Changes in Lower Limb Biomechanics Across Various Stages of Maturation and Implications for ACL Injury Risk in Female Athletes: a Systematic Review

BACKGROUND

Female athletes are four to six times more likely to sustain an anterior cruciate ligament (ACL) injury than male athletes. Jump-landing biomechanics are influenced by maturation, with post-pubertal female athletes at a heightened risk of ACL injuries.

OBJECTIVE

The aim of our systematic review was to identify and summarise the current evidence regarding the changes in kinematic and kinetic risk factors associated with ACL injuries during jump-landing tasks in female athletes at various stages of maturity.

METHODS

A systematic search was conducted in PubMed, CINAHL, Web of Science, SPORTDiscus, EMBASE and Scopus. Articles were included if they: (1) conducted the research on uninjured female athletes with no restriction on playing level/experience; (2) provided information regarding the stage of the maturity and the scale used for estimating the maturity status of the participants; and (3) reported a biomechanical risk factor associated with ACL injuries during jump-landing tasks across at least two different maturity groups (e.g. pre-pubertal vs post-pubertal).

RESULTS

Sixteen articles involving 2323 female athletes were included in our review. A total of 12 kinematic and 8 kinetic variables were identified across these studies. Of the 12 kinematic variables reported in our review, we found strong evidence for higher peak knee abduction angle in post-pubertal female individuals compared with pre-pubertal girls (p < 0.05). With regard to the 8 kinetic variables, we found strong evidence for lower relative peak vertical ground reaction force, higher external knee abduction moment and internal rotation moment in post-pubertal compared with pre-pubertal athletes. The strength of evidence for the remaining kinematic and kinetic variables ranged from conflicting to moderate and, in some instances, could not be determined.

CONCLUSIONS

Our study provides an overview of the changes in biomechanical risk factors in female athletes during jump-landing tasks at various stages of maturity. We found moderate-to-limited evidence for most kinematic and kinetic variables, highlighting the need for further research.

Children's strategies in drop-landing

INTRODUCTION

Landing is a critical motor skill included in many activities performed in the natural environment by young children. Yet, landing is critically relevance to ensure proper stability and reduce injury. Furthermore, landing is an integral part of many fundamental motor skills which have been linked to greater physical activity, sport participation, and perceived competence in children. Our aim was to examine the drop-landing strategies of young children focusing on the lower extremity with a multi-variant approach.

METHODS

Forty-four children divided into four age groups (G1:3-4.5 y, G2:4.5-6 y, G3:6-7.5 y, G4:7.5-9 y) performed 20 drop-land trials in four different conditions: predictable stationary landing, running to the left, to the right, and stay in place. Fifteen reflective markers, two force plates, and ten surface electromyography (sEMG) sensors were used to collect data. MANOVAs (Group x Condition) were conducted separately for the kinematic, kinetic, and sEMG variables.

RESULTS

Only significant group effects were found (kinematic MANOVA p = 0.039, kinetic MANOVA p = 0.007, and sEMG MANOVA p = 0.012), suggesting that younger groups (G1, G2) differed to the older groups (G3, G4). G1 showed less knee flexion and slower ankle dorsi-flexion during the braking phase compared to G3, while G2 presented smaller ankle dorsi-flexion at the braking phase and smaller ankle range of motion than G3. Overall kinetic variables analysis showed a group difference but no group differences for any single kinetic variable alone was found. Regarding sEMG, G1 during the flight phase exhibited longer tibialis anterior and hamstrings activity than G3 and G3 & G4, respectively; and an earlier start of the hamstrings' impact burst than G4. In addition, distal to proximal control was primarily used by all groups to coordinate muscle activity (in response to impact) and joint motion (after impact).

DISCUSSION

Perhaps a developmental critical point in landing performance exists at 4-5 years of age since G1 presented the largest differences among the groups. This suggests that to improve landing strategies could start around this age. Future studies should examine if playground environments that include equipment conducive to landing and practitioners in the kindergarten schools are adequate vehicles to empower this type of intervention.

