Sex differences in the kinematics and neuromuscular control of landing: biological, environmental and sociocultural factors

Landing error scoring system: A scoping review about variants, reference values and differences according to sex and sport

OBJECTIVE

The Landing Error Scoring System (LESS) is a movement analysis tool proposed to identify the risk of anterior cruciate ligament injuries, very useful for injury prevention. The aim of this study is to review the variants of the LESS, their normative scores and the differences according to sex and sport practiced.

METHODS

PubMed, Scopus and ScienceDirect databases were searched from inception to October 19, 2023. Studies were eligible if the objective was finding normative or reference scores for the LESS, analyze the differences between sexes or sports, or used some variant of the test. Results were limited to available full-text articles published in English in peer-reviewed journals.

RESULTS

Of the 360 articles identified, 20 were included for a full analysis (18,093 participants, age = 8-30 years, males = 70.6%). The military population was the most frequently analyzed (7 studies, n = 16,603). Results showed six variants of the LESS and average values ranged from 2.56 to 7.1. Males and females showed different pattern landing with errors in different planes.

CONCLUSIONS

Our findings highlight the need for more field studies on LESS reference scores, particularly for females and basketball or hockey players. Further research is required before conducting a systematic review and meta-analysis.

Examining the Effects of Dynamic and Isometric Resistance Training on Knee Joint Kinetics During Unplanned Sidesteps in Elite Female Athletes

ABSTRACT

Kadlec, D, Jordan, MJ, Alderson, J, and Nimphius, S. Examining the effects of dynamic and isometric resistance training on knee joint kinetics during unplanned sidesteps in elite female athletes. J Strength Cond Res XX(X): 000-000, 2024-The purpose of this study was to examine the effects of a 4-week block of isometric (isometricRT) and dynamic resistance training (dynamicRT) on kinetic variables associated with anterior cruciate ligament (ACL) injury risk during unplanned sidesteps in elite female athletes. Twenty-one elite female athletes competing for a women's international rugby union team were recruited with 15 (n = 15; age: 23.4 ± 4.7 years; 170.7 ± 8.4 cm; 84.4 ± 15.4 kg) completing assessment of knee flexion moment, knee valgus moment (KVM), knee internal rotation moment (KIRM), knee joint power during unplanned sidesteps, and lower limb strength before and after a 4-week intervention. Linear mixed effects models and one-dimensional statistical parametric mapping assessed the effect of the interventions. Statistical significance was set at α = 0.05. Postintervention the isometricRT group revealed reduced peak KVM during early stance (p = 0.04) while the dynamicRT group decreased peak KIRM (p < 0.01) and KIRM over 8.8-86.6% (p < 0.01) and 96.9-98.5% (p = 0.047). An exploratory combined group analysis revealed reductions in KVM over 7.9-21.8% (p = 0.002) and in KIRM over 8.3-90.5% (p < 0.01) and 96.2-98.5% (p = 0.046). Most lower limb isometric and dynamic strength measures increased after both resistance training interventions. Overall, both groups increased lower-body maximum strength while reducing kinetic knee joint variables associated with ACL injury risk during unplanned sidesteps. These results highlight the importance of increasing single-joint and multijoint strength in female athletes to mitigate the mechanical knee joint demands during sidestepping.

Differences in Biomechanical Determinants of ACL Injury Risk in Change of Direction Tasks Between Males and Females: A Systematic Review and Meta-Analysis

BACKGROUND

Change of direction (COD) movements are associated with non-contact anterior cruciate ligament (ACL) injuries in multidirectional sports. Females appear at increased risk compared to males, which could be attributable to whole body kinematic strategies and greater multiplanar knee joint loads (KJLs) during COD which can increase ACL loading.

OBJECTIVE

The aim of this systematic review and meta-analysis was to examine and quantitatively synthesise the evidence for differences between males and females regarding KJLs and their biomechanical determinants (whole body kinematic strategies determining KJLs) during COD tasks.

