Joint dynamics of rear- and fore-foot unplanned sidestepping

Effect of a tailored exercise programme on kinematics and kinetic knee injury risk during different side-cutting

Despite the high incidence of knee injuries reported in non-professional sports, the implementation of specific training programmes aimed at mitigating the kinematic and kinetic factors associated with these injuries remains limited. To determine the effects of a tailored exercise programme on kinematic and kinetic variables during side-cutting activities. Fifty-seven physically active participants were randomised into control group (CG; n: 28) that received no intervention, and an experimental group (EG; n: 29), that performed an individualised exercise programme that included a combination of strength, neuromuscular, proprioceptive, eccentric training and whole-body vibration (WBV) exercises. Knee, hip and trunk angles, vertical ground reaction force (VGRF), force in the antero-posterior (AP) and medio-lateral (ML) axes, acceleration, contact time and impulse were assessed during three types of side-cutting, two open manoeuvres (30º and 45º - SC30 and SC45 -respectively) and one closed manoeuvre (45º - SC45cl-). After the 12-week intervention, EG participants had lower knee extension during all side-cuttings, shorter contact time and lower acceleration, VGRF and impulse compared to CG during side-cutting manoeuvres. A tailored exercise programme could be an effective neuromuscular and biomechanical strategy to reduce risk factors for knee injury in healthy, physically active young people.

Effect of foot strike patterns and angles on the biomechanics of side-step cutting

Objectives

The study aimed to determine how foot strike patterns and cutting angles affect lower extremity (LE) kinematics, kinetics, and muscle activity during side-step cutting.

Methods

Twenty male college sport athletes participated in this research. Three-dimensional motion analysis featuring ground reaction force (GRF) and electromyography (EMG) of the dominant leg was used. LE kinematics, kinetics, and EMG data parameters were obtained during a 45° and 90° side-step cutting involving rearfoot strikes (RFS) and forefoot strikes (FFS).

Results

The significant foot strike pattern × angle interactions were observed for the ankle eversion range of motion (ROM) at the loading phase. Cutting of 90° had greater knee flexion ROM, knee valgus ROM, and knee varus moment compared to that of 45°. RFS cutting had greater knee flexion, hip flexion, knee valgus, knee varus moment, knee varus moment, and ankle eversion ROM. FFS cutting produced a lower vertical GRF, lateral GRF, and a loading rate. Both vastus medialis and vastus lateralis muscle activities were remarkably greater during cutting of 90° than 45°. At the loading phase, semitendinosus, biceps femoris, and the lateral head of gastrocnemius muscle activities during FFS cutting were considerably greater than those during RFS cutting.

Conclusion

The FFS pattern can better protect the anterior cruciate ligament (ACL) and improve the flexibility of athletes by increasing the plantarflexion torque of the ankle. The injury risk also increases with the larger cutting angle. The EMG activities of semitendinosus and biceps femoris are vital for the stability of knee joint during side-step cutting, which helps reduce ACL stress during buffering.

Mind your step: predicting maximum ankle inversion during cutting movements in soccer

The objective of this investigation was to identify parameters at initial contact that would predict the subsequent maximum ankle inversion angle during cutting movements. We conducted a secondary data analysis and calculated kinematics of 1,400 cuttings performed by 46 male soccer athletes. The movement task consisted of an approach run, followed by a pre-planned cutting movement. A linear mixed regression model was applied to predict the maximum ankle inversion angle during the first 100 ms of ground contact. The prediction was made based on six predictors that describe change-of-direction intensity and foot placement as found to be relevant in the literature. The model explained 62% of the variance of maximum ankle inversion angles. A change of the main predictors (foot rotation, cutting angle and initial ankle inversion) by 1 SD caused a reduction of the subsequent maximum ankle inversion angle by 2.6-4.4°. Regarding the intensity of a change-of-direction movement, cutting angle seems to have a higher influence on maximum ankle inversion angle than approach velocity. With respect to the individual foot positioning, the maximum ankle inversion angle can be reduced by increasing exorotation and eversion of the foot while shifting towards forefoot landing.

Anterior cruciate ligament injury prevention in sport: biomechanically informed approaches

This paper reviews a series of studies contributing to a framework for preventing anterior cruciate ligament (ACL) injuries in sport. As the majority of these injuries are non-contact in nature, theoretically, these injuries are preventable. The studies presented in this paper focus on understanding biomechanical countermeasures of ACL injury and how this knowledge can inform both screening and training intervention research and practice in sport. These countermeasures include: 1) modifying an athlete's technique to reduce externally applied loads to the knee; 2) increasing the muscle support around the knee and hip to counter elevated loads applied to the knee and; 3) improving an athlete's perception during dynamic sports tasks to increase planning time to coordinate desirable movement patterns. By furthering the empirical evidence of modifiable biomechanical countermeasures of ACL injury risk, we can better understand best practices for developing interventions on a mass scale to prevent ACL injuries in the sporting community.

