAs were conducted to test the effect of fatigue on the vertical ground reaction force and the predictors. For the vertical ground reaction force, the knee joint stiffness and the knee angle at initial contact were the main predictors at no fatigue. The peak knee flexion angle and knee power were the main predictors at medium fatigue. However, the peak ankle plantarflexion moments became the main predictor at severe fatigue. The vertical ground reaction force decreased from no to medium fatigue (p = 0.001), and then increased from medium to severe fatigue (p = 0.034). The knee joint stiffness decreased from no to medium fatigue (p = 0.049), and then remained unchanged from medium to severe fatigue. The peak knee flexion angle increased from no to medium fatigue (p = 0.001), and then slightly decreased from medium to severe fatigue (p = 0.051). The results indicate that fatigue progression causes a transition from stiff to soft landing, and then to stiff landing. Participants used ankle joints more to control the landing intensity at severe fatigue. [ABSTRACT FROM AUTHOR]

PURPOSE We examined the immediate effect on ankle or knee joint cooling on the lower-extremity activation during a single-leg drop jump. METHODS Twenty healthy adults randomly completed three data collection sessions (a 20-minute ankle or knee joint cooling, or control). Two wireless surface electromyography (EMG, 2,000 Hz) electrodes were attached over the vastus medialis (VM) and the medial gastrocnemius (MG) on their right limb. Subjects were asked to drop down from a wooden box (a 30-cm height) on their right foot onto the force platform (2,000 Hz) and then performed an immediate jump as high as they could. Whole EMG signals (normalised by the mean EMG value recorded during a reference position) within the preactivation (100-ms prior to contact) and the ground contact (on the force platform) during the drop jump task were analysed using functional linear models(p=.05, Cohen’s d effect size: ES). RESULTS After knee joint cooling, (1) the VM activation was decreased during the ground contact (6 to 14%, 30 to 45%, 60 to 90% for ES of 0.50, 0.47, and 0.61, respectively) and (2) the MG activation was increased during the preactivation (84- to 29-ms prior to initial contact, ES=1.30) and the ground contact (59 to 100%, ES=1.40). No changes were observed under the condition of ankle joint cooling or control. CONCLUSIONS A 20-minute unilateral knee joint cooling may result in an ipsilateral quadriceps inhibition during a drop jump task. The gastrocnemius appears to increase activation as a compensatory strategy responding to the quadriceps inhibition. The altered neuromuscular activations do not seem to put an individual at risk of injury, resulting from compressive forces in the sagittal plane.

During landing, the lower limb joints work concertedly to reduce landing forces. Changing the biomechanics of one joint can alter landing strategies in other joints thus affecting the probability of injury. Therefore, understanding the mutual effects between the joints is crucial for the prevention of lower extremity injuries. The purpose of this study is to evaluate the effect of joint displacement and initial contact posture on the impact forces and joint kinematics during drop landing, via computational modeling. The impact dynamics of drop landing is modeled by a three link planar model. Different landing scenarios are then simulated to investigate how restricting the displacement of one joint and changing its initial contact angle affect the other joints' ranges of motion, the trunk motion, and the impact forces. Our study suggests that the impact force increases by up to 68 % , 100 % and 42 % , by restricting the hip, knee and ankle joints, respectively. Restricting each one of the hip and knee joints decreases the displacement of the other one. The association between the ankle displacement and the hip/knee motion depends on joints' stiffness and landing posture. Moreover, changing the landing posture affects the joints kinematics and impact forces significantly. A safe landing posture is a fore-foot landing with knee flexion angle of around 30° to 40° and a foot-ground angle of 40° to 55°, which decreases the impact force by more than 75 % in comparison to the erect posture with horizontal foot. The obtained results are of practical importance in training landing skills and designing force-reducing external components. [ABSTRACT FROM AUTHOR]

This study investigated the relationship between front foot contact (FFC) ground reaction forces (GRF) during the delivery stride, lower-limb strength, eccentric dexterity and power, and ball release speed (BRS) among pace bowlers. Thirteen high-level male pace bowlers performed double and single leg drop landings; isometric mid-thigh pull; countermovement jump; and pace bowling (two-over bowling spell measuring BRS and FFC GRF). The relationship between assessed variables and BRS was determined via frequentist and Bayesian multiple linear regression. The model including peak braking force was the most probable given the data (Bayes Factor=1.713) but provided only weak evidence in comparison to the null model. The results of frequentist and Bayesian modelling were comparable with peak braking force explaining 23.3% of the variance in BRS (F(1, 11)=4.64, P=0.054). Results indicate pace bowlers with greater peak braking GRF during FFC generally elicit higher BRS. However, the weak relationship between peak braking force and BRS, and the lack of a linear relationship between BRS and other variables, highlights the complexities and inter-individual variability inherent to pace bowling at a high-level. A more individual-focused analysis revealed varied strategies within pace bowlers to deliver the outcome (e.g., BRS) and should be considered in future study designs. [ABSTRACT FROM AUTHOR]

