1 334spo all lectures
TRANSCRIPT
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334SPO Mechanics of theMusculoskeletal System
Animal tissues
Structure
Function
Biomechanical properties
Including failure
Lectures from RJ & AP: 20 hours for 334SPOand 239SPO, 12 hours for 333SPO/335SPO
Tutorials/Labs/workshops RJ et al: 10hours (often in vivoassessments)
Reading list
Marking criteria & CW proformas
Timetable & corrections
Notice board
CUOnline
Online quizzes (1 tutorial)
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What Happened 2007/8232SPO?Mean scores
= excellent, 1 = very bad
Module well organised: 3.75
Module met aims and Objectives: 4.00
Teaching methods effective: 3.75
Assessment methods effective: 4.00
Satisfied with this module: 4.50
Effective lecturer RJ: 5.00
Specific comments
Liked the small group tutorials Liked the book of lecture notes at the start
Wanted last lab earlier in the year (it is now)
Wanted more information on handouts (there isnow)
Lectures to be done on PowerPoint (they arenow)
94% of students attended >60% of taughtclasses
64% of students passed 232SPO pre resit
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Attendance
Significant relationship betweenattendance and module mark
R2 = 0.205 P = 0.002
0
1020
30
40
50
60
7080
0 20 40 60 80 100 120
Lecture attendance (%)
Modulemark(%)
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Resourcesmodule handbook:
Books
Videos
CUOnline site
Quiz
Practice short answer quizzes for each book
chapter Module handbook
Timetable
Tutorial topics list
Handouts
Journal articles to download
References stated on many handouts
Some on CUOnline 334SPO site
Some in library or via library portal
Some via document supply service or ask Rob
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Module marks 2010/11
34SPO (BSc Sport and Ex Sci students)
50% for 1500 word CW essay (term 2)
50% for 2 hour Exam
33SPO/335SPO (BSc Sports Therapy students
50% for 2000 word CW essay (term 2)
50% for Critical appraisal of physiologicalscenario. Maximum 1500 words (Mike Pricewill set this)
39SPO (BSc Rehab Eng; BSc Assist Tech)
50% for 2000 word CW essay (term 2)
50% for 30 minute phase test (term 1)
Turnitin: submit essay to Turnitin via
CUOnline site.
Can submit draft to check, pre real
essay submission
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Labs/Workshops
Whole body analysis
Kinematics: 2D low speed videoanalysis
Usage of electromyography andelectrogoniometer
Tissue mechanics
Instrom bone mechanics and workloop muscle mechanics
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Structure andProperties of
MaterialsWhat is the material composed of?
How do we test the biomechanicalproperties of the material?
What are the biomechanical properties?
What should the material be used for?
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Muscle Structure
Muscle
TendonTendon
erve supply
Blood supply
Muscle
fibres
Thick filaments
Thin filaments
Muscle Sarcomere
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Muscle filament structureThin filament
Helical arrangement
(i) Double strand of actin monomers
(grey and white circles)
(ii) Troponin complexes (black circles)
and Tropomyosin (black lines)
which regulate actinomyosin interactions
Thick filament
Myosin: heads, neck and body
Bare zone
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Myosin moleculestructure
Heads
Neck
Hinge
Body
Myosin heavy chains
Head (S1 region) has ATP and actin binding sites
Neck (S2 region) pivots on hinge
Body embedded in thick filament
Myosin light chains stabilise head and neck region
Myosin light chains
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Optical Trap Technique
Isolated actin and myosin filaments
Actin filament attached to plastic beads
Laser beams hold the beadsLasers can move actin filament
Lower actin filament towards freemyosin molecules
Interaction causes beads to move
Very low forces pico Newtons pN
Laser beam Laser beam
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How is force produced?
ATP bound to Myosin head (S1 region)
ATP broken down
Myosin head binds to actin
Myosin head rotatesRotation stretches neck (S2 region)
This causes force to be produced
ADP & Pi & energy released
ATPADP + Pi + energy
Heads (S1)
Neck (S2)
Hinge
Body
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ATPrigor
S1 head
S2 neck
Actinbinding
sites
Body
Myosin molecule
ATP
ADP
Pi
Hydrolysis
ATP
Dissociation
NB. 2 sites for
heads!
ATP Binding and hydrolysis
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Force ProductionDuring isometric activity = constant length and active
so = constant metric = length
While isometric there is no movement of the thick anhin filaments with respect to each other
PiADP
Pi + energy
B
ADP
B
ADP
B
ADP
S2 stretches
Force
neck
B=body
Head
Actin binding site
More stretch of neck (S2 region) = more force
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Force-velocity Relationship
Thick
ilament
Thinfilament
A) Filament sliding
ADP
B
S2 stretch
aster velocity of shortening = less myosin heads bind
and neck stretches less
increased shortening velocity = decreased force
B) S2 head rotation
During concentric actions (muscle shortening and active)
Velocity
Forc
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Full Cross-bridge Cycle(Diagramme)
ATP
ATP
ATP
ADP
Pi PiADP
Pi + energy
ADP
ADP
ADPrigor
Force
produce
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Full Cross-bridge cycle
Myosin is bound to actin (rigor state)
ATP binds to myosin
Myosin dissociates from actin
ATP is hydrolyzed and myosin head
rotates
Myosin binds to actin
Phosphate and energy release
Rotation of head causes force
production
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The Muscle Switch:activation
Depolarization of nerve
Depolarization of muscle membrane
ACh Neuromuscular junction
Calcium release from SR
Depolarization of T-tubules
Sarcoplasmic
reticulum
T tubul
Surface membrane
Nerve
ACh
receptor
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The Muscle Switch:
Levelofrespo
nse
Nerve
Tim
Muscle
AP AP Ca2+ Force
Calcium in cytoplasm binds to troponin C
Change in shape of troponin T
Troponin I no longer physically blocking actin
binding site
Strong binding of myosin head with actin binding sit
Force production
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Calcium Binding
ActinActin
Tn-T
TM (Tropomyosin)
Tn-I
Tn-C
Binding site
Tn-T
Actin
TMTn-I
Tn-C
Strong AM
binding
Weak AM
inding
Tn-I inhibits Myosin ATPase
Calcium concentrationincreases
Cross-section through thin filament
Troponin complex = TnC, TnT, TnI
Relaxed
Active
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Muscle Relaxation
Cessation of neural stimulus Decreased Calcium release
Decreased calciumconcentration decreaseschance of calcium binding toTnC
Decreased muscle force
Calcium binding in cytoplasm byparvalbumin
Further decreased Calciumconcentration
Decrease in calcium binding byTn-C
Calcium pumped fromcytoplasm to sarcoplasmicreticulum (requires ATP)
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Whose muscle is it anyway?
