The Effects of the Functional Garment on the Biomechanics During the Single Leg Drop Landing.

Background: Female athletes with an anterior cruciate ligament (ACL) injury should decrease both dynamic valgus of the knee and related kinematics of the lower limb during single leg drop landing (SLDL). A functional biomechanics garment (FBG) may help prevent injury by improved kinematics during motion. The purpose of this study was to investigate the effects of the FBG on the biomechanics of SLDL.Methods: Seventeen female university basketball players participated in this study. Characteristics of the FBG were designed based on biomechanics during weight-loaded performance of human movement such as gait, running, and jumping. Lower limb kinematic and kinetic data were calculated using a three-dimensional motion analysis system during a SLDL task with and without the FBG. The hip, knee, and ankle angles and joint moments were automatically calculated from the standard plug-in gait lower body model. The average values of lower limb kinematics and kinetics in the sagittal and frontal planes from 3 SLDL with and without FBG were measured and compared.Results: The maximum varus angle of the knee showed a significant difference between with FBG (15.3±15.1 degrees) and without FBG (5.9±15.4 degrees). (p<0.01; effect size 0.6) Conclusion: Use of the FBG decreases dynamic knee valgus, which reduces risk of knee injury. The FBG can reduce dynamic knee valgus during SLDL in athletic rehabilitation and to play a role in the prevention of knee injury.

Variability in Touchdown Technique and Ground Reaction Force Components during Drop Landing of 107 Healthy Adults

The article's abstract is not available.

Drop Landing Biomechanics in Individuals With and Without a Concussion History

Research has identified an increased risk of lower extremity injury postconcussion, which may be due to aberrant biomechanics during dynamic tasks. The purpose of this study was to compare the drop landing biomechanics between individuals with and without a concussion history. Twenty-five individuals with and 25 without a concussion history were matched on age (±3 y), sex, and body mass index (±1 kg/m2). Three-dimensional landing biomechanics were recorded to obtain dependent variables (peak vertical ground reaction force, loading rate, knee flexion angle and external moment, knee abduction angle and external moment, and knee flexion and abduction angle at ground contact). A 1-way multivariate analysis of variance compared outcomes between groups. There was no difference in drop landing biomechanics between individuals with and without a concussion history (F10,39 = 0.460, P = .877, Wilk Λ = .918). There was an effect of time since concussion on knee flexion characteristics. Time since most recent concussion explained a significant amount of variation in both peak (ΔR2 = .177, β = −0.305, ΔP = .046) and initial ground contact (ΔR2 = .292, β = −0.204, ΔP = .008) knee flexion angle after covarying for sex and body mass index. Therefore, time since concussion should be considered when evaluating biomechanical patterns.

Comparisons of Vastus Lateralis Architecture and Biomechanical Characteristics during Drop Landing in Young Football Players

PURPOSE: The purpose of this study was to compare the vastus lateralis (VL) architecture and exercise biomechanics indices during drop landing in young football players.METHODS: Fifteen young football players were divided into a long vastus lateralis muscle fascicle length group (LFG, n=8) and short vastus lateralis muscle fascicle length group (SFG, n=7). All of the participants performed drop landing onto the ground reaction force plate from a platform 30 cm high. The muscle activities of the VL, tibialis anterior (TA), and gastrocnemius (GCM), angular velocity, and ground reaction force in the ankle, knee, and hip joints were measured during drop landing.RESULTS: The VL muscle activity (<i>p</i>=.032), ankle ground contact angle (<i>p</i>=.027), ankle maximum flexion angle (<i>p</i>=.014), knee maximum flexion angle (<i>p</i>=.007), and ground reaction force per body weight (<i>p</i>=.032) were significantly higher in the LFG than in the SFG. Muscle activity of the TA (<i>p</i>=.017), ankle (<i>p</i>=.033), and hip (<i>p</i>=.045) time to stability and the ground reaction force time to stability (<i>p</i>=.043) were significantly lower in the LFG than in the SFG. Muscle activity of the GCM (<i>p</i>=.053) and knee time to stability (<i>p</i>=.057) tended to be lower in the LFG than in the SFG.CONCLUSIONS: These results confirmed that muscle activity, angular velocity, and ground reaction force variables during drop landing are affected by the VL muscle fascicle length in young football players.