Eccentric Resistance Training in Youth: Perspectives for Long-Term Athletic Development

The purpose of this narrative review is to discuss the role of eccentric resistance training in youth and how this training modality can be utilized within long-term physical development. Current literature on responses to eccentric exercise in youth has demonstrated that potential concerns, such as fatigue and muscle damage, compared to adults are not supported. Considering the importance of resistance training for youth athletes and the benefits of eccentric training in enhancing strength, power, speed, and resistance to injury, its inclusion throughout youth may be warranted. In this review we provide a brief overview of the physiological responses to exercise in youth with specific reference to the different responses to eccentric resistance training between children, adolescents, and adults. Thereafter, we discuss the importance of ensuring that force absorption qualities are trained throughout youth and how these may be influenced by growth and maturation. In particular, we propose practical methods on how eccentric resistance training methods can be implemented in youth via the inclusion of efficient landing mechanics, eccentric hamstrings strengthening and flywheel inertia training. This article proposes that the use of eccentric resistance training in youth should be considered a necessity to help develop both physical qualities that underpin sporting performance, as well as reducing injury risk. However, as with any other training modality implemented within youth, careful consideration should be given in accordance with an individual's maturity status, training history and technical competency as well as being underpinned by current long-term physical development guidelines.

Sex Differences in the Footprint Analysis During the Entire Gait Cycle in a Functional Equinus Condition: Novel Cross Sectional Research

Some studies suggest that gender is related to gait. Females show significantly higher ankle motion and vertical ground reaction forces. Males have significantly larger plantar contact surface areas in all regions of the foot than females in most, but not all, prior studies. However, there is no research on sex differences in a functional equinus condition. In this study, 119 individuals, including 59 females (29.7 ± 5.15 years, 58.74 ± 6.66 kg, 163.65 ± 5.58 cm) and 60 males (31.22 ± 6.06 years, 75.67 ± 9.81 kg, 177.10 ± 6.16 cm), with a functional equinus condition walked onto a pressure platform. In two separate testing sessions, five trials of each foot were conducted for the first, second, and third steps. We measured the contact surface areas for each of the three phases of the stance phase. We computed the intraclass correlation coefficient and standard error of the mean to assess the reliability. We found significantly greater contact surface areas in males than females in the first, second, and third steps in all phases of the stance phase: heel strike, mid-stance, and take-off. This is important information for the design of footwear and orthotics and gender knowledge. In a functional equinus condition, males have registered greater contact surface areas than females in all phases of the dynamic footprint of the stance phase.

Differences in Hip and Knee Landing Moments across Female Pubertal Development

PURPOSE

The higher prevalence of knee injuries among adolescent females may be related to female pubertal development. The aim of this study was to determine whether girls exhibit higher triplanar knee and hip moments with more advanced pubertal development during a single-limb landing.

METHODS

Lower-limb biomechanics of 93 females grouped according to prepubertal (n = 31), early/midpubertal (n = 31) and late/postpubertal (n = 31) development performed a single-limb drop lateral jump. Peak triplanar knee moments and hip moments at the time of peak knee moments were derived from a Vicon motion analysis system and concealed force plate. Joint moments were normalized to body mass (N·m·kg), height (N·m·kg·m) and body mass by height (N·m·kg·m). Between-group differences were analyzed using a one-way ANOVA with Pearson correlations used to explore relationships between joint moments and anthropometrics.

RESULTS

Girls at latter stages of puberty landed with higher triplanar knee moments and hip flexion moment at time of peak knee flexion moment when normalized separately to body mass and to height (P < 0.05). In contrast, hip internal rotation moments at time of peak knee internal rotation moment normalized to body mass and to body mass by height were lower in late/postpubertal girls compared to their early/midpubescent (P = 0.01) and prepubescent (P = 0.01) counterparts. Positive correlations were identified between triplanar knee moments and body mass (r = 0.73-0.91, P < 0.001) and height (r = 0.61-0.89, P < 0.001) for all participants.

