The analysis of knee joint loading during drop landing from different heights and under different instruction sets in healthy males

Impact of different landing heights on the contact force in the medial tibiofemoral compartment and the surrounding muscle force characteristics in drop jumps

This study explored the impact of landing height on the tibiofemoral joint's medial compartment force (MCF) during drop jumps to help athletes prevent knee injury. Experienced male participants (N = 16) performed drop jumps with landing heights from 0.15 m to 0.75 m. Kinematic/kinetic parameters were collected using a motion capture system and a three-dimensional force platform. The Med-Lat Knee model was used to calculate biomechanical indicators of the knee joint, and data were analyzed using one-way analysis of variance and one-dimensional statistical parametric mapping (SPM1d). Findings indicated that landing height significantly affected the anterior-posterior and vertical MCF, flexion-extension torque, internal-external rotation torque, and vertical ground reaction force (p<0.05)-all increasing with elevated landing height-and significantly impacted the generated force of the vastus medialis, vastus lateralis, and vastus intermedius (p<0.05). SPM1d analysis confirmed these results within specific time intervals. Thus, both the knee moment and the MCF exhibited similar coordinated changes during drop jumps, indicating that these may be adaptive movement strategy. The impact of varying drop jump heights on muscle groups around the knee joint varied suggests that different heights induce specific muscular responses and improve muscle coordination to prevent knee joint injuries.

Response of Knee Joint Biomechanics to Landing Under Internal and External Focus of Attention in Female Volleyball Players

The aim of this study was to examine the effect of attentional focus instructions on the biomechanical variables associated with the risk of anterior cruciate ligament injury of the knee joint during a drop landing task using a time series analysis. Ten female volleyball players (age: 20.4 ± 0.8 years, height: 169.7 ± 7.1 cm, mass: 57.6 ± 3.1 kg, experience: 6.3 ± 0.8 years) performed landings from a 50 cm height under three different attentional focus conditions: (1) external focus (focus on landing as soft as possible), (2) internal focus (focus on bending your knees when you land), and (3) control (no-focus instruction). Statistical parameter mapping in the sagittal plane during the crucial first 30% of landing time showed a significant effect of attentional focus instructions. Despite the similarity in landing performance across foci instructions, adopting an external focus instruction promoted reduced vertical ground reaction force and lower sagittal flexion moment during the first 30% of execution time compared to internal focus, suggesting reduced knee loading. Therefore, adopting an external focus of attention was suggested to reduce most biomechanical risk variables in the sagittal plane associated with anterior cruciate ligament injuries, compared to internal focus and control condition. No significant differences were found in the frontal and horizontal planes between the conditions during this crucial interval.

Knee joint biomechanics and cartilage damage prediction during landing: A hybrid MD-FE-musculoskeletal modeling

Understanding the mechanics behind knee joint injuries and providing appropriate treatment is crucial for improving physical function, quality of life, and employability. In this study, we used a hybrid molecular dynamics-finite element-musculoskeletal model to determine the level of loads the knee can withstand when landing from different heights (20, 40, 60 cm), including the height at which cartilage damage occurs. The model was driven by kinematics-kinetics data of asymptomatic subjects at the peak loading instance of drop landing. Our analysis revealed that as landing height increased, the forces on the knee joint also increased, particularly in the vastus muscles and medial gastrocnemius. The patellar tendon experienced more stress than other ligaments, and the medial plateau supported most of the tibial cartilage contact forces and stresses. The load was mostly transmitted through cartilage-cartilage interaction and increased with landing height. The critical height of 126 cm, at which cartilage damage was initiated, was determined by extrapolating the collected data using an iterative approach. Damage initiation and propagation were mainly located in the superficial layers of the tibiofemoral and patellofemoral cartilage. Finally, this study provides valuable insights into the mechanisms of landing-associated cartilage damage and could help limit joint injuries and improve training programs.

