Anterior-Posterior Center of Pressure Is Associated With Knee Extensor Moment During Landing After Anterior Cruciate Ligament Reconstruction.

CONTEXT: A reduced knee extensor moment (KEM) in the involved limb and asymmetry in the KEM during landing tasks are observed after anterior cruciate ligament reconstruction (ACLR). There is limited information about the association of kinetic and kinematic parameters with the KEM during landing after ACLR. This study investigated the association of the anterior-posterior center of pressure (AP-COP) position, vertical ground reaction force (VGRF), and lower limb joint angles with the KEM during landing in female athletes following ACLR. DESIGN: Cross-sectional study. METHODS: Twenty-two female athletes who underwent ACLR performed a drop vertical jump at 7.9 (1.7) months after surgery. We evaluated the KEM, AP-COP position, VGRF, and sagittal plane hip, knee, and ankle angles using a 3-dimensional motion analysis system with force plates. RESULTS: The peak KEM in the involved limb was significantly smaller than that in the uninvolved limb during landing (1.43 [0.33] N·m/kg/m vs 1.84 [0.41] Nm/kg/m, P = .001). The VGRF in the involved limb was significantly smaller than that in the uninvolved limb (11.9 [2.3] N/kg vs 14.6 [3.5] N/kg, P = .005). The limb symmetry index of the KEM was predicted by that of the VGRF (P < .001, R2 = .621, ß = 0.800). The KEM was predicted by the AP-COP position in the involved limb (P = .015, R2 = .227, ß = 0.513) and by the VGRF in the uninvolved limb (P = .018, R2 = .213, ß = 0.500). No significant correlation was noted between the KEM and the lower limb joint angles. CONCLUSIONS: The AP-COP position and VGRF were associated with the KEM during landing. Evaluating the VGRF and AP-COP position, not the lower limb joint angles, may contribute to understanding the KEM during double-leg landing after ACLR in the clinical setting.

Subsequent Jumping Increases the Knee and Hip Abduction Moment, Trunk Lateral Tilt, and Trunk Rotation Motion During Single-Leg Landing in Female Individuals.

Single-leg landings with or without subsequent jumping are frequently used to evaluate landing biomechanics. The purpose of this study was to investigate the effects of subsequent jumping on the external knee abduction moment and trunk and hip biomechanics during single-leg landing. Thirty young adult female participants performed a single-leg drop vertical jumping (SDVJ; landing with subsequent jumping) and single-leg drop landing (SDL; landing without subsequent jumping). Trunk, hip, and knee biomechanics were evaluated using a 3-dimensional motion analysis system. The peak knee abduction moment was significantly larger during SDVJ than during SDL (SDVJ 0.08 [0.10] N·m·kg-1·m-1, SDL 0.05 [0.10] N·m·kg-1·m-1, P = .002). The trunk lateral tilt and rotation angles toward the support-leg side and external hip abduction moment were significantly larger during SDVJ than during SDL (P < .05). The difference in the peak hip abduction moment between SDVJ and SDL predicted the difference in the peak knee abduction moment (P = .003, R2 = .252). Landing tasks with subsequent jumping would have advantages for evaluating trunk and hip control as well as knee abduction moment. In particular, evaluating hip abduction moment may be important because of its association with the knee abduction moment.

Sex difference in frontal plane hip moment in response to lateral trunk obliquity during single-leg landing.