CONCLUSIONS

Higher triplanar knee and sagittal plane hip moments with more advanced pubertal stage is attributed to growth-related increases in body mass and height. Given that growth is a crucial element of puberty, further research is required to quantify the impact of pubertal growth-related changes on risk of adolescent female anterior cruciate ligament injury.

Differences in Hip and Knee Running Moments across Female Pubertal Development

PURPOSE

This study aimed to investigate whether knee and hip running moments differ across stages of female pubertal development.

METHODS

This was a cross-sectional study comparing the barefoot running moments of 91 prepubertal (n = 31, Tanner stage I), early/midpubertal (n = 30, Tanner stages II and III), and late/postpubertal (n = 30, Tanner stages IV and V) girls. External peak moments for knee abduction (KAbM), knee adduction (KAM), knee flexion (KFM), and knee internal rotation (KIRM) were analyzed. Secondary measures of hip adduction moment at the time of peak KAbM and hip flexion moment at the time of peak KFM were also derived. Between-group differences were analyzed using a series of one-way ANOVAs and ANCOVAs.

RESULTS

At the knee, the late/postpubertal girls displayed a higher peak KFM and KAM compared with the prepubertal group (P < 0.05), and the early/midpubertal group exhibited a higher peak KFM than the prepubertal group (P = 0.034). No between-group differences were found for peak KAbM or KIRM (P > 0.05). At the hip, both the late/postpubertal (P = 0.03) and early/midpubertal girls (P = 0.039) ran with a lower hip adduction moment at the time of peak KAbM than the prepubertal girls. The hip flexion moment at the time of peak KFM in late/postpubertal girls was also significantly lower than both the early/mid- and prepubertal girls (P < 0.001).

CONCLUSION

Girls at the latter stages of puberty exhibit higher peak external knee flexion and adduction moments, but not abduction or internal rotation moments. This may be partly attributed to a lower hip flexion but higher hip abduction moment at the time of peak knee moments. Future research should examine whether these differences in knee kinetics between pubertal stages have implications for knee injuries such as patellofemoral pain syndrome.

Neuromuscular Training Improves Lower Extremity Biomechanics Associated with Knee Injury during Landing in 11-13 Year Old Female Netball Athletes: A Randomized Control Study

The purpose of this study was to examine the effects of a neuromuscular training (NMT) program on lower-extremity biomechanics in youth female netball athletes. The hypothesis was that significant improvements would be found in landing biomechanics of the lower-extremities, commonly associated with anterior cruciate ligament (ACL) injury, following NMT. Twenty-three athletes (age = 12.2 ± 0.9 years; height = 1.63 ± 0.08 m; mass = 51.8 ± 8.5 kg) completed two testing sessions separated by 7-weeks and were randomly assigned to either a experimental or control group. Thirteen athletes underwent 6-weeks of NMT, while the remaining 10 served as controls and continued their regular netball training. Three-dimensional lower-extremity kinematics and vertical ground reaction force (VGRF) were measured during two landing tasks, a drop vertical jump and a double leg broad jump with a single leg landing. The experimental group significantly increased bilateral knee marker distance during the bilateral landing task at maximum knee-flexion range of motion. Knee internal rotation angle during the unilateral landing task at maximum knee flexion-extension range of motion was significantly reduced (p ≤ 0.05, g > 1.00). The experimental group showed large, significant decreases in peak vertical ground reaction force in both landing tasks (p ≤ 0.05, g > −1.30). Control participants did not demonstrate any significant pre-to-post-test changes in response to the 6-week study period. Results of the study affirm the hypothesis that a 6-week NMT program can enhance landing biomechanics associated with ACL injury in 11–13 year old female netball athletes.