Muscle mechanics similar betweenvertebrate species
Frog muscle main one used as easy touse!
Why little human data?
Ethics problems of invasive experiments
Experimental rigor of non-invasive
These lectures
Will use any muscle data as typical of
vertebrate muscle
Will try to highlight any relevant humandata where available
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Muscle MechanicsMuscle fibres vs. whole
muscle vs. sarcomerein vivo =in life; in vitro= in glass; in situ= inlace
Whole muscle simulates in vivo
Easier to dissect
Larger preparations have:
Increased risk of anoxia (diffusion distance)
Increase in passive structures
Increased problems of diversity of fibreorientation
Muscle>muscle fibre bundle>muscle fibre>
sarcomere
O2
Parallel fibredPennate fibred
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Sarcomere levelCould use a muscle biopsy
Chemical treat muscle (skinned) to
remove membranes
Clamp single fibre so only monitoring a
single sarcomere
Use chemical solutions to:
Activate (high calcium concentration)
Relax (low calcium concentration)
Measure force-length properties
Length
Force
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Fibre/muscle level
Muscle removed from animal and test:
Whole muscle
Fibre bundle
Single fibre
Electrical stimulation (via nerve/direct)
Activates muscle
Force production
Different types of studies
Isometric = constant length Isotonic = constant force
Isovelocity = constant speed
Work loop (simulate in vivo)
Force-velocity
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Muscle rig
Oxygenated
Ringer
Krebs inalt solution) Ringer out
Muscle
MotoForce transducer
Platinum electrodes
Salt solution composition to mimic blood plasma
and includes an energetic substrate e.g. glucose
Temperature regulation of salt solution
35 to 37C for mammalian work
historically 0 to 20C for ease!
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Isometric Tests of Muscle
Force
Stimulation (V
Twitch: used to optimise muscle lengthand stimulation amplitude
Tetanus: used to optimise stimulation frequency
Force
Stimulation
Time
Response
Stim. frequency =
# of stimuli per secondfused
unfused
Multiple stimuli cause multiple releases of calciumLeading to summation of twitches and greater force
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Isometric Times
Twitch
Tetanus
Time
Stimulus
Force(%maximum)
THPT
THPTet
HPT = time to half peak twitch
PHR = time from peak twitch to half relaxation
HPTet = time to half peak tetanus
etPHR = time from peak tetanus to half relaxation
Rates of activation and relaxation
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Force-length Curve
Force
1
3
2
4
1SarcomerLength
2 3
4
Passive
(collagen)
Total
Active
Sarcomere
Actin binding
sites covered
Only bare zonuncovered on
thick filament
Nooverlap
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Titin filamentsTitin
Z line M line
Titin (also sometimes referred to asonnectin)Runs from Z line to M lineTwo sections of titin with differenttiffnesses
These correlate to the mechanicalmodels of muscle passive stiffness
So titin has two functionsProvides passive stiffness (protective)Stability of sarcomere structure
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Force-velocity(Isovelocity version
Force
Stimulation
Length
Velocity
ForceFmax
aster Vmax
lower Vmax
Tim
Vmax = maximum
shortening velocity
Fmax = maximumtetanic force
Can compare muscles:
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Eccentric vs ConcentricWhat is the difference?
Eccentric = lengthening and active Concentric = shortening and active
When might eccentric force be important?
large external force braking/controlling movement
Velocity
Force
ConcentricEccentric
0
Isometric
peed and direction of movement affects forceia stretch of myosin neck and # of cross-bridges
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Power output-force/velocityCurves
Velocity
Power
OutputPeak P.O. at V/Vmax of
c. 0.3-0.4
Force
Power
Output
Peak P.O. at F/Fmax of
c. 0.3-0.4
ower output (P.O.) = force velocity
V = velocity
Vmax = maximum
velocity
F = force
Fmax = maximum
force
Velocity
Force
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Efficiency
Work output energetic costenergy cost in ATP
work done = Force distance
Power output = work done time taken
Efficiency
Maximum efficiency around 0.3 to 0.4 V/Vmax
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Tendon Tendon
Parallel fibred muscle
Increased length
TendonTendon
Pennate muscle e.g. Bipennate, multipennate
ncreased physiological cross-sectional area,
measured perpendicular to fibre longitudinal axis)ncreased force
Lower fibre length,
E.g. gastrocnemius, soleus, quadriceps
E.g. Extensor digitorum longus
Muscle Pennation
Angle of
pennation
Longitudinal axis
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Design of MuscleImagine we have a muscle of constant volume
We can alter the muscle length but this will alsochange muscle cross-sectional area
What effects would such changes have on musclemechanics?
Muscles with higher cross-sectional area = highforce production, good for stabilizing limbs
A fictional muscle
one sarcomere long
but many sarcomeres wide
Muscle length
Musclecross-sec
tionalarea
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Design of Muscle 2Each sarcomere generates force and pulls thesarcomere next to it
Along the length of a muscle some of the forceswill effectively cancel each other out
Essentially we just need to count the number ofsarcomeres across the cross-sectional area (the
sarcomeres at the end) to determine the forceproducing capacity of the muscle
Longer muscle: 4 sarcomeres wide
Wider muscle: 12 sarcomeres wide
So wider muscle would produce
3 times more force
FF
width
Length
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Design of Muscle 3
Longer muscle: 3 sarcomeres long
Wider muscle: 1 sarcomere long
If we assume each sarcomere can
shorten at the same speed
The longer muscle would produce
3 times more shortening speed
FF
width
Length
Longer muscles = higher absolute speed,acceleration and deceleration
peed = distance moved time taken for movement
Acceleration = change in speed time taken forchange
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Wider muscle but same length
For review see Lieber, R. & Friden, J. (2000) Muscle & Nerve23 1647-1666 (not in library: ask Rob)
Length
Force Larger PCSA:
Smaller PCSA
Velocity
Force
Larger PCSA:
Smaller PCSA
sometric force-length curves
Same length = same range of motion
sovelocity force-velocity curves
ame length = same maximum shortening velocity
Higher force at all
lengths
Higher force at all
velocities
0
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Longer muscle but same PCSA
Force
Length
Force
Shorterfibres
Longer fibres
Velocity
horter
bres
sometric force-length curves
ame cross-sectional area = same maximum force
Longer fibres
Longer muscle has
larger ROM
sovelocity force-velocity curves
ame length = same maximum shortening velocity
Longer muscle has
higher Vmax, so lower V/Vmaxat each V, so higher force
For review see Lieber, R. & Friden, J. (2000) Muscle & Nerve23 1647-1666 (not in library: ask Rob)
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Human MusclePennation Effects
Fibre Length
PCSA
Pennation angle 0-30
Fibre length ROM (range of motion)
Fibre physiological csa F maximum
Increased pennation tends to causeecreased fibre length
soleus
EDL SemitendinosusFDL
Less pennate
more pennate
For review see Lieber, R. & Friden, J. (2000) Muscle & Nerve23 1647-1666 (not in library: ask Rob)
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Muscle PennationAssume muscle of fixed volume
If used lower pennation angle (moreparallel fibred)
longer fibred and longer muscle
Faster shortening velocityGreater range of motion
But pennate muscle fibres do not need
to shorten as fast as the muscle!pennate muscle = higher PCSA = highe
force
So produce more force at same velocity
Pennation changes during activation!