BACKGROUND: Lateral trunk obliquity during landing is a characteristic of anterior cruciate ligament (ACL) injuries in female athletes and affects their knee and hip kinetics and kinematics. However, it is unclear whether these effects differ between females and males. The purpose of this study was to compare the effects of lateral trunk obliquity on knee and hip kinetics and kinematics in females and males during single-leg landing. METHODS: Eighteen female (aged 22.1 ± 1.5 years) and 18 male participants (aged 21.8 ± 1.1 years) performed single-leg landings under two conditions: (1) without any instructions about trunk position (natural) and (2) with leaning their trunks laterally 15° from the vertical line (trunk obliquity). The kinetics and kinematics of their hip and knee were analyzed using a three-dimensional motion analysis with a force plate. Two-way repeated-measures ANOVA (sex × trunk obliquity) and Bonferroni pairwise comparisons were conducted. RESULTS: The trunk obliquity angle at initial contact was significantly greater in the trunk-obliquity landing condition than in the natural landing condition (natural 4.0 ± 2.2°, trunk-obliquity 15.1 ± 3.6°, P < 0.001) with no sex difference (95% CI - 1.2 to 2.2°, P = 0.555). The peak knee abduction moment was significantly larger in the trunk-obliquity landing condition than in the natural landing condition (trunk-obliquity, 0.09 ± 0.07 Nm/kg/m; natural, 0.04 ± 0.06 Nm/kg/m; P < 0.001), though there was no sex or interaction effect. A significant interaction between sex and landing condition was found for the peak hip abduction moment (P = 0.021). Males showed a significantly larger peak hip abduction moment in the trunk-obliquity landing condition than in the natural landing condition (95% CI 0.05 to 0.13 Nm/kg/m, P < 0.001), while females showed no difference in the peak hip abduction moment between the two landing conditions (95% CI - 0.02 to 0.06 Nm/kg/m, P = 0.355). CONCLUSIONS: The knee abduction moment increased with a laterally inclined trunk for both female and male participants, while the hip abduction moment increased in males but not in females. It may be beneficial for females to focus on frontal plane hip joint control under lateral trunk-obliquity conditions during single-leg landing.

Postural Stability and Muscle Activation Onset during Double- to Single-Leg Stance Transition in Flat-Footed Individuals.

The effects of foot posture on postural stability and on muscular activation pattern for postural control remain unclear. This study aimed to investigate postural stability and muscular activation onset during the transition task from double- to single-leg stance in individuals with different foot postures. Twenty-seven healthy men (age: 21.5 ± 1.5 years) were divided into 3 groups using the Foot Posture Index: neutral foot (n = 10); flatfoot (n = 8); and high-arched foot (n = 9). Center of pressure (COP) data and muscle activation onset times of the tibialis anterior, peroneus longus, gastrocnemius medialis, and soleus during the transition task with eyes closed were compared among groups using one-way analysis of variance and a post-hoc Tukey honestly significant difference test (p < 0.05) when the data were normally distributed and the Kruskal-Wallis test and a post-hoc Mann-Whitney U-test with Bonferroni correction (p < 0.0167) when the data were not normally distributed. The COP displacements in the mediolateral and anteroposterior directions and the resultant COP displacement during the first 3 s after a stability time point, as determined by sequential estimation during the single-leg stance phase, differed significantly among the three groups (p < 0.05). Post-hoc tests showed that the displacements were significantly greater in the flatfoot group than in the neutral and high-arched foot groups (p < 0.05), and the effect sizes for these results were large. No muscular activation onset times showed significant intergroup differences. Postural stability was significantly decreased only in the flatfoot group, while muscle activation onsets did not differ significantly by foot posture during the transition task. Decreased postural stability may be one mechanism underlying the link between flatfoot and risk of lower limb injury, and foot posture represents a potential confounder for measuring postural stability during the transition task.

Landing instructions focused on pelvic and trunk lateral tilt decrease the knee abduction moment during a single-leg drop vertical jump.

OBJECTIVES: To investigate the effects of pelvic and trunk lateral tilt-focused landing instructions on the knee abduction moment during the single-leg drop vertical jump task. DESIGN: Descriptive laboratory study. SETTING: Motion analysis laboratory. PARTICIPANTS: Fifteen young, healthy female participants. MAIN OUTCOME MEASURES: The participants performed 15 single-leg drop vertical jumps. Landing instructions with self-video recordings were provided so that the participants' pelvis and trunk remained horizontal in the frontal plane. Pelvic, trunk and knee kinematics and kinetics were evaluated using a three-dimensional motion analysis system before and after the landing instructions. RESULTS: The peak knee abduction moment significantly decreased postinstruction (preinstruction 22.6 ± 15.3 Nm, postinstruction 17.9 ± 15.4 Nm, P = 0.004), as did pelvic and trunk lateral tilt (P < 0.01). The knee abduction and internal rotation angles at initial contact significantly decreased postinstruction (P = 0.037, P = 0.007), with no significant change in the peak knee abduction and internal rotation angles from pre-to postinstruction. CONCLUSIONS: Landing instructions focused on pelvic and trunk lateral tilt are effective in decreasing the knee abduction moment during the single-leg drop vertical jump. Pelvic and trunk lateral tilt should be controlled to decrease the knee abduction moment during single-leg landing.