Predictive simulation of single-leg landing scenarios for ACL injury risk factors evaluation

The Anterior Cruciate Ligament (ACL) rupture is a very common knee injury during sport activities. Landing after jump is one of the most prominent human body movements that can lead to such an injury. The landing-related ACL injury risk factors have been in the spotlight of research interest. Over the years, researchers and clinicians acquire knowledge about human movement during daily-life activities by organizing complex in vivo studies that feature high complexity, costs and technical and most importantly physical challenges. In an attempt to overcome these limitations, this paper introduces a computational modeling and simulation pipeline that aims to predict and identify key parameters of interest that are related to ACL injury during single-leg landings. We examined the following conditions: a) landing height, b) hip internal and external rotation, c) lumbar forward and backward leaning, d) lumbar medial and lateral bending, e) muscle forces permutations and f) effort goal weight. Identified on related research studies, we evaluated the following risk factors: vertical Ground Reaction Force (vGRF), knee joint Anterior force (AF), Medial force (MF), Compressive force (CF), Abduction moment (AbdM), Internal rotation moment (IRM), quadricep and hamstring muscle forces and Quadriceps/Hamstrings force ratio (Q/H force ratio). Our study clearly demonstrated that ACL injury is a rather complicated mechanism with many associated risk factors which are evidently correlated. Nevertheless, the results were mostly in agreement with other research studies regarding the ACL risk factors. The presented pipeline showcased promising potential of predictive simulations to evaluate different aspects of complicated phenomena, such as the ACL injury.

Parametric analysis of landing injury : The effect of landing posture and joint displacement

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 [Formula: see text], [Formula: see text] and [Formula: see text], 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 [Formula: see text] 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.

Contribution of Lower Extremity Joints on Energy Absorption during Soft Landing

Soft landing after jumping is associated with the prevention of lower extremity injuries during sports activities in terms of the energy absorption mechanisms. In this study, the contribution of lower extremity joints during soft landing was investigated. Subjects comprised 20 healthy females. Kinetics and kinematics data were obtained during drop vertical jumps using a three-dimensional motion analysis system. Negative mechanical work values in the lower extremity joints were calculated during landing. A multiple regression analysis was performed to determine which lower extremity joints contributed more in achieving soft landing. The means of mechanical work of the hip, knee, and ankle in the sagittal plane were −0.30 ± 0.17, −0.62 ± 0.31, and −1.03 ± 0.22 J/kg, respectively. Results showed that negative mechanical work in the hip and knee is effective in achieving soft landing. These findings indicate that energy absorption in the hip and knee joints might be an important factor in achieving soft landing, whereas that in the ankle has a negative effect. Therefore, when improving soft landing techniques, we should consider energy absorption in the hip and knee via eccentric activation of the hip and knee extensors during landing.

THE INFLUENCE OF ATTENTIONAL FOCUS ON LANDING STIFFNESS IN FEMALE ATHLETES: A CROSS-SECTIONAL STUDY

BACKGROUND

Anterior cruciate ligament injury prevention often involves instructing athletes to reduce landing stiffness. Instructions promoting an external focus appear to result in superior motor performance for a wide range of tasks; however, the effect of attentional focus on landing stiffness has not been examined.

HYPOTHESIS/PURPOSE

The purpose of this study was to compare the influence of instructions promoting an internal focus vs. those promoting an external focus on landing stiffness. It was hypothesized that both types of instructions would reduce landing stiffness vs. landings performed prior to instruction. It was also hypothesized that participants would demonstrate a greater reduction in landing stiffness when provided with instructions promoting an external focus.

STUDY DESIGN

Cross-sectional, quasi-experimental.

METHODS

Sixteen female athletes (basketball, soccer, volleyball) completed drop landings while force and kinematic data were collected. Participants first performed drop landings with their typical technique (baseline). They then received instructions promoting an internal focus and an external focus before performing additional drop landings. Peak force, time-to-peak force, leg stiffness, and hip, knee, and ankle sagittal plane angles were analyzed.