Knee loading patterns in a simulated netball landing task

The knee is a common site of injury in netball players. In this study, 10 high-performance netball players underwent a biomechanical assessment of their single leg landing technique whilst receiving a pass. Three-dimensional video and ground reaction force data were recorded using a motion analysis system. Net internal knee joint moments were calculated using a rigid body analysis and inverse dynamics. The kinematics of the support leg and front-on video footage was used to investigate whether players adhered to guidelines on safe and effective landing strategies. Results indicated that for most players the internal valgus moment was the largest frontal plane knee moment during the landing phase. This may reflect a relatively greater need to resist varus knee excursion or may be related to the kinematics of the hip. For 6 of the 10 players the rapid change to an internal knee valgus moment coincided with hip adduction. Since an increase in the magnitude of the internal valgus moment may increase the compressive forces in the medial compartment of the knee, further work should be undertaken to determine if a neuromuscular training intervention to improve the strength of the hip musculature may be beneficial for these players. A large relative excursion of the knee compared to the hip may indicate that these players had a greater reliance on the more distal segments of the lower extremity for the attenuation of the ground reaction forces. This information may be used to better understand potential knee injury mechanisms in netball players.

No association of time from surgery with functional deficits in athletes after anterior cruciate ligament reconstruction: evidence for objective return-to-sport criteria

BACKGROUND

Release for full activity and return to sport after anterior cruciate ligament reconstruction (ACLR) is often dictated by time from surgery and subjective opinion by the medical team. Temporal guidelines for return to sport may not accurately identify impaired strength and neuromuscular control, which are associated with increased risk for second injury (contralateral and/or ipsilateral limb) after ACLR in athletes.

HYPOTHESES

Athletes undergoing ACLR and returning to sport would demonstrate functional deficits that would not be associated with time from surgery.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty-three male (n = 10) and female (n = 23) athletes with unilateral ACLR, who were cleared by a physician to return to their sport after surgery and rehabilitation, performed the single-legged vertical hop test for 10 seconds on a portable force plate. Matched teammates of each patient were recruited to serve as sex-, sport-, and age-matched controls (CTRL; n = 67). Maximum vertical ground-reaction force (VGRF) was measured during each single-limb landing. Single-limb symmetry index (LSI) was calculated as the ratio of the involved divided by uninvolved limb, expressed as a percentage.

RESULTS

The single-limb vertical jump height LSI was reduced in the ACLR group, 89% (95% confidence interval [CI], 83%-95%), compared with the matched CTRL group, 101% (95% CI, 96%-105%; P < .01). The LSI for VGRF normalized to potential energy achieved during flight of the hop was increased in ACLR at 112% (95% CI, 106%-117%) relative to the CTRL group at 102% (95% CI, 98%-106%; P < .01). Linear regression analysis indicated that time from surgery was not associated with limb symmetry deficits in the ACLR group (P > .05; R (2) = .002-.01).

CONCLUSION

Deficits in unilateral force development (vertical jump height) and absorption (normalized VGRF) persist in an athlete's single-limb performance after ACLR and full return to sports. These symmetry deficits appear to be independent of time after reconstruction.

CLINICAL RELEVANCE

On the basis of these results, clinicians should consider assessment of single-limb power performance in the decision-making process for return-to-sport release. Persistent side-to-side asymmetries may increase the risk of contralateral and/or ipsilateral injury.

Knee-muscle activation during landings: developmental and gender comparisons

PURPOSE

This study determined anteroposterior knee-joint muscle activation differences among children and adult males and females landing from a self-initiated vertical jump (VJ) under normal and offset-target conditions to further understand physical maturation's influence on anterior cruciate ligament (ACL) injury risk.