The future of in-field sports biomechanics: wearables plus modelling compute real-time in vivo tissue loading to prevent and repair musculoskeletal injuries

This paper explores the use of biomechanics in identifying the mechanistic causes of musculoskeletal tissue injury and degeneration. It appraises how biomechanics has been used to develop training programmes aiming to maintain or recover tissue health. Tissue health depends on the functional mechanical environment experienced by tissues during daily and rehabilitation activities. These environments are the result of the interactions between tissue motion, loading, biology, and morphology. Maintaining health of and/or repairing musculoskeletal tissues requires targeting the "ideal" in vivo tissue mechanics (i.e., loading and deformation), which may be enabled by appropriate real-time biofeedback. Recent research shows that biofeedback technologies may increase their quality and effectiveness by integrating a personalised neuromusculoskeletal modelling driven by real-time motion capture and medical imaging. Model personalisation is crucial in obtaining physically and physiologically valid predictions of tissue biomechanics. Model real-time execution is crucial and achieved by code optimisation and artificial intelligence methods. Furthermore, recent work has also shown that laboratory-based motion capture biomechanical measurements and modelling can be performed outside the laboratory with wearable sensors and artificial intelligence. The next stage is to combine these technologies into well-designed easy to use products to guide training to maintain or recover tissue health in the real-world.

Individualized Technique Feedback for Instant Technique Improvements and Knee Abduction Moment Reductions - A New Approach for 'Sidestepping' ACL Injuries?

Background

Sidestep cutting technique is highly individual and has been shown to influence knee joint loading. However, studies assessing whether individualized technique feedback improves technique and ACL injury-relevant knee joint loads instantly in a sport-specific task are lacking.

Purpose

To determine the instant effects of individualized augmented technique feedback and instructions on technique and the peak external knee abduction moment (pKAM) in a handball-specific sidestep cut. Additionally, to determine the effects of technique modifications on the resultant ground reaction force and its frontal plane moment arm to the knee joint center.

Study Design

Controlled laboratory cohort study.

Methods

Three-dimensional biomechanics of 48 adolescent female handball players were recorded during a handball-specific sidestep cut. Following baseline cuts to each side, leg-specific visual and verbal technique feedback on foot strike angle, knee valgus motion, or vertical impact velocity using a hierarchically organized structure accounting for the variables' association with performance was provided. Subsequently, sidestep cuts were performed again while verbal instructions were provided to guide technique modifications. Combined effects of feedback and instructions on technique and pKAM as well as on the resultant ground reaction force and its frontal plane moment arm to the knee joint center were assessed.

Results

On average, each targeted technique variable improved following feedback and instructions, leading to instant reductions in pKAM of 13.4% to 17.1%. High inter-individual differences in response to feedback-instruction combinations were observed. These differences were evident in both the adherence to instructions and the impact on pKAM and its components.

Conclusion

Most players were able to instantly adapt their technique and decrease ACL injury-relevant knee joint loads through individualized augmented technique feedback, thereby potentially reducing the risk of injury. More research is needed to assess the retention of these adaptations and move towards on-field technique assessments using low-cost equipment.

Level of Evidence

Level 3.

The inter-laboratory equivalence for lower limb kinematics and kinetics during unplanned sidestepping

Much inter-intra-tester kinematic and kinetic repeatability research exists, with a paucity investigating inter-laboratory equivalence. The objective of this research was to evaluate the inter-laboratory equivalence between time varying unplanned kinematics and moments of unplanned sidestepping (UnSS). Eight elite female athletes completed an established UnSS procedure motion capture laboratories in the UK and Australia. Three dimensional time varying unplanned sidestepping joint kinematics and moments were compared. Discrete variables were change of direction angles and velocity. Waveform data were compared using mean differences, 1D 95%CI and RMSE. Discrete variables were compared using 0D 95% CI. The mean differences and 95%CI for UnSS kinematics broadly supported equivalence between laboratories (RMSE≤5.1°). Excluding hip flexion/extension moments (RMSE = 1.04 Nm/kg), equivalence was also supported for time varying joint moments between laboratories (RMSE≤0.40 Nm/kg). Dependent variables typically used to characterise UnSS were also equivalent. When consistent experimental and modelling procedures are employed, consistent time varying UnSS lower limb joint kinematic and moment estimates between laboratories can be obtained. We therefore interpret these results as a support of equivalence, yet highlight the challenges of establishing between-laboratory experiments or data sharing, as well as establishing appropriate ranges of acceptable uncertainty. These findings are important for data sharing and multi-centre trials.

Characterization of movement patterns using unsupervised learning neural networks: Exploring a novel approach for monitoring athletes during sidestepping

The monitoring of athletes is crucial to preventing injuries, identifying fatigue or supporting return-to-play decisions. The purpose of this study was to explore the ability of Kohonen neural network self-organizing maps (SOM) to objectively characterize movement patterns during sidestepping and their association with injury risk. Further, the network's sensitivity to detect limb dominance was assessed. The data of 67 athletes with a total of 613 trials were included in this study. The 3D trajectories of 28 lower-body passive markers collected during sidestepping were used to train a SOM. The network consisted of 1247 neurons distributed over a 43 × 29 rectangular map with a hexagonal neighbourhood topology. Out of 61,913 input vectors, the SOM identified 1247 unique body postures. Visualizing the movement trajectories and adding several hidden variables allows for the investigation of different movement patterns and their association with joint loading. The used approach identified athletes that show significantly different movement strategies when sidestepping with their dominant or non-dominant leg, where one strategy was clearly associated with ACL-injury-relevant risk factors. The results highlight the ability of unsupervised machine learning to monitor an individual athlete's status without the necessity to reduce the complexity of the data describing the movement.