Increased pennation angle as shorten
For review see Lieber, R. & Friden, J. (2000) Muscle & Nerve23 1647-1666 (not in library: ask Rob)
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Muscle rolesPower (FV)
e.g. for jumping
long muscle for high speed
high csa for high force
Acceleration to rapidly increase speed
long fibres and muscle
Brakesstabilisation
high force
high pcsa, high pennation
Endurance/efficiency
reduce energetic cost?
slower fibre type
minimise muscle size
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Effects of Muscular Fatigue
Decreased force production at any speed
Slower activation and relaxation rates
Decreased maximum shortening
velocity
Test muscle properties
Fatigue muscle
Test muscle properties
Fatigue tests (performance over time)
Fatigue resistance(endurance)
orce
Time
Fresh
Fatigued
Isometric Isovelocity
Force
Velocity
Fresh
Fatigued
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Why use work loops?Isometrics measure at constant length
Isovelocity at constant velocityIsotonic at constant force
In vivoall these conditions are likely to vary
I.e. dynamic
Work loop technique (also called oscillatorywork technique) to simulate/approximate invivo
Isotonic/isovelocity overestimate power output
Isometric underestimate rate of forceactivation and relaxation
All these ignore passive properties of muscledue to collagen etc
James, R.S., Young, I.S., Cox, V.M., Goldspink, D.F.,and Altringham, J.D. (1996) Pflugers Archive432 767-774.
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Work loops
Time
ength
Activity
Force
Plot force against length
o create work loop
The area of the loop net work done
.g. James, R.S., Altringham, J.D., and Goldspink, D.F.995 J Ex Biol. 198 491-502
1 length change
cycle
his example uses a sinusoidal length change waveform
strain
e.g. 0.10 (5%)
stress
strain
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Why use stress and strain?
Measurements normalised (realtive) to muscle size
tress (N.m-2) = force (N) cross-sectional area (m2)
train = length change initial length
= L L0
.g. 0.1m 1m = 0.10 (i.e. 10% length change)train has no units
Force
L0L
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Passive Stress-strain curves
Stress (force csa)
Strain
(length change initial length
Modulus of elasticity/stiffness/Youngs modulus
= stress strain = the slope of the line =
tiff = lots of force required to cause a small strain
.g. bone more stiff than muscle
x
y
y x
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Elasticity 1
Perfectly elastic material (doesnt exist)
tress-strain relationship is linear and identica
n extension and compression of material
Energy required to stretch the material =
nergy released during shortening
No net energy cost to undergo length change
cycle
Stress
Strain
We are now considering passive properties
Elasticity = wish to return to original shape
.g. length
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Stress
Strain
Perfectly viscous material
Deforms when force is appliedWhen force stops the material does
ot return to its original shape.
e. no elastic recoil
Blue tac is fairly viscous!
Elasticity 2
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Strain
Visco-elastic material
Stress
Biological materials (e.g. muscles and tendons
equire energy input during stretch which is
ot fully returned during recoil
Area within work loop = net energy required to
undertake length change cycle
Work (energy) = force distance
Elasticity 3
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Muscle stress-strain curves 1
Strain
Stress
Stress
Stress
Strain
Strain
During stretch:
Work (energy) input
During shortening
Work (energy) output
Net work done on the material
during the length change cycle
(energy cost)
Passive
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Muscle Stress-Strain curves 2
Strain
Stress
Stress
Strain
Work input to stretch
work done on the muscle
by antagonist or other external force
Work output
Stress
Strain
Net work
Active when shortening
concentric exercise)
During
shortening
work is done
by the muscle
Net work done by muscle during length change cycl
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Ultimate Properties ofTissue
The maximal performance of a tissuebefore it breaks (total failure occurs) Strength Extensibility Toughness
Vary between tissues
Vary between parts of body
Depends on cost of failure!
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StrengthThe maximal stress (force csa) a material can
withstand before it breaks
Failure strength
stress at failure
Yield strength
(damage begins)
i.e.. micro damage
Strain
Stress
Ultimate strength
(maximal stress)
Plastic
Deformation (damage)
Elastic
Deformation
o no damageHookes law)
e.g. bone stress-strain curve:
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Extensibility
The maximal strain a material can be subjectedto before it breaks
Breaking point
Stress
Strain
Strength
Extensibility
Maximal strain
Maximalstress
Tendon extensibility > bone
Bone strength > tendon
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The energy required to break a material
= the area under the stress-strain curve
Energy (work) = Force distance
Stress
Strain
Less tough
More tough
(but less strong
and more extensible
Toughness
Large area
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Typical Mechanical Properties ofMammalian TissueMuscle Tendon Cortical
Bone
Mild Steel
Maximalextensibilitystrain)
0.25 0.09 0.02 0.1
Ultimateensile
strengthMPa)
0.4 90 150 400
UltimateToughnessKJ kg-1)
? 5.6 25 Higherthan bone
Modulus ofelasticityGPa)
Low orhigh cf.tendon
1.5 20 200
Pa = 1N m-2
000 Pa = 1 KPa 1000 KPa = 1MPa
000 MPa = 1GPa
Compact bone = cortical bone
Tensile = during stretch (under tension)Modulus of elasticity = slope of stress-strain curv
stiffnessStiffness higher in active than passive muscle
low
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Shear vs. Tension
ForceForce
Material in tension
Fracture
Force
Force
Material in shear
Fracture
Forces applied are directly opposite to each other
orces applied are parallel but not directly opposite to
ach other
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Compression vs. Bending
ForceForce
Material in compression
Fracture
Material in bending
Fracture
Forces applied are directly opposite to each other
Compression
Force ForceTension
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Safety Factors
If we could design a person:
How would you decide how strongto make the long bones in your leg?
