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This study determined anterior cruciate ligament (ACL) force and its contributors during a standardized drop-land-lateral jump task using a validated computational model. Healthy females (n=24) who were recreationally active performed drop-land-lateral jump and straight run tasks. Three-dimensional whole-body kinematics, ground reaction forces, and muscle activation patterns from eight lower limb muscles were collected concurrently during both tasks, but only the jump was analyzed computationally, with the run included for model calibration. External biomechanics, muscle-tendon unit kinematics, and muscle activation patterns were used to model lower limb muscle and ACL forces. Peak ACL force (2.3±0.5 BW) was observed at 13% of the stance phase during the drop-land-lateral jump task. The ACL force was primarily developed through the sagittal plane, and muscle was the dominant source of ACL loading. The gastrocnemii and quadriceps were main ACL antagonists (i.e., loaders), while hamstrings were the main ACL agonists (i.e., supporters).

Background: Rates of anterior cruciate ligament (ACL) rupture in young people have increased by >70% over the past two decades. Adolescent and young adult females are at higher risk of ACL injury as compared with their prepubertal counterparts. Purpose: To determine ACL loading during a standardized drop-land-lateral jump in females at different stages of pubertal maturation. Study Design: Controlled laboratory study. Methods: On the basis of the Tanner classification system, 19 pre-, 19 early-/mid-, and 24 late-/postpubertal females performed a standardized drop-land-lateral jump while 3-dimensional body motion, ground-reaction forces, and surface electromyography data were acquired. These data were used to model external biomechanics, lower limb muscle forces, and knee contact forces, which were subsequently used in a validated computational model to estimate ACL loading. Statistical parametric mapping analysis of variance was used to compare ACL force and its causal contributors among the 3 pubertal maturation groups during stance phase of the task. Results: When compared with pre- and early-/midpubertal females, late-/postpubertal females had significantly higher ACL force with mean differences of 471 and 356 N during the first 30% and 48% to 85% of stance, and 343 and 274 N during the first 24% and 59% to 81% of stance, respectively, which overlapped peaks in ACL force. At the point of peak ACL force, contributions from sagittal and transverse plane loading mechanisms to ACL force were higher in late-/postpubertal compared with pre- and early-/midpubertal groups (medium effect sizes from 0.44 to 0.77). No differences were found between pre- and early-/midpubertal groups in ACL force or its contributors. Conclusion: The highest ACL forces were observed in late-/postpubertal females, consistent with recently reported rises of ACL injury rates in females aged 15 to 19 years. It is important to quantify ACL force and its contributors during dynamic tasks to advance our understanding of the loading mechanism and thereby provide guidance to injury prevention. Clinical Relevance: Growth of ACL volume plateaus around 10 years of age, before pubertal maturation, meaning that a late-/postpubertal female could have an ACL of similar size to their less mature counterparts. However, late-/postpubertal females have higher body mass requiring higher muscle forces to accelerate the body during dynamic tasks, which may increase ACL loading. Thus, if greater forces develop in these females, in part because of their increased body mass, these higher forces will be applied to an ACL that is not proportionally larger. This may partially explain the higher rates of ACL injury in late-/postpubertal females.

This study determined anterior cruciate ligament (ACL) force and its contributors during a standardized drop-land-lateral jump task using a validated computational model. Healthy females (n=24) who were recreationally active performed drop-land-lateral jump and straight run tasks. Three-dimensional whole-body kinematics, ground reaction forces, and muscle activation patterns from eight lower limb muscles were collected concurrently during both tasks, but only the jump was analyzed computationally, with the run included for model calibration. External biomechanics, muscle-tendon unit kinematics, and muscle activation patterns were used to model lower limb muscle and ACL forces. Peak ACL force (2.3±0.5 BW) was observed at 13% of the stance phase during the drop-land-lateral jump task. The ACL force was primarily developed through the sagittal plane, and muscle was the dominant source of ACL loading. The gastrocnemii and quadriceps were main ACL antagonists (i.e., loaders), while hamstrings were the main ACL agonists (i.e., supporters).

Rates of anterior cruciate ligament (ACL) rupture in young people have increased markedly over the past two decades, with females experiencing greater growth in their risk compared to males. In this study, we determined the effects of low- and high-support athletic footwear on ACL loads during a standardized drop–land–lateral jump in 23 late-/post-pubertal females. Each participant performed the task unshod, wearing low- (Zaraca, ASICS) or high- (Kayano, ASICS) support shoes (in random order), and three-dimensional body motions, ground-reaction forces, and surface electromyograms were synchronously acquired. These data were then used in a validated computational model of ACL loading. One-dimensional statistical parametric mapping paired t-tests were used to compare ACL loads between footwear conditions during the stance phase of the task. Participants generated lower ACL forces during push-off when shod (Kayano: 624 N at 71–84% of stance; Zaraca: 616 N at 68–86% of stance) compared to barefoot (770 N and 740 N, respectively). No significant differences in ACL force were observed between the task performed wearing low- compared to high-support shoes. Compared to barefoot, both shoe types significantly lowered push-off phase peak ACL forces, potentially lowering risk of ACL injury during performance of similar tasks in sport and recreation.

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Neuromusculoskeletal models often require three-dimensional (3D) body motions, ground reaction forces (GRF), and electromyography (EMG) as input data. Acquiring these data in real-world settings is challenging, with barriers such as the cost of instruments, setup time, and operator skills to correctly acquire and interpret data. This study investigated the consequences of limiting EMG and GRF data on modelled anterior cruciate ligament (ACL) forces during a drop–land–jump task in late-/post-pubertal females. We compared ACL forces generated by a reference model (i.e., EMG-informed neural mode combined with 3D GRF) to those generated by an EMG-informed with only vertical GRF, static optimisation with 3D GRF, and static optimisation with only vertical GRF. Results indicated ACL force magnitude during landing (when ACL injury typically occurs) was significantly overestimated if only vertical GRF were used for either EMG-informed or static optimisation neural modes. If 3D GRF were used in combination with static optimisation, ACL force was marginally overestimated compared to the reference model. None of the alternative models maintained rank order of ACL loading magnitudes generated by the reference model. Finally, we observed substantial variability across the study sample in response to limiting EMG and GRF data, indicating need for methods incorporating subject-specific measures of muscle activation patterns and external loading when modelling ACL loading during dynamic motor tasks.