Anticipatory effects on side-step cutting biomechanics in Women's Australian Football League players

Objectives

Reactive side-step cutting manoeuvres are linked to anterior cruciate ligament (ACL) injuries in Women's Australian Football League (AFLW) matches. We explored knee joint moments and ground reaction forces (GRFs) in AFLW players when performing anticipated and unanticipated side-stepping.

Methods

Sixteen AFLW players (age=25.3±4.2 years; height=1.71±0.06 m; mass=68.4±4.7 kg) completed anticipated and unanticipated side-stepping trials during which full-body three-dimensional kinematics and kinetics were recorded. One-dimensional statistical parametric mapping paired t-tests were used to compare three-dimensional knee moments during weight acceptance and GRFs during the stance phase between anticipated and unanticipated conditions.

Results

Unanticipated side-stepping incurred lower knee flexion (18%-39% of stance, p<0.01) and abduction (11%-24% of stance, p<0.01) moments. Braking and propulsive GRFs were lower and higher, respectively, across the majority of stance phase (6%-90% of stance, p<0.01) in unanticipated side-stepping. Vertical GRFs were lower in unanticipated side-stepping in the early stance phase (14%-29% of stance, p<0.01).

Conclusion

Contrary to existing literature, AFLW players exhibited knee joint moments associated with reduced ACL loading when performing unanticipated side-stepping. Players appeared to adopt a 'cautious' approach to the unanticipated side-step (ie, decelerating at the change of direction), by reducing braking and vertical GRFs in the early stance phase of cutting. This approach may be implausible to employ or detrimental to performance during matches. AFLW ACL injury prevention programmes may be enhanced with greater exposure to scenarios that replicate reactive match-play demands when aiming to improve side-stepping biomechanics.

Change the direction: 3D optimal control simulation by directly tracking marker and ground reaction force data

Optimal control simulations of musculoskeletal models can be used to reconstruct motions measured with optical motion capture to estimate joint and muscle kinematics and kinetics. These simulations are mutually and dynamically consistent, in contrast to traditional inverse methods. Commonly, optimal control simulations are generated by tracking generalized coordinates in combination with ground reaction forces. The generalized coordinates are estimated from marker positions using, for example, inverse kinematics. Hence, inaccuracies in the estimated coordinates are tracked in the simulation. We developed an approach to reconstruct arbitrary motions, such as change of direction motions, using optimal control simulations of 3D full-body musculoskeletal models by directly tracking marker and ground reaction force data. For evaluation, we recorded three trials each of straight running, curved running, and a v-cut for 10 participants. We reconstructed the recordings with marker tracking simulations, coordinate tracking simulations, and inverse kinematics and dynamics. First, we analyzed the convergence of the simulations and found that the wall time increased three to four times when using marker tracking compared to coordinate tracking. Then, we compared the marker trajectories, ground reaction forces, pelvis translations, joint angles, and joint moments between the three reconstruction methods. Root mean squared deviations between measured and estimated marker positions were smallest for inverse kinematics (e.g., 7.6 ± 5.1 mm for v-cut). However, measurement noise and soft tissue artifacts are likely also tracked in inverse kinematics, meaning that this approach does not reflect a gold standard. Marker tracking simulations resulted in slightly higher root mean squared marker deviations (e.g., 9.5 ± 6.2 mm for v-cut) than inverse kinematics. In contrast, coordinate tracking resulted in deviations that were nearly twice as high (e.g., 16.8 ± 10.5 mm for v-cut). Joint angles from coordinate tracking followed the estimated joint angles from inverse kinematics more closely than marker tracking (e.g., root mean squared deviation of 1.4 ± 1.8 deg vs. 3.5 ± 4.0 deg for v-cut). However, we did not have a gold standard measurement of the joint angles, so it is unknown if this larger deviation means the solution is less accurate. In conclusion, we showed that optimal control simulations of change of direction running motions can be created by tracking marker and ground reaction force data. Marker tracking considerably improved marker accuracy compared to coordinate tracking. Therefore, we recommend reconstructing movements by directly tracking marker data in the optimal control simulation when precise marker tracking is required.