Consider:
function of structure
direction and magnitude of loadingcost of production of structure
cost of repair
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How safe is the structure?
afety factor = Failure stress functional stress
e.g. failure stress (strength) = 4 MPa
functional (everyday) stress = 2 MPa
Safety factor = 4 MPa 2 MPa = 2
Cost of failure Vs. cost of structure
e.g. broken leg bone c.f. broken finger
Increased material = increased cost
synthesis and maintenance
(replacement & repair) costs
material and locomotory costs(including overcoming inertia)
internal space cost
weight = locomotory cost (muscleactivation; higher in lower limbs)
Safety Factors
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Complications inSafety Factors
Variation in expected loaddepend on direction of impact
e.g. in long bones usually loaded in
compression and tension, weaker in
shear
Deterioration in material
previous damage
ageing
Unpredictable strength of material
Increased strength if loads less
predictable and tissue more
mportant for survival
weight
Ground reaction
force
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Safety Factors in Bone1.4 - 4 for bone (i.e. failure stress
functional stress) e.g. Weightlifter: backbone safety factor 1.0-1.7
Bone remodeling in shape, elasticity,
density and mass
density = mass volume
Load dependent tissue growth and atrophy
Atrophy: astronauts in microgravity (lower
loading so decreased osteoblast activity )
Growth (hypertrophy): exercise (weightlifters,
tennis players)
Load generates strain
Strain causes micro damage
damage induces remodeling (overcompensation)
OR strain detected by nerves in periosteum (bon
sheath)?
all, S.J. (2007)Basic Biomechanics. Boston: McGraw-Hill
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Leg Bone Stresses
Stress on long bone at impact depends on angle unpredictable
curved bones bend focussing peak force
predictable)
Higher strength at focus (minimise bone weight
nd minimise locomotory cost)
High strength and safety factor along bone length
for compression and tension
Lower strength for side impact (shear)
Use force platform to measure forcesinverse dynamics to calculate bone stresses
Ground reaction force
weight
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Bending
Fracture
Compression
Force ForceTension
predictable focus of forces
strengthen here
Force
Force
Shear forces:
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Measurement ofin vivo action
Muscle activity: Electromyography
surface (external) EMG electrode cuffs
problems of cross-talk (interference from
other muscles): so better on larger muscles conductance of skin changes between
people, with exercise: affects signal
internal EMG electrode wires
ethical issues signal is definitely from the muscle of
interest
Muscle
TendonTendon
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EMG signals
Raw EMG indicates motor unit actionpotentials
indicates duration of action potential
doesnt indicate muscle force or timing
of force production
force rise and relaxation delayed with
respect to EMG onset and finish
Integrated EMG (IEMG)calculation of amplitude of action
potential
affected by subcutaneous tissue, firing
rate, # active muscle fibres
Measurement ofin vivo action 2
Raw EMG
IEMG
Time
Amplitude
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Measurement ofin vivo action 3
Muscle lengthDirect measurement: Sonomicrometry
crystals implanted into muscle
measure time taken between crystals
calculate distance
Calculation from joint angles 1: use external markers on joints
use motion analysis to track movement of
markers to calculate changes in joint angle assumptions of tendon vs. muscle strain
E.g. James, R.S., Altringham, J.D., andGoldspink, D.F. (1995) J Exp Biol. 198 491-502: onCUOnline
Mouse ankle angle for EDL and soleus musclelengths
2: use X-ray video or cine to track bone movement
could use markers on tendon ends
Direct measurement via ultrasound
emitter receiver
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Strain from joint angles
Mouse muscle strains calculated from anklejoint angles (measured from high speed video)
See James et al. (1995) J. Exp. Biol. 198 491-
502. [Figure 7]: On 232SPO CUOnline siteBut when are the muscles active?
NB. EMG from rat Nicolopoulos-Stournaras &Iles (1984) J. Zool. Lond. 203 427-440.
Muscle functioning as? power producer =
active and shortening; stabiliser if active andnear constant length
0 150 300 450 600
2.4
2.6
2.8
3.0
LIMB CYCLE PHASE (0)
0 150 300 450 600
2.2
2.4
2.6( )
SoleusEDL
train = change in length initial length
Velocity = length change time
EMG
EMG
strain
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In vivo (in life) V/Vmax
V/Vmax
V = in vivoshortening velocity
Vmax = maximum shortening velocity
Mouse soleus trot 0.20 0.31
Mouse soleus gallop 0.34 0.48
Mouse EDL trot 0.24 0.39
Mouse EDL gallop 0.37 0.52
Remember peak power produced atV/Vmax c. 0.3 0.4
So peak muscle power at trot?
See James et al. (1995) J. Exp. Biol.198 491-502. [Table 2].
Force
Velocity
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In vivo (in life) SLSarcomere length-force curve based on ratfilament lengths and isometric (constantlength)
Calculated range of sarcomere lengths used invivo
Calculated sarcomere length at L0 (length for
maximal in vitroforce)In vivolength ranges close to maximal force
Descending limb usage
See James et al(1995) J. Exp. Biol. 198 491-502.[Figure 6].