The quantification of plantar pressure distribution is widely done in the diagnosis of lower limbs deformities, gait analysis, footwear design, and sport applications. To date, a number of pressure insole layouts have been proposed, with different configurations according to their applications. The goal of this study is to assess the validity of a 16-sensors (1.5 × 1.5 cm) pressure insole to detect plantar pressure distribution during different tasks in the clinic and sport domains. The data of 39 healthy adults, acquired with a Pedar-X® system (Novel GmbH, Munich, Germany) during walking, weight lifting, and drop landing, were used to simulate the insole. The sensors were distributed by considering the location of the peak pressure on all trials: 4 on the hindfoot, 3 on the midfoot, and 9 on the forefoot. The following variables were computed with both systems and compared by estimating the Root Mean Square Error (RMSE): Peak/Mean Pressure, Ground Reaction Force (GRF), Center of Pressure (COP), the distance between COP and the origin, the Contact Area. The lowest (0.61%) and highest (82.4%) RMSE values were detected during gait on the medial-lateral COP and the GRF, respectively. This approach could be used for testing different layouts on various applications prior to production. [ABSTRACT FROM AUTHOR]

Purpose: this study aimed to investigate the footwear cushioning effects on impact forces and joint kinematics of the lower extremity during bipedal drop landings before and after acute exercise-induced fatigue protocol. Methods: in this case, 15 male collegiate basketball athletes performed drop landings from a 60 cm platform wearing highly-cushioned shoes (HS) and less cushioned shoes (control shoes, CS) before and after acute fatigue-inducing exercises (i.e., shuttle run combined with multiple vertical jumps). Force plates and motion capturing systems were synchronised to measure ground reaction forces and kinematic data during drop landings. Maximum jump height was analysed with one-way ANOVA. Two-way repeated measure ANOVAs were performed on each of the tested variables to examine if there was significant main effects of shoe and fatigue as well as the interaction. The significance level was set to 0.05. Results: rearfoot peak impact forces and loading rates significantly reduced when the participants wore HS in pre- and post-fatigue conditions. The peak loading rates in forefoot significantly reduced when HS were worn in post-fatigue. Compared with pre-fatigue, wearing HS contributed to with 24% and 13% reduction in forefoot and rearfoot peak loading rates, respectively, and the occurrence times of first and second peak impact forces and loading rates were much later. In the post-fatigue, a significant increase in the initial contact and minimum angles of the ankle were observed in HS compared with CS. Conclusion: these findings suggest that footwear cushioning can reduce landing-related rearfoot impact forces regardless of fatigue conditions. In a situation where the neuromuscular activity is reduced or absent such as post-fatigue wearing better cushioning shoes show superior attenuation, as indicated by lower forefoot and rearfoot impacts.

Context: Latency is a reliable temporal metric used to evaluate sensorimotor integration of the fibularis longus (FL) and fibularis brevis (FB) during lateral ankle sprain perturbations. Currently, no clinical recommendations exist to select appropriate thresholds to evaluate the closed-loop reflex response of the lateral ankle musculature. The purpose of this study was to assess threshold value on latency of the FL and FB during an unanticipated inversion perturbation that simulates the mechanism of a lateral ankle sprain., Design: Descriptive laboratory study., Methods: Twenty healthy adults with no history of lateral ankle sprain injury completed an unanticipated single-leg drop landing onto a 25° laterally inclined force platform from a height of 30 cm. Surface electromyography recorded muscle activity data from the FL and FB during the inversion perturbation. Latency was identified at points where muscle activity exceeded 2, 5, and 10 SD above the average muscle activity 200 milliseconds prior to foot contact, and compared across threshold value using a 1-way analysis of variance (P < .05)., Results: The 2 SD threshold was significantly shorter than both 5 SD and 10 SD thresholds for the FL (P < .01) and FB (P < .01). Likewise, the 5 SD threshold was significantly shorter than the 10 SD thresholds for FL (P = .004) and FB (P = .003)., Conclusions: More sensitive thresholds results in a shorter closed-loop reflexive response compared to the more rigorous thresholds. We recommend that selection of the appropriate threshold to identify latency of the lateral ankle musculature should be based on the device used to simulate a lateral ankle sprain and the ankle inversion velocity produced during the ankle inversion perturbation.

The quantification of plantar pressure distribution is widely done in the diagnosis of lower limbs deformities, gait analysis, footwear design, and sport applications. To date, a number of pressure insole layouts have been proposed, with different configurations according to their applications. The goal of this study is to assess the validity of a 16-sensors (1.5 × 1.5 cm) pressure insole to detect plantar pressure distribution during different tasks in the clinic and sport domains. The data of 39 healthy adults, acquired with a Pedar-X® system (Novel GmbH, Munich, Germany) during walking, weight lifting, and drop landing, were used to simulate the insole. The sensors were distributed by considering the location of the peak pressure on all trials: 4 on the hindfoot, 3 on the midfoot, and 9 on the forefoot. The following variables were computed with both systems and compared by estimating the Root Mean Square Error (RMSE): Peak/Mean Pressure, Ground Reaction Force (GRF), Center of Pressure (COP), the distance between COP and the origin, the Contact Area. The lowest (0.61%) and highest (82.4%) RMSE values were detected during gait on the medial-lateral COP and the GRF, respectively. This approach could be used for testing different layouts on various applications prior to production.

