Sagittal knee joint kinematics and energetics in response to different landing heights and techniques

Six weeks of core stability training improves landing kinetics among female capoeira athletes: a pilot study

Core stability training (CST) has increased in popularity among athletes and the general fitness population despite limited evidence CST programmes alone lead to improved athletic performance. In female athletes, neuromuscular training combining balance training and trunk and hip/pelvis dominant CST is suggested to reduce injury risk, and specifically peak vertical ground reaction forces (vGRF) in a drop jump landing task. However, the isolated effect of trunk dominant core stability training on vGRF during landing in female athletes had not been evaluated. Therefore, the objective of this study was to evaluate landing kinetics during a drop jump test following a CST intervention in female capoeira athletes. After giving their informed written consent, sixteen female capoeira athletes (mean ± SD age, stature, and body mass of 27.3 ± 3.7 years, 165.0 ± 4.0 cm, and 59.7 ± 6.3 kg, respectively) volunteered to participate in the training program which consisted of static and dynamic CST sessions, three times per week for six weeks. The repeated measures T-test revealed participants significantly reduced relative vGRF from pre- to post-intervention for the first (3.40 ± 0.78 vs. 2.85 ± 0.52 N·NBW-1, respectively [p<0.05, effect size = 0.60]), and second landing phase (5.09 ± 1.17 vs. 3.02 ± 0.41 N·NBW-1, respectively [p<0.001, effect size = 0.87]). The average loading rate was reduced from pre- to post-intervention during the second landing phase (30.96 ± 18.84 vs. 12.06 ± 9.83 N·NBW·s-1, respectively [p<0.01, effect size = 0.68]). The peak loading rate was reduced from pre- to post-intervention during the first (220.26 ± 111.51 vs. 120.27 ± 64.57 N·NBW·s-1 respectively [p<0.01, effect size = 0.64]), and second (99.52 ± 54.98 vs. 44.71 ± 30.34 N·NBW·s-1 respectively [p<0.01, effect size = 0.70]) landing phase. Body weight, average loading rate during the first landing phase, and jump height were not significantly different between week 0 and week 6 (p=0.528, p=0.261, and p=0.877, respectively). This study provides evidence that trunk dominant core stability training improves landing kinetics without improving jump height, and may reduce lower extremity injury risk in female athletes.

What is normal? Female lower limb kinematic profiles during athletic tasks used to examine anterior cruciate ligament injury risk: a systematic review

BACKGROUND

It has been proposed that the performance of athletic tasks where normal motion is exceeded has the potential to damage the anterior cruciate ligament (ACL). Determining the expected or 'normal' kinematic profile of athletic tasks commonly used to assess ACL injury risk can provide an evidence base for the identification of abnormal or anomalous task performances in a laboratory setting.

OBJECTIVE

The objective was to conduct a systematic review of studies examining lower limb kinematics of females during drop landing, drop vertical jump, and side-step cutting tasks, to determine 'normal' ranges for hip and knee joint kinematic variables.

DATA SOURCES

An electronic database search was conducted on the SPORTDiscus(TM), MEDLINE, AMED and CINAHL (January 1980-August 2013) databases using a combination of relevant keywords.

STUDY SELECTION

Studies identified as potentially relevant were independently examined by two reviewers for inclusion. Where consensus could not be reached, a third reviewer was consulted. Original research articles that examined three-dimensional hip and knee kinematics of female subjects during the athletic tasks of interest were included for review. Articles were excluded if subjects had a history of lower back or lower limb joint injury or isolated data from the female cohort could not be extracted.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two reviewers independently assessed the quality of included studies. Data on subject characteristics, the athletic task performed, and kinematic data were extracted from included studies. Studies were categorised according to the athletic task being examined and each study allocated a weight within categories based on the number of subjects assessed. Extracted data were used to calculate the weighted means and standard deviations for hip and knee kinematics (initial contact and peak values). 'Normal' motion was classified as the weighted mean plus/minus one standard deviation.

RESULTS

Of 2,920 citations, a total of 159 articles were identified as potentially relevant, with 29 meeting all inclusion/exclusion criteria. Due to the limited number of studies available examining double-leg drop landings and single-leg drop vertical jumps, insufficient data was available to include these tasks in the review. Therefore, a total of 25 articles were included. From the included studies, 'normal' ranges were calculated for the kinematic variables of interest across the athletic tasks examined.