METHODS

Databases including SPORTDiscus, Web of Science, and PubMed were systematically searched (July 2021-June 2023) for studies that compared differences in knee joint loads and biomechanical determinants of KJLs during COD between males and females. Inclusion criteria were: (1) females and males with no prior history of ACL injury (18-40 years); (2) examined biomechanical determinants of KJLs and/ or KJLs during COD tasks > 20°; (3) compared ≥ 1 outcome measure between males and females. Studies published between 2000 and 2023 examining a cutting task > 20° with a preceding approach run that compared KJLs or the whole body multiplanar kinematics associated with them, between sexes, using three-dimensional motion analysis.

RESULTS

This meta-analysis included 17 studies with a pooled sample size of 451 participants (227 males, 224 females). Meta-analysis revealed females displayed significantly less peak knee flexion during stance (SMD: 0.374, 95% CI 0.098-0.649, p = 0.008, I2: 0%); greater knee abduction at initial contact (IC) (SMD: 0.687, 95% CI 0.299-1.076, p = 0.001, I2: 55%); less hip internal rotation (SMD: 0.437, 95% CI 0.134-0.741, p = 0.005, I2: 34%) and hip abduction at IC (SMD: -0.454, 95% CI 0.151-0.758, p = 0.003, I2: 33%). No significant differences were observed between males and females for any internal or externally applied KJLs. All retrieved studies failed to control for strength, resistance training or skill history status.

CONCLUSION

No differences were observed in KJLs between males and females despite females displaying greater knee abduction at IC and less peak knee flexion during the stance phase of CODs, which are visual characteristics of non-contact ACL injury. Further research is required to examine if this translates to a similar injury risk, considering morphological differences in strain characteristics of the ACL between males and females. This observation may in part explain the disproportionate ACL injury incidence in female multidirectional athletes. Further higher quality controlled research is required whereby participants are matched by skill training history, resistance training history and strength status to ensure an appropriate comparison between males and females.

Female athlete health domains: a supplement to the International Olympic Committee consensus statement on methods for recording and reporting epidemiological data on injury and illness in sport

The IOC made recommendations for recording and reporting epidemiological data on injuries and illness in sports in 2020, but with little, if any, focus on female athletes. Therefore, the aims of this supplement to the IOC consensus statement are to (i) propose a taxonomy for categorisation of female athlete health problems across the lifespan; (ii) make recommendations for data capture to inform consistent recording and reporting of symptoms, injuries, illnesses and other health outcomes in sports injury epidemiology and (iii) make recommendations for specifications when applying the Strengthening the Reporting of Observational Studies in Epidemiology-Sport Injury and Illness Surveillance (STROBE-SIIS) to female athlete health data.In May 2021, five researchers and clinicians with expertise in sports medicine, epidemiology and female athlete health convened to form a consensus working group, which identified key themes. Twenty additional experts were invited and an iterative process involving all authors was then used to extend the IOC consensus statement, to include issues which affect female athletes.Ten domains of female health for categorising health problems according to biological, life stage or environmental factors that affect females in sport were identified: menstrual and gynaecological health; preconception and assisted reproduction; pregnancy; postpartum; menopause; breast health; pelvic floor health; breast feeding, parenting and caregiving; mental health and sport environments.This paper extends the IOC consensus statement to include 10 domains of female health, which may affect female athletes across the lifespan, from adolescence through young adulthood, to mid-age and older age. Our recommendations for data capture relating to female athlete population characteristics, and injuries, illnesses and other health consequences, will improve the quality of epidemiological studies, to inform better injury and illness prevention strategies.

Effects of gender and fatigue on strength and activity of gluteus medius muscle during a controlled cutting maneuver in preadolescent athletes

The present study aimed to investigate the effects of gender on hip muscle strength and activity during a controlled cutting maneuver in preadolescent athletes. Fifty-six football and handball preadolescent players participated (35 females and 21 males). Normalized mean activity of the gluteus medius (GM) muscle was measured using surface electromyography during cutting maneuvers in pre-activation and eccentric phases. The stance duration and the strength of hip abductors and external rotators were recorded with a force plate and a handheld dynamometer, respectively. Descriptive statistics and mixed model analysis were used to assess statistical difference (α = 0.05). The results showed that boys activate the GM muscle significantly more than girls during the pre-activation phase (P = 0.022). Boys also demonstrated greater normalized strength of hip external rotation than girls (P = 0.038), but not for hip abduction or duration of stance (P > 0.05). When adjusted for abduction strength, however, boys had significantly shorter stance duration than girls (P = 0.006). It seems that sex-dependent differences are present in preadolescent athletes as observed in the strength of hip external rotator muscles and neuromuscular activity of the GM muscle during a cutting maneuver. Future studies are needed to investigate whether these changes influence risk of lower limb/ACL injury during sport activities.