This study examined the effect of wearing time on comfort perception and landing biomechanics of basketball shoes with different midsole hardness. Fifteen basketball players performed drop landing and layup first step while wearing shoes of different wearing time (new, 2-, 4-, 6- and 8-week) and hardness (soft, medium and hard). Two-way ANOVA with repeated measures was performed on GRF, ankle kinematic and comfort perception variables. Increased wearing time was associated with poorer force attenuation and comfort perception during landing activities (p < 0.05). The new shoes had significantly smaller forefoot (2- and 4-week) and rearfoot peak GRF impacts (all time conditions) in drop landing and smaller rearfoot peak GRF impact (6- and 8-week) in layup; shoes with 4-week of wearing time had significantly better perceptions of forefoot cushioning, forefoot stability, rearfoot cushioning, rearfoot stability and overall comfort than the new shoes (p < 0.05). Compared with hard shoes, the soft shoes had better rearfoot cushioning but poorer forefoot cushioning (p < 0.05). Shoe hardness and wearing time would play an influential role in GRF and comfort perception, but not in ankle kinematics. Although shoe cushioning performance would decrease even after a short wearing period, the best comfort perception was found at 4-week wearing time. [ABSTRACT FROM AUTHOR]

• Lateral ankle sprain injury mechanics are often examined in laboratory research. • Ankle joint and impact kinetics were examined during inversion perturbations. • Anticipating inversion perturbations altered ankle joint and impact kinetics. • Researchers should use protocols that mitigate anticipatory responses. Anticipatory responses to inversion perturbations can prevent an accurate assessment of lateral ankle sprain mechanics when using injury simulations. Despite recent evidence of the anticipatory motor control strategies utilized during inversion perturbations, kinetic compensations during anticipated inversion perturbations are currently unknown. The purpose of this investigation was to examine the influence of anticipation to an inversion perturbation during a single-leg drop landing on ankle joint and impact kinetics. Fifteen young adults with no lateral ankle sprain history completed unanticipated and anticipated single-leg drop landings onto a 25° laterally inclined platform from a height of 30 cm. One-dimensional statistical parametric mapping (SPM) was used to analyze net ankle moments and ground reaction forces (GRF) during the first 150 ms post-landing, while peak GRFs, time to peak GRF, peak and average loading rates were compared using a dependent samples t -test (p ≤ 0.05). Results from the SPM analysis revealed significantly greater plantar flexion moment from 58 to 83 ms post-landing (p = 0.004; d = 0.64–0.77), inversion moment from 89 to 91 ms post-landing (p = 0.050; d = 0.58–0.60), and medial GRF from 62 to 97 ms post-landing (p < 0.001; d = 1.00–2.39) during the unanticipated landing condition. Moreover, significantly greater peak plantarflexion (p < 0.001; d = 1.10) and peak inversion moment (p = 0.007; d = 0.94), as well as greater peak (p = 0.002; d = 1.03) and average (p = 0.042; d = 0.66) medial loading rates, were found during the unanticipated landing condition. Our findings suggest alterations to ankle joint and impact kinetics occur during a single-leg drop landing when inversion perturbations are anticipated. Researchers and practitioners using drop-landings onto a tilted surface to assess lateral ankle sprain injury risk should consider implementing protocols that mitigate anticipatory responses. [ABSTRACT FROM AUTHOR]

Purpose: Overuse injuries are common in sport, but complete understanding of injury risk factors remains incomplete. Although biomechanical studies frequently examine musculoskeletal injury mechanisms, human movement variability studies aim to better understand neuromotor functioning, with proposed connections between overuse injury mechanisms and changes in motor variability.Method: In a narrative review, we discuss the variability-overuse injury hypothesis, which suggests repeated load application leads to mechanical tissue breakdown and subsequent injury when exceeding the rate of physiological adaptation. Due to the multidisciplinary nature of this hypothesis, we incorporate concepts from motor control, neurophysiology, biomechanics, as well as research design and data analysis. We therefore summarize multiple perspectives while proposing theoretical relationships between movement variability and lower extremity overuse injuries.Results: Experimental data are presented and summarized from published experiments examining interactions between experimental task demands and movement variability in the context of drop landing movements, along with comparisons to previous movement variability studies.Conclusion: We provide a conceptual framework for sports medicine researchers interested in predicting and preventing sports injuries. Under performance conditions with greater task demands, we predict reduced trial-to-trial movement variability that could increase the likelihood of overuse injuries. [ABSTRACT FROM AUTHOR]

