Classification of injurious loading cycles

前交叉韧带（ACL）损伤的发生率持续上升，特别是在多方向运动的女运动员中。例如，在高中和大学运动员中，女性前交叉韧带损伤的发生率是男性的2 - 6倍。最近的研究表明，前交叉韧带可能会因过度使用而破裂，特别是在运动员快速改变方向的运动中，在旋转脚的同时以高力量着陆。该项目侧重于使用可穿戴惯性测量单元（IMU）传感器来识别这些类型的潜在伤害着陆。imu由加速度计、速率陀螺仪和磁场传感器组成，可以提供关于一个身体部分相对于另一个身体部分的加速度、速度和位置的信息，并用于估计各种肢体角度和grf（地面反作用力）。项目的第一阶段是使用可穿戴设备研究软组织过度使用性损伤，以确定尸体模型的损伤加载周期。研究结果将在女运动员身上进行验证。该项目将产生关于可穿戴设备测量与肌肉骨骼疲劳负荷之间关系的新知识。研究结果将为预防前交叉韧带过度使用损伤提供更好的方法，并为运动员、军人、消防员和其他有受伤风险的人群监测和预防此类损伤提供框架。来自两所大学（密歇根大学迪尔伯恩分校和密歇根大学安娜堡分校）的研究生和本科生将在这个项目上共同努力，增加他们对研究的接触，并帮助鼓励生物医学科学研究生课程的注册。该项目的目标是使用可穿戴惯性测量单元（IMU）研究软组织过度使用损伤机制，以识别损伤加载周期，并在现场验证这一点，以期制定损伤预防策略。虽然已知前交叉韧带的疲劳失效是可能的，但目前还没有办法确定导致这种失效的载荷条件，运动员进行的哪些类型的活动使他们面临这种加载方式的风险，或者在受伤前数百次的运动中前交叉韧带明显随机失效的机制是什么。为了解决这些识别需求并实现项目目标，研究计划分为三个目标。第一个目标是在体外模型中，基于冲击力、膝关节力矩、角度或胫骨前移位的运动学输入，使用可穿戴IMU识别有害的加载周期。研究旨在验证以下假设，即固定在小腿和大腿上的imu可以准确预测已知会导致前交叉韧带疲劳损伤的加载周期的发生。女性尸体膝关节标本将放置在胫骨扭转装置中，并在胫骨和大腿上使用可穿戴imu。膝关节将在目标着陆力下反复加载（总共100个周期），由重量降至胫骨远端末端，膝关节屈曲力矩和胫骨扭矩设计为模拟枢轴着陆。第二个目标是确定体内与有害负荷条件相对应的运动活动，将各种参数（如GRF和膝关节力矩）与IMU测量相关联，并检查由于软组织运动引起的误差。研究的目的是验证这样一种假设，即在多向运动中存在特定的身体活动，这些活动对应于导致过度使用前交叉韧带损伤的已知负荷条件，IMU测量的线加速度和角加速度值可用于在实验室中识别这些运动。来自大学足球队和篮球队的志愿者将被要求完成可能与受伤相关的任务，例如，用旋转、侧身和交叉切入进行慢跑。志愿者在下肢和膝盖上下都安装了动作捕捉标记和可穿戴imu。将使用Visual 3D软件为每位参与者创建一个6自由度的下肢运动学模型。第三个目标是验证IMU在现实环境中检测和计数潜在危险加载周期的使用。研究旨在验证这样的假设，即在现实环境中使用imu可以识别严重的加载周期，除非受到限制，否则这些加载周期的发生速度可能会因为愈合时间不足而导致前交叉韧带损伤。参加竞争激烈的旅行足球项目的青少年女子足球运动员将在每两周一次的训练中配备4个可穿戴IMU设备。本科生和研究生将参加为期一年的每次实践，收集数据，视频记录活动，并提供技术支持。将使用录像检查剧烈加载周期的时间，以确定这种变化是否会随着时间的推移而变化，这是由于练习中的活动或疲劳造成的，因为已有研究表明疲劳可能会增加前交叉韧带损伤的风险。还将对数据进行比较，以确定优势侧和非优势侧之间是否存在差异，并检查年龄和体重指数（BMI）对所经历的严重负荷循环次数的影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Rates of anterior cruciate ligament (ACL) injuries continue to rise, especially in female athletes who play multidirectional sports. For example, in high school and collegiate athletes, the incidence of ACL injury is 2 - 6 times higher in females than males. Recent studies have demonstrated that the ACL can rupture due to overuse - specifically due to landing at high forces while pivoting the foot as typically occurs during sports where athletes quickly change direction. This project focuses on using wearable inertial measurement unit (IMU) sensors to identify these types of potentially injurious landings. IMUs, which consist of accelerometers, rate gyroscopes, and magnetic field sensors, can provide information about the acceleration, velocity and position of one body segment with respect to another and have been used to estimate various limb angles and GRFs (Ground Reaction Forces). The first phase or the project is to study soft tissue overuse injury using a wearable device in order to identify injurious loading cycles in a cadaver model. Findings obtained will then be validated in the field with female athletes. This project will produce new knowledge about the relationship between measurements taken by wearable devices and musculoskeletal fatigue loading. The results will lead to better methods for preventing ACL overuse injuries and will provide a framework for the monitoring and prevention of such injuries in athletic, military, firefighter and other populations at risk for injury. Graduate and undergraduate students from two universities (University of Michigan-Dearborn and University of Michigan-Ann Arbor) will work together on this project, increasing their exposure to research and helping to encourage enrollment in biomedical sciences graduate programs.The goal of the project is to study soft tissue overuse injury mechanisms using a wearable inertial measurement unit (IMU) to identify injurious loading cycles and to validate