A workflow for automatic, high precision livestock diagnostic screening of locomotor kinematics

Locomotor kinematics have been challenging inputs for automated diagnostic screening of livestock. Locomotion is a highly variable behavior, and influenced by subject characteristics (e.g., body mass, size, age, disease). We assemble a set of methods from different scientific disciplines, composing an automatic, high through-put workflow which can disentangle behavioral complexity and generate precise individual indicators of non-normal behavior for application in diagnostics and research. For this study, piglets (Sus domesticus) were filmed from lateral perspective during their first 10 h of life, an age at which maturation is quick and body mass and size have major consequences for survival. We then apply deep learning methods for point digitization, calculate joint angle profiles, and apply information-preserving transformations to retrieve a multivariate kinematic data set. We train probabilistic models to infer subject characteristics from kinematics. Model accuracy was validated for strides from piglets of normal birth weight (i.e., the category it was trained on), but the models infer the body mass and size of low birth weight (LBW) piglets (which were left out of training, out-of-sample inference) to be "normal." The age of some (but not all) low birth weight individuals was underestimated, indicating developmental delay. Such individuals could be identified automatically, inspected, and treated accordingly. This workflow has potential for automatic, precise screening in livestock management.

Effects of the menstrual cycle phase on anterior cruciate ligament neuromuscular and biomechanical injury risk surrogates in eumenorrheic and naturally menstruating women: A systematic review

BACKGROUND

Eumenorrheic women experience cyclic variations in sex hormones attributed to the menstrual cycle (MC) which can impact anterior cruciate ligament (ACL) properties, knee laxity, and neuromuscular function. This systematic review aimed to examine the effects of the MC on ACL neuromuscular and biomechanical injury risk surrogates during dynamic tasks, to establish whether a particular MC phase predisposes women to greater ACL injury risk.

METHODS

PubMed, Medline, SPORTDiscus, and Web of Science were searched (May-July 2021) for studies that investigated the effects of the MC on ACL neuromuscular and biomechanical injury risk surrogates. Inclusion criteria were: 1) injury-free women (18-40 years); 2) verified MC phases via biochemical analysis and/or ovulation kits; 3) examined neuromuscular and/or biomechanical injury risk surrogates during dynamic tasks; 4) compared ≥1 outcome measure across ≥2 defined MC phases.

RESULTS

Seven of 418 articles were included. Four studies reported no significant differences in ACL injury risk surrogates between MC phases. Two studies showed evidence the mid-luteal phase may predispose women to greater risk of non-contact ACL injury. Three studies reported knee laxity fluctuated across the MC; two of which demonstrated MC attributed changes in knee laxity were associated with changes in knee joint loading (KJL). Study quality (Modified Downs and Black Checklist score: 7-9) and quality of evidence were low to very low (Grading of Recommendations Assessment Development and Evaluation: very low).

CONCLUSION

It is inconclusive whether a particular MC phase predisposes women to greater non-contact ACL injury risk based on neuromuscular and biomechanical surrogates. Practitioners should be cautious manipulating their physical preparation, injury mitigation, and screening practises based on current evidence. Although variable (i.e., magnitude and direction), MC attributed changes in knee laxity were associated with changes in potentially hazardous KJLs. Monitoring knee laxity could therefore be a viable strategy to infer possible ACL injury risk.