RESULTS

Both types of instructions resulted in lower landing forces, less leg stiffness, and greater hip and knee flexion versus at baseline. However, athletes demonstrated more knee flexion at the time of the peak force (59.4 ± 9.6 ° vs. 56.0 ± 9.5 °) and less leg stiffness (69.5 ± 17.9 Nkg^-1/m vs. 84.0 ± 38.1 Nkg^-1/m) when provided with instructions promoting an external focus, compared to when they were provided with instructions promoting an internal focus.

CONCLUSION

Instructions promoting an external focus appear to result in a greater reduction in landing stiffness. Clinicians should consider providing instructions promoting an external focus when training athletes to reduce lower extremity stiffness during drop landings. The findings from this study may help to inform clinicians involved in movement pattern re-training for female athletes.

LEVEL OF EVIDENCE

Level 3b.

The Relationship Between Vertical Ground Reaction Force, Loading Rate, and Sound Characteristics During a Single-Leg Landing

Context:Landing kinetic outcomes are associated with injury risk and may be persistently altered after anterior cruciate ligament injury or reconstruction. However, it is challenging to assess kinetics clinically. The relationship between sound characteristics and kinetics during a limited number of functional tasks has been supported as a potential clinical alternative.Objective:To assess the relationship between kinetics and sound characteristics during a single-leg landing task.Design:ObservationalSetting:Laboratory.Participants:There was total of 26 healthy participants (15 males/11 females, age = 24.8 [3.6] y, height = 176.0 [9.1] cm, mass = 74.9 [14.4] kg, Tegner Activity Scale = 6.1 [1.1]).Intervention:Participants completed single-leg landings onto a force plate while audio characteristics were recorded.Main Outcome Measures:Peak vertical ground reaction force, linear loading rate, instantaneous loading rate, peak sound magnitude, sound frequency were measured. Means and SDs were calculated for each participant’s individual limbs. Spearman rho correlations were used to assess the relationships between audio characteristics and kinetic outcomes.Results:Peak sound magnitude was positively correlated with normalized peak vertical ground reaction force (ρ = .486,P = .001); linear loading rate (ρ = .491,P = .001); and instantaneous loading rate (ρ = .298,P = .03). Sound frequency was negatively correlated with instantaneous loading rate (ρ = −.444,P = .001).Conclusions:Peak sound magnitude may be more helpful in providing feedback about an individual’s normalized vertical ground reaction force and linear loading rate, and sound frequency may be more helpful in providing feedback about instantaneous loading rate. Further refinement in sound measurement techniques may be required before these findings can be applied in a clinical population.

Static loading of the knee joint results in modified single leg landing biomechanics

Background

External loading of the ligamentous tissues induces mechanical creep, which modifies neuromuscular response to perturbations. It is not well understood how ligamentous creep affects athletic performance and contributes to modifications of knee biomechanics during functional tasks.

Hypothesis/purpose

The purpose of this study was to examine the mechanical and neuromuscular responses to single leg drop landing perturbations before and after passive loading of the knee joint.

Methods

Descriptive laboratory study. Male (n = 7) and female (n = 14) participants’ (21.3 ± 2.1 yrs., 1.69 ± 0.09 m, 69.3 ± 13.0 kg) right hip, knee, and ankle kinematics were assessed during drop landings performed from a 30 cm height onto a force platform before and after a 10 min creep protocol. Electromyography (EMG) signals were recorded from rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), semimembranosus (SM), and biceps femoris (BF) muscles. The creep protocol involved fixing the knee joint at 35° during static loading with perpendicular loads of either 200 N (males) or 150 N (females). Maximum, minimum, range of motion (ROM), and angular velocities were assessed for the hip, knee, and ankle joints, while normalized EMG (NEMG), vertical ground reaction forces (VGRF), and rate of force development (RFD) were assessed at landing using ANOVAs. Alpha was set at 0.05.

Results

Maximum hip flexion velocity decreased (p < 0.01). Minimum knee flexion velocity increased (p < 0.02). Minimum knee ad/abduction velocity decreased (p < 0.001). Ankle ROM decreased (p < 0.001). aVGRF decreased (p < 0.02). RFD had a non-significant trend (p = 0.076). NAEMG was significant between muscle groups (p < 0.02).