100
80
60
40
20
0
1.0 1.5 2.0 2.5 3.0 3.5 4.0
soleus in vivosoleus L0
EDLin vivo
EDL L0
Sarcomere Length m
Force(%
maximum)
passivactive
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Real work loopsActive = anticlockwise
Passive = clockwise
Loop represents net work performed (Work =F d)
Passive usually low (collagen) and representsthe work required to cycle the muscle throughone stride
stress falls during shortening due to Force-velocity relationship and shorteningdeactivation
stress
strain
active
passive
Concentric activity
Time
ength
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Real work loops 2Mouse EDL at 8Hz cycle frequency
James et al. (1995) J. Exp. Biol. 198 491-02 [Figure 5]
ncreased muscle starting length =ncreased passive work
ncreased strain = increased passive work
ncreased velocity = increased passivework
Passive due to: collagen & otheronnective proteins
L0
+ 10% L
+ 20% L0
Sarcomere length
Passive
(collagen)
Active
orceL
0
+ 10% L0
0% strain at each length
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Mouse soleus work
cyclefrequency
Network/cycle(Jkg-1 )
Cycle frequency (Hz)
0 2 4 6 8 10
0
2
4
6
8
10
12
14
Work decreases with cycle
(velocity increases causingforce to decrease & work todecrease)
0 2 4 6 8
0
5
10
15
20
25
30
35)
POWEROUTPU
T(W
kg-1
CYCLE FREQUENCY (Hz)
Power = work cycle frequency
= work done time taken
Work measured in Joules (J); power in Watts (W)
Frequency = # per second
Same strain
different stres
NB mice tend to tro
trot c. 5 to 6 Hz
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Strain complicationsSonomicrometry on Bufo americanus
semimembranosus (SM) muscle (hipextensor)
Differential strain along muscle length invivoand in vitro
muscle architecture caused thisAhn et al(2003) J. Physiol. 549 877-888. in library
Sonomicrometry
implants
Distal tendon
(towards toes
Proximal tendon
Pennation changes during activitytrain = change in length initial length
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Strain from sonomicrometryBufo americanusSM
Ahn et al(2003) J. Physiol. 549 877-888. inlibrary
strain differs between regions
velocity differs
different regions of muscle acting ondifferent part of force-length and force-velocity curves
Central segment
Distal segment
Time
Strain
Central segment = increased strain and increasedvelocity
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How active is a muscle?
EMG vs. in vitro
cannot determine % activity from invivo to relate to stimulation to apply in
vitro
best approximations during maximal
activity e.g. sprinting and jumping
assume all of muscle active
Compartmentalisation of muscle
activityCycling of fibres?
increase fatigue resistance
active activeinactive
Complications in muscleactivity
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Fibre typesType ISO
Red (s)Slow
Type IIAFOG
Red (f)FR
Type IIBFG
WhiteFFContractiontime
long short short
Mitochondriaand SDH
high high Low
ATPase atpH 10.0
low high high
Glycogencontent
low high High
Fatigueresistance
high high Low
contraction times = activation, relaxation
OG = fast oxidative glycolytic
R = fast & more fatigue resistant; FF = fast and more
atigueableDH = succinate dehydrogenase (a marker enzyme for
xidative metabolism)
ATPase = myosin ATPase staining (commonly used
to determine fibre type)
Glycogen stores especially important to fuel glycolysis
ifferent fibre types for different jobsMixed muscle fibre types in muscles
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Isoforms of MuscleProteins
Overall phenotype of muscle fibre depends onwhich muscle protein isoforms are expressed
Slow and fast isoforms exist of:
Thick filament proteins
Myosin heavy chain (many)
Myosin light chains
Most thin filament proteins
Tropomyosin
Troponin-C
Tn-T (many)
Tn-I
No known isoforms of actin in skeletal muscle
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Detecting MuscleProtein Isoforms
Determine composition by gelelectrophoresis
e.g. Sodium Dodecyl Sulphatepolyacrylamide gel electrophoresis(SDS-PAGE)
isoforms move in gels according tosize, mass or electrical charge
In humans: co-expression of MHC
isoforms within a fibre: I + I
I + IIA
IIA + IIA
IIA + IIB
IIB + IIB
IIX
Many possible combinations of isoform
combinations
contractile
speed
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Detecting MuscleProtein Isoforms 2
contractile
speed
An example gel
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Myosin HeavyChain Isoforms
Vmax
% MHCIIB
Larsson and Moss (1993)J Physiol 472 595-614.in library
Myosin heavy chain type IIB (fast glycolytic)
In human soleus and quadriceps muscle fibres
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Myosin Lightchain (MLC) Isoforms
Vmax
Ratio of myosin light chain 3 to myosin light chain 2
n rat muscle fibres with same MHC content
Ratio of alkali MLCs : no effect on force
General finding that fibre type has little effect on force
faster muscles produce a little bit higher stress
Bottineli and Reggiani (1995)Eur J Physiol 429 592-94. Not in library
Vmax = maximum muscle shortening velocity
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Histochemical fibre typing 1
Freeze muscle in liquid nitrogen
Cut thin sections (um)
Chemicals used to stain muscleaccording to enzyme activities
SDHase (succinate dehydrogenase)staining (Krebs/TCA cycle) so indicatehow oxidative the muscle is
Myosin ATPase staining indicates
contractile rateAssess ratios of I : IIA : IIB
Semi-quantitative (indicative)
Biochemical activity measurementsare better
e.g. SDHase quantification of enzymeactivity
IIIA
IIB
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Histochemical fibre typing 1
SDHase Myosin ATPase
ibre type I IIA IIB
DHase activity high high low
ATPase activity low high high
dark = fastestarker blue = more oxidative
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Isometric Properties ofFast and Slow Muscle
Force
Stimulation
Twitch
Tetanus
Force
Stimulation
FastSlow
aster muscle = faster activation rate (as fasteralcium release from SR) and faster relaxation rate (as
aster calcium binding [parvalbumin] and reuptake to
R [sarcoplasmic reticulum] via calcium pumps)
Time
Fast
Slow
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Fast vs. slow muscle PO
Cycle Frequency (Hz)
P
oweroutput(W
/kg)
slow
fast
Poweroutput
(%offirstloop)
Duration of activity (s
slow
fast
faster muscles produce more force at anyshortening velocity, therefore more power
Theoretical relationships between fast and
slow muscle for power output and fatigueresistance
Trade-offs.. between sprint and endurancetype activities
SprintEndurance
Power = force velocityelative power in Watts per kilogramme of muscle
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Fast vs. slow muscle PO 2
CYCLE FREQUENCY (Hz)
0 4 8 12 16 20 24
POWEROUTP
UT(W
/kg)
0
50
100
150
Mouse muscle power output-cycle frequency
curvesExtensor digitorum longus extends the toesand is a faster muscle (higher Vmax) producing3 times as much power (power to flick toesforward during swing phase)
soleus is an ankle extensor (stabilisation roleduring stance)
ight: Data from
ames et al. (1995)Exp. Biol. 198 491-502
Mouse EDL & soleus
soleus
slower
EDL faster
stride
maximalgallop
stride trotting
(normal speed)stride
slowest
walk
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Muscular Fatigue
Time
Force
Faster fibres fatigue here IIB
Slower fibres
fatiguing here
IIA
Cycle Number
Force(mN
)
0
20
40
60
80
100
120
140
0 30252015105
A
Above: Theoretical pattern of fatigue
NB effect of fibre type
Below: Pattern of fatigue measured inXenopus
aevis gastrocnemius. all fibres maximally activatedll the time
n 232SPO CUOnline:
Wilson, James & Van Damme (2002)J. Exp. Biol. 205 1145-1152.