Grip socks improve slalom course performance and reduce in-shoe foot displacement of the forefoot in male and female sports players

This study assessed whether grip socks reduce in-shoe foot motion and improve change of direction performance in team sports players and compared the effects between males and females. A sledge and pulley system confirmed the static coefficient of friction was increased in the grip socks (1.17) compared to the regular socks (0.60). Performance during a slalom course was faster in the grip socks compared to regular socks (p = .001). Yet, there was no difference in the utilised coefficient of friction between the shoe-floor interface during a side-cut and turn change of direction manoeuvre. Three-dimensional motion capture revealed the grip socks reduced in-shoe foot displacement during the braking phase, with greater effect during the sharper turn manoeuvre. The magnitude of natural foot spreading within the shoe was greater in the calcaneus region than the metatarsals which suggests in-shoe sliding may only occur at the forefoot. Males tended to have increased in-shoe displacement, which is associated with larger foot spreading due to their increased mass. Findings provide guidance for product developers to enhance the support inside the shoe at the forefoot, and change of direction performance.

The effect of planning time on penultimate and ultimate step kinematics and subsequent knee moments during sidestepping

Frontal plane postures during the ultimate step of sidestepping are linked to increased anterior cruciate ligament injury risk. However, there is a lack of research detailing the kinematic strategies present in the penultimate step. This study, therefore, investigated penultimate and ultimate step kinematics of planned sidestepping (pSS) and unplanned sidestepping (upSS) to further understand the effect of planning time on known ultimate step kinematic and kinetic differences. Sixty male amateur Australian Rules football players performed three trials of straight-line running (RUN), pSS, and upSS in a randomized order. Mediolateral foot placement and three-dimensional joint kinematics for the knee, pelvis, and trunk were measured at final foot contact of the penultimate step and initial foot contact of the ultimate step. Peak knee moments were measured during the weight acceptance phase of the ultimate step. In pSS, at the penultimate step final foot contact, the support foot was placed across the midline of the center of mass, in the frontal plane, contralateral to the sidestep direction. Greater trunk lateral flexion toward the sidestep direction and greater negative pelvic lateral tilt were observed in pSS compared with upSS and RUN. Differences between pSS and upSS frontal plane kinematics at penultimate step final foot contact suggest preparatory reorientation strategies are likely constrained by the amount of planning time available. As there are clear differences in preparatory kinematics, we recommend that planning time be considered when training and assessing sidestepping maneuvers and planned and unplanned maneuvers not be treated as interchangeable skills.

Video Analysis of Anterior Cruciate Ligament Injury Situations in the Women's Australian Football League

Anterior cruciate ligament (ACL) injury rates in the Women's Australian Football League (AFLW) are alarmingly high. Understanding injuries within their sporting context is important to develop effective injury prevention strategies, yet there is currently little knowledge of how ACL injuries occur to AFLW players. This study addressed the common scenarios and characteristics of ACL injuries in the AFLW.

Online match and AFLW club injury reports identified 38 ACL injury cases. After excluding injuries where footage was unavailable (i.e. training, pre-season games), a video analysis of 21 match ACL injuries from the 2017-2020 AFLW seasons was performed. We examined match characteristics, and the player's movements and body postures preceding and at the estimated time of injury. Descriptive frequencies and relative proportions were determined across the assessed categories.

Non-contact ACL injuries were frequently observed (n=13, 61.9%), while contact preceding the injury event (i.e. indirect contact) was also common (n=10, 47.6%). The most common game situation was direct defence (i.e. defending an opponent in possession) (n=14, 66.7%). Sidestep cutting was the most prevalent movement (n=11, 52.4%), with this commonly performed while applying defensive pressure (n=6 of 11, 54.6%).

Sidestep cutting when applying defensive pressure is the most common non-contact ACL injury scenario in the AFLW. Preceding contact potentially contributing to a player's loss of balance was another prominent AFLW scenario. AFLW players may benefit from injury prevention programs emphasising appropriate sidestep cutting technique during reactive defensive scenarios, and maintenance of lower limb postures known to withstand knee loading relative to the sporting task.

Force Production Patterns of Muscles Surrounding Knee During Running and Cutting Maneuvers: A Musculoskeletal Modeling Approach

OBJECTIVES The purpose of this study was to investigate the force production patterns of individual muscles surrounding the knee during running (RUN) and cutting (CUT) tasks.METHODS Thirteen women (24.2±3.5 yrs, 162.8±6.0 cm, 55.3±6.2 kg) performed a series of running and cutting tasks. Running and cutting motions were recorded using a motion capture system and ground reaction force (GRF) was recorded using a force plate. Three-dimensional knee angle, ground reaction force, and knee joint moment were calculated using Visual3D software. OpenSim musculoskeletal modeling software was used to calculate the force of individual muscles including the medial hamstring, biceps femoris long head, biceps femoris short head, rectus femoris, vastus medialis, vastus lateralis, gastrocnemius medialis, and gastrocnemius lateralis. All data were analyzed for loading response (or weight acceptance), mid-stance, and final push-off periods, respectively and were compared between two tasks.RESULTS At loading response: external rotation angle, medial and vertical GRFs, and valgus moment for the CUT task were greater than those of the RUN task. Compared to the RUN task, the CUT task showed: 1) an increase in lateral hamstring muscle force at weight acceptance, 2) a decrease in hamstring muscle force and an increase in medial vastus muscle force at mid-stance, and 3) an increase in lateral gastrocnemius muscle force at final push-off.CONCLUSIONS Selective force production patterns of muscles surrounding the knee seem to offset the external load caused by the cutting motion. We anticipate that our results will provide basic data for future training programs designed to prevent noncontact knee injuries.