LIMITATIONS

Joint forces and other additional elements play a role in ACL injuries, therefore, focusing solely on lower limb kinematics in classifying injury risk may not encapsulate all relevant factors. Insufficient data resulted in no normal ranges being calculated for double-leg drop land and single-leg drop vertical jump tasks. No included study examined hip internal/external rotation during single-leg drop landings, therefore ranges for this kinematic variable could not be determined. Variation in data between studies resulted in wide normal ranges being observed across certain kinematic variables.

CONCLUSIONS

The ranges calculated in this review provide evidence-based values that can be used to identify abnormal or anomalous athletic task performances on a multi-planar scale. This may be useful in identifying neuromuscular factors or specific muscular recruitment strategies that contribute to ACL injury risk.

Using accelerometry to quantify deceleration during a high-intensity soccer turning manoeuvre

Abstract The mechanics of cutting movements have been investigated extensively, but few studies have considered the rapid deceleration phase prior to turning which has been linked to muscle damage. This study used accelerometry to examine the influence of turning intensity on the last three steps of a severe turn. Ten soccer players performed 135° "V" cuts at five different intensities. Resultant decelerations were recorded from a trunk-mounted tri-axial accelerometer. Lower limb kinematics and ground reaction forces (GRF) from the pivot foot-ground contact (FGC) were also monitored. Average peak trunk decelerations were larger at the two preceding steps (4.37 ± 0.12 g and 4.58 ± 0.11 g) compared to the PIVOT step (4.10 ± 0.09 g). Larger peak joint flexion angular velocities were observed at PRE step (ankle: 367 ± 192 deg.s^-1; knee 493 ± 252  deg.s^-1) compared to PIVOT step (ankle 255 ± 183 deg.s^-1; knee 377 ± 229 deg.s^-1). Turn intensity did not influence peak GRF at PIVOT step. This study highlights the importance of steps prior to turning and their high-frequency loading characteristics. It is suggested that investigations of lower limb loading during turning should include this deceleration phase and not focus solely on pivot FGC.

Effect of increased quadriceps tensile stiffness on peak anterior cruciate ligament strain during a simulated pivot landing

ACL injury prevention programs often involve strengthening the knee muscles. We posit that an unrecognized benefit of such training is the associated increase in the tensile stiffness of the hypertrophied muscle. We tested the hypothesis that an increased quadriceps tensile stiffness would reduce peak anteromedial bundle (AM-)ACL relative strain in female knees. Twelve female cadaver knees were subjected to compound impulsive two-times body weight loads in compression, flexion, and internal tibial torque beginning at 15° flexion. Knees were equipped with modifiable custom springs to represent the nonlinear rapid stretch behavior of a normal and increased stiffness female quadriceps (i.e., 33% greater stiffness). Peak AM-ACL relative strain was measured using an in situ transducer while muscle forces and tibiofemoral kinematics and kinetics were recorded. A 3D ADAMS™ dynamic biomechanical knee model was used in silico to interpret the experimental results which were analyzed using a repeated-measures Wilcoxon test. Female knees exhibited a 16% reduction in peak AM-ACL relative strain and 21% reduction in change in flexion when quadriceps tensile stiffness was increased by 33% (mean (SD) difference: 0.97% (0.65%), p = 0.003). We conclude that increased quadriceps tensile stiffness reduces peak ACL strain during a controlled study simulating a pivot landing.

Prevention of anterior cruciate ligament injuries in sports. Part I: systematic review of risk factors in male athletes

PURPOSE

The purpose of this study was to report a comprehensive literature review on the risk factors for anterior cruciate ligament (ACL) injuries in male athletes.

METHODS

All abstracts were read and articles of potential interest were reviewed in detail to determine on inclusion status for systematic review. Information regarding risk factors for ACL injuries in male athletes was extracted from all included studies in systematic fashion and classified as environmental, anatomical, hormonal, neuromuscular, or biomechanical. Data extraction involved general characteristics of the included studies (type of study, characteristics of the sample, type of sport), methodological aspects (for quality assessment), and the principal results for each type of risk factor.

RESULTS

The principal findings of this systematic review related to the risk factors for ACL injury in male athletes are: (1) most of the evidence is related to environmental and anatomical risk factors; (2) dry weather conditions may increase the risk of non-contact ACL injuries in male athletes; (3) artificial turf may increase the risk of non-contact ACL injuries in male athletes; (4) higher posterior tibial slope of the lateral tibial plateau may increase the risk of non-contact ACL injuries in male athletes.