Abstract Non-contact anterior cruciate ligament (ACL) injuries account for 70% of all ACL injuries, and can lead to missed time from activity for athletes and a predisposition for knee osteoarthritis. Prior research has shown that athletes who land in a stiff manner, with larger internal knee adduction and extension moments, are at greater risk for an ACL injury. A three-dimensional accelerometer placed at the tibial tuberosity may prove to be a low-cost means of assessing these risk factors. The primary purpose of this study was to compare tibial accelerations during drop landings with kinematic and kinetic risk factors for ACL injury measured with three-dimensional motion capture. The secondary purpose of this study was to compare these measures between soft and stiff landings. Participants were instructed to land bilaterally in preferred, soft, and stiff manners. Peak knee flexion decreased significantly from soft to stiff landings. Peak internal knee extension moment, peak anterior/posterior knee acceleration, and peak medial knee acceleration all increased significantly from soft to stiff landings. No associations were found between landing condition and either frontal plane knee angle at maximum vertical ground reaction force or peak internal knee adduction moment. Significant positive associations between kinetics and accelerations were found only in the sagittal plane. As such, while a three-dimensional accelerometer could discern between soft and stiff landings in both planes, it may be better suited to predict kinetic risk factors in the sagittal plane. [ABSTRACT FROM AUTHOR]

Purpose: Core stability training (CST) has increased among athletes. The study hypothesis is that neuromuscular training and exercises of central area of trunk, pelvis and hip can reduce injury risk, and specifically peak vertical ground reaction forces in drop landing task. Therefore, the objective of this study was to evaluate kinetics during single leg drop landing test following a CST intervention. Methods: The present research was a quasi-experimental study with pretest/posttest and a control group. After giving their informed written consent, 30 athletes (15 in the experimental group, and 15 in the control group) volunteered to participate in the training program consisting of CST sessions, 3 times per week for 8 weeks. Training group was performed the CST during 8 weeks but control group did not perform these exercises. Kinetics variables in pretest and posttest during single-leg drop landing were measured by motion analysis and force plate device. To compare the obtained data, mixed ANOVA repeated measure at significance level of P

Purpose: The purpose of this study was to examine the effects of landing on a combined inversion and plantarflexion surface on the ankle kinematics and electromyographic (EMG) activities of medial gastrocnemius (MG), peroneus longus (PL), and tibialis anterior (TA) muscles. Methods: Twelve recreational athletes performed five drop landings from an overhead bar of 30 cm height on to three surfaces: a flat surface, a 25° inversion surface, and a combined surface of 25° inversion and 25° plantarflexion. The kinematic variables and integrated EMG (IEMG) of the three muscles were assessed using a one-way repeated measures ANOVA and a 3 × 3 (surface × muscle) ANOVA, respectively (p

Context: Several tasks have been used to examine landing biomechanics for evaluation and rehabilitation, especially as related to anterior cruciate ligament injuries. However, comparing results among studies in which different tasks were used can be difficult, and it is unclear which task may be most appropriate. Objective: To compare lower extremity biomechanics across 5 commonly used landing tasks. Design: Descriptive laboratory study. Setting: University-operated US Air Force Special Operations Forces human performance research laboratory. Patients or Other Participants: A total of 65 US Air Force Special Tactics Operators (age ± 27.7 6 5.0 years, height ± 176.5 6 5.7 cm, mass ± 83.1 6 9.1 kg). Intervention(s): Kinematic and kinetic analysis of doubleand single-legged drop landing, double- and single-legged stop jump, and forward jump to single-legged landing. Main Outcome Measure(s): Hip-, knee-, and ankle-joint kinematics; knee-joint forces and moments; and ground reaction forces (GRFs) were the dependent measures. We used repeated-measures analyses of variance or Friedman tests, as appropriate, to assess within-subject differences across tasks. Results: Peak vertical GRF and peak knee-flexion angle were different among all tasks (P , .001). Single-legged landings generated higher vertical GRF (v2 ± 244.68, P , .001) and lower peak knee-flexion values (F4,64 ± 209.33, P , .001) except for forward jump to single-legged landing, which had the second highest peak vertical GRF and the lowest peak knee-flexion value. The single-legged drop landing generated the highest vertical (v2 ± 244.68, P , .001) and posterior (v2 ± 164.46, P , .001) GRFs. Peak knee-valgus moment was higher during the double-legged drop landing (v2 ± 239.63, P , .001) but similar for all others. Conclusions: Different landing tasks elicited different biomechanical responses; no single task was best for assessing a wide range of biomechanical variables related to anterior cruciate ligament injuries. Therefore, depending on the goals of the study, using multiple assessment tasks should be considered. [ABSTRACT FROM AUTHOR]

Objectives: To date, few rigorous scientific studies have been conducted to understand the impact mechanics and muscle activation characteristics of different landing tasks and the influence of shoe properties. The aim of this study was to examine the effects of shoe cushioning on impact biomechanics and muscular responses during drop landings.Design: A single-blinded and randomized design.Methods: Twelve male collegiate basketball players performed bipedal landings from self-initiated and unexpected drops (SIDL and UDL) from a 60-cm height wearing highly-cushioned basketball shoes (Bball) and less cushioned control shoes (CC). Sagittal plane kinematics, ground reaction forces (GRF), accelerations of the shoe heel-cup, and electromyography (EMG) of the tibialis anterior (TA), lateral gastrocnemius, rectus femoris (RF), vastus lateralis (VL), and biceps femoris (BF) were collected simultaneously.Results: In SIDL, no significant differences were observed in peak vertical GRF, peak heel acceleration, or EMG amplitude (root mean square, EMGRMS) for all muscles between the two shoe conditions. In UDL, however, both peak vertical GRF and heel acceleration were significantly lower in Bball compared to CC. Furthermore, the EMGRMS of TA, RF, VL, and BF muscles showed a significant decrease in Bball compared to CC within the 50ms after contact.Conclusions: These observations suggest that shoe cushioning may make only a limited contribution to reducing landing impact forces provided that neuromuscular adjustments occur properly, as in SIDL. However, in the situation where pre-planned neuromuscular activity is reduced or absent, as in UDL, wearing a highly-cushioned shoe decreases peak impact and muscle activation in the 50ms after ground contact. [ABSTRACT FROM AUTHOR]