IIB fibres fatiguing
slowest fibres
IIA fibres fatiguing
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Fatigue effects on work loopsMouse EDL muscle (a faster muscle)Wilson and James (2004) Proc. Roy. Soc. Lond. B.
(Suppl.) 271 S222-S225. On 232SPO CUOnline
Stress (force per musclecross-sectionalarea) decreases with fatigue
-0.05 0.05
50
100
150
Stress(kNm-2 )
Strain ( L0)
A
1
15
35
0.00 0.05 0.10 0.15 0.20
0
50
100
150
Stress(kNm-2)
Time (s)
1
15
35
B
force
decreased
force-velocity
relationship
changed:
decreased Vma
Relaxation rate
as decreased so
lower to relax
o loop 35 indicates a problem in maintaining force
uring shortening
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Sprint vs. endurance
ntuitive trade-off between sprint and endurance
Endurance performance
Sprintperformance
But in whole animal locomotion normally:
(problems of athlete quality)
Better athlete hypothesis genetics (setting rangeof possible performances) + training andenvironment (determining place in range)
sprint
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Human decathletes Decathletes of similar international
ranking Negative correlation between 100m sprint
(more anaerobic) and 1,500m run (moreaerobic)
Positive correlations between more
anaerobic events: 100m sprint and: longjump, 400m run, 110m hurdles
Negative correlation between shot puttand 1,500m run
Van Damme, Wilson, Vanhooydonck & Aerts (2002)
Nature415 755-756. in library
Why?: fast vs. slow muscles?
positive
relationship
negative
relationship
00m
print
1500m race long jump
100msprint
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Muscle trade-offs betweenSprint and Endurance capacity
End
urance
i.e. how well can force be maintained
during prolonged exercise?R2 = -0.67
0
0.1
0.2
0.3
0.4
0.5
0.6
30 35 40 45 50
Initial power output (W/kg)
Fatigueindexofpower
output(20
thrun/1strun)
sprint
endurance
Bufo viridisgastrocnemius (ankle extensor)muscle
Wilson, James, Kohlsdorf & Cox (2004) J.Comp. Physiol. 174 453-459. on CUOnline
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MoreB
ufo
viri
distrad
e-o
ffs
Max. Power Output (W kg-1
)
30 35 40 45 50
FatigueResistance
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Max. Stress (kN m-2
)
150 200 250 300
FatigueResistance
0.0
0.1
0.2
0.3
0.4
0.5
0.6
B
A
Max. Stress (kN m-2
)
150 200 250 300
Max.PowerOutput(Wkg-1 )
0
10
20
30
40
50
60
C
e
ndurance
endurance
sprint
sprint
sprint
sprint
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Mouse Trade-off Correlations
Mouse EDL work loops & isometrics(constant length)
Work loop sprint and endurance
+ve: Maximal isometric tetanic force &Maximal work loop force
+ve: Maximal work loop force and
power-ve: Maximum work loop power andwork fatigue resistance
-ve: Maximum work loop force and work
loop fatigue resistance
Wilson, R.S. and James, R.S. (2004) Proc. Roy. Soc.Lond. B. (Suppl.) 271 S222-S225. On 232SPOCUOnline
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Sprint and Endurance trainingMale rats trained on a treadmill for 10 weeks
Tested passive stress-strain relationship
Sprint or endurance training increased passivemuscle strength (maximal stress) andtoughness (maximal energy) and stiffness
(change in stress change in strain) but notextensibility (maximal strain)
endurance: lots of lower speed and force
training compared with sprint training
sprint
endurance
control
Strain (length change initial length)
Stress(
force
csa)
Muiz et al (2001)Acta Physiol Scand173 207-212
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What causes muscle fatigue? Why do mammalian muscles fatigue during
high intensity activity?
lactic acid build up unlikely to be the cause at low temperatures lactic acid causes fatigue
at physiological temperatures: minimal effect
impaired calcium release probable
during fatigue less calcium released from SR
so incomplete muscle activation
Mouse EDL work loops at 35C James et al(2004) J. Appl. Physiol. 96 545-552. On
232SPO CUOnline and in library
Power output in fatigued muscle increasedwith10mM caffeine treatment whencompared with controls
Calcium is stored in SR when the muscle isat rest
during fatigue calcium phosphate precipitatesin SR?
Caffeine enhancing opening of calciumchannels in sarcoplasmic reticulum
Remember that Calcium binds to TnC during
activation (muscle switch) so increased force
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10mM Caffeine effects
What causes increase in power output?
-20
30
80
130
180
-5 5 15 25 35 45 55
Time after fatigue run (min)
Maxim
umw
orkloop
stre
ss(kN
m-2)
0
20
40
60
80
100
120
140
-5 5 15 25 35 45 55
Time after fatigue run (min)
Pow
eroutputrelativet
opre-
fatigue(%)
10mM caffeine
Controlwashout
re fatigue
fatigued
Other methylxanthines have similar effects
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Effect of 70uM caffeine on PO So could caffeine improve an athletes
performance? 70M caffeine in blood plasma in
humans (very high caffeine is fatal)
No effect on fatigued muscle but affectsnormal muscle
Mouse EDL work loops
Time from start of caffeine incubation (min)
-20 0 20 40 60 80 100Poweroutput(%oftheoretic
alcontrol)
92
94
96
98
100
102
104
106Washout
James, R.S., Kohlsdorf, T., Cox, V.M. and Navas, C.A. (2005)
Eur. J. Appl. Physiol. 95 74-82.
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What determines
muscle phenotype?Embryonic phenotype
determined by genotype
Birth
Plastic Phenotype
Innervation (EMG)
Volume of work
Peak forces
Hormones(e.g. testosterone
Growth
e muscle phenotype alters to reflect changing
emands made upon the muscleenvironmental effects)
gene expression
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Cross-innervation studies960s cross-innervation experiments on mammals
DL = flexor digitorum longus
FDL soleus
soleus nerveFDL nerve
g. Buller et al. (1960) J Physiol 150 417-430. In library
Twitch force
Stimulation
FDLsoleus
FDL soleus
soleus nerveFDL nerve
Twitch force
Stimulation
FDLsoleus
erves cut and rejoined to itself (sham operated) orother muscle
Experimental
ham operated (rejoined to themselves)
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Development and GrowthIn humans
During foetal development fibrenumber increases (hyperplasia) i.e.development of new fibres to increasemuscle size
Once born muscle developmentconsists of repair to damaged cellsand growth by fibre hypertrophy (i.e.
increase in fibre size)
Fibre hypertrophy: increased numberof myofibrils in muscle fibre =
increased fibre size (increased cross-sectional area)
Although new fibres cannot be formedfibre composition can change
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Growth & DevelopmentAs animal gets older mechanics may
changeMuscles and bones grow in length andwidth
Muscle stretch
Body weight increase so greater forcesinvolved
Minimal escape/prey captureperformance?