CONCLUSION

Anterior cruciate ligament injury in male athletes likely has a multi-factorial aetiology. There is a lack of evidence regarding neuromuscular and biomechanical risk factors for ACL injury in male athletes. Future research in male populations is warranted to provide adequate prevention strategies aimed to decrease the risk of this serious injury in these populations.

Sagittal plane body kinematics and kinetics during single-leg landing from increasing vertical heights and horizontal distances: implications for risk of non-contact ACL injury

PURPOSE

This study identified kinematic and knee energetic variables that reduce the risk of non-contact anterior cruciate ligament (ACL) injury during single-leg landings from increasing vertical heights and horizontal distances.

METHODS

Nine subjects performed single-leg landings from takeoff platforms with vertical heights of 20, 40, and 60 cm onto a force plate. Subjects also performed single-leg landings from a 40 cm high takeoff platform placed at horizontal distances of 30, 50 and 70 cm from a force plate. Kinematic and kinetic data were measured.

RESULTS

Vertical height had a significant and positive effect on peak vertical ground reaction force (VGRF) (p<0.001), peak posterior ground reaction force (PGRF) (p=0.004), knee flexion angle (p=0.0043), trunk flexion angle (p=0.03), knee power (p<0.001) and knee work (p<0.001). There was also a significant and positive effect of horizontal distance on peak PGRF (p<0.001), ankle plantar flexion angle (p=0.008), hip flexion angle (p=0.007), and trunk flexion angle (p=0.001). At increasing vertical height, peak VGRF was significantly correlated to ankle plantar flexion and knee flexion angles (r=-0.77, p=0.02 and r=-0.78, p=0.01, respectively). At increasing horizontal distance, peak PGRF was significantly correlated to ankle plantar flexion angle, knee power and knee work (r=-0.85, p=0.003; r=0.67, p=0.04; and r=0.73, p=0.02, respectively).

CLINICAL RELEVANCE

A better understanding of the risk factors to non-contact ACL injury during single-leg landings from increasing vertical heights and horizontal distances can aid in the design of injury prevention regimen.

Lower extremity energy absorption and biomechanics during landing, part II: frontal-plane energy analyses and interplanar relationships

CONTEXT

Greater sagittal-plane energy absorption (EA) during the initial impact phase (INI) of landing is consistent with sagittal-plane biomechanics that likely increase anterior cruciate ligament (ACL) loading, but it does not appear to influence frontal-plane biomechanics. We do not know whether frontal-plane INI EA is related to high-risk frontal-plane biomechanics.

OBJECTIVE

To compare biomechanics among INI EA groups, determine if women are represented more in the high group, and evaluate interplanar INI EA relationships.

DESIGN

Descriptive laboratory study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Participants included 82 (41 men, 41 women; age = 21.0 ± 2.4 years, height = 1.74 ± 0.10 m, mass = 70.3 ± 16.1 kg) healthy, physically active volunteers.

INTERVENTION(S)

We assessed landing biomechanics with an electromagnetic motion-capture system and force plate.

MAIN OUTCOME MEASURE(S)

We calculated frontal- and sagittal-plane total, hip, knee, and ankle INI EA. Total frontal-plane INI EA was used to create high, moderate, and low tertiles. Frontal-plane knee and hip kinematics, peak vertical and posterior ground reaction forces, and peak internal knee-varus moment (pKVM) were identified and compared across groups using 1-way analyses of variance. We used a χ (2) analysis to evaluate male and female allocation to INI EA groups. We used simple, bivariate Pearson product moment correlations to assess interplanar INI EA relationships.

RESULTS

The high-INI EA group exhibited greater knee valgus at ground contact, hip adduction at pKVM, and peak hip adduction than the low-INI EA group (P < .05) and greater peak knee valgus, pKVM, and knee valgus at pKVM than the moderate- (P < .05) and low- (P < .05) INI EA groups. Women were more likely than men to be in the high-INI EA group (χ(2) = 4.909, P = .03). Sagittal-plane knee and frontal-plane hip INI EA (r = 0.301, P = .006) and sagittal-plane and frontal-plane ankle INI EA were associated (r = 0.224, P = .04). No other interplanar INI EA relationships were found (P > .05).