Few rigorous scientific studies have investigated how the corresponding neuromuscular activity in the lower extremity occurs during different landing control movements in response to different impact signals. This study aimed to determine the potential shoe effects on impact signals, neuromuscular responses and their possible interactions in different human landing movements. Twelve male basketball players were required to wear high-cushioned basketball shoes (BS) and minimally cushioned control shoes (CC) to perform active drop jump landings (DJL) and passive landings (PL). Ground reaction forces and EMG amplitude (root mean square, EMGRMS) of the leg muscles within 50 ms before and after the landing movements were collected simultaneously. No shoe effect was found on the characteristics of impact signals and neuromuscular activity during the contact phase of DJL. By contrast, for PL, the values of maximal ground reaction force and the peak loading rate were evidently lower in the BS condition than in the CC condition (p < 0.05). Meanwhile, the EMGRMS of all muscles demonstrated a significant decrease in the BS condition compared with the CC condition within 50 ms after contact (p < 0.05). These findings suggest that under the condition in which related muscles are activated improperly, a neuromuscular adaptation occurs in response to different impact signals. [ABSTRACT FROM AUTHOR]

Background: Mechanical loading during exercise has been shown to promote tissue remodeling. Safe and accessible exercise may be beneficial to populations at risk of diminished bone and joint health. We examined the effect of drop height and instruction on knee loading during a drop-landing task and proposed a task that makes use of drop heights that may be appropriate for rehabilitation purposes and functional in daily life to examine transient knee joint loads. Methods: Twenty males (22.0 ± 2.8 years) performed drop landings from 22 cm (low) and 44 cm (high) heights, each under three instructions: 'land naturally' (natural), 'softly' (soft), and 'stiffly' (stiff). Knee compression force and external flexion moment were estimated using three-dimensional inverse dynamics and normalized to body mass. Results: Peak knee compression force was larger ( p < 0.001) for high (17.8 ± 0.63 N/kg) than low (14.8 ± 0.61 N/kg) heights. There was an increase ( p < 0.001) in the knee compression force across soft (11.8 ± 0.40 N/kg), natural (17.0 ± 0.62 N/kg), and stiff (20.2 ± 0.67 N/kg) instructions. Peak knee flexion moment in high-natural (2.12 ± 0.08 Nm/kg) was larger ( p < 0.001) than in high-soft (1.88 ± 0.08 Nm/kg), but lower than in high-stiff (2.23 ± 0.08 Nm/kg). No differences in peak knee flexion moment were observed across instructions for the low height. Conclusions: We propose a drop-landing task that creates a scalable increase in knee compression loading. The absence of increased knee flexion moment with drop from the low height, compared to high, suggests that individuals could perform the task without incremental risk of knee injury. This task could be used in future studies to examine the effect of acute bouts of mechanical loading on bone and cartilage metabolism. [ABSTRACT FROM AUTHOR]

Although landing in a plantarflexion and inversion position is a well-known characteristic of lateral ankle sprains, the associated kinematics of the knee and hip is largely unknown. Therefore, the purpose of this study was to examine the changes in knee and hip kinematics during landings on an altered landing surface of combined plantarflexion and inversion. Participants performed five drop landings from 30 cm onto a trapdoor platform in three different conditions: flat landing surface, 25° inversion, or a combined 25° plantarflexion and 25° inversion. Kinematic data were collected using a seven camera motion capture system. A 2 × 3 (leg × surface) repeated measures ANOVA was used for statistical analysis. The combined surface showed decreased knee and hip flexion range of motion (ROM) and increased knee abduction ROM (p < 0.05). The altered landing surface creates a stiff landing pattern where reductions in sagittal plane motion are transferred to the frontal plane, resulting in increased knee abduction. A stiff landing pattern is frequently related to increased risk of anterior cruciate ligament injury. It may be beneficial for athletes at risk to train for alternate methods of increasing their sagittal plane motion of the knee and hip with active knee or trunk flexion. [ABSTRACT FROM AUTHOR]

