Transcript Muscle function and compensatory mechanisms in post

EGGG 101: Introduction
to Engineering
Dr. Jill Higginson
Assistant Professor
Department of Mechanical Engineering
University of Delaware
ME Lecture 4
Today’s objectives
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Introduction
What can MEs do?
What is biomechanics?
Newton’s laws
Introduction to biomechanics lab
Introduction
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Course webpage
Schedule
Engineers…
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Apply tools of math and science to
develop cost-effective solutions to
technological problems in society
Design consumer products
Develop machinery, factories
(processes) and quality control
systems for manufacturing products
Make useful things that work!
Mechanical Engineering
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Liberal arts of engineering
Diverse applications
– Biomechanics
– Composites and materials
– Environmental and bio-fluid mechanics
– Robotics and control
– Fuel cells (clean energy)
– Manufacturing science
Mechanically engineered
products
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Micro-electro-mechanical sensors in airbags
HVAC for office buildings
Off-road construction equipment
Hybrid vehicles
Gears, bearings, machine components
Artificial hip implants
Deep-sea research vessels
Robotic manufacturing systems
Replacement heart valves
Planetary exploration spacecraft
Top Ten Achievements
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Automobile
Apollo program
Power generation
Agricultural
mechanization
Airplane
Integrated-circuit
mass production
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Air conditioning
and refrigeration
Computer-aided
engineering
technology
Bioengineering
Codes and
standards
Automobile
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High power, lightweight
engines (ICE)
Efficient mass production
Safety, fuel economy,
comfort, emission control
Hybrid technology,
antilock brakes, air bags,
composite materials, fuel
injection systems, GPS,
fuel cells
Computer-aided
engineering technology
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Automation technologies
Performing calculations
Preparing technical drawings
Simulating performance
Controlling machine tools
Analysis software
Information databases
Prototyping equipment
What is biomechanics?
The science that
examines forces acting
upon and within a
biological structure and
effects produced by
such forces
CYTOMECHANICS
IMAGING
FLUID
DYNAMICS
EXPERIMENTATION and INTERVENTION
MODELING and
SIMULATION
Running shoes
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Goals
– protect foot, run faster, keep cool
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Materials selection
– Foam, air pockets, gel, springs
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Absorb shock
Promote stability / flexibility
Ventilation (thermodynamics!)
Sensors
Fashion statement!
Injury mechanisms
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Forces on the
musculoskeletal system
Moment = tendency of a
force to make an object
rotate
Depends on force and
lever arm
M=∑Fd
The time rate of change of
momentum of a body is
equal to the magnitude of
the applied force and acts
in the direction of the force
F
d (mv )
dt
Inverse dynamics
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Calculate elbow joint moment (M=∑Fd)
M=(10N)(0.13m) + (20N)(0.30m)
M=7.3 Nm
M=(Fbiceps)(0.025m)
F=10 N
Fbiceps = 292 N
M=?
F=20 N
30 cm
2.5 cm
Optimization
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Estimate muscle
forces from joint
moment
Choose optimization
function
Infinite solutions
possible!
Muscle force
l
l
l
muscle force
Force-length curve
Force-velocity curve
active
lengthening
passive
shortening
muscle fiber length
muscle fiber velocity
Strength
Applications
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Rehabilitation devices
Exoskeleton (rehab, carry load)
Accident reconstruction
Helmet design
Biomechanics Lab
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Objectives:
– To develop the force-length curve based
on isometric strength of the quadriceps
muscle group
– To quantify changes in pressure under
the foot as a function of footwear
– To manipulate ground reaction forces
during dynamic activities
Motivation
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Oscar Pistorius
– Blade Runner
– Fastest man on no legs
– “I’m not disabled, I just don’t have any legs”
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Double amputee world records: 100m, 200m, 400m
– 2008 Paralympic gold (100,200)
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400 m
– 2004 Olympic gold (men): 44.00
– Pistorius world record: 46.56
– 1928 Olympic gold (men): 47.8
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IAAF 2007: ban the use of “any technical device that
incorporates springs, wheels or any other element that
provides a user with an advantage over another athlete not
using such a device”
Does Pistorius have an unfair advantage?
Cheetahs
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Stage 1: absorbs 97% impact, stores energy (higher speed ->
higher force)
Stage 2: gluts and quads provide propulsion
Stage 3: blade releases energy at push-off
Natural leg
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Stage 1: Achilles tendon absorbs and stores impact energy
Stage 2: gluts, quads and plantarflexors provide propulsion
Stage 3: plantarflexors releases energy at push-off
Methods
MAmax
P=F/A
“isometric strength”
“plantar pressures”
Methods
“ground reaction forces”
Lab Report
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Due: Wednesday by 5:00 pm
Answer questions on template!
Describe experimental and analytical methods (brief)
Results
– What measurements were recorded and computed?
– How does strength vary with knee flexion angle?
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Discussion and Conclusions
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At what knee angle is performance best?
How does peak pressure vary with shoe selection?
How does force change with dynamic activities?
What factors should be considered in the design of a prosthesis
for Oscar Pistorius?
Lab report template
Logistics
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Spencer 209
You will rotate through 3 stations
Data may be collected solo or with a
partner
Resources
• Running shoes
• http://people.bath.ac.uk/mnp21/Adv_mat
_sports.htm
• www.basf.com/corporate/elastollan.html
• http://engineeringworks.tamu.edu/?p=29
• Cheetah:
• http://www.wired.com/wired/archive/15.
03/bladefast.html