Classification of injurious loading cycles

前十字韧带(ACL)损伤的发生率持续上升，尤其是在参加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断裂--特别是在运动员迅速改变方向的运动中，通常会在高强度着陆时旋转脚。该项目的重点是使用可穿戴的惯性测量单元(IMU)传感器来识别这些类型的潜在伤害性着陆。IMU由加速计、速率陀螺仪和磁场传感器组成，可以提供一个身体部分相对于另一个身体部分的加速度、速度和位置信息，并已被用于估计各种肢体角度和地面反作用力。第一阶段或项目是使用可穿戴设备研究软组织过度使用损伤，以确定身体模型中的损伤负荷周期。然后，将在现场与女运动员一起验证所获得的发现。这个项目将产生关于可穿戴设备测量和肌肉骨骼疲劳负荷之间关系的新知识。这一结果将为预防前交叉韧带过度使用损伤提供更好的方法，并将为监测和预防运动员、军人、消防员和其他有受伤风险的人群提供一个框架。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合作，增加他们对研究的接触，并帮助鼓励注册生物医学研究生课程。该项目的目标是使用可穿戴惯性测量单元(IMU)来研究软组织过度使用的损伤机制，以识别损伤负荷周期，并在现场验证这一点，以期制定损伤预防策略。尽管已知前交叉韧带疲劳失效是可能的，但目前还没有办法确定在赛场上导致这种失效的负荷条件，运动员进行的哪些类型的活动会使他们面临这种负荷的风险，或者在受伤前数百次的运动动作中，前交叉韧带明显随机失效的机制是什么。为了满足这些鉴定需求并实现项目的目标，研究计划在三个目标下进行组织。第一个目标是在体外模型中，使用基于冲击力、膝力矩、角度或胫骨前平移的运动学输入的可穿戴IMU来识别损伤载荷循环。研究旨在验证这样一种假设，即固定在小腿和大腿上的IMU可以准确地预测已知会导致前交叉韧带疲劳损伤的负荷循环的发生。女性身体膝关节标本将被放置在胫骨扭转装置中，并在胫骨和大腿上安装可穿戴的Imus。膝关节将承受目标落地力的重复载荷(总共100个循环)，通过将重量下降到胫骨远端，利用膝盖屈曲力矩和胫骨扭矩来模拟枢轴着陆。第二个目标是在体内识别与损伤负荷条件相对应的运动活动，将各种参数(如GRF和膝力矩)与IMU测量相关联，并检查软组织运动引起的误差。研究旨在验证这样一种假设，即在多方向运动中，存在与已知负荷条件相对应的特定身体活动，这些活动会导致过度使用前交叉韧带损伤，通过IMU测量的线加速度和角加速度值可以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，带有枢轴和侧步的慢跑和交叉切割。志愿者们将被要求在腿部安装运动捕捉标记，并在膝盖上下穿戴可穿戴的IMU。将使用Visual3D软件为每个参与者创建一个6自由度的腿部运动学模型。第三个目标是验证IMU在真实环境中检测和计算潜在危险加载周期的使用。研究旨在验证这样一种假设，即在真实世界的环境中，可以使用IMUS识别严重的负荷周期，除非受到限制，否则这些负荷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足球运动员将在每两周一次的训练中配备四个可穿戴的IMU设备。本科生和研究生将参加为期一年的每次练习，收集数据，录制活动视频，并提供技术支持。将使用录像来检查严重负荷循环的时间，以确定这是否由于练习中的活动或疲劳而随着时间的推移而改变，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。数据还将进行比较，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BMI(身体质量指数)对经历过的严重负荷循环次数的影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.