Field Measurement of Running Impacts Mid-Semester Paper March 14, 2007 Team Members: Chelsea Wanta, Amanda Feest, Matt Kudek, Lindsey Carlson, Nicole Daehn Client: Dr. Bryan Heiderscheit, PhD, PT Advisor: Paul Thompson2 Table of Contents: Abstract……………………………………………………………………………………3 Problem Statement………………………………………………………………………...3 Client Motivation……………………………………………………………………….....4 Background Information….……………………………………………………………….4 Design Requirements……………………………………………………………………...5 Preliminary Design Ideas………………………………………………………………….6 Design 1: Wired system…………………………………………………………...6 Design 2: Wireless system………………………………………………………...7 Design 3: Microcomputer design………………………………………………….9 Design Matrix……………………………………………………………………………10 Future work……………………………………………………………………………....12 References……………..……………..……………..……………..……………..………14 Appendix One – Product Design Specification...……………….……………………….153 Abstract Dr. Bryan Heiderscheit is a physical therapist whose goal is to identify characteristics of running that lead to stress fractures. The purpose of this project is to create a portable system that records tibial acceleration data to measure the impacts of running. This device will include a lightweight accelerometer which will record data to a data logger. The acceleration data will be used to assess and treat running-related concerns. Three designs alternatives have been considered: a wired system, a wireless system, and a microcomputer. These designs were evaluated using a design matrix, which compared certain design criteria set forth by the client. The best design, the wired system, has been selected and a prototype of this design will be pursued. Future work entails purchasing a data logger and accelerometer, constructing the device, and testing the device to assure accurate data collection. Problem Statement The purpose of this project is to design a portable instrument that records tibial acceleration data to measure the impacts of running. The device should use a lightweight accelerometer, which will record data to an incorporated data logger. The device must be easily worn by the user and should not affect the performance of the runner. This instrument will be used to diagnose stress fractures and other injuries related to running.4 Client Motivation Our client, Dr. Heiderscheit, is a physical therapist who operates the UW Health Runners’ Clinic. One of the goals of his clinic is to identify characteristics of running that lead to stress fractures. By adjusting how his patients run, Dr. Heiderscheit is able to prevent tibial stress fractures and other running-related injuries. Using acceleration data, he can analyze a patient’s running habits to assess and treat running-related concerns. Background Information Stress fractures are one of the most common running injuries, accounting for 50 percent of all injuries in runners and military recruits (Milner 323). Between 33 and 55 percent of all stress fractures occur in the tibia (Milner 323). Tibial stress fractures may be caused by strong, repetitive stress on the bone at the insertion point of the muscles (Derrick 998). The bone absorbs the force of the impact instead of the muscles, and bending stresses in the tibia become too great for it to tolerate. In adults, tibial stress fractures usually occur in the anterior junction of the lower third of the bone, as shown in Figure 1. Figure 1: Anatomy of a typical stress fracture (Smith).5 Correlations may exist between greater amounts of force on the tibia and the risk of obtaining a stress fracture. When the foot contacts the ground, the angle of the knee could have an effect on the severity of the impact (Derrick 836). Tibial stress fractures can be very painful, and can lead to three to six weeks of no activity and up to six to nine months of inability to compete. Therefore, it is very important to study the cause and prevention of tibial stress fractures. Currently, Dr. Heiderscheit studies tibial stress fractures by analyzing tibial acceleration data. In the lab, patients run on a treadmill while wearing an accelerometer. The accelerometer is placed on the anterior of the tibia, a few inches above the ankle. This accelerometer is directly connected to a computer that records and analyzes the data. Dr. Heiderscheit studies the peak accelerations in the data in order to assess the greatest impact forces and relates these forces to running-related injuries. Unfortunately, this current set-up is not optimal. A lack of space in the lab prevents runners from running on force plates. Also, because of the extensive wiring required to connect the current system, runner must run in the lab, and cannot run in a ‘natural’ environment. Because of these flaws, an alternate setup is desired. Design Requirements The most important element of our design is that the new system needs to be portable while still being capable of recording data reliably. It must incorporate a lightweight, uniaxial accelerometer, which has the ability to measure up to 40G peak acceleration. The accelerometer will be used in conjunction with a data logger to record measurements. The data logger must sample 1,000-2,000 Hz from multiple analog6 inputs. This design should not alter the runner’s gait, performance, or speed in any way, and should be comfortable for the runner’s use. Finally, the prototype should be completed for use in studies to be performed this summer. Refer to Appendix 1 for complete outline of design specification. Preliminary Design Ideas Design 1 –
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