Leg Ergometer 1 Leg Ergometer for Blood Flow Studies BME 200/300 University of Wisconsin-Madison October 24, 2007 Team: Amy Weaver, Co-Team Leader Laura Bagley, Co-Team Leader Lacey Halfen, Communicator Deborah Yagow, BSAC Lein Ma, BWIG Client: Dr. William Schrage Dept. of Kinesiology University of Wisconsin-Madison Advisor: Wally Block Dept. of Biomedical Engineering University of Wisconsin-MadisonLeg Ergometer 2 Table of Contents Abstract 3 Problem Statement 3 Background 4 Blood Flow Research 4 Existing Devices 5 Last Semester’s Design 6 Alternative Designs 8 Modification of Bike Design 9 Monark Exercise Bike 10 Proposed Design 12 Budget and Time estimates 13 Future Work 13 Appendix 1: Project Design Specifications (PDS) 16 Appendix 2: Design Matrix 18Leg Ergometer 3 Abstract Dr. William Schrage of the kinesiology department at UW-Madison is conducting research studies involving blood flow through the femoral artery during exercise. He requires a device that will allow test subjects to do constant work by kicking one leg while he images the femoral artery and observes blood flow in the active leg. Some of his major requirements for the device include a passive return of the foot to the start position after each kick, a constant kick rate, a measurable work output, and reliability of the device. Three design alternatives for a resistance mechanism were developed, and the advantages and disadvantages of each one were weighed in order to choose a final design. Because of its relatively low cost, its high reliability, and its ease of use, a servo motor design was chosen over a Monark bicycle design and the proposed improvements on last year’s resistance device. Problem Statement Dr. William Schrage, who is researching blood flow through the femoral artery during exercise, needs a one-legged ergometer that will provide a constant one way resistive force against a test subject’s kicking motion. The force should be applied while the leg kicks out and absent while the leg returns to the starting position. This device will be used in his research lab as part of his studies. While the test subject uses the ergometer, Dr. Schrage will image the subject’s kicking leg femoral artery to determine blood velocity.Leg Ergometer 4 Background Blood Flow Research Dr. William Schrage conducts blood flow research with the UW – Madison Department of Kinesiology. He plans to use the proposed ergometer in his experiments to examine the effects of exercise on blood flow. A Doppler ultrasound probe angled against the upper thigh provides an image of the blood vessels (Figure 1). The data obtained by Dr. Schrage will lead to further research about how smaller blood vessels regulate the flow of blood from the femoral artery. Two main questions will be investigated during this research. First, what are the neural, metabolic, and vascular signals controlling blood flow at rest and exercise? Second, how do conditions such as aging and cardiovascular diseases (i.e. obesity, high blood pressure, and diabetes) alter the regulation of blood flow? The answers gained from this research will lead to a better understanding of what controls blood pressure. This will also provide more information about how blood flow affects people suffering from obesity and diabetes. Once normal and abnormal states of blood flow are understood, tests can be conducted to discover whether exercise can be used to restore normal blood flow. Furthermore, drug Fig 1: Doppler Probe ImageLeg Ergometer 5 companies may then be able to develop drugs to mimic the effects of exercise and possibly correct dysfunction. Existing Devices There are several types of leg ergometers, one of which is an exercise bike. Most of these bicycles are two-leg cycles with a flywheel and a brake system that provides resistive force. In addition to these personal exercise machines, there are leg ergometers designed for medical use. While most look similar to a normal exercise bike, they are one-leg cycles. These ergometers have a simple monitor that displays useful information such as heart rate, distance traveled, or work output. A research facility in Europe used a modified bicycle to isolate the right upper thigh by means of a leg extension motion. This study, which is related to the client’s research, used work outputs of 20-60W and measured pulmonary oxygen uptake, heart rate, leg blood flow, blood pressure and femoral arterial-venous differences for oxygen and lactate between 5 and 10 minutes of the exercise (Anderson, Saltin). Previously, Dr. Schrage used a leg ergometer at Mayo Clinic that was designed for similar studies. The device was composed of a flywheel from an exercise bike and a seat from a car. Two different sized rollerblade boots attached the patient’s foot to the bike pedal through a bar and two ball joints. The larger rollerblade boot had the toe cut out to allow for various foot sizes. A Doppler ultrasound probe held by the researcher was used to observe and measure the blood flow while sensors connected to the resistance system measured wattage and kick rate. Unfortunately, this device was unreliable. The flywheel would occasionally spin backwards, resulting in zero resistive force being applied when the subject kicked forward. Also, the nylon belt attached to theLeg Ergometer 6 flywheel became hot as a result of friction. The heat altered the length of the nylon belt and changed the work output by the patient. Last Semester’s Design Last semester’s prototype had many aspects of the proposed design. Iron plumbing pipes were used to build the frame of the machine. These pipes came pre-cut and pre-threaded, and they provided an extremely stable frame to house the rest of the device. The assembled frame is four feet long, two feet tall, and one and a half feet wide (Figure 2). The frame is slightly smaller than the maximum allowed dimensions to allow for easier attachment of the seat to the frame. Wheels were added to the base of the frame to provide easy transportation from room to room. To meet the client’s requirement for a reclining, adjustable seat, a car bucket seat was used (Fig. 3). This adjustable seat allowed the client easier access to the femoral artery of the test subjects. For a temporary resistance mechanism, a bike was used to supply variable one-way resistance when the test subject’s leg kicked out. The bike was halved and flipped
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