Conclusion

Distinct changes in velocity parameters are attributed to the altered mechanical behavior of the knee joint tissues and may contribute to changes in the loading of the leg during landing.

Strategies of elite Chinese gymnasts in coping with landing impact from backward somersault

This study aimed to investigate how elite Chinese gymnasts manage the landing impact from a backward somersault. Six international-level male gymnasts performed backward somersault tests with a synchronous collection of kinematics (250 Hz), ground reaction forces (1,000 Hz), and surface electromyography (EMG) (2,000 Hz). A 19-segment human model was developed and lower extremity joints torques were calculated by means of a computer simulation. The angles of the lower extremity joints initially extended and then flexed. These angular velocities of extension continued to decrease and the joint torques changed from extensor to flexor within 100 ms before touchdown. The angles of the hips, knees, and ankles flexed rapidly by 12°, 36°, and 29°, respectively, and the angular velocities of flexion, flexor torque, and EMG peaked sharply during the initial impact phase of the landing. The angles of the hips, knees, and ankles flexed at approximately 90°, 100°, and 80°, respectively. The torques were reversed with the extensor torques, showing a relatively high level of muscle activation during the terminal impact phase of the landing. The results showed that the international-level gymnasts first extended their lower extremity joints, then flexed just before touchdown. They continued flexing actively and rapidly in the initial impact phase and then extended to resist the landing impact and maintain body posture during the terminal impact phase of the landing. The information gained from this study could improve our understanding of the landings of elite gymnasts and assist in injury prevention.

Sex and limb impact biomechanics associated with risk of injury during drop landing with body borne load

Increasing lower limb flexion may reduce risk of musculoskeletal injury for military personnel during landing. This study compared lower limb biomechanics between sexes and limbs when using normal and greater lower limb flexion to land with body borne load. Thirty-three participants (21 male, 12 female, age: 21.6±2.5 years, height: 1.7±0.1 m, weight: 74.5±9.0 kg) performed normal and flexed lower limb landings with four body borne loads: 20, 25, 30 and 35 kg. Hip and knee biomechanics, peak vertical ground reaction force (GRF), and the magnitude and direction of the GRF vector in frontal plane were submitted to two separate repeated measures ANOVAs to test the main and interaction effects of sex, load, and landing, as well as limb, load, and landing. Participants increased GRFs (between 5 and 10%) and hip and knee flexion moments when landing with body borne load, but decreased vertical GRF 19% and hip adduction and knee abduction joint range of motion and moments during the flexed landings. Both females and the non-dominant limb presented greater risk of musculoskeletal injury during landing. Females exhibited larger GRFs, increased hip adduction range of motion, and greater knee abduction moments compared to males. Whereas, the non-dominant limb increased knee abduction moments and exhibited a more laterally-directed frontal plane GRF vector compared to the dominant limb during the loaded landings. Yet, increasing lower limb flexion during landing does not appear to produce similar reductions in lower limb biomechanics related to injury risk for both females and the non-dominant limb during landing.

The Efficacy and Safety of Lower-Limb Plyometric Training in Older Adults: A Systematic Review

BACKGROUND

The aging process is associated with a progressive decline of neuromuscular function, increased risk of falls and fractures, impaired functional performance, and loss of independence. Plyometric training may mitigate or even reverse such age-related deterioration; however, little research on the effects of plyometric exercises has been performed in older adults.

OBJECTIVE

The objective of this systematic review was to evaluate the safety and efficacy of plyometric training in older adults.

METHODS

Papers reporting on randomized trials of plyometric training in older adults (≥ 60 years) and published up to December 2017 were sought in the PubMed, SPORTDiscus, Scopus, and EMBASE databases, and their methodological quality was assessed using the Physiotherapy Evidence Database (PEDro) scale. A narrative synthesis of the findings is presented in this systematic review.