Optimizing Whole-Body Kinematics During Single-Leg Jump Landing to Reduce Peak Abduction/Adduction and Internal Rotation Knee Moments: Implications for Anterior Cruciate Ligament Injury Risk

Knee abduction/adduction moment and knee internal rotation moment are known surrogate measures of anterior cruciate ligament (ACL) load during tasks like sidestepping and single-leg landing. Previous experimental literature has shown that a variety of kinematic strategies are associated or correlated with ACL injury risk; however, the optimal kinematic strategies needed to reduce peak knee moments and ACL injury are not well understood. To understand the complex, multifaceted kinematic factors underpinning ACL injury risk and to optimize kinematics to prevent the ACL injury, a musculoskeletal modeling and simulation experimental design was used. A 14-segment, 37-degree-of-freedom, dynamically consistent skeletal model driven by force/torque actuators was used to simulate whole-body single-leg jump landing kinematics. Using the residual reduction algorithm in OpenSim, whole-body kinematics were optimized to reduce the peak knee abduction/adduction and internal/external rotation moments simultaneously. This optimization was repeated across 30 single-leg jump landing trials from 10 participants. The general optimal kinematic strategy was to bring the knee to a more neutral alignment in the transverse plane and frontal plane (featured by reduced hip adduction angle and increased knee adduction angle). This optimized whole-body kinematic strategy significantly reduced the peak knee abduction/adduction and internal rotation moments, transferring most of the knee load to the hip.

Differences in Muscle Activities and Kinematics between Forefoot Strike and Rearfoot Strike in the Lower Limb during 180° Turns

BACKGROUND

A forefoot strike (FFS) could be a safer landing technique than a rearfoot strike (RFS) during a cutting motion to prevent anterior cruciate ligament (ACL) injury.

PURPOSE

This study aimed to determine the joint angles, ground reaction force (GRF), and muscle activity levels associated with FFS and RFS landings during 180° turns.

STUDY DESIGN

Cross-sectional study.

METHODS

Fourteen male soccer players from the University of Tsukuba football (soccer) club participated in this study. The FFS consisted of initial contact with the toes on the force plates followed by the rearfoot; meanwhile, the initial contact was performed with the heels on the force plates followed by the forefoot for the RFS. Ankle, knee, and hip joint angles were recorded using a three-dimensional motion capture system. GRFs were measured using a force plate. Gluteus medius (GM), rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), semitendinosus (ST), biceps femoris (BF), tibialis anterior (TA), and lateral gastrocnemius (GL) activities were measured by electromyography.

RESULTS

The activities of GM, GL, and ST from initial contact to early periods during landing into the ground with the FFS are larger than those with RFS. In addition, the results showed significant differences in lower-limb angles and GRFs between the FFS and RFS.

CONCLUSION

These results suggest that there might be differences in ACL injury risk during a 180° turn between the FFS and the RFS pattern. An investigation into the grounding method that prevents injury is necessary in future studies.

LEVELS OF EVIDENCE

Level 3b.

Biomechanical Determinants of Performance and Injury Risk During Cutting: A Performance-Injury Conflict?

BACKGROUND

Most cutting biomechanical studies investigate performance and knee joint load determinants independently. This is surprising because cutting is an important action linked to performance and non-contact anterior cruciate ligament (ACL) injuries. The aim of this study was to investigate the relationship between cutting biomechanics and cutting performance (completion time, ground contact time [GCT], exit velocity) and surrogates of non-contact ACL injury risk (knee abduction [KAM] and internal rotation [KIRM] moments) during 90° cutting.

DESIGN

Mixed, cross-sectional study following an associative design. 61 males from multidirectional sports performed six 90° pre-planned cutting trials, whereby lower-limb and trunk kinetics and kinematics were evaluated using three-dimensional (3D) motion and ground reaction force analysis over the penultimate (PFC) and final foot contact (FFC). Pearson's and Spearman's correlations were used to explore the relationships between biomechanical variables and cutting performance and injury risk variables. Stepwise regression analysis was also performed.

RESULTS

Faster cutting performance was associated (p ≤ 0.05) with greater centre of mass (COM) velocities at key instances of the cut (r or ρ = 0.533-0.752), greater peak and mean propulsive forces (r or ρ = 0.449-0.651), shorter FFC GCTs (r or ρ = 0.569-0.581), greater FFC and PFC braking forces (r = 0.430-0.551), smaller hip and knee flexion range of motion (r or ρ = 0.406-0.670), greater knee flexion moments (KFMs) (r = 0.482), and greater internal foot progression angles (r = - 0.411). Stepwise multiple regression analysis revealed that exit velocity, peak resultant propulsive force, PFC mean horizontal braking force, and initial foot progression angle together could explain 64% (r = 0.801, adjusted 61.6%, p = 0.048) of the variation in completion time. Greater peak KAMs were associated with greater COM velocities at key instances of the cut (r or ρ = - 0.491 to - 0.551), greater peak knee abduction angles (KAA) (r = - 0.468), and greater FFC braking forces (r = 0.434-0.497). Incidentally, faster completion times were associated with greater peak KAMs (r = - 0.412) and KIRMs (r = 0.539). Stepwise multiple regression analysis revealed that FFC mean vertical braking force and peak KAA together could explain 43% (r = 0.652, adjusted 40.6%, p < 0.001) of the variation peak KAM.