METHODS

Fifty-five recreationally active volunteer subjects grouped by age (children = 9.5 +/- 0.9 yr; adult = 23.9 +/- 2.8 yr) and gender (females = 28; males = 27) completed motion analysis, ground reaction force, and surface electromyography (SEMG) data collection during a two-footed landing under straight (midline-target) and offset-target (adult = 45.7 cm; child = 30.5 cm) conditions. Target height was 50% of maximum VJ height. Co-contraction ratios (CCR) (hamstrings (HAMS)/vastus medialis (VM) activity) from normalized SEMG root mean squares were analyzed in the prelanding (PRE) (100 ms before initial contact (IC)), reflexive (REF) (100 ms after IC), and voluntary (VOL) (end of REF to maximum knee flexion) muscle activity phases. Repeated-measures statistical analyses determined significant gender, physical maturation, and target differences (P < 0.05) in CCR and associated HAMS and VM activity across landing phases.

RESULTS

A significant interaction (P < 0.0001) indicated similar CCR for children and adults during the REF and VOL phases, but during the PRE phase adult CCR (619.04 + 52.01) were two times greater than children's (308.32 +/- 51.04). Significantly more HAMS activity, not less VM activity, increased adult PRE-CCR. Gender and target CCR differences were absent.

CONCLUSIONS

Children's decreased preparatory co-contraction about the knee does not seem to be linked to increased ACL injury risk. Thus, adults may strive for preparatory co-contraction levels about the knee that permit adaptability to varied landing tasks.

Maturation leads to gender differences in landing force and vertical jump performance: a longitudinal study

BACKGROUND

Female athletes have increased risk of anterior cruciate ligament rupture after the onset of puberty.

HYPOTHESES

Male athletes would demonstrate a longitudinal increase in vertical jump height compared with female athletes. There would be longitudinal gender differences in ground-reaction forces and loading rates.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Sixteen female and 17 male adolescent athletes were evaluated for 2 consecutive years. Subjects were included if they were classified as pubertal during the first year of testing and postpubertal during the second year. As subjects performed a drop vertical jump, ground-reaction force, and vertical jump height were measured. Data analysis consisted of a mixed design analysis of variance with post hoc analysis (paired t tests).

RESULTS

The male athletes demonstrated increased vertical jump height with maturation (P < .001); female athletes did not. Boys significantly reduced their landing ground-reaction force (P = .005), whereas girls did not. Takeoff force decreased in girls (P = .003) but not in boys. Both boys and girls had decreased loading rates with maturation (P < .001); however, girls had higher loading rates than did boys at both stages of maturation (P = .037).

CONCLUSION

Male athletes demonstrated a neuromuscular spurt as evidenced by increased vertical jump height and increased ability to attenuate landing force. The absence of similar adaptations in female athletes may be related to the increased risk of anterior cruciate ligament injury.

Knee movement patterns of injured and uninjured adolescent basketball players when landing from a jump: a case-control study

BACKGROUND

A common knee injury mechanism sustained during basketball is landing badly from a jump. Landing is a complex task and requires good coordination, dynamic muscle control and flexibility. For adolescents whose coordination and motor control has not fully matured, landing badly from a jump can present a significant risk for injury. There is currently limited biomechanical information regarding the lower limb kinetics of adolescents when jumping, specifically regarding jump kinematics comparing injured with uninjured adolescents. This study reports on an investigation of biomechanical differences in landing patterns of uninjured and injured adolescent basketball players.

METHODS

A matched case-control study design was employed. Twenty-two basketball players aged 14-16 years participated in the study: eleven previously knee-injured and eleven uninjured players matched with cases for age, gender, weight, height and years of play, and playing for the same club. Six high-speed, three-dimensional Vicon 370 cameras (120 Hz), Vicon biomechanical software and SAS Version 8 software were employed to analyse landing patterns when subjects performed a "jump shot". Linear correlations determined functional relationships between the biomechanical performance of lower limb joints, and paired t-tests determined differences between the normalised peak biomechanical parameters.

RESULTS

The average peak vertical ground reaction forces between the cases and controls were similar. The average peak ground reaction forces between the cases and controls were moderately correlated (r = -0.47). The control (uninjured) players had significantly greater hip and knee flexion angles and significantly greater eccentric activity on landing than the uninjured cases (p < 0.01).