Ankle Proprioception in Male and Female Surfers and the Implications of Motor Experience and Lower-Body Strength

ABSTRACT

Dowse, RA, Secomb, JL, Bruton, M, Parsonage, J, Ferrier, B, Waddington, G, and Nimphius, S. Ankle proprioception in male and female surfers and the implications of motor experience and lower-body strength. J Strength Cond Res 36(12): 3497-3504, 2022-The primary objectives were to evaluate if the active movement extent discrimination apparatus (AMEDA) condition (i.e., front foot and back foot plantarflexion, dorsiflexion, inversion, and eversion) and the level of competition explained ankle movement discrimination scores and, thereafter, examined the contribution of surf experience, physical capacity, and ability to proprioception. It was also considered important to re-evaluate the surf experience, anthropometric characteristics, physical capacities, and abilities of male and female surfers. Twenty-six male ( n = 12, surf experience = 18 ± 8 years) and female surfers ( n = 14, surf experience = 9 ± 6 years) completed a pre-exercise medical questionnaire, anthropometric assessment, 8 AMEDA assessments, countermovement jump, squat jump, and isometric midthigh pull assessment. The AMEDA condition and level of competition did not have a statistically significant main effect on ankle movement discrimination scores; however, the effect of the gender/sex was significant ( p = 0.044). Surf experience ( p = 0.029) and lower-body isometric strength ( p = 0.029) had a statistically significant but small main effect on ankle movement discrimination scores. The results also confirmed that there were significant differences in surf experience, anthropometric characteristics, physical capacity, and jumping ability between male and female surfers. As surf experience and physical capacity were only able to explain a small magnitude of ankle movement discrimination scores, it is suggested that ankle proprioception in surfers may be related to both the volume and quality of the motor experience attained, which may be augmented by environmental and sociocultural factors.

What are gender differences in lower limb muscle activity during jump-landing tasks? A systematic review and meta-analysis

Background

Gender differences in muscle activity during landing have been proposed as a possible contributing factor to the greater incidence of anterior cruciate ligament injuries in women. Conflicting results among a few studies in this regard makes it impossible to reach correct conclusions.

Objectives

The aim of this study was systematic review and the meta-analysis of previous studies which have compared the electromyographic activity of lower limb muscles in gluteus muscles (maximus and medius), quadriceps (rectus femoris, vastus medialis and lateralis), hamstrings (biceps femoris and semimembranosus), and gastrocnemius in men and women in jump–landing task.

Methods

A systematic search of the PubMed, SCOPUS, Science Direct databases was performed for eligible articles in October 2020. Cross-sectional studies that compared the muscle activity of male and female athletes without a history of previous injury in the jump–landing task were included. Unisex and non-athlete's studies were extracted from the included studies. The data were synthesized using a fixed and random effects model.

Results

Eight studies involving 145 participants were included. All participants were people who participated in regular exercises. The meta-analysis of timing and muscle activity was performed in the feedforward (pre contact) and feedback (post contact) stages. There were no significant differences in the muscle activity of biceps femoris (MD = −12.01; 95% CI − 51.49 to 27.47; p = 0.55; I² = 87%), vastus medialis (MD = −53.46; 95% CI − 129.73 to 22.81; p = 0.17; I² = 91%), semimembranosus (MD = 1.81; 95% CI − 6.44 to 10.07; p = 0.67; I² = 0%), gluteus medius (MD = −3.14; 95% CI − 14.24 to 7.96; p = 0.58; I² = 48%), and rectus femoris (MD = −5.83; 95% CI − 14.57 to 2.92; p = 0.19; I² = 87%) in the pre contact phase between two sexes. There was a significant difference between men and women in the activity of vastus lateralis muscle in the post contact phase (MD = −34.90; 95% CI − 48.23 to − 21.57). No significant difference was observed between the men and women in the timing of semimembranosus (MD = 23.53; 95% CI − 14.49 to 61.54; p = 0.23; I² = 56%) and biceps femoris muscle activity (MD = −46.84; 95% CI − 97.50 to 3.83; p = 0.07; I² = 82%).

Conclusion

The results showed that in all lower limb muscles except vastus lateralis there were no significant differences between muscle activity and muscle contraction timing in both sexes before and after foot contact. Therefore, it can be concluded that the reason for the greater susceptibility of ACL injuries in women than men is maybe related to other factors such as biomechanical and hormonal. Additional good quality research in this regard is required to strengthen these conclusions.