Scaling relationshipssmaller animals have faster muscle
protein isoforms so faster stridefrequency
larger animals higher stride length
sprint speed dependent on stridefrequency and stride length
Response to environment
Respond to changes
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Muscle Adaptationto new length
If muscle under stretche.g. growth of limb bones
Length
Force
L1 L2
ResponseAddition of new sarcomeres to length
Maximal active force at longer (L2)resting length
If muscle to slack at rest, atrophy and
hortening (L3)e.g. in plaster cast
L3
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Scaling: Fish Body size effects
Total body length (cm)
5 10 20 30Maximumvelocity(bodylengthss-1)
1
5
10
20
Sculpin swimming
James & Johnston (1998) J. Exp. Biol. 201 913-923. On232SPO CUOnline
As body size increases relative maximumswimming velocity decreases (absolutespeed fairly constant)
so smaller fish using higher stride frequency:how?
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Total body length (cm)
5 10 20 30
V0(musclelengthss-1)
1
2
5
10
Total body length (cm)
5 10 20 30Timetopeak
twitchforce(ms)
10
20
50
100
Total body length (cm)
5 10 20 30Peaktwitchto50%
relaxation(ms)
10
20
50
100
Total body length (cm)
5 10 20 30
Laststimulusto50%
tet
anusrelaxation(ms)
10
20
50
100
Fish mechanicsSculpin fast muscle: Isometrics & Isovelocity
ames et al. (1998) J. Exp. Biol. 201 901-912.
calcium
binding or
pumping?
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Explain fish mechanics?
Total body length (cm)
5 10 20 30
M
yosinATPaseactivity
(u
molreleasedmg-
1min-1)
0.2
0.5
1
2
Sculpin study continued.
Changes in TnI isoformfaster isoform in smaller fish
No changes in thick filament proteins MLC, MHCNo changes in other thin filament proteins:
TnC, TnT, actin or Tm
Affects rate of ATP breakdown
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Mammalian scaling ofmuscle properties
Vmax (maximum shortening velocity)measurements in rat, cat and horsesoleus single muscle fibresRome, Sosnicki & Goble (1990). J. Physiol. 431, 173-185. inlibrary
Large decrease in Vmax of type I musclefibres with increased body size
Smaller decrease in Vmax
of type IIBmuscle fibres with increased body size
Smaller animals tend to have
Faster muscle fibresHigher stride frequencies (strides s-1)
Lower stride length (shorter legs)
Larger animals: slower more efficientmuscles (e.g. decreased calcium pump cost)
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Further Evidence onscaling
Xenopus laevisadductor magnus (slower) andsartorius (faster) muscles from frogs ofdifferent sizes
Work loop experiments to look at cycle
frequency that yielded maximal powerAltringham, Morris, James & Smith (1996) Experimental BiologyOnline1 (6): this is available online for free. You can search for the
journal name via Google
Body Mass (g)
Cyclefrequency(Hz)
slower muscle, larger decreasein cycle frequency for maximal power
sartorius
adductor magnus
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Why should temperatureaffect locomotion?
Temperature affects enzyme activity rates e.g. myosin ATPase
therefore can affect rates of mechanics
e.g. activation rate
Range of muscle temperatures lower in warm
blooded (endothermic) animals but basic
effects the same as in cold blooded(ectothermic) animals
Temperature
Enzymeactivity
o increase temperature causes increase rates.ventually denaturation occurs
rate at which enzyme works
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Human temperature effects
Heating/cooling legs in water thigh muscle 39.3, 36.6, 31.9, 29.0C
Cycle ergometer Sargeant (1987) Eur J Appl Physiol. 56 693-698.
Increased temperature caused
Increased peak force
Increased power
Increased rate of fatigue
Linane, Brooks, Cox and Ball (2004) Eur J ApplPhysiol. 93 159-166.
Full immersion of human in 43C caused 1%increase in muscle power output during subsequentcycling
Why?
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Pedalling rate (rev./min)
Maximumpeak
force(N)
Sargeant (1987)
39.3
36.631.929.0
Thigh muscle temperatures
Maximumpeak
power(W)
Pedalling rate (rev./min)
29.0
39.3
31.9
Hotter muscles have higher maximal shortening V,
igher rates of activation and relaxation. so produce
more force at any velocity than colder muscles
i.e velocity
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Human temperature effects 2
Heating/cooling hands in water
18, 25 or 39C for 30 minutes or inair at room temperature
approximate muscle temperatures of23.5, 28, 32.5 and 37C
Handgrip test: isometric force thenforce-velocity relationship
Binkhorst et al (1977) J ApplPhysiol. 42 471-475. in library
Increased temperature caused
Increased maximal shorteningvelocity
Increased power
No change in maximal isometric
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Temperature Effects on Locomotion
A)
5 10 15 20
Jump
distance(BL)
10
15
20
25
30
35
40
5 10 15 20Jumptake-offvelocity(BLs-1
)
25
30
35
40
45 B)
5 10 15 20
Meanjumppow
eroutput(Wkg
)
100
200
300
400
500
600C)
5 10 15 20Meanswimmingvelocity(BLs-1)
6
8
10
12 D)
Temperature (degrees C)
ana temporaria: Navas, James, Wakeling, Kemp and Johnston (1999)
Comp. Physiol. 169 588-596. see Rob for this
power output per kg muscle mass
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More T. effects on locomotion
Temperature (o
C)
0 5 10 15 20 25 30 35MaximumSwimmingSpeed(ms-1)
0.0
0.4
0.8
1.2
1.6
Xenopus laevis
Wilson, James and Johnston (2000)J Comp. Physiol B 170 117-124.n 232SPO CUOnline
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0 5 10 15 20 25 30 35
TwitchForce(%ofmax.)
60
70
80
90
100
Temperature (oC)
0 5 10 15 20 25 30 35
Tetani
cForce(%ofmax.)
60
70
80
90
100
Effects on Isometric Force
Wilson, James and Johnston (2000)J Comp. Physiol B 170 117-124.