Landing on the ground on one’s feet implies that the energy gained during the fall be dissipated. The aim of this study is to assess human motor control of landing in different conditions of fall initiation, simulated gravity, and sensory neural input. Six participants performed drop landings using a trapdoor system and landings from self-initiated counter-movement jumps in microgravity conditions simulated in a weightlessness environment by different pull-down forces of 1-, 0.6-, 0.4-, and 0.2 g. External forces applied to the body, orientation of the lower limb segments, and muscular activity of 6 lower limb muscles were recorded synchronously. Our results show that 1) subjects are able to land and stabilize in all experimental conditions; 2) prelanding muscular activity is always present, emphasizing the capacity of the central nervous system to approximate the instant of touchdown; 3) the kinetics and muscular activity are adjusted to the amount of energy gained during the fall; 4) the control of landing seems less finely controlled in drop landings as suggested by higher impact forces and loading rates, plus lower mechanical work done during landing for a given amount of energy to be dissipated. In conclusion, humans seem able to adapt the control of landing according to the amount of energy to be dissipated in an environment where sensory information is altered, even under conditions of non-self-initiated falls. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this study was to examine the effects of landing on a combined inversion and plantarflexion surface on the ankle kinematics and electromyographic (EMG) activities of medial gastrocnemius (MG), peroneus longus (PL), and tibialis anterior (TA) muscles. Methods Twelve recreational athletes performed five drop landings from an overhead bar of 30 cm height on to three surfaces: a flat surface, a 25° inversion surface, and a combined surface of 25° inversion and 25° plantarflexion. The kinematic variables and integrated EMG (IEMG) of the three muscles were assessed using a one-way repeated measures ANOVA and a 3 × 3 (surface × muscle) ANOVA, respectively ( p < 0.05). Results The IEMG results showed a significant muscle by surface interaction. The flat surface induced higher TA activity than the two tilted surfaces. The inverted surface produced significantly higher inversion peak angle and velocity than the flat surface, but similar PL activity across the surfaces. The MG IEMG, ankle plantarflexion angle, and inversion range of motion were significantly higher for the combined surface compared to the inverted surface. Conclusion These findings suggest that compared to the inversion surface, the combined plantarflexion and inversion surface seems to provide a more unstable surface condition for lateral ankle sprains during landing. [ABSTRACT FROM AUTHOR]

The ankle joint’s role in shock absorption during landing has been researched in many studies, which have found that landing with higher amounts of plantarflexion (PF) results in lower peak vertical ground reaction forces and loading rates. However, there has not yet been a study that compares drop landings within participants along a quantitative continuum of PF angles. Using a custom-written real-time feedback program, participants adjusted their ankles to an instructed PF angle and dropped onto two force platforms. For increasing PF, peak ground reaction force and peak loading rate during weight acceptance decreased significantly. The hip’s contribution to peak support moment decreased as PF at initial contact increased up to 30°. The ankle and knee contributions increased over this same continuum of PF angles. There appears to be no optimal PF angle based on peak ground reaction force and loading rate measurements, but there may be an optimum where joint contributions to peak support moment converge and the hip moment’s contribution is minimised. [ABSTRACT FROM AUTHOR]

Context: People with chronic ankle instability (CAI) exhibit less weight-bearing dorsiflexion range of motion (ROM) and less knee flexion during landing than people with stable ankles. Examining the relationship between dorsiflexion ROM and landing biomechanics may identify a modifiable factor associated with altered kinematics and kinetics during landing tasks. Objective: To examine the relationship between weightbearing dorsiflexion ROM and single-legged landing biomechanics in persons with CAI. Design: Cross-sectional study. Setting: Laboratory. Patients or Other Participants: Fifteen physically active persons with CAI (5 men, 10 women; age = 21.9 ± 2.1 years, height = 168.7 ± 9.0 cm, mass = 69.4 ± 13.3 kg) participated. Intervention(s): Participants performed dorsiflexion ROM and single-legged landings from a 40-cm height. Sagittal-plane kinematics of the lower extremity and ground reaction forces (GRFs) were captured during landing. Main Outcome Measure(s): Static dorsiflexion was measured using the weight-bearing-lunge test. Kinematics of the ankle, knee, and hip were observed at initial contact, maximum angle, and sagittal displacement. Sagittal displacements of the ankle, knee, and hip were summed to examine overall sagittal displacement. Kinetic variables were maximum posterior and vertical GRFs normalized to body weight. We used Pearson product moment correlations to evaluate the relationships between dorsiflexion ROM and landing biomechanics. Correlations (r) were interpreted as weak (0.00-0.40), moderate (0.41- 0.69), or strong (0.70-1.00). The coefficient of determination (r²) was used to determine the amount of explained variance among variables. Results: Static dorsiflexion ROM was moderately correlated with maximum dorsiflexion (r = 0.49, r² = 0.24), ankle displacement (r = 0.47, r² = 0.22), and total displacement (r = 0.67, r² = 0.45) during landing. Dorsiflexion ROM measured statically and during landing demonstrated moderate to strong correlations with maximum knee (r = 0.69-0.74, r² = 0.47-0.55) and hip (r = 0.50-0.64, r² = 0.25-0.40) flexion, hip (r = 0.53- 0.55, r² = 0.28-0.30) and knee (r = 0.53-0.70, r² = 0.28-0.49) displacement, and vertical GRF (-0.47- -0.50, r² = 0.22-0.25). Conclusions: Dorsiflexion ROM was moderately to strongly related to sagittal-plane kinematics and maximum vertical GRF during single-legged landing in persons with CAI. Persons with less dorsiflexion ROM demonstrated a more erect landing posture and greater GRF. [ABSTRACT FROM AUTHOR]