The effects of virtual reality immersion on drop landing mechanics

Virtual reality (VR) can be used to alter the environment and challenge sensory calibration which rehabilitation and return-to-sport testing lack. The purpose was to establish how VR manipulation of the environment changes knee landing biomechanics. Twenty-nine healthy active adults (22 males; 20.52 ± 1.21 years; 1.75 ± 0.09 m; 78.34 ± 14.33 kg) were recruited. Three drop landing trials (31 cm height box) were performed for three conditions: eyes-open (EO), eyes-closed (EC), and VR, consisting of a head-mounted display of a 360° photo of a steep man-made edge or drop. Knee kinematics and kinetics were evaluated using 3D motion capture. The VR condition significantly increased Landing Error Score System errors relative to EO (1.28 ± 0.20, p < 0.001) and EC (0.98 ± 0.22, p < 0.001) and increased vertical ground reaction force relative to EO (0.41 ± 0.09 N·bw-1, p < 0.001) and EC (0.34 ± 0.07 N·bw-1, p < 0.001). The VR condition had less knee flexion at initial contact compared to EO (4.39 ± 0.75°, p = 0.001) and EC (1.83 ± 0.63°, p = 0.021). The VR condition had more knee abduction at initial contact compared to EO (0.71 ± 0.24°, p = 0.002) and EC (0.69 ± 0.22°, p = 0.002) and increased knee abduction at maximum flexion compared to EO (2.01 ± 0.58°, p = 0.026). Landing in VR increased injury risk landing biomechanics, indicating that VR may option to incorporate into return-to-play or injury risk assessment.

Thermodynamics of Animal Locomotion

Muscles are biological actuators extensively studied in the frame of Hill's classic empirical model as isolated biomechanical entities, which hardly applies to a living organism subjected to physiological and environmental constraints. Here we elucidate the overarching principle of a living muscle action for locomotion, considering it from the thermodynamic viewpoint as an assembly of actuators (muscle units) connected in parallel, operating via chemical-to-mechanical energy conversion under mixed (potential and flux) boundary conditions. Introducing the energy cost of effort as the generalization of the well-known oxygen cost of transport in the frame of our compact locally linear nonequilibrium thermodynamics model, we analyze oxygen consumption measurement data from a documented experiment on energy cost management and optimization by horses moving at three different gaits. Horses adapt to a particular gait by mobilizing a nearly constant number of muscle units minimizing waste production per unit distance covered; this number significantly changes during transition between gaits. The mechanical function of the animal is therefore determined both by its own thermodynamic characteristics and by the metabolic operating point of the locomotor system.

Anterior cruciate ligament injuries in Australian football: should women and girls be playing? You're asking the wrong question

Anterior cruciate ligament (ACL) injuries have been a rising concern in the early years of the women’s Australian Football League (AFLW), eliciting headlines of a ‘knee crisis’ surrounding the league. There has been a focus on female biology as the primary factor driving the high rate of ACL injuries in the AFLW. Emphasising Australian football (AF) as being dangerous predominantly due to female biology may be misrepresenting a root cause of the ACL injury problem, perpetuating gender stereotypes that can restrict physical development and participation of women and girls in the sport. We propose that an approach addressing environmental and sociocultural factors, along with biological determinants, is required to truly challenge the ACL injury problem in the AFLW. Sports science and medicine must therefore strive to understand the whole system of women in AF, and question how to address inequities for the benefit of the athletes.

Focus of attention effects on lower extremity biomechanics during vertical jump landings

This study examined biomechanical differences between external and internal foci of attention during vertical jump landings in males and females. Twenty-four healthy adults performed eight vertical jump landings using both internal and external foci while three-dimensional kinematic and ground reaction force (GRF) data were obtained. Two (focus) by two (sex) analyses of variance (α = 0.05) and Cohen's d effect sizes (ES) were used to compare differences in vertical GRF, joint angular positions and displacements, and lower limb joint angular work between foci and between sexes. Significantly greater knee contributions to total angular work occurred during external versus internal focus landings regardless of sex (p = .013; ES = 0.30). Significantly smaller plantarflexion angles (p = .019; ES = 0.53) and significantly greater knee flexion angles were observed at ground contact (p < .001; ES = 1.11) in males during external focus landings. Females exhibited significantly smaller knee flexion angles at both ground contact during external versus internal focus landings (p = .031; ES = 0.20) and compared to males during external focus landings (p < .001; ES = 1.76). Both peak vertical GRF (p = .003; ES = 1.54) and the ankle contributions to total angular work during loading (p = .026; ES = 1.07) were greater in females versus males regardless of foci, whereas the knee contributions to total angular work during loading were smaller in women (p = .026; ES = 1.07). Males and females might consider adopting an external focus during vertical jump landings to increase knee joint contributions to lower limb energy absorption. Females, in particular, might consider external focus use to decrease peak vertical GRF and increase the knee joint's contribution to total energy absorption to magnitudes similar to those exhibited by males.