this in the field with a view toward developing injury prevention strategies. Although it is known that fatigue failure of the ACL is possible, there is currently no way to identify loading conditions that cause this failure in the field, what types of activities athletes perform that put them at risk for this manner of loading or what mechanism underlie the apparently random failure of the ACL during athletic moves made hundreds of times before injury. To address these identification needs and achieve the project's goal, the Research Plan is organized under three objectives. The FIRST Objective is to identify injurious loading cycles using a wearable IMU based on kinematic inputs of impact force, knee moments, angles or anterior tibial translation in an in vitro model. Studies are designed to test the hypothesis that IMUs secured to the lower leg and thigh can accurately predict the occurrence of a loading cycle that is known to cause fatigue damage to the ACL. Female cadaver knee specimens will be placed in a tibial torsional device and instrumented with wearable IMUs on the tibia and thigh. Knees will be subjected to repeated loading (100 cycles total) at targeted landing forces, imposed by a drop weight to the end of the distal tibia, with a knee flexion moment and tibial torque designed to simulate a pivot landing. The SECOND Objective is to identify in vivo the athletic activities that correspond to injurious loading conditions, correlate various parameters such as GRF and knee moments to IMU measurements and examine error due to soft tissue motion. Studies are designed to test the hypothesis that there are specific physical activities that occur during multidirectional sports that correspond to known loading conditions that cause overuse ACL injury and linear acceleration and angular acceleration values measured by an IMU can be used to identify these movements in the laboratory. Volunteers from college soccer and basketball teams, instrumented with motion capture markers located on lower extremities and wearable IMUs above and below the knee, will be asked to complete possible injury related tasks, e.g. a jog with a pivot and sidestep and crossover cuts. A 6 degree-of-freedom kinematic model of the lower extremity will be created for each participant using Visual 3D software. The THIRD Objective is to validate the use of an IMU to detect and count potentially dangerous loading cycles in a real-world setting. Studies are designed to test the hypothesis that severe loading cycles can be identified using IMUs in a real-world setting and, unless restricted, these loading cycles can occur at a rate which could cause injury to the ACL because of inadequate time for healing. Adolescent female soccer players who participate in a highly competitive travel soccer program will be fitted with four wearable IMU devices during bi-weekly practices. Undergraduate and graduate students will attend each practice over a one-year period to collect data, video record the event, and provide technical support. The timing of severe loading cycles will be examined using the video recordings to determine whether this changes over time either due to activities in practice or fatigue, as it has been suggested that fatigue may increase the risk of ACL injury. Data will also be compared to determine whether there is a difference between the dominant and non-dominant sides and to examine the effects of age and BMI (Body Mass Index) on the number of severe loading cycles experienced.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.