Background: The ankle is prone to injury during drop landing with usual residual symptoms, and functional ankle instability (FAI) is the most common. Vision guarantees the postural stability of patients with FAI, and visual deprivation (VD) increases their risk of injury when completing various movements. This study explored injury risk during drop landing in patients with FAI under VD through the kinetics of lower extremities. Methods: A total of 12 males with FAI participated in the study (age, 23.0 ± 0.8 years; height, 1.68 ± 0.06 m; weight, and 62.2 ± 10.4 kg) completed single-leg drop landings under visual presence (VP) and VD conditions. Ground reaction force (GRF), time to peak GRF, joint torque, and vertical length variation (ΔL) were measured. Results: Significant effects were detected in the group for time to peak lateral GRF ( p = 0.004), hip extensor torque ( p = 0.022), ankle plantarflexion torque ( p < 0.001), ankle varus torque ( p = 0.021), lower extremity stiffness ( p = 0.035), and ankle stiffness ( p < 0.001). Significant effects of conditions were detected for vertical GRF, time to peak vertical and lateral GRF, loading rate, hip extensor torque, knee extensor torque, hip varus torque, knee varus torque, lower extremity stiffness, and ankle stiffness ( p < 0.05). ΔL was affected by VD with a significant difference ( p < 0.001). Conclusion: In patients with FAI, an unstable extremity has a higher injury risk than a stable extremity, and VD increases such risk. However, because the influence of the central nervous system on hip strategy is also affected, the effect on the unstable extremity is more significant and more likely to result in injury. Deepening the squat range may be an effective preventive measure for reducing injury risk of unstable extremities during drop landing., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Meng, Kong, Kong, Zhang, Shen and Hao.)

Inhibitions in the acquisition of accurate information about the environment can affect control of the lower extremities and lead to anterior cruciate ligament injury. This study aimed to clarify the effects of limited prior knowledge of the height of the fall, as well as limited visual input, on lower limb and trunk motion and ground reaction force during landing. Twenty healthy university students were recruited. Drop landings from a 30-cm platform were measured under three conditions: (1) unknown, without prior knowledge of the height of the fall and without visual input; (2) known, with prior knowledge of the height of the fall and without visual input; and (3) control, with prior knowledge of the height of the fall and visual input. In the unknown condition, the peak ground reaction force for the vertical and posterior directions was significantly higher than that in the known and control conditions; leg and knee stiffness, ankle joint work, and joint flexion motion of the knee, ankle, and trunk after landing were decreased as well. In the known condition, there were no significant differences in leg and knee stiffness and vertical ground reaction force compared to the control condition. The results of this study indicate that the risk of anterior cruciate ligament injury during landing increases when individuals have limited visual input and prior knowledge of the height of the fall. This finding suggests that an accurate perception of the surrounding environment may help prevent anterior cruciate ligament injuries. • The effect of prior knowledge of the height the fall on landing was examined. • Lower limb joint motion was small when participants were not informed of the height the fall. • The ground reaction force was large when participants were not informed of the height the fall. • Accurate perception of one's falling height may help prevent anterior cruciate ligament injury. [ABSTRACT FROM AUTHOR]

The article discusses the changes made in biomechanics of drop-jump landing during intermittent exercise. It mentions the factors associated with ligament injury risk, followed by intermittent exercise protocol (IEP) and a control session with no exercise enhanced the performance. It reflects that knee shear force and ankle loading decreased due to IEP and sport specific IEP produced better results on landing.