CONCLUSION

Techniques and mechanics associated with faster cutting (i.e. faster COM velocities, greater FFC braking forces in short GCTs, greater KFMs, smaller hip and knee flexion, and greater internal foot progression angles) are in direct conflict with safer cutting mechanics (i.e. reduced knee joint loading, thus ACL injury risk), and support the "performance-injury conflict" concept during cutting. Practitioners should be conscious of this conflict when instructing cutting techniques to optimise performance while minimising knee joint loading, and should, therefore, ensure that their athletes have the physical capacity (i.e. neuromuscular control, co-contraction, and rapid force production) to tolerate and support the knee joint loading during cutting.

Single leg hop for distance symmetry masks lower limb biomechanics: time to discuss hop distance as decision criterion for return to sport after ACL reconstruction?

Background

We evaluated the lower limb status of athletes after anterior cruciate ligament reconstruction (ACLR) during the propulsion and landing phases of a single leg hop for distance (SLHD) task after they had been cleared to return to sport. We wanted to evaluate the biomechanical components of the involved (operated) and uninvolved legs of athletes with ACLR and compare these legs with those of uninjured athletes (controls).

Methods

We captured standard video-based three-dimensional motion and electromyography (EMG) in 26 athletes after ACLR and 23 healthy controls during SLHD and calculated lower limb and trunk kinematics. We calculated lower limb joint moments and work using inverse dynamics and computed lower limb muscle forces using an EMG-constrained musculoskeletal modelling approach. Between-limb (within ACLR athletes) and between-group differences (between ACLR athletes and controls) were evaluated using paired and independent sample t-tests, respectively.

Results

Significant differences in kinematics (effect sizes ranging from 0.42 to 1.56), moments (0.39 to 1.08), and joint work contribution (0.55 to 1.04) were seen between the involved and uninvolved legs, as well as between groups. Athletes after ACLR achieved a 97%±4% limb symmetry index in hop distance but the symmetry in work done by the knee during propulsion was only 69%. During landing, the involved knee absorbed less work than the uninvolved, while the uninvolved knee absorbed more work than the control group. Athletes after ACLR compensated for lower knee work with greater hip work contribution and by landing with more hip flexion, anterior pelvis tilt, and trunk flexion.

Conclusion

Symmetry in performance on a SLHD test does not ensure symmetry in lower limb biomechanics. The distance hopped is a poor measure of knee function, and largely reflects hip and ankle function. Male athletes after ACLR selectively unload the involved limb but outperform controls on the uninvolved knee.

Effect of Foot-Planting Strategy on Anterior Cruciate Ligament Loading in Women During a Direction Diversion Maneuver: A Musculoskeletal Modeling Approach

Background

Although there is a higher prevalence of noncontact anterior cruciate ligament (ACL) injuries during a direction diversion maneuver (DDM), no previous studies have reported how foot-planting strategies affect ACL loading.

Purpose

To investigate the effect of foot-planting strategies on ACL loading in women during a DDM task using a musculoskeletal modeling approach.

Study Design

Descriptive laboratory study.

Methods

A total of 13 female participants performed a DDM task, which involved running at 4.5 ± 0.2 m/s and turning left at 35° to 55° under a foot-planting strategy in 3 directions: neutral, toe-in, and toe-out. Kinematic and kinetic data were measured with the use of a 3-dimensional motion capture system and force platform to calculate variables such as joint angle, shear force, and moment. Anterior ACL and posterior ACL forces were extracted using musculoskeletal modeling.

Results

The peak anterior ACL force was significantly larger for the toe-out condition (31.29 ± 4.02 N/body weight [BW]) compared with the toe-in condition (25.43 ± 5.68 N/BW) (P = .047), with no significant difference in the neutral condition. The toe-out condition had a higher knee valgus angle (2.98° ± 4.20°; P = .041), knee shear force (10.20 ± 1.69 N/BW; P = .009), and knee internal rotation moment (-0.18 ± 0.16 N·m/BW×height; P = .012) than the toe-in and neutral conditions.

Conclusion

Through musculoskeletal modeling, we were able to conclude that the toe-out condition during the DDM might result in a higher risk of ACL injuries. Athletes and sports practitioners should avoid the toe-out foot-planting strategy when participating in a sporting activity.

Clinical Relevance

Based on these findings, medical professionals and athletic coaches can gain knowledge on how foot-planting strategy affects ACL loading. Understanding the actual cause of an ACL injury can be useful for designing preventive training programs or strategies to decrease the risk of such injuries.