Xenopus laevis gastrocnemius fibre bundles
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Effects on Isometric Times
0 5 10 15 20 25 30 35
TimetoPeaktwitch(s)
20
40
60
80
100
120
140
Temperature (oC)
0 5 10 15 20 25 30 35
TPT
1/2Relax.(s)
0
100
200
300
400
Xenopus laevis gastrocnemius fibre bundles
Wilson, James and Johnston (2000)J Comp. Physiol B 170 117-124.
TPT PTHR
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Overall temperature effectsOn work loops
Increased temperature:More rapid force activation
Increased maximal force output
Increased maximal shortening velocity
so can work at higher cycle frequency
Better maintenance of force duringshortening
More rapid force relaxation
so larger area of work loop = morework
so more power output
higher temperature
lower temperature
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Comparison of species
0
50
100
150
0
1020
3040
05
1015
POW
EROUTPUT(W
kg-1)
TEMPE
RATU
RE(
0C)
CYCLEFREQUENCY(Hz)
12
11
10
9
8 654
3
2
1
7
Increased optimal cyclefrequency for power outputwith temperature
Increased optimal cyclefrequency increases poweroutput
cold vs. warm blooded.
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Eccentric muscle activityMuscle active & being stretched
Extra stretch of myosin neck region(S2) causes:
more rapid force rise
enhanced force production
E.g. quadriceps and gastrocnemiuswhen walking down stairs
stabilise/brake the limb
Eccentric activity before concentric
activity enhances force duringconcentric as well!
Velocity
Force
Concentric
(muscle shortening)Eccentric
muscle lengthening)
0
0 velocity =
isometric
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Eccentric Muscle Stress-Straincurves
Strain
Stress
Stress
Stress
Strain
Strain
Work output
Net work
Active (eccentric exercise)
Work input
energy required
to stretch
low energy outpu
during shortening
as c. passive
net energy costto cycle this muscl
braking action
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Is long jumpingperformance dependent on
tissue mechanics?
Review long jumping performance in differentanimals
Review tissue mechanics in different animals
Conclusions
See James et al. (2007) Journal of Experimental Biologyreview paper on CUOnline
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What does jumping depend upon?
dis distance jumped (e.g. m)
vis take-off velocity (e.g. m s-1)
is take-off anglegis the acceleration due to gravity(approximately 9.8 m s-2)
jump distance largely dependent ontake off velocity
How increase velocity?
Increase acceleration rate
Increase distance over which accelerate
g
vd
2sin2
Centre of mass
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What else does jumpingdepend on?
Wis total average power required forthe jump
L is the distance from the centre ofmass to the tip of the toes
Mb is body mass of the animal
So increase power
Maybe: increase muscle mass, energystorage, increase muscle speed and/orforce?
Increase L by increased relative leglength?
Minimise body mass?
gM
LWd
b
2sin32
Power = force speed
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How can muscle poweroutput be increased?
Increased proportion of fast muscle
fibres in jumping muscles (legextensors)
In jumping frogs:
Jumping muscles 89% fastest fibres
Non-jumping muscles 29%As % of fastest fibres increases from 0
to 100% there was a 57% increase inpower output and 22% increase in stressand increased shortening velocity
NB. Trade off in muscle function
Increased temperature (mainly ectotherms)
Endotherms regulate, ectothermsbehavioural thermoregulation
Increased rates of activation andrelaxation
Increased power output
Energy storage and returnee James et al. (2007) Journal of Experimental Biology
view paper on CUOnline
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Energy storageIn many animals including man
CountermovementActive lengthening of extensor muscle
prior to shorteningForce enhancement
OR rapid early shortening of musclewithout movement of body e.g. frogsFrog muscle produce only c.30% of
power for the jump!
OR catch mechanism (insects)
Elastic potential energy storageMainly in tendons of extensor muscles
Amplifies power
Virtually temperature independent
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Body Size affects muscleperformance
As body size increases Muscle fibre type tends to become slower
(slight decrease in force)
Rate of muscle activation and relaxation tendsto decrease
Maximum relative muscle shortening velocitydecreases (in muscle lengths s-1)
But larger animals have longer muscles
Power output (W kg-1
) and stress unaffected NB PO = F V
So larger animals can afford to have slowermuscle fibre type and still achieve similar powe
output But why are slower fibres useful?
So why dont smaller animals jump as far aslarger animals?
Drag
Shorter limbs so shorter time to accelerate overso need greater peak power, so need fastermuscles
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Body Size affects long jumpperformance
Long jump performance increases withincreased body size
But muscle performance?
Body length (m)
Longjumpdistance(m)
Line indicates 100 W.kg-1 BM
Compare with 100 W kg-1 muscle mass
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Hindlimb length
Hindlimb length increases with increasingbody size
Jumping vs. non-jumping mammals
L
oghindlimblength(cm)
Log cubed root of body mass (g)
merson, S.B. (1985) In Functional Vertebrate MorphologyCambridge: Harvard University Press.
Jumping specialists (mammals)
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MorphologyLeg length
Frog and lizard species with relativelylonger legs tend to jump further
Muscle mass
Jumping c.f. non jumping frog &mammal species increased leg extensomuscle mass
In frogs higher relative muscle mass =
longer jump distance (leg extensormuscle mass as % of body mass)
Muscle architecture Tend to be longer & less pennate in larger
animal speciesSo increased maximum shortening velocity
Muscle insertion more proximal
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Predicting jump performance
Jump performance often assessed as
jump distance or jump take-off velocityOne predicts the other
Domestic cat jump take of velocity:
62%, lean body mass residuals ofhindlimb length and fat massSo fat cats with short legs dont jump as far Harris, M.A. and Steudel, K. (2002) JEB205 3877-3889.
Frog (Hyla multilineata) jump distance:43%, body length residuals of hindlimbmuscle mass and pyruvate kinaseactivity
So frogs with more extensor muscle massand more glycolytic muscle jump further James, R.S., Wilson, R.S., Carvalho, J.E., Kohlsdorf, T.,
Gomes, F.R., Navas, C.A. (2005) PBZ78 857-867.
Jumping performance linked to fitnessin some species
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Accelerated development
Adults (post-metamorphr2=0.01 P>0.05
Juveniles (metamorph)Mb
0.53 r2=0.67 P
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Modelling jumpperformance
In a human like animal: countermovement andcatapult jumps yield similar jump distances >squat jump
Squat jump = no or limited energy storage
In bush baby and insect like animals catapultjump>countermovement jump
Increased muscle shortening velocity
increased jump distance in all animals (moreimportant in human)