Identification of the most effective muscles in landing impact forces

The aim of this study was to evaluate the role of the main lower limb muscles in increasing or decreasing each lower limb joint impact force during drop landing. To do so, the body was modeled by a four-link musculoskeletal model consisting of eight main Hill-type muscles. Different drop landing scenarios were modeled by changing the activation levels of the considered muscles. In each landing simulation, the impact GRF and impact joint forces were obtained. In order to compare and rank the muscles with respect to their effect on each impact force, a computationally feasible zero-one (off-on) muscle activation analysis was proposed. The proposed approach revealed important features regarding the relation between different impact forces and muscle activations. Specifically, the results can be interpreted in terms of the role that each muscle potentially plays in causing or preventing certain injuries. Moreover, the results obtained from the analysis were further used to classify the muscles into four categories, depending on the effect they have on each impact force. The proposed theoretical analysis is seen to be a promising tool in predicting the role of muscles and their order of importance in the generation of lower limb impact forces in landing, without the need for experimental tests.

Differences in strength and landing biomechanics between female jumpers and swimmers

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.

Hybrid Parallel Compliance Allows Robots to Operate With Sensorimotor Delays and Low Control Frequencies

Animals locomote robustly and agile, albeit significant sensorimotor delays of their nervous system and the harsh loading conditions resulting from repeated, high-frequent impacts. The engineered sensorimotor control in legged robots is implemented with high control frequencies, often in the kilohertz range. Consequently, robot sensors and actuators can be polled within a few milliseconds. However, especially at harsh impacts with unknown touch-down timing, controllers of legged robots can become unstable, while animals are seemingly not affected. We examine this discrepancy and suggest and implement a hybrid system consisting of a parallel compliant leg joint with varying amounts of passive stiffness and a virtual leg length controller. We present systematic experiments both in computer simulation and robot hardware. Our system shows previously unseen robustness, in the presence of sensorimotor delays up to 60 ms, or control frequencies as low as 20 Hz, for a drop landing task from 1.3 leg lengths high and with a compliance ratio (fraction of physical stiffness of the sum of virtual and physical stiffness) of 0.7. In computer simulations, we report successful drop-landings from 3.8 leg lengths (1.2 m) for a 2 kg quadruped robot with 100 Hz control frequency and a sensorimotor delay of 35 ms.

The Influence of Kinesio Tape and an Ankle Brace on the Lower Extremity Joint Motion in Fatigued, Unstable Ankles during a Lateral Drop Landing

Background: An unstable ankle along with plantar flexor muscle fatigue may exacerbate landing performance. External support may be an option to control the ankle motion and protect joints from injuries. Research goal: To investigate the immediate changes in the joint motion of a lower extremity under ankle plantar flexors fatigue conditions in athletes with unstable ankles using different external supports. Methods: A total of 44 participants were allocated to a control (Cn) group, an ankle brace (AB) group, and a kinesio tape (KT) group, and were asked to perform a lateral drop landing before and after a fatigue protocol. The outcome measures were fatigue-induced changes in the maximal joint angle and changes in the angle ranges of the hip, knee, and ankle. Results: Smaller changes in the maximal hip abduction were found in the AB group (p = 0.025), and the KT group exhibited smaller changes in the maximal ankle dorsiflexion (p = 0.009). The AB group landed with a smaller change in the range of hip flexion and knee flexion (p = 0.008 and 0.006). The Cn group had greater fatigue-induced changes in the COM range than AB and KT group (p = 0.002 and 0.028). Significance: Despite the beneficial effect in the postural control in the frontal plane, the use of AB might constrain the distal joint motion which might lead to an extended knee landing posture resulting in secondary injuries to the knee joint. Therefore, the use of AB in conjunction with an additional training of landing strategy might be recommended from the injury prevention perspective.