Biomechanical Determinants of Knee Joint Loads Associated with Increased Anterior Cruciate Ligament Loading During Cutting: A Systematic Review and Technical Framework

Background

Cutting actions are associated with non-contact ACL injuries in multidirectional sports due to the propensity to generate large multiplanar knee joint loads (KJLs) that have the capacity to increase ACL loading and strain. Numerous studies have investigated the biomechanical determinants of KJLs in cutting tasks. The aim of this systematic review was to comprehensively review the literature regarding biomechanical determinants of KJLs during cutting, in order to develop a cutting technical framework alongside training recommendations for practitioners regarding KJL mitigation.

Methods

Databases (SPORTDiscus, Web of Science and PubMed) were systematically searched using a combination of the following terms: “Biomechanical determinants”, or “Knee abduction moment”, or “Technical determinants”, or “Knee loading”, or “Knee loads”, or “Mechanical determinants”, or “ACL strain”, or “Knee adduction moment”, or “Anterior tibial shear”, or “Knee internal rotation moment”, or “Knee valgus moment” AND “Change of direction”, or “Cutting manoeuvre”, or “Run and cut”, or “Run-and-cut”, or “Sidestepping”, or “Side-stepping”, or “Shuttle run”. Inclusion criteria were as follows: studies examining a cutting task < 110° with a preceding approach run that examined biomechanical determinants of KJLs using three-dimensional motion analysis.

Results

The search returned 6404 possibly eligible articles, and 6 identified through other sources. Following duplicate removal, 4421 titles and abstracts were screened, leaving 246 full texts to be screened for inclusion. Twenty-three full texts were deemed eligible for inclusion and identified numerous determinants of KJLs; 11 trunk, 11 hip, 7 knee, 3 multiplanar KJLs, 5 foot/ankle and 7 identifying ground reaction forces (GRFs) as determinants of KJLs.

Conclusion

Using the framework developed from the results, cutting KJLs can be mitigated through the following: reducing lateral foot-plant distances, thus lowering hip abduction and orientating the foot closer to neutral with a mid-foot or forefoot placement strategy; minimising knee valgus and hip internal rotation angles and motion at initial contact (IC) and weight acceptance (WA); avoiding and limiting lateral trunk flexion and attempt to maintain an upright trunk position or trunk lean into the intended direction; and finally, reducing GRF magnitude during WA, potentially by attenuation through increased knee flexion and emphasising a greater proportion of braking during the penultimate foot contact (PFC).

A novel test reliably captures hip and knee kinematics and kinetics during unanticipated/anticipated diagonal hops in individuals with anterior cruciate ligament reconstruction

Unanticipated land-and-cut maneuvers might emulate lower limb mechanics associated with anterior cruciate ligament (ACL) injury. Reliability studies on landing mechanics of such maneuvers are however lacking. This study investigated feasibility and within-session reliability of landing mechanics of a novel one-leg double-hop test, mimicking a land-and-cut maneuver, in individuals with ACL reconstruction (ACLR). Our test comprised a forward hop followed by a diagonal hop in either of two directions (medial/lateral) under anticipated and unanticipated conditions. Twenty individuals with a unilateral ACLR (aged 24.2 ± 4.2 years, 0.7-10.8 years post-surgery) performed three successful hops/direction per leg. We determined reliability (intraclass correlation coefficient [ICC]) and agreement (standard error of measurement [SEM]) of 3-dimensional hip and knee angles and moments during the deceleration phase of the land-and-cut maneuver (vulnerable for non-contact ACL injuries). Mean success rate for unanticipated hops was 71-77% and for anticipated hops 91-95%. Both limbs demonstrated moderate-excellent reliability (ICC 95% confidence intervals: 0.50-0.99) for almost all hip and knee peak angles and moments in all planes and conditions, with a few exceptions: poor-good reliability for hip and knee frontal and/or transverse plane variables, especially for lateral diagonal hops. The SEMs were ≤5° and ≤0.23 N·m/kg·m for most peak angles and moments, respectively. Our test seems feasible and showed satisfactory reliability for most hip and knee angles and moments; however, low knee abduction and internal rotation angles and moments, and moderate reliability of these moments deserve consideration. The test appears to challenge dynamic knee control and may prove valuable in evaluation during knee rehabilitation.

Coordination and variability during anticipated and unanticipated sidestepping

BACKGROUND

Numerous investigations have attempted to link the incidence and risk of non-contact anterior cruciate ligament injuries to specific intrinsic and extrinsic mechanisms. However, these are often measured in isolation.

RESEARCH QUESTION

This study utilizes a dynamical systems approach to investigate differences in coordination and coordination variability between segments and joints in anticipated and unanticipated sidestepping, a task linked to a high risk of non-contact anterior cruciate ligament injuries.

METHODS

Full body, three-dimensional kinematics and knee kinetic data were collected on 22 male collegiate soccer players during anticipated and unanticipated sidestepping tasks. A modified vector coding technique was used to quantify coordination and coordination variability of the trunk and pelvis segments and the hip and knee joints.