RESULTS

Of the 2236 identified papers, 18 were included in the review, reporting on 12 different studies with a mean PEDro score of 6.0 (range 4-7). Altogether, 289 subjects (176 females and 113 males) were included in 15 intervention groups with plyometric components (n = 8-36 per group); their mean age ranged from 58.4 to 79.4 years. The plyometric training lasted from 4 weeks to 12 months. Muscular strength, bone health, body composition, postural stability, and jump and physical performance were the most often reported outcomes. No study reported increased occurrence of injuries or other adverse events related to plyometric exercises.

CONCLUSION

Plyometric training is a feasible and safe training option with potential for improving various performance, functional, and health-related outcomes in older persons.

Difference of neuromuscular responses by additional loads during plyometric jump

Plyometric training is a training method to increase the motor output, stretch-shortening cycle which could be associated with power output. To increase the neuromuscular output, various training variables have been incorporated in training programs. Weight vest is one of the variables to develop it. However, how much load can effectively develop the neural response is still not clearly understood. The aim of this study was to identify the effects of additional external loads on neuromuscular response of lower body during plyometric jump. Total 19 men performed jump tests with weight vest (two jumps in each additional load; 0%, 10%, 15% and 20% of bodyweight [BW]). During the tests, neuromuscular responses of lower extremity were measured. In vertical jump, 0%BW group was higher than the other heavier loads. In rate of force development (RFD), 10%BW was higher than 15%BW and 20%BW. In 0-30 msec of interval RFD, the heavier load groups were greater than 0%BW and in 0-50 msec, 15%BW and 20%BW were higher than 0%BW. In neuromuscular efficiency (NME), 15%BW and 20%BW were greater than 0%BW in ankle joint. This research indicated that plyometric jump with additional load causes greater RFD and NME of lower extremity compared with jump training without additional load. During weight vest plyometric jump, 10%-20% of BW load is advantageous to NME of lower body and 10% of BW load is effective to develop RFD of lower extremity.

Shock absorbing ability in healthy and damaged cartilage-bone under high-rate compression

Articular cartilage is a soft tissue that distributes the loads in joints and transfers the compressive load to the underlying bone. At high rate and magnitudes of mechanical loading, cartilage and subchondral bone together are susceptible to damage. In addition, any disruption to the cartilage's structure, caused by injury, trauma or disorder such as osteoarthritis (OA), can alter the mechanism of load transfer from the cartilage to the underlying bone. Changes in the cartilage structure can also alter the ability of cartilage-bone to absorb and dissipate the impact energy. To investigate the effects of cartilage degradation on cartilage-bone shock absorption ability, the top 50% of the cartilage thickness was removed (modified cartilage) to mimic the cartilage thickness reduction in Grade III cartilage lesion and the remaining cartilage-bone unit (modified cartilage-bone) was compressed at high-rate (4% strain at 5 Hz). High-speed camera and microscope were used to capture microscopic deformation, and digital image correlation technique (DIC) employed to quantify the deformation of cartilage and bone. The mechanical properties (i.e. stiffness, strain, absorbed and dissipated energies) of cartilage and bone were calculated before and after the removal of the top 50% of the cartilage thickness, consisting of both the superficial tangential zone (STZ) and part of the middle zone of the cartilage. The results showed a significant degradation in the mechanical properties of the cartilage-bone unit after the removal of the top 50% cartilage thickness. The stiffness of the modified cartilage reduced significantly (by ~39%) and energy absorption in underlying bone increased by 32%, which can make the bone more vulnerable to damage in the modified cartilage-bone unit. In addition, the energy dissipation in the modified cartilage-bone unit was also increased by approximately 14%. These changes in mechanical properties suggest a crucial role of the STZ and middle zone (within the top 50% cartilage thickness) in protecting the underlying bone from the severe compressive impact loading. Results also indicated that under physiological contact stress of 7 MPa, strain in damaged cartilage was increased by 3.22% without affecting the mechanical behaviour of the underlying bone.