Knee Forces During Landing in Men and Women

Sex differences in biomechanics may provide one explanation for the greater incidence of knee injuries in women, but few studies have compared internal forces. In this study, a musculoskeletal model was used to compare male and female, bilateral and unilateral landings based on motion capture and force plate data. Participants were classified as landing medially or laterally loaded based upon the mediolateral load share at the knee (bilateral: p < 0.001, η²=0.452; unilateral: p < 0.001, η² = 0.444). Knee kinematics and ground reaction forces were not different between the two groups (p > 0.05, η² = 0.001 - 0.059), but there were differences in muscular recruitment. Landing strategy did not appear to be dependent on sex. However, for both medially and laterally loaded bilateral landings men had greater gluteal (p = 0.017, η² = 0.085) and hamstrings forces (p < 0.001, η² = 0.183), whereas women had greater quadriceps forces (p = 0.004, η² = 0.116). This study demonstrates an association between muscular recruitment and medially loaded landings. Landing strategy seems to be a function of skill not sex; however, within a particular landing strategy there may be sex differences in muscular activation that contribute to the difference in injury rates.

Spike jump biomechanics in male versus female elite volleyball players

There are well-known biological differences between women and men, especially in technical-coordinative variations that contribute to sex differences in performance of complex movements like the most important offensive action in volleyball, the spike jump. The aim of this study was to investigate sex-dependent performance and biomechanical characteristics in the volleyball spike jump. Thirty female and male sub-elite volleyball players were analysed while striking a stationary ball with maximal spike jump height. Twelve MX13 Vicon cameras with a cluster marker set, two AMTI force plates, surface EMG, and a Full-Body 3D model in Visual3D were used. Main findings include sex differences (P< .05) in jump height (pη² = .73), approach [speed (pη² = .61), step length], transition strategy [plant angle, neuromuscular activation (pη² = .91), horizontal force maxima and impulses], acceleration distances [centre of mass displacement (pη² = .21), minimal knee and hip angles], use of torso and arms [incline, angular velocity (pη² = .23)]. Correlations support that the results cannot be explained fully by strength and power differences between sexes but represent the product of technical-coordinative variations. Their relevance is acknowledged for both sexes and numerous performance determinants displayed sex differences. The integration of such attributes into sex-specific training seems promising but its effect requires further investigation.

Comparison of lower limb stiffness between male and female dancers and athletes during drop jump landings

Repetition of jumps in dance and sport training poses a potential injury risk; however, non-contact landing injuries are more common in athletes than dancers. This study aimed to compare the lower limb stiffness characteristics of dancers and athletes during drop landings to investigate possible mechanisms of impact-related injuries. Kinematics and kinetics were recorded as 39 elite modern and ballet dancers (19 men and 20 women) and 40 college-level team sport athletes (20 men and 20 women) performed single-legged drop landings from a 30-cm platform. Vertical leg stiffness and joint stiffness of the hip, knee, and ankle were calculated using a spring-mass model. Stiffness data, joint kinematics, and moments were compared with a group-by-sex 2-way analysis of variance. Multiple linear regression was used to assess the relative contribution of hip and knee and ankle joint stiffness to variance in overall vertical leg stiffness for dancers and athletes. Dancers had lower leg (P < 0.001), knee joint (P = 0.034), and ankle joint stiffness (P = 0.043) than athletes. This was facilitated by lower knee joint moments (P = 0.012) and greater knee (P = 0.029) and ankle joint (P = 0.048) range of motion in dancers. Males had higher leg (P < 0.001) and ankle joint stiffness (P < 0.001) than females. This occurred through lower ankle range of motion (P < 0.001) and greater ankle moment (P = 0.022) compared to females. Male and female dancers demonstrated reduced lower limb stiffness compared to athletes, indicating a more pliable landing technique. Dance training techniques could potentially inform approaches to injury prevention in athletes.