CONCLUSIONS

Greater frontal-plane INI EA was associated with less favorable frontal-plane biomechanics that likely result in greater ACL loading. Women were more likely than men to use greater frontal-plane INI EA. The magnitudes of sagittal- and frontal-plane INI EA were largely independent.

Gender, Vertical Height and Horizontal Distance Effects on Single-Leg Landing Kinematics: Implications for Risk of non-contact ACL Injury

There is a lack of studies investigating gender differences in whole-body kinematics during single-leg landings from increasing vertical heights and horizontal distances. This study determined the main effects and interactions of gender, vertical height, and horizontal distance on whole-body joint kinematics during single-leg landings, and established whether these findings could explain the gender disparity in non-contact anterior cruciate ligament (ACL) injury rate. Recreationally active males (n=6) and females (n=6) performed single-leg landings from a takeoff deck of vertical height of 20, 40, and 60 cm placed at a horizontal distance of 30, 50 and 70 cm from the edge of a force platform, while 3D kinematics and kinetics were simultaneously measured. It was determined that peak vertical ground reaction force (VGRF) and the ankle flexion angle exhibited significant gender differences (p=0.028, partial η ² =0.40 and p=0.035, partial η ² =0.37, respectively). Peak VGRF was significantly correlated to the ankle flexion angle (r= −0.59, p=0.04), hip flexion angle (r= −0.74, p=0.006), and trunk flexion angle (r= −0.59, p=0.045). Peak posterior ground reaction force (PGRF) was significantly correlated to the ankle flexion angle (r= −0.56, p=0.035), while peak knee abduction moment was significantly correlated to the knee flexion angle (r= −0.64, p=0.03). Rearfoot landings may explain the higher ACL injury rate among females. Higher plantar-flexed ankle, hip, and trunk flexion angles were associated with lower peak ground reaction forces, while higher knee flexion angle was associated with lower peak knee abduction moment, and these kinematics implicate reduced risk of non-contact ACL injury.

Hamstrings and quadriceps muscle contributions to energy generation and dissipation at the knee joint during stance, swing and flight phases of level running

BACKGROUND

Human movements involve the generation and dissipation of mechanical energy at the lower extremity joints. However, it is unclear how the individual knee muscles contribute to the energetics during running.

OBJECTIVE

This study aimed to determine how each hamstring and quadricep muscle generates and dissipates energy during stance, swing and flight phases of running.

METHODS

A three-dimensional lower extremity musculoskeletal model was used to estimate the energetics of the individual hamstrings (semimembranosus, semitendinosus, biceps femoris long and short-heads) and quadriceps (rectus femoris, vastus medialis, vastus intermedius and vastus lateralis) muscles for a male subject during level running on a treadmill at a speed of 3.96 m/s.

RESULTS

Our findings demonstrated that the knee flexors generated energy during stance phase and dissipated energy during swing phase, while the knee extensors dissipated energy during the flexion mode of both stance and swing phases, and generated energy during the extension mode. During flight phase, the knee flexors generated energy during the flight phase transiting from toe-off to swing, while the knee extensors generated energy during the flight phase transiting from swing to heel-strike.

CONCLUSION

Individual knee flexors and extensors in the hamstrings and quadriceps play important roles in knee joint energetics, which are necessary for proper execution and stabilization of the stance, swing and flight phases of running.

The application of musculoskeletal modeling to investigate gender bias in non-contact ACL injury rate during single-leg landings

The central tenet of this study was to develop, validate and apply various individualised 3D musculoskeletal models of the human body for application to single-leg landings over increasing vertical heights and horizontal distances. While contributing to an understanding of whether gender differences explain the higher rate of non-contact anterior cruciate ligament (ACL) injuries among females, this study also correlated various musculoskeletal variables significantly impacted by gender, height and/or distance and their interactions with two ACL injury-risk predictor variables; peak vertical ground reaction force (VGRF) and peak proximal tibia anterior shear force (PTASF). Kinematic, kinetic and electromyography data of three male and three female subjects were measured. Results revealed no significant gender differences in the musculoskeletal variables tested except peak VGRF (p = 0.039) and hip axial compressive force (p = 0.032). The quadriceps and the gastrocnemius muscle forces had significant correlations with peak PTASF (r = 0.85, p < 0.05 and r = - 0.88, p < 0.05, respectively). Furthermore, hamstring muscle force was significantly correlated with peak VGRF (r = - 0.90, p < 0.05). The ankle flexion angle was significantly correlated with peak PTASF (r = - 0.82, p < 0.05). Our findings indicate that compared to males, females did not exhibit significantly different muscle forces, or ankle, knee and hip flexion angles during single-leg landings that would explain the gender bias in non-contact ACL injury rate. Our results also suggest that higher quadriceps muscle force increases the risk, while higher hamstring and gastrocnemius muscle forces as well as ankle flexion angle reduce the risk of non-contact ACL injury.