The focus of this research was to determine if female dancers have differing kinematic and kinetic characteristics when landing from three heights (0.2, 0.5, and 0.8 m) both with and without vision compared to non-dancers. It was hypothesized that dancers would show differing kinematic and kinetic patterns of control due to their increased proprioceptive awareness. Eight collegiate dancers and seven collegiate controls who were neither dancers nor collegiate jumping athletes volunteered for this study. Sagittal plane lower limb joint angles were measured at 100 Hz prior to landing through stability with a high-speed camera, and peak vertical ground reaction forces relative to body weight were recorded with an indwelling force plate. Results indicated biomechanical differences across height and vision conditions, as well as between groups. Kinetic results showed a significant height effect with respect to vertical ground reaction forces. From the 0.8 m drop, both dancers and non-dancers produced significantly greater ground reaction forces when landing without vision compared to when they landed with vision. No significant kinetic differences were found between groups. Kinematic results revealed a significant height effect for the hip and knee angles across groups and vision conditions, meaning that as drop height increased, the participants demonstrated greater range of motion in their hip and knee joints. Dancers and non-dancers responded differently when dropping from 0.8 m without vision. Dancers significantly increased hip flexion compared to landing with vision, while non-dancers tended to stiffen up and reduced hip flexion. These findings suggest that dancers utilize proprioceptive input more effectively as they adopted a hip strategy (flexion of the hips) to maintain stability. Training dancers without vision may impact dance instruction and reduce the risk of injuries when landing. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: The purpose of this study was to examine effects of a sport version of a semi-rigid ankle brace (Element™) and a soft ankle brace (ASO) on ankle biomechanics and ground reaction forces (GRFs) during a drop landing activity in subjects with chronic ankle instability (CAI) compared to healthy subjects with no history of CAI. Methods: Ten healthy subjects and 10 subjects who had multiple ankle sprains participated in the study as the control and unstable subjects, respectively. The CAI subjects were age, body mass index and gender matched with the control subjects. The arch index and ankle functions of the subjects were measured in a subject screening session. During the biomechanical test session, participants performed five trials of drop landing from 0.6 m, wearing no brace (NB), Element™ brace and ASO brace. Simultaneous recording of three-dimensional kinematic (240 Hz) and GRF (1200 Hz) data were performed. Results: The CAI subjects had lower ankle functional survey scores. The arch index and deformity results showed greater arch deformity of Element™ against a static load than in NB and ASO due to greater initial arch position held by the brace. CAI participants had greater eversion velocity than healthy controls. The ASO brace reduced the first peak vertical GRF whereas Element™ increased 2nd peak vertical GRF. Element™ brace reduced eversion range of motion (ROM) and peak eversion velocity compared to NB and ASO. In addition, Element™ reduced dorsiflexion ROM and increased peak plantarflexion moment compared to NB and ASO. Conclusion: Results of static arch measurements and dynamic ankle motion suggest that the restrictions offered by both braces are in part due to more dorsiflexed ankle positions at contact, and higher initial arch position and stiffer ankle for Element™. [Copyright &y& Elsevier]

There is currently no consensus in the literature on whether the magnitude of the ground reaction force or loading rate decreases or increases with muscle fatigue. In this article, the effects of lower extremity muscle fatigue on the magnitude of the ground reaction force and loading rate during running and drop landing are examined. Through a systematic search of the literature, 24 articles are identified that satisfy the inclusion criteria and study the relationship between fatigue and the ground reaction force variables during running, single-leg drop landing, and bilateral drop landing. The articles are categorized based on the type of locomotion they study. To determine whether or not the ground reaction force peaks/loading rate are markedly affected by fatigue, meta-analyses are conducted both separately for each type of locomotion and for an aggregate of all studies. The results of the meta-analyses show that the ground reaction force active peak significantly decreases for the following study groups: aggregate of all included studies, studies of drop landing (both single-leg and bilateral), and studies of bilateral landing only. The ground reaction force active peak did not significantly change in running and single-leg drop landing. The effects of muscle fatigue on the magnitude of the ground reaction force impact peak and loading rate was always insignificant. [ABSTRACT FROM AUTHOR]

Abstract: The biomechanical difference between the dominant and non-dominant limb has seldom been studied during double-leg landing. The objective of this study was to evaluate the effectiveness of limb laterality on the ankle kinematics, kinetics and electromyogram (EMG) during drop landing. Sixteen healthy adults were recruited and dropped individually from platforms with three different heights (0.32m, 0.52m, and 0.72m). The ground reaction force, ankle joint kinematics, and surface EMG of tibialis anterior (TA) and lateral gastrocnemius (LG) were measured in both lower extremities. Two-way analysis of variance was used to analyze the effects of laterality and dropping height. The peak angular velocities in dorsiflexion and abduction were significantly higher in the dominant ankle, whereas the pre- and post-landing EMG amplitudes of the TA were significantly higher in the non-dominant limb. Compared with the dominant side, the non-dominant ankle has a more effective protective mechanism in that excessive joint motion is restrained by greater ankle flexor activity. Compared with the non-dominant side, the dominant ankle joint is in greater injury risk during drop landing, and data measured in the dominant limb may produce more conservative conclusions for injury protection or prediction. [Copyright &y& Elsevier]

[Purpose] The purpose of this study was to determine the effect of two different drop landing tasks on knee kinematics and muscle activities. [Subjects] Nine healthy males participated in this study. [Methods] The subjects performed two different drop landing tasks from a box (height, 30 cm), with the dominant leg and both legs. A motion analysis system was used to obtain knee valgus and maximal flexion angles in the frontal and sagittal planes. An electromyography system was used to record muscle activities of the lower extremities during the drop landing task. [Results] Single leg landing increased the knee valgus angle, decreased the knee flexion angle, and increased the activity of the lower extremity muscles as compared to double leg landing. [Conclusion] Increased knee valgus angle and decreased knee flexion angle with single leg landing may be related to the increased risk of anterior cruciate ligament injury. [ABSTRACT FROM AUTHOR]

The article examines the association of lower-extremity and frontal plane motions in squatting and landing, the existence of gender differences and the relationship of squat or hip abduction strength with knee valgus while landing. It notes that squat strength and observing squat kinematics is not likely the method of identifying those at risk on anterior cruciate ligament (ACL) injuries, however, women may have hip abduction strength. The discussion of the findings is also included.