Sex Differences in Drop Landing: More Apparent in Recreational Surfers Than in Competitive Surfers or Nonsurfers

We suspected that the observed inconsistency of sex differences in drop-landing motor skills might be due to the confounding factor of prior experience. Thus, in this study, we explored the role of experience in shaping male and female surfboard riders' motor skill kinematics during drop landings while surfboard riding. We recruited 42 participants (21 females and 21 males) from three groups of surfing experience levels (competitive surfers, recreational surfers, and nonsurfers), each equally comprising seven males and seven females. Sagittal plane kinematics and vertical ground reaction force data were collected from all participants during a laboratory-based 60-cm drop-landing task. Knee flexion and ankle dorsiflexion at initial ground contact were greater among male participants, independent of experience level. In both sexes, greater range of motion at these joints was related to greater experience. Recreational female surfers landed in a more upright posture with more extended ankle and knee angles and less ankle dorsiflexion at the end of landing than participants in all other groups. We discuss our results in the context of possible remaining experience differences between male and female participants despite being grouped in the same experience levels in our study, individualized motor patterns that may still achieve similar success, and a need for continued research.

Sex differences in unilateral landing mechanics from absolute and relative heights

BACKGROUND

The prevalence of anterior cruciate ligament injuries in athletic populations and the sex disparity in injury rates are well documented. It is also recognized that landing from a jump is a common noncontact injury mechanism. Yet, most studies utilize absolute landing heights, and few have utilized landing heights equal to participants' maximal jumping ability. The purpose of this study was to examine unilateral landing mechanics from relative and absolute heights.

METHODS

Twenty-one female and twenty male participants completed a series of landings from absolute heights of 30, 40, and 50cm, as well as a height equal to their maximum jumping ability. Right leg three-dimensional kinematics, kinetics, and energetics were calculated from initial contact to maximum knee flexion.

RESULTS

Females landed with greater peak posterior ground reaction force compared to males. Additionally, both female and male participants utilized the knee as the primary energy absorber, but females appear to emphasize greater ankle energy absorption compared to males. Females also displayed increased peak knee adduction moment, while males displayed decreased peak hip abduction moment as landing height increased.

CONCLUSIONS

It appears that females and males respond to increasing landing heights differently. However, landings from 40 and 50cm may have represented an unrealistic mechanical demand for females, and influence subsequent inferences regarding ACL injury risk. Therefore, we suggest that comparisons between studies utilizing different landing heights be made with caution, and participants jumping ability be taken into account whenever possible.

CLINICAL RELEVANCE

The findings of this study offer novel insights with regard to landing height and lower extremity mechanics with the potential to inform anterior cruciate ligament injury intervention programs.

The influences of sex and posture on joint energetics during drop landings

Previous observations suggest that females utilize a more erect initial landing posture than males with sex differences in landing posture possibly related to sex-specific energy absorption (EA) strategies. However, sex-specific EA strategies have only been observed when accompanied by sex differences in initial landing posture. This study (a) investigated the potential existence of sex-specific EA strategies; and (b) determined the influences of sex and initial landing posture on the biomechanical determinants of EA. The landing biomechanics of 80 subjects were recorded during drop landings in Preferred, Flexed, and Erect conditions. No sex differences in joint EA were identified after controlling for initial landing posture. Males and females exhibited greater ankle EA during Erect vs Flexed landings with this increase driven by 12% greater ankle velocity, but no change in ankle extensor moment. No differences in hip and knee EA were observed between conditions. However, to achieve similar knee EA, subjects used 7% greater mean knee extensor moment but 9% less knee angular velocity during Flexed landings. The results suggest that sex-specific EA strategies do not exist, and that the magnitude of knee joint EA can be maintained by modulating the relative contributions of joint moment and angular velocity to EA.