CONCLUSION

The findings of the study indicate that players with a history of knee injuries had biomechanically compromised landing techniques when compared with uninjured players matched for gender, age and club. Descriptions (norms) of expected levels of knee control, proprioceptive acuity and eccentric strength relative to landing from a jump, at different ages and physical developmental stages, would assist clinicians and coaches to identify players with inappropriate knee performance comparable to their age or developmental stage.

Age and gender effects on lower extremity kinematics of youth soccer players in a stop-jump task

BACKGROUND

Gender differences in lower extremity motion patterns were previously identified as a possible risk factor for non-contact anterior cruciate ligament injuries in sports.

HYPOTHESIS

Gender differences in lower extremity kinematics in the stop-jump task are functions of age for youth soccer players between 11 and 16 years of age.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Three-dimensional videographic data were collected for 30 male and 30 female adolescent soccer players between 11 and 16 years of age performing a stop-jump task. The age effects on hip and knee joint angular motions were compared between genders using multiple regression analyses with dummy variables.

RESULTS

Gender and age have significant interaction effects on standing height (P = .00), body mass (P = .00), knee flexion angle at initial foot contact with the ground (P = .00), maximum knee flexion angle (P = .00), knee valgus-varus angle (P = .00), knee valgus-varus motion (P = .00), and hip flexion angle at initial foot contact with the ground (P = .00).

CONCLUSION

Youth female recreational soccer players have decreased knee and hip flexion angles at initial ground contact and decreased knee and hip flexion motions during the landing of the stop-jump task compared to those of their male counterparts. These gender differences in knee and hip flexion motion patterns of youth recreational soccer players occur after 12 years of age and increase with age before 16 years.

CLINICAL RELEVANCE

The results of this study provide significant information for research on the prevention of noncontact anterior cruciate ligament injuries.

Knee Biomechanics during Landings: Comparison of Pre- and Postpubescent Females

PURPOSE

The purpose of this investigation was to examine lower-extremity biomechanical differences between prepubescent and postpubescent female recreational athletes during three drop jump-landing sequences (static landing, vertical landing, and lateral landing) to determine whether maturation influenced injury risk.

METHODS

Sixteen recreationally active postpubescent women (18-25 yr of age) and 16 recreationally active girls (8-11 yr of age) participated in this study. High-speed three-dimensional videography and force plate data were recorded for each subject's performance of the landing tasks and an inverse dynamics procedure was used to estimate knee joint resultant moments and forces. Kinematic and kinetic dependent variables were analyzed in three separate mixed-design 2 x 3 (maturation level x landing sequence) repeated measures multivariate analysis of variance.

RESULTS

Statistical analyses indicated significant maturation level x landing sequence interactions for postpubescent participants who exhibited reduced knee flexion (4.5 degrees ) at initial contact, increased mediolateral knee joint forces [prepubescent: -0.63 +/- 0.21 N.(kg. radicalLH)(-1), postpubescent: 0.55 +/- 0.21 N.(kg. radicalLH)(-1)], and reduced knee extensor moments [prepubescent: -0.0124 +/- 0.001 N.m.(kg.BH. radicalLH)(-1), postpubescent: -0.0079 +/- 0.001 N.m.(kg.BH. radicalLH)(-1)] compared with their prepubescent counterparts.

CONCLUSION

These findings suggest that developmental changes influence knee mechanics during landings in female athletes and highlight the need to examine multiple landing patterns when investigating landing strategies.

Optimal handle angle of the fencing foil for improved performance

Improperly designed hand tools and sports equipment contribute to undesired injuries and accidents. The idea of bending the tool, not the wrist, has been applied to sports equipment. According to Bennett's idea, the design of an ideal handle angle should be in the range of 14 degrees to 24 degrees. Thus design of the handle angle in the sport of fencing is also important. A well-designed handle angle could not only reduce ulnar deviation to avoid wrist injury but also enhance performance. An experiment with several different handle angles was conducted to analyze the effect on performance. Analysis showed an angle of 18 degrees to 21 degrees provided best overall performance in fencing.