Dynamic postural stability for double-leg drop landing

Dynamic postural stability has been widely studied for single-leg landing, but seldom considered for double-leg landing. This study aimed to evaluate the dynamic postural stability and the influence mechanism of muscle activities during double-leg drop landing. Eight recreationally active males and eight recreationally active females participated in this study and dropped individually from three heights (0.32 m, 0.52 m, and 0.72 m). Ground reaction force was recorded to calculate the time to stabilisation. Electromyographic activities were recorded for selected lower-extremity muscles. A multivariate analysis of variance was carried out and no significant influence was found in time to stabilisation between genders or limb laterals (P > 0.05). With increasing drop height, time to stabilisation decreased significantly in two horizontal directions and the lower-extremity muscle activities were enhanced. Vertical time to stabilisation was not significantly influenced by drop height. Dynamic postural stability improved by neuromuscular change more than that required due to the increase of drop height. Double-leg landing on level ground is a stable movement, and the body would often be injured before dynamic postural stability is impaired. It is understandable to protect tissues from mechanical injuries by the sacrifice of certain dynamic postural stability in the design of protective devices or athlete training.

A Mechanics Comparison Between Landing From a Countermovement Jump and Landing From Stepping Off a Box

It is common practice to study jump landing mechanics by having subjects step off a box set at a certain height instead of landing from a jump. This practice assumes that the landing mechanics are similar between stepping off a box and a countermovement jump as long as the heights can be matched. The mechanics of the two methods had never been compared when landing from identical heights. Thus, the purpose of this study was to compare the mechanics of landing from a countermovement jump to landing from a step-off. Participants performed three maximal countermovement jumps. The mechanics of one countermovement jump was compared with a center of mass fall height matched step-off landing. The step-off landing showed a more rapid time to peak ground reaction force (GRF) in both genders and greater GRF peak and loading rate in males only. No difference was observed between joint angles at initial contact; however, the countermovement jump showed significantly greater joint flexion angles at peak GRF for both genders. EMG showed greater muscle activity during the countermovement jump condition in all subjects. It was concluded that countermovement jump landings are different from step-off landings; thus, results from analyses involving step-off landings should be taken with caution if the aim is to relate them to landing from a jump.

Shod landing provides enhanced energy dissipation at the knee joint relative to barefoot landing from different heights

Athletic shoes can directly provide shock absorption at the foot due to its cushioning properties, however it remains unclear how these shoes may affect the level of energy dissipation contributed by the knee joint. This study sought to investigate biomechanical differences, in terms of knee kinematics, kinetics and energetics, between barefoot and shod landing from different heights. Twelve healthy male recreational athletes were recruited and instructed to perform double-leg landing from 0.3-m and 0.6-m heights in barefoot and shod conditions. The shoe model tested was Brooks Maximus II. Markers were placed on the subjects based on the Plug-in Gait Marker Set. Force-plates and motion-capture system were used to capture ground reaction force (GRF) and kinematics data respectively. 2×2-ANOVA (barefoot/shod condition×landing height) was performed to examine differences in knee kinematics, kinetics and energetics between barefoot and shod conditions from different landing heights. Peak GRF was not significantly different (p=0.732-0.824) between barefoot and shod conditions for both landing heights. Knee range-of-motion, flexion angular velocity, external knee flexion moment, and joint power and work were higher during shod landing (p<0.001 to p=0.007), compared to barefoot landing for both landing heights. No significant interactions (p=0.073-0.933) were found between landing height and barefoot/shod condition for the tested parameters. While the increase in landing height can elevate knee energetics independent of barefoot/shod conditions, we have also shown that the shod condition was able to augment the level of energy dissipation contributed by the knee joint, via the knee extensors, regardless of the tested landing heights.