RESULTS

Sagittal and frontal plane trunk-pelvis coordination were more in-phase during unanticipated sidestepping. Sagittal plane hip-knee and hip (rotation)-knee (flexion/extension) coordination were more in-phase with the knee dominating the movement during unanticipated sidestepping (P < 0.05). Coordination variability was greater in unanticipated sidestepping for trunk (flexion)-pelvis (tilt), trunk (lateral flexion)-pelvis (obliquity), hip (flexion/extension)-knee (flexion/extension) and hip (rotation)-knee (flexion/extension) (P < 0.05). In unanticipated sidestepping where there is limited time to pre-plan the movement, multiple kinematic solutions and high coordinative variability is required to achieve the task.

SIGNIFICANCE

Our results suggest that coordination becomes more in-phase and the variability of this coordination increases as a function of task complexity and reduced planning time as that which occurs in unanticipated sporting task scenarios. Consequently, injury prevention programs must incorporate perceptual components in order to optimise planning time and coordinate appropriate postural adjustments to reduce external knee joint loading and subsequent injury risk in sport.

Predicting Athlete Ground Reaction Forces and Moments From Spatio-Temporal Driven CNN Models

The accurate prediction of three-dimensional (3-D) ground reaction forces and moments (GRF/Ms) outside the laboratory setting would represent a watershed for on-field biomechanical analysis. To extricate the biomechanist's reliance on ground embedded force plates, this study sought to improve on an earlier partial least squares (PLS) approach by using deep learning to predict 3-D GRF/Ms from legacy marker based motion capture sidestepping trials, ranking multivariate regression of GRF/Ms from five convolutional neural network (CNN) models. In a possible first for biomechanics, tactical feature engineering techniques were used to compress space-time and facilitate fine-tuning from three pretrained CNNs, from which a model derivative of ImageNet called "CaffeNet" achieved the strongest average correlation to ground truth GRF/Ms [Formula: see text] 0.9881 and [Formula: see text] 0.9715 ([Formula: see text] 4.31 and 7.04%). These results demonstrate the power of CNN models to facilitate real-world multivariate regression with practical application for spatio-temporal sports analytics.

Exploring individual adaptations to an anterior cruciate ligament injury prevention programme

BACKGROUND

Individual responses to anterior cruciate ligament injury prevention programmes (ACL IPPs) have received little attention. This study examined the effects of an ACL IPP on neuromuscular control and lower limb biomechanics during landing at the group and individual levels.

METHODS

Sixteen female athletes were randomly allocated to training (n=8) or control (n=8) groups. Electromyography, and three-dimensional kinematic and kinetic data were collected during landing at two testing sessions. Repeated measures ANOVA and effect sizes (Cohen's d) examined the effect of the IPP at the group and individual levels. A sub-group analysis comparing the effect of the IPP on 'high-' (i.e. large peak knee abduction moment at baseline) versus 'low-risk' individuals was also conducted.

RESULTS

At the group level; the IPP increased activation of the medial hamstrings prior to landing (p<0.001; d=0.264) and the medial gastrocnemius at landing (p<0.001; d=0.426), and increased hip external rotation early after initial contact (p<0.001; d=0.476). Variable adaptations were seen across individuals within the training group for all variables (p<0.001). The IPP had a large effect in reducing frontal plane knee moments for 'high-risk' individuals (d>0.91), however these results did not reach statistical significance (p>0.05).

CONCLUSIONS

The IPP induced adaptations during landing, however, individual data revealed dissimilar responses to the programme. Individuals displaying a pre-existing high-risk strategy may incur greater benefits from IPPs, yet only if the programme targets the relevant high-risk strategy.

Effects of a dynamic core stability program on the biomechanics of cutting maneuvers: A randomized controlled trial

Deficits in trunk control predict ACL injuries which frequently occur during high-risk activities such as cutting. However, no existing trunk control/core stability program has been found to positively affect trunk kinematics during cutting activities. This study investigated the effectiveness of a 6-week dynamic core stability program (DCS) on the biomechanics of anticipated and unanticipated side and crossover cutting maneuvers. Thirty-one male, varsity footballers participated in this randomized controlled trial. Three-dimensional trunk and lower limb biomechanics were captured in a motion analysis laboratory during the weight acceptance phase of anticipated and unanticipated side and crossover cutting maneuvers at baseline and 6-week follow-up. The DCS group performed a DCS program three times weekly for 6 weeks in a university rehabilitation room. Both the DCS and control groups concurrently completed their regular practice and match play. Statistical parametric mapping and repeated measures analysis of variance were used to determine any group (DCS vs control) by time (pre vs post) interactions. The DCS resulted in greater internal hip extensor (P=.017, η² =0.079), smaller internal knee valgus (P=.026, η² =0.076), and smaller internal knee external rotator moments (P=.041, η² =0.066) during anticipated side cutting compared with the control group. It also led to reduced posterior ground reaction forces for all cutting activities (P=.015-.030, η² =0.074-0.105). A 6-week DCS program did not affect trunk kinematics, but it did reduce a small number of biomechanical risk factors for ACL injury, predominantly during anticipated side cutting. A DCS program could play a role in multimodal ACL injury prevention programs.