Leg Ergometer for Blood Flow Studies

Amy Weaver, Cali Roen, Lacey Halfen, Hyungjin Kim

BME 201March 9, 2007

Client: William SchrageDept. of Kinesiology

Advisor: Paul ThompsonDept. of Biological Systems

Engineering

Overview

Problem statement Background Design requirements Design alternatives Proposed Design Future work

Problem Statement

Test subject will use the ergometer to maintain a constant kicking motion

Leg must passively return to original position Femoral artery is imaged using an ultrasound Used to determine blood flow to the leg

during exercise

Background: Blood Flow Research

Measure blood flow in femoral artery Examine how smaller blood vessels regulate

upstream (femoral) blood flow Infuse drugs into the femoral artery

Background Blood Flow Research

Two research questions:1. What are the neural, metabolic, and vascular

signals controlling blood flow at rest and exercise? 2. How do conditions like aging and cardiovascular

diseases (obesity, high blood pressure, etc) alter the regulation of blood flow

Wider implications understanding blood pressure control correlated with obesity, diabetics, and high

blood pressure

Background: Existing Devices Current device in use at Mayo Clinic Used part of an exercise bike and a car seat Boot is a rollerblade boot with the toe cut out Device was unreliable, and had variable forces

Background: Existing Devices Cont.

http://www.rehab.research.va.gov/jour/01/38/1/chin.html

http://www.hanix.net/en/powermax.htm

Design Requirements

Streamlined and compact with minimal loose parts

Minimum lifespan of five years Easily portable (with wheels) 5’ long x 3’ wide Chair positioned at various angles from

vertical and 3’ above ground Adjust for people of heights 5’4” to 6’4” Flexible range of motion for full leg extension

while kicking

Design Requirements

Passive return to rest position of the leg after kicking

Set up for right leg testing Wattage (0-100 W) and kick rate (30-60 KPM)

output to a laptop through an A/D converter Maintain a constant wattage throughout

testing Adjustable force between tests Under $2,000

Design Alternatives: Seat for pateint

Reclining Adjustable height

“Boot” for foot Straps to hold shoe

Adjustable force Wheels for movement Sensors

Wattage Kicking rate

Design Alternatives: Gas Spring Shock

Force from compression of gas in a cylinder Function of velocity

Can be purchased in various sizes with variable force Use a cable, allowing for full range of kicking motionDisadvantages Springs back to initial position

http://www.globalspec.com/FeaturedProducts/Detail/IndustrialGasSprings/Stainless_Steel_Gas_Springs_/34982/0?fromSpotlight=1

Design Alternatives: One Way Clutch

Allows rotation in only one direction

When clutch locks, friction device is engaged

When foot is returning, clutch freely rotates

Clutch attached to boot by a bar with ball joints

http://adcats.et.byu.edu/WWW/Publication/94-1/Paper1-12_6.html

http://www.mie.utoronto.ca/staff/projects/cleghorn/Textbook/DataFiles/Appendix-B/Appendix-B.html

Design Alternatives:with Drum Brake

Shoes push out against drum providing friction

Force is constant Adjustable by altering

force normal to drumDisadvantages Properties change with

heat Brake pedals need to

be replaced http://www.howstuffworks.com/drum-brake.htm/printable

Proposed Design:with Viscous Friction

Viscous friction for force against kick Two pieces of metal

with liquid between Force = μ*A*v / t Force altered by

changing area Force remains constant

through minor temperature changes

Rotating Axle

http://galileo.phys.virginia.edu/classes/152.mf1i.spring02/Viscosity.htm

Design MatrixWeight

Gas Spring Shock

One Way Clutch w/ viscous friction

One Way Clutch w/ Drum Brake

Overall Reliability 20 0.75 0.9 0.65

Ease to Construct 5 1 0.8 0.8

Maintenance Required 15 0.8 0.8 0.6

Ease of Use 10 0.7 0.7 0.6

Consistent Force 15 0.6 0.8 0.6

Flexible Kicking Motion 10 1 0.8 0.8

Passive Kicking Return 20 0.25 1 1

Force Adjustability 5 1 1 0.7

Total (Out of 100) 68 86 72.5

Future Work

Finalize design Order components Construct design Test and modify

References Maximal Perfusion of Skeletal Muscle in Man (Per Andersen

and Bengt Saltin) 1984 Professor Fronczak ADCATS at Brigham Young University

http://adcats.et.byu.edu/WWW/Publication/94-1/Paper1-12_6.html