Non-linear flexion relationships of the knee with the hip and ankle, and their relative postures during landing

The knee joint, together with the hip and ankle, contributes to overall shock absorption through their respective flexion motions during landing. This study sought to investigate the presence of a lower extremity coordination pattern by determining mathematical relationships that associate knee flexion angles with hip flexion and ankle dorsiflexion angles during landing phase, and to determine relative postures of the hip and ankle, with reference to the knee, and examine how these relative postures change during key events of the landing phase. Eight healthy male subjects were recruited to perform double-leg landing from 0.6-m height. Motion capture system and force-plates were used to obtain kinematics and ground reaction forces (GRF) respectively. Non-linear regression analysis was employed to determine appropriate mathematical relationships of the hip flexion and ankle dorsiflexion angles with knee flexion angles during the landing phase. Relative lower extremity postures were compared between events of initial contact, peak GRF and maximum knee flexion, using ANOVA on ranks. Our results demonstrated a lower extremity coordination pattern, whereby the knee flexion angles had strong exponential (R(2) = 0.92-0.99, p < 0.001) and natural logarithmic (R(2) = 0.85-0.97, p < 0.001) relationships with hip flexion and ankle dorsiflexion angles respectively during the landing phase. Furthermore, we found that the s ubjects adopted distinctly different relative lower extremity postures (p < 0.05) during peak GRF as compared to initial contact. These relative postures were further maintained till the end of the landing phase. The occurrence of these relative postures may be a reflexive mechanism for the subjects to efficiently absorb the impact imposed by the peak GRF.

Modifying landing mat material properties may decrease peak contact forces but increase forefoot forces in gymnastics landings

This study investigated how changes in the material properties of a landing mat could minimise ground reaction forces (GRF) and internal loading on a gymnast during landing. A multi-layer model of a gymnastics competition landing mat and a subject-specific seven-link wobbling mass model of a gymnast were developed to address this aim. Landing mat properties (stiffness and damping) were optimised using a Simplex algorithm to minimise GRF and internal loading. The optimisation of the landing mat parameters was characterised by minimal changes to the mat's stiffness (<0.5%) but increased damping (272%) compared to the competition landing mat. Changes to the landing mat resulted in reduced peak vertical and horizontal GRF and reduced bone bending moments in the shank and thigh compared to a matching simulation. Peak bone bending moments within the thigh and shank were reduced by 6% from 321.5 Nm to 302.5Nm and GRF by 12% from 8626 N to 7552 N when compared to a matching simulation. The reduction in these forces may help to reduce the risk of bone fracture injury associated with a single landing and reduce the risk of a chronic injury such as a stress fracture.

The association between lower extremity energy absorption and biomechanical factors related to anterior cruciate ligament injury

BACKGROUND

Greater total energy absorption by the lower extremity musculature during landing may reduce stresses placed on capsuloligamentous tissues with differences in joint contributions to energy absorption potentially affecting anterior cruciate ligament injury risk. However, the relationships between energy absorption and prospectively identified biomechanical factors associated with non-contact anterior cruciate ligament injury have yet to be demonstrated.

METHODS

Sagittal plane total, hip, knee and ankle energy absorption, and peak vertical ground reaction force, anterior tibial shear force, knee flexion and knee valgus angles, and internal hip extension and knee varus moments were measured in 27 individuals (14 females, 13 males) performing double leg jump landings. Correlation coefficients assessed the relationships between energy absorption during three time intervals (initial impact phase, terminal phase, and total landing) and biomechanical factors related to anterior cruciate ligament injury.

FINDINGS

More favorable values of biomechanical factors related to non-contact anterior cruciate ligament injury were associated with: 1) Lesser total (R(2)=0.178-0.558), hip (R(2)=0.229-0.651) and ankle (R(2)=0.280), but greater knee (R(2)=0.147) energy absorption during the initial impact phase; 2) Greater total (R(2)=0.170-0.845), hip (R(2)=0.599), knee (R(2)=0.236-0.834), and ankle (R(2)=0.276) energy absorption during the terminal phase of landing; and 3) Greater knee (R(2)=0.158-0.709), but lesser hip (R(2)=0.309) and ankle (R(2)=0.210-0.319) energy absorption during the total landing period.

INTERPRETATION

These results suggest that biomechanical factors related to anterior cruciate ligament injury are influenced by both the magnitude and timing of lower extremity energy absorption during landing.